Ensuring food safety by combining phytoremediation and food crop cultivation: a case study in farmlands near a lead-zinc mine in Southwest China.

Environmental pollution by heavy metals (HMs) in mining areas is a major concern worldwide since it pollutes the surrounding surface water, groundwater, and farmland soils. Once in the food chain, HMs can cause mild to life-threatening side effects thereby negatively affecting the environment and human health. To remedy this situation, cost-effective and environmentally friendly remediation approaches are needed to ensure food safety. Phytoremediation is a remediation technique that meets these criteria; however, it is still unclear whether co-cultivation of food crops during phytoremediation can produce crops that meet the required safety standards. In this study, we investigate the effectiveness of phytoremediation and food crop co-cultivation to produce "HM-free" crops from farmland soils in Sidi village in Xingping Town of Guangxi Zhuang Autonomous Region in China, contaminated by HMs from a lead-zinc mine. Our results show that (1) After 19 months of phytoremediation, the redistribution of HMs (cadmium, lead, and arsenic) from acidic to slightly acidic, neutral, and mostly weakly alkaline soils was promoted. This resulted in a reduction in HMs availability and consequently the amount absorbed by food crops. (2) The concentrations of important nutrients including nitrogen, phosphorus, and potassium were significantly increased during phytoremediation. This translated to increased plant biomass in Celosia Argentea L. (26.09%), Sedum erythrostictum Migo (18.52%), and Amaranthus cruentus L. (21.67, 33.33, and 66.67%, for consecutive harvests). (3) Co-cultivation of maize crops with low HM accumulator plants in slightly and moderately polluted sites or a rotation of rapeseed-sunflower plants with hyperaccumulator plants in the highly polluted site ensured 100% compliance with the food crop and feed safety standards. Our findings can provide an important reference for studies aimed at managing polluted sites and ensuring food safety.