Air pollution with nitrates as one of the major factors in the chemical composition of water in shallow-supplied mountain springs

Abstract

The prolonged pressure of air pollutants on ecosystems weakens their resistance and changes the way they function. An example of this phenomenon can be found in the Silesian Beskid Mountains, which have long been influenced by pollutants such as NO3− coming from the Upper Silesia and Ostrava industrial districts. Air pollution containing nitrates has contributed to the spruce stand diebacks in the area. The depositional influence of NO3− can be even greater. NO3− ions accompany precipitation into the region's surface waters and are found in high concentrations in spring water. In this study NO3− concentrations exceeding 5 mg∙dm−3 and 10 mg∙dm−3 were found in 46% and 11% respectively, of 751 samples taken from 98 springs located in the Skrzyczne range. All these springs represented shallow water supply systems, meaning that they were supplied by precipitation only. Vegetation plays a significant role in the NO3− cycle by taking up NO3− ions from underground water to build biomass. In the research area, this process was most efficient in the youngest tree stands. Tree stands younger than 21 years old reduced NO3− concentration in spring water to a median value of 1.95 mg∙dm−3. The factor connected with the NO3− cycle was found to be one of four major factors determining spring water chemistry in the research area and explained from 7.99% to 10.71% of the variability in that chemistry, depending on the measuring session. The other three factors were connected with bedrock and soil weathering (which explained about 50% of the variance), terrain physiography and plant cover (which explained about 15% of variance) and organic matter decomposition (which explained about 8% of the variance).