Effects of phosphorus-containing material application on soil cadmium bioavailability: a meta-analysis

Diverse phosphorus-containing materials (PCMs) were widely applied in remediation of cadmium-contaminated soils, and their effects on the change of soil cadmium availability (SCA) varied with their physicochemical characteristics and environmental conditions. Investigation on the effect of various PCMs on reducing SCA under different conditions favors the safe utilization of Cd-contaminated soil. Herein, a meta-analysis of literature published before August 2021 was carried out. A total of 342 independent observations were obtained from 42 published papers which included 9 factors that may affect the passivation effect of fertilizer content: phosphorus type, phosphorus application rate, soil pH, soil CEC, soil organic matter, experiment type, and time. Results of boosted regression tree analysis showed that the application rate is the most important factor contributing to the SCA, followed by soil pH and duration. Results of this meta-analysis showed that medium P input shows potential for reactivating the SCA. Under alkaline soil conditions and high soil CEC values, PCM input can better deactivate SCA. In addition, the difference from the previous understanding is that under the medium input of phosphorus-containing fertilizer (90-500 mg P∙kg^-1), it will significantly increase the content of available cadmium in soil. In addition, future recommendation for exploring novel PCMs and suitable strategies for controlling the SCA though PCM application were also proposed. Our works may promote the interpretation of the interference factors on the SCA changes and fill the research gaps on utilization of PCM in Cd-polluted soil remediation.