Zmiany wskaźników fizykochemicznych wody kanału Dąbrówka spowodowane działalnością kopalni rud cynku i ołowiu

The paper presents changes of physicochemical indices of water in the Dąbrówka channel which is the receiving water of waters originating in the first place from drainage of zinc and zinc ores mines from ZGH Bolesław Company in Bukowno. Mining wastewaters are treated as a specific kind of sewage which do not form during a technological process but are the natural outcome of conducted mining activity. Beside mining wastewaters pumped out from the Pomorzany mine, the Dąbrówka channel drains also post-floatation waters from tailings ponds and runoffs from industrial wastes heaps. Hydrochemical tests were conducted in 2012. Water for analyses was collected once a month (total of 12 dates) in 3 control points: point 1 – at km 4+800 of the Dąbrówka channel – discharge of mining waters from the mine through the Dąbrowka shaft, point 2 – at 1+600 of the watercourse (below the national road 94), point 3 – at 3–50 m before the confluence of the Dąbrówka channel and the Biała River. The area of the Dąbrówka catchment is 16.64 km2. Settlement and industrial areas are situated in the upper part of the catchment, the area below is used as forest grounds. Bolesław town is situated in the central part (between points 1 and 2). The lower part of catchment is managed for agriculture with a minor share of settlement areas. Hydrochemical tests conducted on site comprised measurement of water pH, electrolytic conductivity (EC), dissolved oxygen concentration and degree of water saturation with oxygen. Laboratory assessments comprised total suspended solids by drying and weighing method, total dissolved solids by evaporation, concentrations of Ca2+, Mg2+, Na+, K+, Mn2+, Fe2+, Fe3+ (total iron) and heavy metals Zn and Pb by means of atomic absorption spectrometry (ASA) on UNICAM SOLAR 969 spectrometer. Concentration of ammonium nitrogen (N-NH4+), nitrite (N-NO2-) and nitrate (N-NO3-) nitrogen as well as phosphates (PO43-) and chlorides (Cl-) were determined using flow colorimetric analysis on FIAstar 5000 apparatus, whereas sulphate (SO4-2)concentration was assessed by precipitation method. Quality of the Dąbrówka channel water was estimated in compliance with the Regulation of the Minister of the Environment of 30 October 2014. Statistical inference about the significance of differences between the indices values among the control points was conducted using Kruskal-Wallis non-parametric test and then by non-parametric Mann-Whitney U-test on the significance level α = 0.05. On the basis of the investigations it was determined that water along the whole length of the Dąbrówka channel does meet the requirements of class II. Because of high concentration of lead, the water was classified to the state below good. The mining wastewater discharged from the zinc and lead ore mines was characterized by statistically lower concentrations of salinity indices, ammonium, and Fe and Mn, but higher content of heavy metals (Zn) and nitrate nitrogen than waters in the lower course of the channel.