Changes in fractions of metals in soil affecting their accumulation, bioaccessibility, and risk in vegetables cultivated under plastic sheds

Fractions of metals in plastic-shed soil (PSS), which are easily affected by human activities, are essential factors influencing their uptake by vegetables. However, the correlations among human activities, metal fractions in PSS, and metal migration in PSS-vegetable-human chain remain poorly understood. Here the abovementioned correlations were elaborated using the PSS and vegetable samples collected from the Yangtze River Delta, China. Results showed that changes in pH, organic matter content, and Cd concentration in PSS induced by fertilisation and industrial wastewater irrigation promoted the transformation of acid-soluble Cd into reducible Cd in PSS. The increased reducible Cd in PSS decreased its pollution, bioaccessible fractions, and non-cancer risk in vegetables. In contrast, the acid-soluble Zn increased by 18.3% because of the prominent build-up of Zn in PSS caused by heavy fertilisation. Conversely, the increased acid-soluble Zn enhanced its bioaccessible level and non-cancer risk in vegetables. Additionally, the remarkable increment of Cr in PSS induced by industrial wastewater irrigation slightly increased acid-soluble and reducible Cr, which enhanced bioaccessible Cr and its cancer risk in vegetables. Therefore, minimising acid-soluble Cr, reducible Cr, and acid-soluble Zn in PSS via controlling anthropogenic input of Cr and Zn can abate their health risk in vegetables.