Effects of temperature on soil geochemical properties and accumulation of heavy metals in rapeseed (Brassica napus)

The global surface temperature is predicted to increase by 1.0°C to 5.7°C by the end of the twenty-first century from the Inter-governmental Panel on Climate Change (IPCC) report, but the effects of higher temperatures on soil properties and heavy metal accumulation in plants are unclear. To investigate the effects of soil temperature on soil geochemical properties and the accumulation of heavy metals in plants, we grew rapeseeds ( Brassica napus ) in pots filled with contaminated field soil at four different temperatures (22.5, 22.9, 23.7, and 24.6°C) in a controlled growth chamber. The concentration of heavy metals in the rapeseed samples at different temperatures showed a positive partial correlation coefficient with the soil temperatures. The order of partial correlation coefficients was Zn (0.50) > Cd (0.21) > Cu (0.19) > As (0.15) > Pb (0.13). However, only the Zn concentration in rapeseed showed a significant moderate positive correlation (r = 0.50, p < 0.01) with soil temperature. In terms of soil properties, soil pH positively correlated (r = 0.49, p < 0.01), whereas the cation exchange capacity (CEC) negatively correlated (r = -0.55, p < 0.001) with soil temperatures. These results suggest that increasing soil temperatures affect the plant metabolisms and soil geochemical properties and enhance the soil-to-plant transfer of heavy metals. Therefore, future global warming may lead to unforeseen losses in crop productivity and pollutant accumulation, consequently resulting in detrimental effects on the health of animals and human beings.