草甘膦对重金属毒性的抑制效应研究——以发光菌(Photobacterium phosphoreum T3)为例

草甘膦分子(C3H8NO5P)中含有较多配位基团如羧基、氨基、磷酸基,对重金属阳离子有很强的络合能力,可能会影响重金属的生物有效性进而影响其毒性。为了解草甘膦(GPS)和铜(Cu)、镉(Cd)交互对发光菌毒性效应,以明亮发光杆菌T3小种(Photobacterium phosphoreum T3)为例,进行了室内模拟试验研究。结果表明:Cu、Cd对发光菌有很强的毒性(EC50分别为1.28、0.89mg·L-1);没有控制p H的草甘膦能够降低溶液p H,对发光菌亦有较强的毒性(EC50为35.9 mg·L-1);但控制p H值为5.0的草甘膦对发光菌无明显毒性,并且能够显著降低Cu、Cd对发光菌的抑制,同时随着GPS/Cu、GPS/Cd摩尔比值的增大使毒性降低,直至无明显毒性。据此认为,在重金属和农药草甘膦共存的环境当中,草甘膦能够影响重金属的形态,进而影响重金属的生物有效性和毒性。

Inhibitory Effect of Glyphosate on Toxicity of Heavy Metals:A Case Study on Photobacterium phosphoreum T3

Glyphosate(N-phosphonomethyl]-glycine, GPS) is one of the most widely used herbicides in agricultural and forestry production. It contains functional groups of amine, carboxylate and phosphonate that can form strong coordination bonds with metal ions and thus may affect the bioavailability and toxicity of heavy metals in soils. Therefore, a laboratory experiment was conducted to investigate the interactions between GPS and heavy metals(Cu and Cd) with respect to their acute toxicity to Photobacterium phosphoreum T3. Results showed that the toxicity of Cu and Cd to photobacterium was very strong(EC₅₀ was 1.28 mg·L^-1 and 0.89 mg·L^-1 for Cu and Cd, respectively). The GPS obviously decreased pH in the media and possessed much greater toxicity to photobacterium(EC₅₀ was 35.9 mg·L^-1) when the medium pH remained unadjusted. However, GPS did not show toxicity when the medium pH maintained at 5.0. The presence of GPS obviously relieved the acute toxicity of Cu and Cd to photobacterium. Increasing molar ratios of GPS/Cu and GPS/Cd significantly decreased the toxicity of Cu and Cd to photobacterium. Copper toxicity disappeared at GPS/Cu molar ratio greater than 1. In conclusion, GPS could modify speciation of heavy metals, and thus their toxicity in GPS and heavy metals co-existing systems.