An Integrated Case Study for Evaluating the Impacts of an Oil Refinery Effluent on Aquatic Biota in the Delaware River: Sediment Quality Triad Studies
Posted on: Thursday, 6 October 2005, 06:00 CDT
By Hall, Lenwood W Jr; Dauer, Daniel M; Alden, Raymond W III; Uhler, Allen D; Et al
ABSTRACT
Triad studies consisting of chemical characterizations in sediment, sediment toxicity testing, and benthic community assessments were used to determine the impacts of Motiva Enterprises oil refinery effluent [primarily polynuclear aromatic hydorcarbons (PAHs)] on aquatic biota in the Delaware River. Triad studies were conducted at 15 near-field, mid-field, and far-field sites near the Refinery in the Delaware River during the spring and summer of 2001 and 2002. Fingerprinting analysis showed that Motiva-related PAHs may be present at four near-field sites. A summary of all Triad data by site for 2001 shows a strong case for contaminant-induced degradation at one near-field site in the discharge canal of the Refinery and two far-field sites as all three lines of evidence suggest impairment. Stressful conditions for benthic communities at the near-field site include elevated temperature conditions and various pesticides (Dieldrin, 4,4'-DDD and 4,4'-DDT). Toxicity at the near-field site may also be related to the presence of pesticides exceeding sediment quality guidelines. Due to exceedances of individual Effects Range Low (ERL) guidelines for two individual PAHs, the Motiva effluent cannot be eliminated as a potential stressor at the near-field site during the summer of 2001. A summary of Triad data for the 15 Delaware River sites sampled in 2002 shows only one mid-field site where all three lines of evidence suggest impairment. Toxicity and benthic community impairment at this mid- field site may be related to PCBs and low molecular weight PAHs. Three individual PAH ERL values were exceeded at three near-field sites in 2002. The source of these PAHs is a combination of both background signature and the Motiva effluent. Multivariate analysis, using a weight of evidence approach, is used to address ecological effects of the Motiva effluent in more detail in Alden et al. (2005).
Key Words: triad studies, PAHs, pesticides, metals, PCBs, Delaware River.
INTRODUCTION
As discussed in detail in the preceding paper (Hall and Burton 2005), Motiva Enterprises LLC owns and operates a large oil Refinery on the Delaware River in Delaware City, Delaware. The Refinery is located in the transition zone of the Delaware estuary that is characterized as a region of relatively high turbidity, variable salinity (0 to 18 ppt) and low productivity. The goal of this study was to use the Sediment Quality Triad (Triad) to determine the impacts of PAHs from Motiva's effluent (as required from a Court order) on aquatic biota in this transition zone of the Delaware River estuary. The Triad is a well established "weight of evidence" approach used to integrate chemistry, sediment toxicity testing, and biological observations to determine pollution-induced degradation (Chapman et al. 1987; Long 1989; Chapman 1996; among others). Specifically, the Triad involves three separate components, each of which comprise one or more measurement endpoints: sediment chemistry analyses that measure contaminants that contribute to exposure; laboratory toxicity tests that measure effects of sediment collected in the study area under standardized conditions, and biological community assessments (typically benthos), which are used to measure the status of resident communities. All three lines of evidence and their associated interrelationships are used to identify potential degradation in aquatic systems.
Triad sampling for this study specifically included the following three components: (1) contaminant exposure characterizations for PAHs, chlorinated pesticides, polychlorinated biphenyls (PCBs), bulk and simultaneously extracted (SEM) metals, grain size, and various pore water/sediment parameters in sediment; (2) 28-day chronic survival, growth, and reproduction sediment toxicity tests with the epifaunal and infaunal amphipods, Hyaklla azteca and Leptocheirus plumulosus, respectively; and (3) macrobenthic community assessments. These three types of assessments were conducted at the 15 study sites in the Delaware River during the spring and summer of 2001 and 2002 as described in Figure 1. A description of each component of the Triad, including objectives, methods, and results/ discussion, is presented in this article.
SELECTION OF STUDY SITES IN THE DELAWARE RIVER
In August of 1999 a total of 53 candidate sites in Motiva's discharge canal, nearfield, mid-field, and far-field areas were sampled for total PAHs, total organic carbon, and grain size distributions to aid in the selection of sample sites (Hall et al. 2004). Criteria used for the selection of sample sites were proximity to Motiva's discharge canal and potential influence of the Refinery effluent, presence of PAH concentrations exceeding sediment quality guidelines, toxicity of sediments based on laboratory studies, and presence of degraded benthic communities. Reference sites selected were the least impacted (or best attainable) sites in the study area that were not influenced by Motiva's effluent. The data collected in August of 1999 were used in combination with fate and transport data, including a dye tracer study, to select the 15 sample sites described in Figure 1. The dye tracer study, which mapped Motiva's effluent from four tidal phases and two depths, showed that the effluent plume was located on the Delaware side of the river with a maximum coverage of approximately 3 miles upriver and 7 miles downriver depending on tidal cycle. A hydrodynamic plume model-adapted to delineate the transport of conservative dissolved constituents-was also used in conjunction with the dye study to identify the spatial extent of Motiva's effluent (Hall et al. 2004). The 15 sample sites in Figure 1 (including 2 reference sites) covered approximately 12 nautical miles from the upstream to the most downstream site. Five sites were located above the discharge canal, nine sites were below the discharge canal, and one site was located in the discharge canal.
Figure 1. Sample sites used in the 2001-2002 triad study.
OBJECTIVES OF CHEMICAL CHARACTERIZATIONS
The objective of this task was to measure PAHs, chlorinated pesticides, PCBs, bulk and SEM metals, grain size, and various pore water/sediment parameters from 5 replicate sediment samples collected from 15 sites in the Delaware River during the spring and summer of 2001 and 2002. Means and standard deviations were presented for each constituent but actual replicate concentrations were excluded due to space limitations. All replicate data for all constituents are available in Hall et al. (2004).
METHODS FOR CHEMICAL CHARACTERIZATIONS
A 100 m x 100 m square grid was established at each station presented in Figure 1. It was not uncommon to find heterogeneous sediment in these various grids. Five random locations within each grid were selected for collecting 5 replicate sediment samples with a standard Ponar grab sampler (volume of 8.2 L). For the discharge canal, the grid configuration was modified to include a rectangle of the same area (10,000 m^sup 2^) because the discharge canal is not 100 m wide. The full suite of chemical analyses including PAHs, chlorinated pesticides, PCBs, bulk and SEM metals, and various pore water/sediment parameters described in detail in Hall et al. (2004) was conducted on each replicate sediment sample collected from each site. Each replicate was retained in a separate container for the chemical analyses and sediment toxicity tests described in this article; contaminants were evaluated concurrently with toxicity tests. Benthic communities were also evaluated on replicates as described later in this article. Quantification of the contaminants (described earlier) in the sediment provides valuable insights if high concentrations of potentially toxic contaminants are observed in conjunction with biological effects or impaired benthic communities.
All chemical measurements described herein followed quality assurance/quality control procedures as described in detail in Hall et al. (2004). Battelle Duxbury Laboratory (Battelle), Duxbury, Massachusetts, measured the Western States Petroleum Association (WSPA) list of PAHs for parent and isomer-specific 2 through 6 ring compounds (Hall et al. 2004). To aid in confident identification of the nature and source of PAH assemblages in sediment (petrogenic versus pyrogenic), the distribution of parent and alkyl homologue PAHs listed in Hall et al. (2004) were also analyzed. Analysis of the parent and alkyl homologue PAHs provided a useful way to represent the broad distribution of unsubstituted and GI to C4 alkyl homologues of PAHs in the environment. This representation is more diagnostic than selected isomers because it provides a wider spectrum of compositional information than the compound-specific target analytes (see Uhler et al. 2005, in this issue). Battelle measured these compounds in sediment using gas chromatography/mass spectrometry (GC/MS) techniques following Battelle SOP 5-157 (Modified SW 846 Method 8270; see Hall et al. 2004 for descrip\tion of method). The categories of hydrocarbons generated from this analysis were as follows: selected cyclic hydrocarbons (decalins through benzo(b)thiophenes), total PAHs with alkyl homologues including both low molecular weight (LMW) PAHs with 2 and 3 aromatic rings and high molecular weight (HMW) PAHs with 4 to 6 aromatic rings, PAH isomers, and total analytes.
Chlorinated pesticides and PCBs identified as priority pollutants by EPA and target compounds of the NOAA Status and Trends Program were also measured by Battelle (Hall et al. 2004). Samples were measured for the organics using a GC equipped with an electron capture detector (ECD) following procedures described in Battelle SOP 5-128 (Modified SW846 Method 8081; see Hall et al. 2004 for description of method).
Bulk metals analyses were performed by Battelle on all sediment samples using ICP/MS and cold vapor for mercury (Hall et al. 2004). Specific methods and detection limits are presented in Hall et al. (2004). In addition, acid volatile sulfides (AVS) and simultaneously extracted metals (SEM) were also measured by Battelle on all sediment samples as described in Hall et al. (2004) using the method described by Alien et al. (1991). The concentrations of the SEMs were determined by the same analytical methods as bulk metals (see Hall et al. 2004). The concentrations were converted to moles/g dry weight sediment and summed to yield total SEM. For all SEM metals that were below the detection limit, the detection limit was used as the assigned value when calculating final total SEM. SEM results were used in conjunction with the AVS data to estimate the potential toxicity of the sediment due to metals.
Sediment samples were also analyzed by Battelle or Battelle subcontractors for total organic carbon (TOC), ammonia-N, nitrite- N, and sulfides occurring in sediment and pore water (Hall et al. 2004). Sediment grain size and distribution (between 0.4 and 2,000 um) were determined on all five replicates at each site (Hall et al. 2004).
Concentrations of PAHs (total, LMW and HMW), pesticides, PCBs, and bulk metals were compared with Sediment Quality Guidelines (SQG) to predict concentrations of potential ecological concern. Sediment concentrations of the aforementioned classes of contaminants were compared to the 10% probability of effects, Effects Range Eow (ERL) values, and the 50% probability of effects, Effects Range Median (ERM) values, established by Long et al. (1995) and reported by Buchman (1999) in the NOAA SQUIRT tables. These ERL and ERM values are widely used guidelines based on correlations between toxicity data and measured concentrations from large data sets (Long et al. 1995).
RESULTS AND DISCUSSION
Chemical data collected during the spring (April and May) and summer (August) of 2001 and 2002 are summarized in the following sections by sampling period and type of chemical.
Spring 2001
Total PAH concentrations expressed as a mean of 43 analytes for the 5 replicates at each site ranged from 1,242 ng/g dry weight sediment at site DRlO (reference site) to 16,658 ng/g at DR67 (Table 1). The same spatial trend, lowest concentrations at DRlO and highest concentrations at DR67, was also found for selected cyclic hydrocarbons, PAH isomers, and total analytes (Table 1). Variability of PAHs by replicate was low to moderate for most of the sites (Table 1). For cases where PAHs were variable among the five replicates as indicated by the standard deviation at a site, grain size was a likely factor influencing the PAH concentrations (i.e., a negative correlation between percent sand and total PAH concentration).
Table 1. Site means and standard deviations (S.D.) of PAH concentrations (ng/g dry weight sediment) from 15 Delaware River sites and a Control site (Magothy River, Maryland) sampled in Spring 2001.
A conservative (worst case scenario) comparison of the 43 parent PAHs and alkyl homologues measured during this study with exceedences of various NOAA toxicity benchmarks (Buchman 1999) in Table 1 showed the following: (1) mean total PAHs exceeded the ERL value of 4,022 ng/g at 9 of the 15 Delaware River sites; (2) mean total LMW PAHs exceeded the ERL value of 552 ng/g at all sites except DRlO and the ERM value of 3,160 ng/g was exceeded at five sites and (3) mean total HMW PAHs exceeded the ERL value of 1,700 ng/ g at 11 sites. Exceedences for total PAHs in the various categories described earlier are a bias approach because the total PAH values were based on 43 different parent PAHs and alkyl homologues in contrast to the NOAA benchmarks that are based on only 13 PAHs. A summary of exceedences in Table 2 based on the 13 PAH analytes used by NOAA resulted in the following: (1) the mean total PAH ERL was only exceeded at one site (DR67); (2) mean total LMW PAHs exceeded the ERL at seven sites (DR56, DR52, DR53, DR55, DR67, DR68, and DR83) and (3) mean total HMW PAH exceeded the ERLs at three sites (DR53, DR67, and DR68). There were no exceedences of ERM values for total, LMW, or HMW PAHs.
Individual PAH ERLs were exceeded frequently for the LMW PAHs fluorene (mean values from DR45, DR56, DR26, DR51, DR52, DR53, DR55, DR67, DR68, and DR83), naphthalene (mean values from DR56, DR52, DR53, DR55, DR67, DR68, and DR83), and 2-methylnaphthalene (mean values from DR56, DR52, DR53, DR55, DR67, DR68, and DR83) (Table 2). Mean site value ERLs were exceeded at six sites or less for acenaphthylene, acenaphthene, anthracene, phenanthrene, benz(a)anthracene, chrysene, benzo(a)pyrene, and dibenz(a.h) anthracene. There were no exceedences of mean site individual PAH ERLs for fluoranthene or pyrene. Individual PAH ERM values were not exceeded for any replicate at any site.
Total mean pesticide concentrations at the 15 Delaware River sites ranged from 0 to 35 ng/g dry weight sediment (Table 3). Higher pesticide concentrations were reported upstream from the Refinery discharge canal at sites DR51, DR26, DR45, and DR9B. Concentrations of total pesticides were much lower at the downstream sites below DR55. Mean site concentrations of the insecticide Dieldrin exceeded ERL values at 9 sites upstream from site DR53. Mean site concentrations of 4,4'-DDD exceeded ERL values at DR9B, DR45, DR26, DR51, DRl, and DR23. ERL values for 4,4'- DDE were exceeded for mean site concentrations measured at DR9B, DR45, DR26, and DR23. Mean site concentrations of 4,4'-DDT exceeded ERL values at DR9B, DR45, and DR23. The ERM value for 4,4'-DDT was also exceeded at DR9B.
Total mean PCB concentrations ranged from 0.01 to 503.29 ng/g at the 15 study sites (Table 3). High total PCB concentrations were found both upstream (DR56, DR45, and DR26)"and downstream (DR52 and DR53) of the Refinery discharge canal. The total mean PCB concentration of 503.29 ng/g at DR53 was significantly higher than the other sites. Much lower concentrations of total PCBs were generally reported at the four downstream sites (DR55, DR67, DR68, and DR83) and the upstream site (DRl O). Total mean PCB concentrations exceeded ERL values at DR45, DR56, DR26, DR52, and DR53. Total mean PCB concentrations also exceeded the ERM value at DR53.
Concentrations of bulk metals exceeding ERL values in descending order by number of Delaware River sites were as follows: arsenic (14 sites), nickel (14 sites), mercury (11 sites), zinc (11 sites), chromium (9 sites), lead (9 sites), copper (8 sites), and cadmium (3 sites) (Table 4). The only two metals to exceed ERM values were mercury and zinc. Exceedences for both of these metals generally occurred below the Motiva Refinery at DR52, DR53, DR67, DR68, and DR83 (Table 4).
Table 2. Mean concentrations and standard deviations (D.D.) of PAHs (ng/g dry weight sediment) used by NOAA for determinig ERL and ERM values (Buchman 1999) for 15 Delaware River sites and a Control site (Magothy River, Maryland) sampled during Spring 2001.
Table 2. Mean concentrations and standard deviations (D.D.) of PAHs (ng/g dry weight sediment) used by NOAA for determinig ERL and ERM values (Buchman 1999) for 15 Delaware River sites and a Control site (Magothy River, Maryland) sampled during Spring 2001.
Table 3. Means and standard deviations of pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River sites and a Control site (Magothy River, Maryland) sampled during Spring 2001.
Table 3. Means and standard deviations of pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River sites and a Control site (Magothy River, Maryland) sampled during Spring 2001.
Table 3. Means and standard deviations of pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River sites and a Control site (Magothy River, Maryland) sampled during Spring 2001.
Table 3. Means and standard deviations of pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River sites and a Control site (Magothy River, Maryland) sampled during Spring 2001.
Table 4. Means, standard deviations (S.D.), and detection limits (D.L.) of metals concentrations (g/g dry weight sediment) from 15 Delaware River sites and one control site (Magothy River, Maryland) during Spring 2001 sampling.
The analysis of total metal residues in sediments does not always provide definitive information about the potential bioavailability of the measured concentrations. Some investigators (DiToro et al. 1990, 1992) believe that there are some components in the sediments that bind with certain metals such that they are no longer available and therefore not toxic to the benthic organisms. Sulfides in sediments have the ability to bind with divalent metals such as cadmium, copper, lead, mercury, nickel, and zinc and may render these metals unavailable to the extent that sulfides are available. Sediments from the study area were analyzed for the amount of acid volatile sulfides (AVS) and for the amount of freely available divalent metals as simultaneously extractable metals (S\EM). Assuming that the sulfides would bind with the metals on a 1:1 molar basis, dividing SEM by the amount of AVS would suggest that these metals are available when the ratio is greater than 1. Zinc was by far the most abundant metal in the SEM pool from sediment samples collected during this study. Zinc forms less stable sulfides than copper and lead as reported by Casas and Crecelius (1994) so it is likely that the most bioavailable metal as defined by SEM/AVS is zinc. However, there are other substances that can be found in the sediments that can bind with, and effectively prevent these and other metals from being toxic to in-situ benthic organisms and benthic test organisms used in sediment bioassays (e.g., organic carbon). Thus, it has been proposed that when the ratio is less than 1, no toxicity due to the SEM metals is likely (DiToro et al. 1990, 1992). When the ratio is greater than 1, toxicity due to the SEM metals may be possible as metals may be bioavailable. The concentration of bioavailable metals determines toxicity. It is only when the ratio is much greater than 1 that toxicity due to any one of these metals becomes more likely.
Mean SEM/AVS ratios for all Delaware River sites ranged from 0.18 at DR23 to 6.23 at DR55 (Table 5). Stations DR53 and DR2 were the only sites with all SEM/AVS ratios greater than 1 for all replicates (Hall et al. 2004). The highest SEM/AVS ratios (24 to 25) were found in one replicate at both DR56 and DR55 (Hall et al. 2004). For these replicates, toxicity due to metals is highly likely.
The mean percent sand, silt, and clay for all 15 Delaware River study sites combined was 38.4, 49.4, and 12.3%, respectively (Table 6). The mean percent sand ranged from 19.5 at DR83 to 84.6 at DR2. Percent silt ranged from 12.7 at DR2 to 63.8 at DR45. The percent clay ranged from 2.7 at DR2 to 19.3 at DR83. Variability in grain size distributions among replicates, as indicated by the standard deviation, was generally low for all sites except DR51, DRl, and DR2.
A summary of the porewater/sediment parameter data in Table 7 showed that mean sulfide concentrations ranged from 51 to 392 mg/kg dry weight sediment; mean ammonia concentrations ranged from 0.9 to 11.9 mg/kg; and mean nitrate + nitrite concentrations ranged from 5 to 5.8 mg/kg (Table 7). Mean concentrations for sulfide, ammonia, and nitrate + nitrite at all Delaware River sites were 159,5.6 and 5.1 mg/kg, respectively. Total organic carbon ranged from 1.18% at station DR51 to 4.48% at DR68. The mean total organic carbon for all Delaware River sites was 3.1%.
Summer 2001
Total PAH concentrations expressed as a mean of 43 analytes for the five replicates at each site ranged from 2,678 ng/g dry weight sediment at site DR23 to 22,403 ng/g at DR67 (Table 8). The same spatial trend, lowest concentrations at DR23 and highest concentrations at DR67, occurred for total analytes (Table 8). Reasonably high variability of PAHs by replicate was found at DR10, DR56, DR51, DR2, DR55, and DR67. Differences in grain size among replicates (see later section) was a likely contributing factor influencing these variable PAH concentrations.
Table 5. Means and standard deviations (S.D.) of acid volatile sulfide (AVS), simultaneously extracted metals (SEM) metals, and the SEM/AVS ratio in 15 Delaware River sites and one Control site (Magothy River, Maryland) sediment sampled during Spring 2001.
The 43 parent PAHs and alkyl homologues measured during this study in Table 8 were compared in a conservative (worst case scenario) format with exceedences of various NOAA toxicity benchmarks (Buchman 1999). The following results were found: (1) mean total PAHs exceeded the ERL value of 4,022 ng/g at 10 of the 15 Delaware River sites; (2) mean total LMWPAHs exceeded the ERL value of 552 ng/g at all sites and the ERM value of 3,160 ng/g was exceeded at 6 sites, and (3) mean total HMW PAHs exceeded the ERL value of 1,700 ng/g at all sites. Exceedences for total PAHs in the various categories described earlier are bias because the total PAH values were based on 43 different parent PAHs and alkyl homologues in contrast to the NOAA benchmarks that are based on only 13 PAHs. A summary of exceedences in Table 9 based on the 13 PAH analytes used by NOAA resulted in the following: (1) the mean total PAH ERL was exceeded at DR67, DR68, and DR83; (2) mean total LMW PAHs exceeded the ERL at DR56, DR52, DR53, DR55, DR67, DR68, and DR83, and (3) mean total HMW PAH exceeded the ERLs at DR67, DR68, and DR83. There were no exceedences of ERM values for mean total, LMW, or HMW PAHs.
Table 6. Means and standard deviations (S.D.) of grain size data from 15 Delaware River and one Control site (Magothy River, Maryland) sampled during Spring 2001.
Individual PAH ERLs were exceeded frequently for the LMW PAHs fluorene (mean values from DR10, DR9B, DR45, DR56, DR26, DR51, DR1, DR23, DR52, DR53, DR55, DR67, DR68, and DR83), 2-methylnaphthalene (mean values from DR45, DR56, DRl, DR52, DR53, DR55, DR67, DR68, and DR83), naphthalene (mean values from DR56, DR52, DR53, DR55, DR67, DR68, and DR83) and acenaphthene (DR56, DR52, DR53, DR55, DR67, DR68, and DR83) (Table 9). Mean site value ERLs were exceeded at 6 sites or less for acenaphthylene, anthracene, phenanthrene, fluoranthene, pyrene, benz(a)anthracene, chrysene, benzo(a)pyrene, and dibenz(a,h) anthracene. There was at least one exceedence of a mean site individual PAH ERL for all 13 PAHs listed in Table 9.
Table 7. Means and standard deviations (S.D.) of porewater/ sediment concentrations of sulfide, ammonia, nitrate (mg/kg dry weight sediment), and % total organic carbon (TOC) for 15 Delaware River sites and one Control site (Magothy River, Maryland) sampled during Spring 2001.
Total mean pesticide concentrations at the 15 Delaware River sites ranged from 0 to 391 ng/g dry weight (Table 10). Higher pesticide concentrations were found upstream from the Refinery discharge canal at sites DR51, DR26, DR45, and DR9B; total pesticide concentrations were not detected at the downstream sites below DR55. Mean site concentrations of the insecticide Dieldrin exceeded ERL values at 10 sites upstream from site DR55. Mean site concentrations of 4,4'-DDD exceeded ERL values at DR9B, DR45, DR26, DR51, DRl, DR2, DR23, DR52, and DR53. ERL values for 4,4'-DDE were exceeded for mean site concentrations measured at DR9B, DR45, DR26, DRl, and DR23. Mean site concentrations of 4,4'-DDT exceeded ERL values at DR51. The ERM value for 4,4'-DDT was also exceeded at DR51.
Total mean PCB concentrations ranged from 0.45 to 531.1 ng/g at the 15 study sites (Table 10). The highest total PCB concentrations were found between sites DR52 and DR53. The total PCB concentration of 531 ng/g at DR53 was significantly higher than the other sites. Much lower concentrations of total PCBs were generally reported at the 4 downstream sites (DR55, DR67, DR68 and DR83) and the upstream site (DRlO). Total mean PCB concentrations exceeded ERL values at DR45, DR56, DR26, DR2, DR52, and DR53. Total mean PCB concentrations also exceeded the ERM value at DR52 and DR53.
Table 8. Site means and standard deviations (S.D.) of PAH concentrations (ng/g dry weight sediment) from 15 Delaware River and one Control site (Magothy River, Maryland) sampled during Summer 2001.
Concentrations of bulk metals exceeding ERL values in descending order by number of Delaware River sites were as follows: mercury (14 sites), arsenic (13 sites), nickel (13 sites), chromium (11 sites), zinc (11 sites), copper (10 sites), lead (9 sites), and cadmium (3 sites) (Table 11). The only two metals to exceed ERM values were mercury and zinc. Exceedences of ERMs for both of these metals occurred concurrently at sites DR67 and DR68 below the Motiva Refinery (Table 11). Exceedences of mercury ERMs were also reported at DR56 and DR83; exceedences for zinc occurred at DR52 and DR53.
Table 9. Mean concentrations and standard deviations (S.D.) of PAHs (ng/g dry weight sediment) used by NOAA (Buchman 1999) for determining ERL (Effects Range-Low) and ERM (Effects Range-Mdeian) values for 15 Delaware River and one Control site (Mogothy River) sampled during Summer 2001.
Table 9. Mean concentrations and standard deviations (S.D.) of PAHs (ng/g dry weight sediment) used by NOAA (Buchman 1999) for determining ERL (Effects Range-Low) and ERM (Effects Range-Mdeian) values for 15 Delaware River and one Control site (Mogothy River) sampled during Summer 2001.
Table 10. Pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River and one Control site (Magothy River, Maryland) sampled during Summer 2001.
Table 10. Pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River and one Control site (Magothy River, Maryland) sampled during Summer 2001.
Table 10. Pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River and one Control site (Magothy River, Maryland) sampled during Summer 2001.
Table 10. Pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River and one Control site (Magothy River, Maryland) sampled during Summer 2001.
Table 11. Means and standard deviations (S.D.) of metals concentrations (g/g dry weight sediment) for 15 Delaware River and one Control site (Magothy River, Maryland) from Summer 2001 sampling.
As previously discussed, analysis of total metal residues in sediments does not always provide definitive information about the potential bioavailability of the measured concentrations. Therefore, the use of SEM/AVS ratios is often used to determine the bioavailability of metals. When ratios are less than 1 toxicity due to SEM metals is unlikely. A ratio greater than 1 suggest that toxicity due to metal is possible. It is only when a ratio is much greater than 1 that toxicity of metals is likely.
Mean SEM/AVS ratios for all Delaware River sites ranged from 0.20 at DR45 to 2.42 at DR68 (Table 12). The h\ighest ratios (1.7 to 2.4) were found at sites DR53, DR55, DR67, and DR68. All of these sites were downstream of the Motiva Refinery.
Table 12. Means and standard deviations (S.D.) of acid volatile sufide (AVS), simultaneously extracted metals (SEM), and the SEM/ AVS ratio in sediment from 15 Delaware River and one Control site (Magothy River, Maryland) sampled in Summer 2001.
Table 13. Means and standard deviations (S.D.) of grain size data from 15 Delaware River and one Control site (Magothy River, Maryland) sampled during Summer 2001.
The mean percent sand, silt, and clay for all 15 Delaware River study sites combined was 37.1, 49.8, and 12.9%, respectively (Table 13). The mean percent sand ranged from 16.7 at DR83 to 74.9 at DR2. Percent silt ranged from 16.9 at DR2 to 64.5 at DR83. The percent clay ranged from 3.6 at DR2 to 18.8 at DR83. Variability in grain size distributions among replicates was generally low for all sites except DR51 and DR2. The distance between these two sites is approximately 1 km (Figure 1).
A summary of the porewater/sediment parameter data in Table 14 showed that mean sulfide concentrations ranged from 42 to 86 mg/kg dry weight sediment; mean ammonia concentrations ranged from 0.5 to 6.2 mg/kg; and mean nitrate + nitrite concentrations ranged from 5 to 7.1 mg/kg (Table 14). Mean concentrations for sulfide, ammonia, and nitrate + nitrite at all Delaware River sites were 60, 2.2, and 5.4 mg/kg, respectively. Total organic carbon ranged from 1.3% at station DR51 to 7.0% at DR1. The mean total organic carbon for all Delaware River sites was 3.8%.
Spring 2002
Total PAH concentrations expressed as a mean of 43 analytes for the five replicates at each site ranged from 1,475 ng/g dry weight sediment at site DR2 to 16,916 ng/g at DR67 (Table 15). The same spatial trend-lowest concentration at DR2 and highest concentration at DR67-was also found for total analytes (Table 15). For six sites- DR10, DR51, DR1, DR2, DR53, and DR55-variability among replicates, as suggested by the standard deviation, occurred for total PAH concentrations. Differences in grain size among replicates was likely a factor contributing to these variable PAH concentrations.
Table 14. Means and standard deviations (S.D.) of porewater/ sediment concentrations of sulfide, ammonia, nitrate, nitrite (mg/ kg dry weight sediment), and % total organic carbon (TOC) for 15 Delaware River and one Control site (Magothy River, Maryland) sampled during Summer 2001.
The 43 parent PAHs and alkyl homologues measured during this study in Table 15 were compared in a conservative (worst case scenario) format with exceedences of various NOAA toxicity benchmarks (Buchman 1999). The following results were found: (1) mean total PAHs exceeded the ERL values of 4,022 ng/g at 8 of the 15 Delaware River sites; (2) mean total LMW PAHs exceeded the ERL value of 552 ng/g at all sites except DR10 and the control; (3) the LMW PAH ERM value was also exceeded at 6 sites, and (4) mean total HMW PAHs exceeded the ERL value of 1,700 ng/g at 8 sites. The exceedences reported earlier for various categories of PAHs are highly bias because the total PAH values were based on 43 different parent PAH and alkyl homologues in contrast to the NOAA benchmarks that are based on only 13 different PAHs. A summary of exceedences in Table 16 based on the 13 PAH analytes used by NOAA resulted in the following: (1) the mean total PAH ERL was exceeded at only one site (DR67); (2) mean total LMW PAH ERLs were exceeded at DR56, DR52, DR53, DR55, DR67, DR68, and DR83, and (3) mean total HMW PAH ERLs were exceeded at DR56, DR53, DR55, DR67, DR68, and DR83. There were no exceedences of ERM values for mean total, LMW, or HMW PAHs.
Table 15. Site means and standard deviations (S.D.) of PAH concentrations (ng/g dry weight sediment) from 15 Delaware River and one Control site (Wye River, Maryland) sampled during Spring 2002.
Individual PAH ERLs were exceeded frequently for the LMW PAHs fluorene (mean values from DR45, DR56, DR1, DR52, DR53, DR55, DR67, DR68, and DR83), acenaphthene (mean values from DR56, DR52, DR53, DR55, DR67, DR68, and DR83), naphthalene (mean values from DR56, DR52, DR53, DR55, DR67, DR68, and DR83), and 2-methlynaphthalene (mean values from DR56, DR52, DR53, DR55, DR67, DR68, and DR83) (Table 16). Mean site value ERLs were exceeded at seven sites or less for acenaphthylene, anthracene, phenanthrene, fluoranthene, pyrene, benz (a) anthracene, chrysene, benzo(a)pyrene and dibenz(a,h) anthracene. For all 13 PAHs, the mean ERL value was exceeded for at least 1 site. All 13 PAH ERL values were exceeded at site DR67.
Table 16. Means and standard deviations (S.D.) of PAHs (ng/g dry weight sediment) used by NOAA (Buchman 1999) for determing ERL (Effects Range-Low) and ERM (Effects Range-Median) values for 15 Delaware River and one Control site (Wye River, Maryland) sampled during Spring 2002.
Table 16. Means and standard deviations (S.D.) of PAHs (ng/g dry weight sediment) used by NOAA (Buchman 1999) for determing ERL (Effects Range-Low) and ERM (Effects Range-Median) values for 15 Delaware River and one Control site (Wye River, Maryland) sampled during Spring 2002.
Total mean pesticide concentrations ranged from 0 at DR10, DR55, DR67, and DR83 to 24.1 ng/g dry weight sediment at DR45 (Table 17). Higher pesticide concentrations were generally found at sites upstream from the intake canal of the Refinery (sites north of DR23). Lower total pesticide concentrations were found at sites downstream from site DR52. Mean site concentrations of the insecticide Dieldrin exceeded ERL values at 10 sites. Mean site concentrations of 4,4'-DDD exceeded ERL values at DR9B, DR45, DR26, and DR23. ERL values for 4,4'-DDE were exceeded for mean site concentrations measured at DR9B, DR45, DR26, DR1, and DR23.
Total mean PCB concentrations ranged from 0 at DR10 to 422 ng/g at DR53 (Table 17). Total PCB concentrations exceeding ERM values were reported at DR53 and DR68. The total PCB values at site DR68 were significantly higher than values reported at this site during the spring and summer of 2001. Total PCB concentrations exceeding ERL values were also found at DR45, DR56, DR1, DR52, DR53, and DR68.
Bulk metals concentrations exceeding ERL values in descending order by number of Delaware River sites were as follows: arsenic (15 sites), nickel (14 sites), mercury (11 sites), zinc (11 sites), lead (10 sites), copper (9 sites), chromium (8 sites), and cadmium (4 sites) (Table 18). Sites DR52, DR53, DR67, and DR68 had the highest number of ERL exceedences for the various bulk metals. The ERM values for both zinc and mercury were exceeded at five sites and two sites, respectively. At sites DR53 and DR68 the ERMs for both zinc and mercury were exceeded.
As previously discussed in this article, analysis of total metal residues in sediments does not always provide definitive information about the potential bioavailability of the measured concentrations. Therefore, the use of SEM/AVS ratios is often used to determine the bioavailability of metals. When ratios are less than 1 toxicity due to SEM metals is unlikely. A ratio greater than 1 suggest that toxicity due to metals is possible. It is only when a ratio is much greater than 1 that toxicity of metals is likely.
Mean SEM/AVS ratios for all Delaware River sites ranged from 0.28 at DR45 to 70.1 at DR51 (Table 19). The 2 highest SEM/AVS ratios (14 and 70) were observed at 2 sites (DR2 and DR51) near the Refinery.
The mean percent sand, silt, and clay for all 15 Delaware River sites combined was 40.5, 46.9, and 12.5%, respectively (Table 20). The mean percent sand ranged from 16% at DR83 to 86.3% at DR51. Mean percent silt ranged from 10.7% at DR51 to 64.3% at DR26. The mean percent clay ranged from 3% at DR51 to 20.3% at DR83. The sites that showed the highest variability among replicates for all grain sizes were DR1 and DR2.
The mean porewater/sediment parameter data in Table 21 for the 15 Delaware River sites showed that mean sulfide concentrations ranged from 38 to 166 mg/kg dry weight sediment, mean ammonia concentrations ranged from 1.0 to 18.4 mg/kg, mean nitrate + nitrite concentrations were consistently 5 mg/kg and mean percent TOC ranged from 0.72 to 6.58. The mean concentrations for sulfide, ammonia, nitrate + nitrite and TOC all Delaware River sites sampled in the Spring of 2002 were 64, 5.4, 5.0 mg/kg, and 3.81%, respectively.
Table 17. Means and standard deviations (S.D.) of pesticide and PCB exceedences (ng/g dry weight sediment from 15 Delaware River and on Control site (Wye River, Maryland) sampled during Spring 2002.
Table 17. Means and standard deviations (S.D.) of pesticide and PCB exceedences (ng/g dry weight sediment from 15 Delaware River and on Control site (Wye River, Maryland) sampled during Spring 2002.
Table 17. Means and standard deviations (S.D.) of pesticide and PCB exceedences (ng/g dry weight sediment from 15 Delaware River and on Control site (Wye River, Maryland) sampled during Spring 2002.
Table 17. Means and standard deviations (S.D.) of pesticide and PCB exceedences (ng/g dry weight sediment from 15 Delaware River and on Control site (Wye River, Maryland) sampled during Spring 2002.
Table 17. Means and standard deviations (S.D.) of pesticide and PCB exceedences (ng/g dry weight sediment from 15 Delaware River and on Control site (Wye River, Maryland) sampled during Spring 2002.
Table 17. Means and standard deviations (S.D.) of pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River and on Control site (Wye River, Maryland) sampled during Spring 2002.
Table 18. Means, standard deviations (S.D.), and detection limits (D.L.) of metals (g/g dry weight sediment) for 15 Delaware River and one Control site (Wye River, Maryland) from Spring 2002 sampling.
Summer 2002
Total PAH concentrations expressed as a mean of 43 analytes for the 5 replicates at each sit\e ranged from 1,317 ng/g dry weight sediment at site DR2 to 14,537 ng/g at site DR83 (Table 22). A similar spatial trend was also observed for total hydrocarbon analytes. The lowest mean total analyte concentration (1,400 ng/g) was found at DR2 and the highest concentration occurred at DR83 (15,298 ng/g). Variability in total PAH concentrations among replicates was found at DRlO, DR56, DR51, DR1, and DR83.
Table 19. Means and standard deviations (S.D.) of acid volatile sulfide (AVS), simultaneously extracted metals (SEM), and the SEM/ AVS ratio for 15 Delaware River and one Control Site (Wye River, Maryland) sampled during Spring 2002.
The 43 parent PAH and alkyl homologues measured during this study in Table 22 were compared in a conservative (worst case scenario) format with exceedences of various NOAA toxicity benchmarks (Buchman 1999). The following results were found: (1) mean total PAHs exceeded the ERL value of 4,022 ng/g at DR56, DR52, DR53, DR55, DR67, DR68, and DR83; (2) mean total LMW PAHs exceeded the ERL value of 552 ng/g at all 15 sites; (3) mean total LMW PAHs exceeded the ERM value 3,160 ng/g at DR56, DR53, DR67, DR68, and DR83, and (4) mean total HMW PAHs exceeded the ERL value of 1,700 ng/g at DR45, DR56, DRl, DR52, DR53, DR55, DR67, DR68, and DR83. The exceedences reported earlier for the various categories of PAHs are highly bias and overprotective because the total PAH values are based on 43 different parent PAH and alkly homologues in contrast to the NOAA benchmarks that are based on only 13 different PAHs. A summary of exceedences in Table 23 based on the 13 PAH analytes used by NOAA results in the following: (1) mean total PAHs exceeded the ERL value of 4,022 ng/g at DR67, DR68, and DR83; (2) mean total LMW PAHs exceeded the ERL value of 552 ng/g at DR56, DR52, DR53, DR55, DR67, DR68, and DR83, and (3) the mean total HMWPAHs exceeded the ERL value of 1,700 ng/g at DR56, DR53, DR67, DR68, and DR83. There were no exceedences of ERM values for mean total, LMW, or HMW PAHs.
Table 20. Means and standard deviations (S.D.) of grain size data from 15 Delaware and one Control site (Wye River, Maryland) sampled during Spring 2002.
Individual PAH ERLs were frequently exceeded for the LMW PAHs fluorene (mean values from DR45, DR56, DR26, DR51, DR23, DR52, DR53, DR55, DR67, DR68, and DR83), acenaphthene (mean values from DR56, DR52, DR53, DR55, DR67, DR68, and DR83), naphthalene (mean values from DR56, DR52, DR53, DR55, DR67, DR68, and DR83), anthracene (DR56, DR52, DR53, DR55, DR67, DR68, and DR83) and 2- methylnaphthalene (mean values from DR56, DR52, DR53, DR55, DR67, DR68, and DR83) (Table 23). Mean site value ERLs were exceeded at five sites or less for acenaphthylene, phenanthrene, ben [a] anthracene, chrysene, dibenz[a,h] anthracene, and pyrene. The only mean PAHs that did not exceed ERL values for any sites were benzo [a] pyrene and fluoranthrene. The ERLs for 10 individual mean PAHs were exceeded at DR67, DR68, and DR83.
Table 21. Porewater/sediment means and standard deviations (S.D.) of sulfide, ammonia, nitrate, nitrite (mg/kg dry weight sediment), arid % total organic carbon (TOC) for 15 Delaware River and one Control site (Wye River, Maryland) sampled during Spring 2002.
Total mean pesticide concentrations ranged from 0.03 ng/g dry weight sediment at DR10 to 31.20 ng/g dry weight at DR45 (Table 24). Higher pesticide concentrations were generally found north of site DR26 (above the Refinery intake canal). Total pesticide concentrations were generally low (≤2.7 ng/g) below site DR52. Mean site concentrations of dieldrin exceeded ERL values at DR9B, DR45, DR26, DR51, DR1, DR2, DR23, DR52, and DR53. Mean site concentrations of 4,4'-DDT exceeded ERL values at DR9B, DR45, DR26, DR1, DR23, and DR53. ERLs for mean site concentrations of 4,4'-DDD were exceeded at DR9B, DR45, DR26, and DR23. Mean site concentrations of 4,4'-DDE were exceeded at DR9B, DR45, DR26, and DR23.
Total PCB concentrations ranged from 0.12 ng/g dry weight at DR10 to 566 ng/g at DR53 (Table 24). Total mean PCB concentrations exceeded ERL values at DR45, DR26, DR52, DR53, and DR68. Total mean PCB concentration exceeded the ERM value at DR53.
Bulk metals concentrations exceeding ERL values in descending order by number of Delaware River sites were as follows: arsenic (15 sites), nickel (12 sites), zinc (10 sites), mercury (9 sites), copper (7 sites), lead (6 sites), chromium (4 sites), and cadmium (1 site) (Table 25). Sites DR56, DR52, DR53, DR67, DR68, and DR83 had the highest number of exceedences for the various bulk metals. The ERM values for both zinc (DR53) and mercury (DR68) were exceeded.
Table 22. Means and standard deviations (S.D.) of PAH concentrations (ng/g dry weight sediment) from 15 Delaware River and one Control site (Wye River, Maryland) sampled during Summer 2002.
Table 23. Means and standard deviations (S.D.) of PAHs (ng/g dry weight sediment) used by NOAA (Buchman 1999) for determining ERL (Effects Range-Low) and ERM (Effects Range-Median) values for 15 Delaware River and one Control site (Wye River, Maryland) Sampled during Summer 2002.
Table 23. Means and standard deviations (S.D.) of PAHs (ng/g dry weight sediment) used by NOAA (Buchman 1999) for determining ERL (Effects Range-Low) and ERM (Effects Range-Median) values for 15 Delaware River and one Control site (Wye River, Maryland) Sampled during Summer 2002.
Table 24. Means and standard deviations (S.D.) of pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River and Control site (Wye River, Maryland) sampled during Summer 2002.
Table 24. Means and standard deviations (S.D.) of pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River and Control site (Wye River, Maryland) sampled during Summer 2002.
Table 24. Means and standard deviations (S.D.) of pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River and Control site (Wye River, Maryland) sampled during Summer 2002.
Table 24. Means and standard deviations (S.D.) of pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River and Control site (Wye River, Maryland) sampled during Summer 2002.
Table 24. Means and standard deviations (S.D.) of pesticide and PCB exceedences (ng/g dry weight sediment) from 15 Delaware River and Control site (Wye River, Maryland) sampled during Summer 2002.
Table 25. Means, standard deviations (S.D.), and detection limits (D.L.) of metals for five replicates per site (g/g dry weight sediment) for 15 Delaware River and one Control site from Summer 2002 sampling.
As previously discussed, the use of SEM/AVS ratios is often used to determine the bioavailability of metals. When ratios are less than 1, toxicity due to SEM metals is unlikely. A ratio greater than 1 suggests toxicity due to metals is possible. Toxicity is only likely when a ratio is much greater than 1.
Table 26. Means and standard deviations (S.D.) of acid volatile sulfide (AVS), simultaneously extracted metals (SEM) and the SEM/ AVS ratio for 15 Delaware River and one Control site (Wye River, Maryland) sampled during Summer 2002.
Mean SEM/AVS ratios for all Delaware River sites ranged from 0.19 at DR9B to 2.59 at DR51 (Table 26). The highest ratios were generally found downstream from the refinery in the area from DR51 downstream to DR68.
The mean percent sand, silt, and clay for all Delaware River sites combined was 37.1, 49.8, and 13.1%, respectively (Table 27). The mean percent sand ranged from 15.8% at DR83 to 70.3% at DR2. The mean percent silt ranged from 24.4% at DR2 to 65.6% at DR26. The mean percent clay ranged from 5.3% at DR2 to 20.1% at DR83. The sites with the highest variability among replicates were DR51, DR1, and DR2.
Table 27. Means and standard deviations (S.D.) of grain size data from 15 Delaware River and one Control site (Wye River, Maryland) sampled during Summer 2002.
The mean porewater/sediment parameter data in Table 28 for the 15 Delaware River sites showed that mean sulfide concentrations ranged from 42 to 158 mg/kg dry weight sediment, mean ammonia concentrations ranged from 1.8 to 17.8 mg/kg, mean nitrate + nitrite concentrations were consistently 5 mg/kg, and mean percent TOC ranged from 1.09 to 6.64. The mean concentrations for sulfide, ammonia, nitrate + nitrite, and TOC for all Delaware River sites in the summer of 2002 were 65, 8.2, 5.0 mg/kg, and 3.4%, respectively.
Temporal and Spatial Patterns for Chemical Characterizations
Total PAHs
Mean total PAH concentrations for all 15 Delaware River sites sampled during the spring and summer of 2001 and 2002 showed somewhat higher concentrations in the summer of 2001 when compared with the other three sampling periods (Table 29). However, there were no statistically significant differences (p < 0.05) among mean total PAH concentrations for the four sampling periods. Temporal changes in total PAH concentrations by site were most pronounced for DR1. An increase occurred from the summer of 2001 to the spring of 2002 followed by a reduction in the summer of 2002. A increase in total PAHs of ~50% also occurred at DR83 from the spring to the summer of 2001.
Table 28. Means and standard deviations (S.D.) of porewater/ sediment concentrations of sulfide, ammonia, nitrate, nitrite (mg/ kg dry weight sediment), and % total organic carbon (TOC) for 15 Delaware River and one Control site (Wye River, Maryland) sampled during Summer 2002.
Spatial patterns of total PAH concentrations presented in Table 29 for all 4 sampling periods showed higher mean concentrations at the 3 downstreams sites (DR67, DR68, and DR83). The highest concentrations of PAHs were consistently found at downstrean site DR67. The highest mean total PAH concentrations reported at the upstream sites near the Refinery were at DR56. The lowest mean total PAH concentrations were found at DR10, DR9B, DR51, DR2, and DR23. The only sites that did not ha\ve mean total PAHs significantly higher than the reference sites were DR51, DR2, and DR23 (Table 29).
PAHs associated with the Refinery effluent were primarily petrogenic 4-ring PAHs as described in detail in the fingerprinting article by Uhler et al. (2005). The spatial scale of Motiva derived PAHs was limited to the discharge canal (DR1) and the near-field area near the Refinery (DR2, DR23, and DR26). The hydrodynamic model described in Hall et al. (2004) shows that the highest concentrations of effluent occur in the discharge canal and near- field. The total mean PAH concentrations at these discharge canal and near-field sites are less than the downstream sites where background pyrogenic and diagenic PAHs are the dominant source (Uhler et al. 2005).
Total pesticides
Mean total pesticide concentrations for the Delaware River sites sampled during the spring and summer of 2001 and 2002 showed somewhat higher concentrations of mean total pesticides in the summer of 2001 when compared with the other three sampling periods (Table 30). A high total pesticide value found at DR51 during the summer of 2001 was an influential data point for this elevated seasonal value. Despite this high value, there was no statistical difference (p < 0.05) among the mean pesticide concentrations for the four sampling periods. Temporal changes by site were observed for DR9B (decrease from spring to summer of 2001), DR45 (decrease from summer of 2001 to spring 2002), and DR1 (increase from spring to summer of 2001 and a decrease from the spring to the summer of 2002).
Table 29. Means and standard deviations (S.D.) of total PAH concentrations (ng/g dry weight sediment) for the Spring and Summer 2001 and 2002 for 15 Delaware River sites.
Spatial patterns of mean total pesticide concentrations by site in Table 30 showed higher concentrations south of DR9B and north of DR53 (Figure 1). The highest total mean pesticide concentrations were found at DR51, DR45, and DR26. Total pesticide concentrations were generally much lower at the six downstream sites and upstream site DR10.
Table 30. Means and standard deviations (S.D.) of total pesticide concentrations (ng/g dry weight sediment) for the Spring and Summer 2001 and 2002 for 15 Delaware River sites.
Total PCBs
Mean total PCB concentrations for the Delaware River sites sampled during the spring and summer of 2001 and 2002 were somewhat lower in the spring of 2001 when compared with the other three sampling periods (Table 31). However, there were no statistically significant differences (p < 0.05) in mean PCB concentrations among the four sampling periods. A three-fold increase did occur in total PCB concentrations (influenced by one high replicate concentration) at DR2 from the spring to the summer of 2001; total PCB concentrations were similar to the spring concentrations at this site for the spring and summer of 2002. An 80-fold increase in total PCB concentrations occurred at DR68 from the summer of 2001 to the spring of 2002 followed by a 3-fold decrease in the summer of 2002. Total PCB values at DR68 increased substantially from 2001 (4.2 ng/ g dry weight) to 2002 (138 ng/g dry weight).
Spatial patterns of total mean PCB concentrations by site in Table 31 showed that the highest concentrations were consistently reported at DR53. The second highest mean value was reported approximately 1 km upstream from DR53 at DR52 (Figure 1). The third highest total PCB concentration was found at downstream site DR68. The lowest mean total PCB concentrations were found at upstream site DR10 and downstream site DR55.
Table 31. Means and standard deviations (S.D.) of total PCB concentrations (ng/g dry weight sediment) for the Spring and Summer 2001 and 2002 for 15 Delaware River sites.
SEM/AVS
The SEM/AVS ratio data for metals is often used to determine bioavailability as previously discussed. Therefore, this ratio was used to express potential metal toxicity to aquatic life (i.e., ratios much greater than 1 suggest toxicity due to metals). Mean total SEM/AVS ratios for the Delaware River sites sampled during the spring and summer of 2001 and 2002 indicated that a higher ratio may have occurred in the spring of 2002 (Table 32). However, this value was not statistically higher (p < 0.05) than the mean SEM/AVS ratios for the other 3 sampling periods. A high ratio of 70 at DR51 was a significant factor influencing the high mean spring 2002 value during this period. A decrease in mean SEM/AVS ratios occurred from spring to summer of 2001 at DR9B, DR56, and DR55. An increase in SEM/ AVS ratios occurred at DR51 and DR2 from the summer of 2001 to the spring of 2002.
Spatial patterns of mean SEM/AVS ratios in Table 32 showed highest ratios at DR51 (18.82), DR2 (4.65), and DR55 (3.72). The lowest mean SEM/AVS ratios (<1) were found at DR45, DR26, DR1, and DR23.
Grain size
Mean grain size data (expressed as percent sand) for the 15 Delaware River sites sampled in the spring and summer of 2001 and 2002 generally showed consistent grain size (37 to 41% sand) for all 4 sampling periods (Table 33). Temporal comparisons by site showed a higher percentage increase in mean percent sand at DR51 and DR1 from the summer of 2001 to the spring of 2002.
Table 32. Means and standard deviations (S.D.) of SEM/AVS ratios for the Spring and Summer 2001 and 2002 for 15 Delaware River sites.
Spatial patterns by site in Table 33 showed highest mean percent sand at DR2 and DR51. Both of these sites are ~1 km from each other near the Refinery effluent canal (Figure 1). The lowest mean percent sand (highest percent silt and clay) was found at downstream site DR83.
Porewater/Sediment parameters
Temporal and spatial trends for mean sulfide, ammonia, nitrate + nitrite-N, and percent TOC measured during the spring and summer of 2001 and 2002 are presented in Table 34. Mean sulfide concentrations were approximately 60% higher in the spring of 2001 when compared with the other 3 sampling periods. Mean sulfide concentrations for the summer of 2001 and spring/summer 2002 were similar. Decreases in sulfide concentrations occurred from spring to summer of 2001 at all sites except DR2. The highest mean sulfide concentrations was found at DR26 (175 mg/kg) (near-field of the Refinery). The lowest concentration was found at DR55 (50 mg/kg).
Temporal patterns of mean ammonia concentrations showed highest mean values in summer of 2002 (8.2 mg/kg) and lower values in summer of 2001 (2.2 mg/kg) (Table 34). Ammonia values generally increased at most sites between the spring of 2002 and the summer of 2002. The highest mean ammonia concentrations by site for all 4 sampling periods was found at DR1 (11.2 mg/kg); the lowest value was reported at DR67 (1.8 mg/kg).
Table 33. Means and standard deviations (S.D.) of grain size (% sand only) for the Spring and Summer 2001 and 2002 for 15 Delaware River sites. Means and standard deviations by site and season for the four sample periods are also presented.
Temporal patterns of mean nitrate + nitrite concentrations in Table 34 were consistent for all Delaware River sites sampled over the 4 sampling periods (~5 mg/kg). Mean site concentrations of nitrate + nitrite sampled over the four sampling periods were also consistent. The highest mean value was found at DR23 and DR68 (5.5 mg/kg); the lowest mean value (5.0 mg/kg) occurred at 8 different sites.
Temporal patterns of mean percent TOC ranged from 3.1% in the spring of 2001 to 3.8% during the summer of 2001 and spring of 2002 (Table 34). The highest mean percent TOC concentration was found at DR1 (6.1%); lowest mean concentration occurred at DR51 (1.1%).
OBJECTIVES OF SEDIMENT TOXICITY TESTS
The objective of this task was to measure the toxicity of ambient Delaware River sediment from the 15 sites presented in Figure 1 using 28-day chronic survival, growth, and reproduction tests with the epifaunal and infaunal amphipods, Hyalella azteca and Leptocheirus plumulosus. Sediment toxicity tests were conducted during the spring and summer of 2001 and 2002.
Table 34. Means and standard deviations (S.D.) of pore water/ sediment parameters for the Spring and Summer 2001 and 2002 for 15 Delaware River sites.
Table 34. Means and standard deviations (S.D.) of pore water/ sediment parameters for the Spring and Summer 2001 and 2002 for 15 Delaware River sites.
METHODS FOR SEDIMENT TOXICITY TESTS
Twenty-eight day chronic survival, growth, and reproduction tests were conducted with the epifaunal and infaunal amphipods, Hyalella azteca and Leptocheirus plumulosus, respectively, using test procedures described in McGee and Fisher (1998). Both of these species have been reported to be sensitive to contaminants such as PAHs (Hall et al. 1991; Hall et al. 2000). These species have also been tested extensively by the University of Maryland in low salinity areas of the Chesapeake Bay similar to the Delaware River habitat of concern in this study.
Sediment samples for toxicity testing (and chemical characterizations as previously described) were collected from all sites in the Delaware River during the spring and summer of 2001 and 2002. Sediment samples were collected using a Ponar grab sampler (Volume 8.2 L); only the first 2 to 5 cm of surficial sediment material was retained for testing. After sediment collection, samples were returned to the laboratory for testing. General sediment collection, handling, and storage procedures described in Hall et al. (1991) were used.
True field replicate samples were maintained separately for the laboratory toxicity tests and chemical analysis described previously. Sediment was collected at each station by first randomly identifying 5 grab sample (replicate) locations within a 100 m 100 m square grid. At each of the 15 sample sites, a discrete field replicate was collected for toxicity tests, chemical analysis, and benthic community assessments. All samples were maintained out of direct sunlight and transported o\n ice in coolers. Samples for toxicity tests were held at 4C until initiation of the toxicity tests within 14 days of collecting the sediment. Samples for contaminant analyses were stored in accordance with the requirements of the respective analytical methods to be used (Hall et al. 2004). QA/QC for all components of the study from field collection through data analysis followed the USEPA guidance reported in McGee and Fisher (1998).
Survival ≥80% and measurable growth at the end of the 28-d exposure were used as the performance criteria for Hyaklla in the negative control sediment; survival ≥80%, measurable growth, and reproduction were used for Leptocheirus. Negative control sediment was collected from the Magothy River (2001) and Wye River (2002) in Chesapeake Bay. Statistically significant differences between the endpoints for each species (survival, growth, and/or reproduction) in reference station sediments (DR10 and DR9B) versus ambient sediments from other Delaware River sites were evaluated via analysis of variance (ANOVA). A priori tests of each endpoint in a given treatment were contrasted to reference responses to discern which sediments differ from reference endpoints. Endpoint data were subjected to appropriate statistical transformation (e.g., arcsine transformation for percent data) if needed prior to statistical analyses. Hyalella growth was measured by changes in length (taken from the second antenna to the base of the urosome along the dorsal surface). Reproduction was determined by the proportion of gravid females. Leptocheirus growth was determined by calculating growth rate (mg/d) via drying to a constant weight at 100C. The reproductive endpoint for Hyalella was percent gravid females; number of neonates released during the test was the endpoint for Leptocheirus. Toxicity was inferred in test sediments with endpoints that were significantly (p < 0.05) lower than those observed for reference sediments. Both Hyalella and Leptocheirus negative control species met the acceptability criteria during all tests.
RESULTS AND DISCUSSION
Spring 2001
Acomparison of Hyalella survival, growth, and reproduction endpoints from reference sites (DR10 and DR9B) with ambient Delaware River sites showed no significant (p < 0.05) differences for any of the endpoints (Table 35). A fungal type growth occurred in various replicates at both the reference and ambient Delaware River test sites (but not in the Magothy River negative control replicates) during the Spring 2001 Leptocheirus toxicity test. Because this fungal growth was randomly found in the Delaware River reference conditions and ambient test conditions, all replicates that contained the fungus were discarded before conducting the statistical analysis. Test acceptability requirements (>80% reference survival in DR10) was met after discarding the replicates infected with the fungus.
Table 35. Survival, growth (total length mm), and reproduction (% gravid females) means and standard deviations (S.D.) for Hyalella tested at 15 Delaware River sites in Spring 2001.
Survival of Leptocheirus was significantly reduced at DR53 when compared with reference site DR9B (Table 36). Survival of this amphipod was not reduced at any other sites when compared with the Delaware River reference sites. Reproduction was also significantly reduced at DR1, DR53, and DR83 when compared with the Delaware River reference site DR9B. Growth (final weight) of Leptocheirus was not reduced at any of the Delaware River sites when compared with the reference sites.
Summer 2001
Survival of Hyalella was significantly reduced at DR53, DR67, DR68, and DR83 when compared to Delaware River reference sites (Table 37). Hyalella growth and reproductive endpoints were not reduced at any of the Delaware River sites when compared with the reference sites. Survival of Leptocheirus was significantly reduced at DR67 when compared with either Delaware River reference site (DR9B and DR10) (Table 38). Growth of this test species was significantly reduced at DR68 when compared with DR9B. Reproduction of Leptocheirus was significantly reduced at DR53 when compared with both Delaware River reference sites.
Spring 2002
A comparison of Hyalella survival, growth, and reproduction endpoints from the reference sites (DR10 and DR9B) with Delaware River sites showed no significant (p < 0.05) differences during the Spring of 2002 (Table 39). A comparison of Leptocharus survival from both reference sites with the other Delaware River sites in Table 40 showed no significant differences. However, Leptocheirus reproduction was significantly lower at sites DR56, DR1, DR52, and DR53 when compared to either of the reference sites (DR10 and DR9B).
Table 36. Survival, growth (final weight mg) and reproduction (number offspring/adult) means and standard deviations (S.D.) for Leptocheirus tested at 15 Delaware River sites in Spring 2001.
Summer 2002
There were no significant differences in Hyaklla survival and reproduction among all Delaware River sites when compared with either reference site (Table 41). Hyaklla growth was significantly reduced at DR56 and DR53 when compared with reference site DR10. There were no significant differences in Leptocharus survival and reproduction among all Delaware River sites and the reference sites (Table 42). Leptocharus growth was significantly reduced at DR55 when compared with reference site DR9B.
Temporal and Spatial Patterns in Toxicity
A temporal comparison of toxicity data for both test species with three endpoints (survival, growth, and reproduction) for the spring and summer of 2001 and 2002 shows that the highest number of significant endpoint effects (seven) for four stations in the summer of 2001 (Table 43). Hyalella survival was significantly reduced at DR53 and the three most downstream sites (DR67, DR68, and DR83). Leptocharus reproduction, survival, and growth was also significantly reduced in the summer of 2001 at DR53, DR67, and DR68, respectively. Temporal comparisons of tox
Source: Human and Ecological Risk Assessment
Related Articles
- Verizon Wireless Activates New Cell Site in Delaware County, Ohio
- Raven Gold Corp. Amended - Announces Today the First Load of Concentrate Totaling Approximately 10 Tonnes Has Been Delivered to the Smelter in Torreon
- Raven Gold Corp. Amended - Announces Today That a Second Load of Concentrate Totalling Approximately 6.5 Tonnes Has Been Delivered to the Smelter in Torreon
- La Currita Mill Ships Second Load of Concentrate and Increases Recovery Rates
- Raven Gold Corp. Announces Today That a Second Load of Concentrate Totalling Approximately 6.5 Tonnes Have Been Delivered to the Smelter in Torreon
- Raven Gold Corp. Announces Today the First Load of Concentrate Totalling Approximately 10 Tonnes Has Been Delivered to the Smelter in Torreon.
- Golden River Resources Announces High Grade Surface Results
- Golden River Resources Advances Slave Craton Projects
- Residue Level and Manure Application Timing Effects on Runoff and Sediment Losses
 |
 |
User Comments (0)
RSS Feeds