The Impact of Water from Sand Pit Lakes on Plant Growth, Soil, and Leachate

Abstract

Sand mining in the municipality of Seropedica, Rio de Janeiro, Brazil, has created large acidic lakes. This study evaluated the impact of water from sand pit lakes on the soil, leachate, and growth of Urochloa plants. Soil columns were sown with these plants and watered with five irrigation rates (treatments) with sand pit water and one treatment with pit water (control). A bottle was placed under each soil column to collect the leachate solution. The Ca2+, Mg2+, K+, Na+, Al3+, Fe3+, Si, P, N-NO3−, and SO42− contents in the leachate, and the soil pH, EC, (H+ + Al), Ca2+, Mg2+, K+, Na+, Al3+, Fe3+, and P contents were determined. Plant height, shoot and root dry matter, the contents, and accumulation of Ca, Mg, K, Na, Al, Fe, Mn, P, and N were evaluated. The results were analyzed by analysis of variance and regression models. The increase of the water from the pit lake reduced plant height, dry root, and shoot matter linearly. The Al and Fe contents in the roots were 10 times higher than in the shoots. No salinization or sodification of the soil occurred, but the Al3+ solubilization due to the low soil pH leads the increase of (H+ + Al). The acidity of the water and the low buffer capacity of the soil reduce its capacity to retain chemical elements. The Al, Fe, SO42−, and N-NO3− concentrations in the leachate were higher than those allowed by Brazilian groundwater laws. Under the experimental conditions, there is a potential risk of groundwater contamination.