Environmental soil quality and vegetable safety under current greenhouse vegetable production management in China

Rapid expansion of greenhouse vegetable production (GVP) in China over the last few decades has substantially promoted vegetable production and farmers' incomes. However, the semi-closed GVP environment can lead to accumulation of soil contaminants and impose a threat to human health through consumption of vegetables. This paper reviews the current environmental soil status and vegetable safety in Chinese GVPs. Furthermore, we propose several lines of future research to better understand the sources and pathways of GVP contaminants and to identify alternative management to achieve sustainable development. Our review suggests that legacy agricultural practices, including intensive application of agrochemicals and frequent irrigation, have led to significant soil acidification and salinization, as well as accumulation of nutrients and emerging contaminants in human-altered and human-transported soils used for GVP and in GVP vegetables. Over fertilization has led to very low nutrient use efficiencies, particularly for phosphorus and nitrogen. In addition, high inputs of manure, plastic films, and pesticides have promoted significant accumulation of organochlorines, antibiotics, phthalic acid esters, and heavy metals in soils and vegetables at levels exceeding or close to their permitted environmental threshold values. Leafy vegetables with large surface area have the highest levels of contaminants which, in turn, can cause health risks to consumers. Nevertheless, the sources and the paths of contaminants entering the soils and vegetables have not been widely investigated, particularly in the southwestern and northern Chinese provinces. Future research should include detailed documentation of agrochemicals and soil properties involved in the retention, degradation, and mobilization of contaminants. Furthermore, new cleaning technologies should be taken in practice to mitigate or prevent contamination of soil and vegetables.