Delimitation of Nitrates Pollution Source Areas on the Base of Vegetation Indices Derived from MODIS

摘要

The intensively cultivated zones are considered as a potential source areas of the non-point nitrate pollution of the surface and groundwater water due to intense fertilization. In order to control and reduce the nitrogen pollution of water the European Union has obliged its members to define zones which the outflow of nitrates from the agricultural sources should decrease. The aim of the study is to analyze MODIS data in order to check the possibility of estimation the nitrates pollution to map the most endangered zones in Poland. Remote Sensing data enable the detection of parameters directly related to the N-stress: evapotranspiration, chlorophyll content in the biomass (NDVI), moisture content (NDII, NDWI). The chosen indexes were obtained from MODIS images and correlated with nitrate content, in soil with the use of 5000 in-situ measurements (National Water Management Authority). Results differ with type of land cover. The homogeneity of pixel have influence on possibility of detection N-stress. Therefore, the function which relates vegetation index and nitrate content for meadows and pastures is more accurate than the function for arable lands. Results show that relation between bands 7 and 6 and bands 6 and 2 are useful to analyze nitrate pollution over the meadows.