CORPUS CHRISTI, Texas (24 Sep 2001) -- Environmentalists have long-maintained that pollutants generated in any one place can show up to contaminate land, air and water thousands of miles away. Now a team of geoscientists at Texas A&M University has discovered a portion of the mechanism by which the chemicals travel. Gaseous pollutants spilled into water can evaporate into the air and travel long distances from where they were produced or used. Working as part of the university's Geochemical and Environmental Research Group, June-Soo Park, Steve Sweet, and Terry Wade sampled rain to determine how pollutants such as polynuclear aromatic hydrocarbons (PAHs), pesticides, and polychlorinated biphenyls (PCBs) are transported in the atmosphere to Galveston and Corpus Christi bays and removed by rain and dust. Unexpectedly, they discovered that gaseous water pollutants can evaporate into the atmosphere instead of staying in the ocean. "Our most surprising result is that there is a flux of contaminants currently coming out of Corpus Christi Bay to the atmosphere," Wade says. "We previously assumed that all the flux of contaminants would be into the water." Wade suggests that PAHs might be released by the evaporation of small petroleum spills from oil production facilities into Galveston and Corpus Christi bays. "In an area where we produce petroleum, there is natural seepage and accidental releases, so if you spill PAH in the ocean, a lot of it evaporates and then can be transported long distances," he says. Discharges of pollution into Galveston Bay come from municipal and industrial facilities, bypasses and overflows from municipal sewage systems, unpermitted and illegal dischargers, and water from oil and gas operations. The Texas A&M team found not all of them stay in the water. | | "Scientists assumed that when you spray DDT on crops, the insecticides stay in the soil. They might be washed into rivers when it rains and be transported down rivers to coastal areas," Wade says. "To our surprise, we discovered that the pesticide can volatilize into the gaseous state and be transported in the air over long distances fairly rapidly." As a result, high levels of pesticides such as DDT, chlordane and toxaphene are present in beluga whales from the Arctic, where they were not used. "What we do here in Texas can affect what is happening in the Arctic," Wade says. "We have added these contaminants to the environment, and now we can see that they are showing up in areas where we would not have expected them to be." To assess the whereabouts of the pollutants, Wade and his team used rain and air samplers that they installed close to Galveston and Corpus Christi bays and monitored for more than a year. The sampling site was also equipped with sensors that look at wind speed and direction, relative humidity, and barometric pressure. "The general principle of the experiments," Wade says, "is that you take a sample of air or rain and you measure how much contaminant is present in the rain or in the air. Then using models, you try to estimate the amount of contaminants that are coming down into the bay." Scientists are now trying to design pesticides that break down more quickly than those used today and can be biodegraded more rapidly to prevent them from being transported to remote locations by the atmosphere. "We may alter our environment as long as we keep it sustainable," Wade says. "If we can put something in the environment that degrades at a rate that prevents it from building up, then there should be no harm caused to the environment." SOURCE - ENN |
