Using a gis based geostatistical approach for mapping atmospheric SO2 concentrations in Balikesir City, Turkey

Abstract

Some compounds especially sulphur dioxide (SO2) is considered as typical indicators of the urban air quality. To inform decisions regarding, for instance, the protection of public health from elevated SO2 levels in Balikesir, high-resolution maps are necessary. Therefore, the main objectives of this paper were to: (1) analyze the spatial distribution of SO2 levels using geostatistical techniques; (2) incorporate this information in a GIS to produce accurate SO2. Geostatistics provides useful technique to get estimates of values of the studied variable at un-sampled locations, considering the spatial distribution pattern and integrating information from sample points and observed trends. In the study, the data were compiled from 20 monitoring stations, using passive sampling, geographically distributed throughout the study area, which provide information about the SO2, spatial coordinates, and collection time. The period of temporal data collection was from March 10 to March 17, 2010. From a modeling point of view, Geographical Information System (GIS) was used mainly for the preprocessing and postprocessing of data to be displayed in digital map layers. Firstly, statistical analysis of samples, such as normal QQ Plot distribution, histograms, trend analysis and a half variation/covariance analysis were used to check the normality to find the appropriate statistical analysis model. Spatial correlation was quantified with semivariograms. And also, estimated SO2 levels at unsampled locations were carried out with the ordinary kriging method, integrating the spatial correlation structures described with the variograms. The results of the passive sampling study show that the winter and summer average concentrations are 30,97 mu g/m3 for SO2. It is expected that where industrial activity is not excessively important, traffic and domestic heating system are the main source of SO2 precursors. Results were shown on the maps. It was demonstrated that geostatiscal tools are quite appropriate techniques for air quality management in small city area like Balikesir.