Petroleum induces soil water repellency and impedes the infiltration and evaporation processes in sandy soil

Abstract

Contamination with petroleum could alter the soil hydrological processes and degrade soil and vegetation. Reclamation of petroleum contaminated soil is limited by the absence of scientific data regarding contaminated soil hydrological properties. In this study, we determined the effects of petroleum contamination on the hydrological properties of sandy soil with different contamination levels (0 g kg−1, 5 g kg−1, 10 g kg−1, 20 g kg−1, and 40 g kg−1), through the Water Drop Penetration Time (WDPT) test, infiltration and evaporation experiment in soil columns. The results showed that petroleum contamination increased the water repellency of sandy soil (hydrophilic) to slightly hydrophobic (5 g kg−1), strongly hydrophobic (10 g kg−1), extremely hydrophobic (20 g kg−1, 40 g kg−1). With the increased water repellency, the average infiltration rate decreased from 5.65 mm min−1 to 2.88, 1.17, 0.24, 0.13 mm min−1, and the accumulated evaporation decreased from 59.62 mm to 55.26, 53.91, 45.03, 37.76 mm. Our study indicated that petroleum contamination reduced the soil infiltrability and evaporation in sandy soil, and the increased water repellency was the main reason for these changes. However, more researches were still deserved to explore the effects of hydrological properties on soil water, rainfall-runoff, and pollutant migration in petroleum contaminated soil, especially in the future of global warming and intensified hydrological cycles. Our findings provide the scientific data for understanding the hydrological properties to remove pollution and restore vegetation successfully in petroleum contaminated soil.