Presenter : Biplab Biswas
Previous works suggest that the organic matter and micro-organism plays a catalytic role on the heterogeneity in spatial distribution of arsenic (As) contaminated tube wells. But the association of As contaminated domestic tube wells and the Land use land cover (LULC) categories is not clear. The present study uses “average weight score” method to investigate the association between LULC categories with the distribution domestic tube wells. Arsenic contaminated tube well data has been obtained from the Public Health Engineering Department (PHED), Govt. of West Bengal. Open source satellite images, Resourcesat-1: LISS-III, Jan 2013 (from Bhuvan) have been downloaded. Open source ILWIS (v. 3.3) has been used to classify the satellite Image while the open source QGIS (v. ESSEN 2.14.2) has been used to analyze the LULC categories and As data of the study region. The identified LULC categories are (re-) grouped into five classes, viz. Class-1, denotes homestead with dominant agricultural land in neighboring sites; Class-2 refers to homestead clusters without dominance of any other classes; Class-3 represents homestead with significant neighboring water bodies; While Class-4 & Class-5 refer to homestead with neighboring marshy land & homestead with dominance of more than two land use land cover classes respectively. For, analyzing spatial association between the LULC categories and As contaminated tube wells, LULC classes within a 100 meter buffer centering each tube well is considered. Based on the “weighted on evidence” method scores are assigned to the tube wells as per its level of As contamination. +0.5 is assigned to the mild contaminated wells i.e. > 0.010 to 0.049 mg/l; and +1.0 is assigned to the highly contaminated wells i.e. > 0.05 mg/l. The average weighted score (Ci) are calculated and normalized with the total weighted value for the all contaminated wells. GIS based weight on evidence model indicates that maximum contaminated wells are situated at close proximity to reframed LULC Class 3 & 4. We can conclude that domestic tube wells near the wet lands (water body and marshy lands) are prone to arsenic contamination.