土壤锌 镉单一及复合污染对蚯蚓金属硫蛋白含量的影响

Effect of Zn and Cd Single and Combined Pollution on Metallothionein Content of Earthworm in Soils

蚯蚓金属硫蛋白(MT)是指示土壤污染程度的生物标志物。为揭示土壤镉(Cd)、锌(Zn)污染的生态效应,采用土壤染毒法,研究了Cd、Zn单一与复合污染对赤子爱胜蚓体内金属硫蛋白(MT)含量的影响。结果表明,无论是单一还是复合污染,Cd都明显诱导了蚯蚓MT的合成,随着Cd胁迫浓度和时间的增加,蚯蚓MT的含量均显著上升。与Cd相比,单一Zn污染对MT的影响要小得多,胁迫28d后MT含量才有升高。Cd、Zn复合污染的效应在不同的Cd、Zn浓度组合下存在较大差异,同时也与暴露时间密切相关。当Cd处理为100mg·kg-1时,Zn完全表现为拮抗作用;而在300mg·kg-1Cd胁迫浓度下,Cd、Zn复合对MT的影响随Zn浓度和暴露时间变化而出现不同的效应:当Zn为100mg·kg-1时,MT表现出协同-拮抗-无影响的趋势,而在500mg·kg-1的Zn处理下,MT含量在28d后显著下降。研究结果显示,蚯蚓MT是指示土壤Cd污染的有效指标,而Zn在一定程度上能缓解Cd对蚯蚓的毒害作用。

Metallothionein （MT） in earthworm may be used as a biomarker to indicate the soil quality. In this study, a bioassay was conducted to investigate the effects of single and combined applications of Cd and Zn in soil on the MT content in earthworm（Eisenia fetida）. Resuhs showed that Cd clearly induced the MT in earthworms with or without Zn applications to the soil. The MT content significantly rose with the concentration and time of Cd exposure. In contrast, single Zn treatment did not have a strong effect on the earthworm MT, which did not increase until the 28th day after the Zn exposure. The effects of Cd and Zn combined pollution differed among the various treatments and were closely related to the exposure time. When the soil was treated with 100 mg ·kg^-1 Cd, Zn additions decreased the MT content in earthworms. However, the application of 300 mg·kg^-1 Cd in soil caused an increase of MT even in the presence of Zn. No constant effect on MT was observed for the lower Zn treatment（ 100 mg·kg^-1） during the experimental period. In contrast, the addition of 500 mg·kg^-1 Zn counteracted the Cd toxicity by significantly decreasing the MT content at the end of the incubation. In summary, the results of this study suggest that the MT is a useful indicator for Cd pollution in soil, while the Cd toxicity to earthworm may be alleviated by Zn under certain conditions.