PHOSPHATE POLLUTION IN THE GROUNDWATER OF LOWER VAMSADHARA RIVER BASIN, INDIA

The lower Vamsadhara river basin, spreading over an area of 817 sq.km in northern Andhra Pradesh, represents a typical rural setting. The oc currence of phosphorus-bearing minerals reported in literature, and th e increasing application of phosphatic fertilizers in the area have pr ompted these studies. Water samples from 113 wells were analysed for C a, Mg, Na, K, Cl, SO4, HCO3, F, NO3 and PO4. The results indicate the presence of phosphate in the groundwater ranged from 0.72 to 7.07 mg/l , which is beyond the limits recommended for domestic and water treatm ent purposes. Samples of soils and weathered rocks were analyzed for t heir water-soluble phosphate and other chemical parameters. The water- soluble phosphate in the widely used fertilizers of the area was deter mined. The spatial variation of phosphate in the aquifer and the soil leachate characteristics supplemented by the chemical equilibrium calc ulations clearly indicate the dominance of geological sources over the fertilizer sources in contributing PO4 to the groundwaters.