Impact of heavy metal contamination and seasonal variations on enzyme’s activity of Yamuna river soil in Delhi and NCR

Yamuna river is one of the most important rivers of India and is highly polluted. The river water and the adjacent soil are contaminated with various pollutants including heavy metals. Soil enzymes play important role in various bio-geochemical cycles and help in maintaining nutrient availability of soil. They are very sensitive toward changing environment and therefore act as a key indicator of soil health. In the present study, effects of seasonal variations and heavy metals contamination in Yamuna river water were observed on physicochemical properties and enzyme activities of soil. Soil samples were collected from ten different locations, along the course of the Yamuna river in Delhi–NCR, in three different seasons, i.e., summer, rainy and winter. These sampling sites were divided into three segments, up, middle and lower streams. The concentrations of heavy metals were found to be higher than their safe limit at all the ten sampling points. The total organic carbon content and soil respiration was significantly higher in lower stream. Dehydrogenase enzyme activity was higher in winter season, while urease and arginine deaminase enzyme activity was higher in summer season. Dehydrogenase, arginine deaminase and nitrate reductase enzyme activities were higher in lower streams, while urease enzyme shows maximum activity in the up stream. Thus, we conclude that the continuous application of Yamuna water for irrigation may degrade the soil quality.