恢复湿地土壤重金属含量变化及污染评价

李海兴; 孙晓新; 满秀玲; 王清波; 李东; 胡艳玲

doi:10.12171/j.1000-1522.20190338

恢复湿地土壤重金属含量变化及污染评价

Changes of soil heavy metal contents and pollution evaluation during the restoration of wetlands

摘要

摘要:
目的为探究退耕还湿对土壤重金属含量及其潜在危害的影响。
方法取黑龙江三江国家级自然保护区内大豆田、不同退耕年限的杂草草甸或湿地和天然臌囊苔草—小叶章沼泽土样，测定土壤重金属含量。利用Hankanson潜在生态危害指数法，进行潜在生态危害评价。
结果三江自然保护区退耕湿地恢复过程中土壤重金属污染物主要为Pb，其次是Cu，而Zn、Mn和Cr的影响很小。随土壤深度增加，Cu、Pb、Zn、Mn和Cr含量呈波动变化。Cu和Pb含量在退耕还湿11年之前，在0 ~ 10 cm土壤深度含量最高，而在退耕还湿11年之后，在40 ~ 50 cm土壤深度含量最高。其他重金属含量随着土壤深度变化没有表现出一定的规律。退耕恢复期间，土壤Cu、Pb、Zn与Cr含量随退耕时间先增加后减少，但Zn含量增加与减少未达到显著程度（P > 0.05）。而退耕样地土壤Mn含量从恢复第1年开始就显著低于大豆田（P < 0.05）。大豆田和退耕前6年的恢复样地具有强烈的潜在生态风险危害，退耕8、11年样地和天然沼泽的潜在生态风险危害指数为中度，退耕15和25年样地的潜在生态风险危害指数为轻度。
结论随着退耕还湿时间的延长，土壤中Cu、Pb、Zn和Cr含量先增加后减少，分别在退耕15、12、2和10年左右恢复到天然湿地水平。而土壤Mn含量在退耕开始后便与天然湿地没有显著性差异（P > 0.05）。随着退耕年限增加，生态系统潜在生态风险危害逐渐降低。

Abstract:
ObjectiveThis study was designed to evaluate the effects of converting farmland to wetland on the contents of heavy metals in soil.
MethodWe measured heavy metal contents of the soil in soybean fields, restored reclaimed wetlands and natural Carex schmidti-Deyeuxia angustifolia marsh in Heilongjiang Sanjiang National Nature Reserve of northeastern China. We also evaluated the effects of converting farmland to wetland on the potential ecological hazard by the Hankanson potential ecological hazard index method.
ResultThe results showed that the highest heavy metal pollutant in the soil of restored sites in this reserve was Pb, followed by Cu, while the effects of Zn, Mn and Cr were small. The contents of Cu, Pb, Zn, Mn and Cr fluctuated with the soil deepened. The contents of Cu and Pb were highest in the soil layer of 0−10 cm during the begining 11-years restoration. However, those were the highest in the soil layer of 40−50 cm after 11-years restoration. Other heavy metal contents had no certain trends along with soil depth. The contents of Cu, Pb, Zn and Cr in soil increased first and then decreased with prolonged restoration time, while the increasing and reducing of Zn content were not reaching significant level (P > 0.05). The contents of Mn in restoration sites were significantly lower than that in soybean field (P < 0.05) from the first year of restoration. The soybean fields and plots within 6-years restoration had strong potential ecological risk hazards. The potential ecological risk hazard indexes of sample plots after 8-years, 11-years restoration as well as C. schmidti- D. angustifolia marsh were moderate, while that of sample plots after 15 years restoration was mild.
ConclusionThe contents of Cu, Pb, Zn and Cr in soil increase first and then decrease with prolonged restoration time. Those contents reach the level of natural wetlands after 15, 12, 2 and 10 years restoration, respectively. However, there is no significant differences in soil Mn content between restored wetlands and natural marsh (P > 0.05). The potential ecological risk of ecosystems reduces gradually with the restoration time extends.

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