ENVIRONMENTAL IMPACT OF CLOSING OF OIL SHALE MINES ON RIVER WATER QUALITY IN NORTH-EASTERN ESTONIA; pp. 169–183

Abstract

Chemical and biological characteristics of the Pühajõgi and Kunda catch­ments were determined in 1995, 2000 and 2005. During last ten years the concentration of total nitrogen in the samples of the river water from the Püha­jõgi catchment has decreased on the average almost 90% since four mines were closed. The concentrations of total nitrogen in the water samples of the Kunda catchment decreased on the average ca 20% during these ten years. The conductivity values of the river water samples of the Pühajõgi catchment between 800 and 1800 µS cm–1 indicated a significant amount of ionic species in the river water. The water was microbiologically unpolluted according to the results of the analysis in 2005.