Influences of lithium on soil properties and enzyme activities

Lithium is an emerging environmental contaminant under the current sustainable energy strategy, but little is known about its contamination characteristic in soil. In this study, soil properties and enzyme activities in soils treated with 10–1280 mg kg−1 lithium were measured. The results showed that the content of ammonium nitrogen, total nitrogen, and exchangeable potassium significantly increased by 64.39%–217.73%, 23.06%–131.86%, and 4.76%–16.10%, while electric conductivity and available phosphorus content in lithium treated soils was respectively as 1.10-fold–13.44-fold and 1.27-fold–6.66-fold comparing to CK value. Soil pH and cation exchange capacity slightly declined and increased, respectively, and there was no significant variation in total organic carbon. However, nitrate nitrogen and sulfate content significantly decreased under higher lithium stress. On the other hand, lower lithium treatment level of 10, 20, 40, or 80 mg kg−1 selectively promoted the activities of sucrase, urease, aryl sulfatase, and peroxidase, while the protease, neutral phosphatase, phytase, and lipase were significantly inhibited under all lithium levels, indicating a weaken geochemical cycling of carbon, nitrogen, phosphorus, and sulfur. Then, lithium's 10% and 50% ecological dose (ED10 and ED50) was respectively fitted as 21.18 and 1408.67 mg kg−1 basing on Geometric Mean Index. The influences of lithium on soil were adverse. This study provided important insights into understanding the characteristics of lithium contamination, informing risk assessment and guiding remediation.