December 3, 2008

Baltic Sea Pollution Hotspots Overlooked

According to research from Sweden, large sources of pollution to the Baltic Sea have been missed by existing monitoring effects.

The Baltic Sea has had more and more health issues since the 1960s, due to the disposal of untreated human waste and toxic materials such as heavy metals.

The countries that border the Baltic Sea have put together an action plan to stem the tide of contaminants entering the sea.

Gia Destouni, a professor from Stockholm University, said these areas were being left without systematic environmental monitoring.

The Baltic Sea is also being harmed by "nutrients" from fertilizer used in agriculture.

The sea water is naturally more prone to dead zone episodes, which is when water has a very low concentration of dissolved oxygen, because of the lack of water exchange between the Baltic and the Atlantic and Arctic Oceans.

The problem is made worse by the use of fertilizer, which runs off fields into streams and rivers.  When it reaches the ocean, it provides nutrients for algae, which can form blooms.

This leads to more organic matter reaching the bottom of the sea, where bacteria breaks it down, using oxygen required by marine animals on the sea floor.

"Because of practical difficulties, you cannot monitor everywhere. So people do focus on the big rivers, for a number of different reasons," Professor Destouni told BBC News.

"You have these 'blind spots' in coastal zones all over the world. But the Baltic Sea is one of the most polluted and (nutrient-filled) seas in the world."

"In earlier work, when we tried to quantify these holes, we saw that Sweden had an extra large fraction of these blind spots and an extra large population in them," she added.

The areas extend along most of Sweden's coastline and are home to a large proportion of the country's population.

It was discovered that Sweden has an unmonitored area where water drains into the Baltic of 20%.  This same area is home to 55% of the country's population.

Research shows that concentrations of nitrogen and phosphorus and organic pollutants in the water flowing from these unmonitored areas may be much larger than in the main rivers that are subject to systematic environmental monitoring.

Professor Destouni and her colleagues reported in the journal Global Biogeochemical Cycles, that loads of nitrogen and phosphorous from Sweden to the Baltic Sea are significantly smaller than expected.

This is based on strong connections between a country's loads of different contaminants and its population size, area and economic activity.

"If we look at the reported nutrient loads from all around the Baltic Sea drainage basin, and compare the rest of the countries - which have a much more similar fraction of blind spots - with the Swedish reports - which have a higher fraction of blind spots - we should see a significant difference," explained Destouni.

"We see a very significant difference between what Sweden is reporting and what the other countries are reporting in relation to the area that is contributing, to the population that is contributing, and the GDP of each country."

Sweden has set up 10 new stations this year, to augment the monitoring network.

Some observers stress that calculations of the pollutant load are not based on water monitoring data. 

The unmonitored areas are studied when Swedish nutrient loads to the Baltic Sea are estimated.  The data gaps are connected with the help of computer modeling.

The authors of the latest study, point out that because these results cannot be checked against real data for the unmonitored areas, they could significantly be wrong.


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