Geografiska informationssystem för studier av polyaromatiska kolväten (PAH) : undersökning av djupvariation i BO01-området, Västra hamnen, Malmö, samt utveckling av en matematisk formel för beräkning av PAH-koncentrationer från ett kontinuerligt utsläpp

At the end of August 1999, the local government council of Malmö city decided that the area known as Kvarteret Bilen would be made available for the European Housing Exhibition 2001 (Bo01-mässan). Kvarteret Bilen extends over approximately 80 hectars and includes the western parts of the Western Harbour area (Västra hamnen) of Malmö. Kvarteret Bilen as a whole, but especially the western sections of this area, the socalled Bo01 section, has been the subject of heated discussions. This is mainly due to the fact that the ground in question has proven to be contaminated to a certain extent by different chemical compounds. Investigations undertaken during 1998 showed sporadically high concentrations for especially one chemical group: polycyclic aromatic hydrocarbons (PAH). The first part of the paper describes the use of a mathematical equation (Fetter 1994) to calculate the concentration of PAH from a continuous discharge at a given time by employing Geographical Information System (GIS). Even the constraints of the equation are discussed, as well as the consequences that follow as a result of using GIS. The second part of the paper focuses on the connections between the content of carcinogenic PAH in Kvarteret Bilen and the ground water level and type of filling material. It also describes several interpolation methods, none of which was successful in the analysis however. Known point values of PAH had to be used in the analysis instead. In order to study the relationships (mentioned above), four hypotheses were put forward: 1) the PAH will show low concentration values in the interval where the ground water is fluctuating; 2) the concentration level of PAH will be higher in the saturated zone as well as in the uppermost layer of the unsaturated zone; 3) every PAH compound will vary in a similar way from the ground level and downwards and, 4) areas containing remains of asphalt, foundry discharge and impregnated wood, ought to present the highest concentration levels. During the analysis, all of the hypotheses were confirmed. The interpolation techniques could not be carried out since the levels of concentration of PAH varied too much between known points. Applying GIS to the mathematical equation in Fetter (1994) had some advantages. One was the possibility to calculate concentrations for an entire area and not just for a specific point. The results showed that if there is a continuous discharge, the concentration values get higher closer to the discharge area compared to values further away, if the time level is set to be the same. Also, a longer time limit generates higher concentration values provided the distances are the same.