RELATIONSHIP BETWEEN NITRATE AMOUNT IN GROUNDWATER AND NATURAL FACTORS
In Lithuania almost the whole drinking water is derived from groundwater sources. The concept of ground@water vulnerability is based on an assumption that a physical environment may provide some degree of protection to groundwater against human impact.The earth materials may act as natural filters to screen out some contaminants. Groundwater vulnerability depends on the natural characteristics of a site and relates to the pathways and rate of downward movement of pollutants. Pollutant migration through the soil zone depends just on the depth of waterlogging, texture, organic matter content, quantity of precipitation.. Pollutants accumulating in shallow groundwater in the Lithuanian area are, first of all, nitrates and organic matter. Regularities of groundwater chemistry can be determined only after investigation into the processes of their formation. That is why we need to find out the main factors of nitrate concentrations in groundwater. Investigation took place in Karkiškes object of Educational Farm of Lithuanian University of Agriculture in 1997–2002. Also, the data from publications were used. The regime of groundwater level and the quantity of nitrates in it was an object of the investigation. The objective of the thesis is to estimate correlation between nitrate concentrations in groundwater and natural factors, such as textural composition of the soil, the quantity of clay and humus particles in the soil, the depth up to the groundwater level, the depth of a restrictive layer and annual precipitation amount. The correlation analysis was used to determine relationship among these factors. The investigation shows that the concentration of nitrogen in groundwater and nitrate leaching are under the influence of humus and clay particles in the soil. It also shows that, when the content of clay particles in the soil increases, nitrogen leaching decreases. Relationship between nitrate content in groundwater and its level from the soil surface, precipitation amount were identified by the investigation. The obtained relationship is close enough, and the correlation coefficients are high (0,86–0,98).