淋洗脱盐对滨海滩涂不同植被演替带土壤重金属的影响

为研究围垦对滨海滩涂土壤重金属的影响,采用土柱实验模拟淋洗脱盐过程,分析了滨海滩涂不同植被演替带(光滩、互花米草滩、碱蓬滩、芦苇滩)土壤在淋洗脱盐前后重金属(As、Hg、Cd、Cr、Pb、Cu、Zn)含量的变化,评估了围垦可能导致的滩涂重金属流失量。研究表明,淋洗脱盐后,各植被演替带土壤重金属均显著降低,相比而言,Hg、Cr更易淋洗(淋洗率分别为57.2%、49.9%),而Zn不易淋洗(淋洗率18.5%);不同植被演替带土壤重金属淋洗率表现为:光滩互花米草滩碱蓬滩芦苇滩,光滩土壤重金属更易淋洗,而芦苇滩重金属不易淋洗;根据土壤容重、含水率、淋洗率及重金属含量计算重金属流失量发现,不同植被演替带重金属流失量同样表现为:光滩互花米草滩碱蓬滩芦苇滩;除互花米草滩As流失量较高外(19.26 kg·ha-1),其他重金属流失量均表现为光滩最高,光滩围垦可能会造成更多的重金属流失;在仅考虑淋洗脱盐情况下,以江苏省2010~2020年围垦规划270万亩计,仅表层20 cm滩涂土壤,通过围垦即可能导致As、Hg、Cd、Cr、Pb、Cu、Zn流失2 102.5、7.4、421.3、8 587.9、4 376.3、2 404.3 t,由围垦导致的滩涂重金属流失风险值得关注。

Effects of Leaching Desalination on the Heavy Metals in Soils of Vegetation Successions of the Pristine Tidal Flat

To explore the effect of reclamation on the heavy metals in soils of coastal tidal flat, we analyzed the variation of concentrations of heavy metals (As, Hg, Cd, Cr, Pb, Cu, and Zn) in soils of vegetation successions of the pristine tidal flat before and after fresh water leaching desalination using a soil column simulation experiment. The losses of heavy metals induced by reclamation of tidal flat were also evaluated. Results showed that the concentrations of heavy metals in soils of vegetation successions all decreased significantly after leaching desalination. Comparatively, Hg and Cr could be eluted more easily (the leaching percentages were 57.2% and 49.9%, respectively), and Zn could be eluted harder (the leaching percentages was 18.5%). The leaching percentages of the vegetation successions were showed: bare flat > Spartina alterniflora flat > Suaeda glauca flat > Phragmites australi flat. The heavy metals in bare flat could be eluted more easily, which in Phragmites australi flat could be eluted harder. The losses of heavy metals in tidal flat calculated by the soil bulk density, moisture content, leaching percentage and heavy metal concentration were also showed: bare flat > Spartina alterniflora flat > Suaeda glauca flat > Phragmites australi flat. The losses of heavy metals were all higher in bare flat, except for As in Spartina alterniflora flat (19.26 kg·ha-1). Based on the reclamation programme of Jiangsu province (2.7 million mu from 2010 to 2020), reclamation could make As, Hg, Cd, Cr, Pb, Cu, and Zn in topsoil (0-20 cm) loss 2102.5, 7.4, 421.3, 8587.9, 4376.3, and 2404.3 t, respectively, under the condition that we only think about the fresh water leaching desalination. More attention should be paid to the loss risk of heavy metals induced by the reclamation of tidal flat.