Effects of Waste Drilling Fluid on Physiological Characteristics of Two Leguminous Plants and Soil Properties Under Abiotic Stress

Oil and gas drilling waste drilling fluid is a complex alkaline mixture that poses risks to plants and soil ecosystems during transportation and disposal due to potential leakage. This study investigates the effects of waste drilling fluid on the growth of Trifolium pratense (L.) and Astragalus sinicus (L.) and on the soil ecosystem, aiming to provide a theoretical reference for ecological restoration of oil and gas field sites. Four gradients of waste drilling fluid stress were established by mixing 0, 50, 100, and 150 mL of waste drilling fluid into the substrate, with 0 mL serving as the control. Seed germination, morphological development, physiological, and biochemical indices of the two leguminous plants, as well as soil nutrients and enzyme activities, were analyzed, followed by a comprehensive evaluation. Waste drilling fluid stress inhibited the growth of both leguminous plants. Their physiological and biochemical parameters, such as antioxidant enzyme activities and osmotic regulatory substances, exhibited a gradually increasing trend with increasing waste drilling fluid concentration. Concurrently, waste drilling fluid stress reduced soil nutrient availability and decreased soil enzyme activities. Notably, soil nutrient content increased after planting compared to the original soil without plants. Planting these two leguminous plants can effectively alleviate the negative impacts of waste drilling fluid stress, thereby indirectly contributing to soil remediation.