地下水位对尾矿中重金属释放及其在土壤中吸附的影响研究

doi:10.13745/j.esf.sf.2024.2.21

摘要/Abstract

摘要：

自然降水易引起矿区地下水位变化,造成尾矿及矿区土壤中重金属污染风险加剧。本文通过模拟不同地下水位条件,研究地下水位对尾矿中重金属释放及其在土壤中吸附行为的影响。研究结果表明,地下水位显著变化明显促使尾矿中Cd、Pb和Zn等重金属释放;持续高地下水位条件更易导致尾矿中重金属在表层土壤中累积;水位波动条件明显有利于尾矿中重金属向深层土壤中迁移;土壤水中Cd、Pb和Zn对地下水有较大的输入风险。在土壤处于持续饱和状态条件下,土壤中残渣态Cd和Pb向活性较强的酸可提取态转化;矿区土壤溶液中Eh呈下降趋势,促使体系中Fe³⁺还原、土壤有机质还原分解和Cd、Pb释放。土壤中无定形态氧化铁与重金属的吸附和共沉淀降低了尾矿和土壤中重金属的迁移风险。然而,在地下水位变化频繁的区域,特别是在氧气有限、富含有机质的包气带,土壤中重金属释放进入地下水的潜在风险明显提高。上述研究结果表明,管控矿区地下水位明显变化对防控矿区重金属潜在污染风险具有重要意义。

关键词: 尾矿, 地下水位, 土壤污染, 重金属, 赋存形态

Abstract:

Natural precipitation can significantly alter the water table in mining areas, increasing the risk of heavy metal pollution in tailings and mining soils. This study investigates the influence of water table fluctuations on the release of heavy metals from tailings and their adsorption in soil through simulation experiments. The results indicate that substantial changes in the water table significantly enhance the release of heavy metals such as Cd, Pb, and Zn. A high water table promotes the accumulation of heavy metals in surface soil, while alternating wet and dry conditions facilitate the migration of heavy metals into deeper soil layers. Cd, Pb, and Zn in soil water pose a considerable risk of leaching into groundwater. Under simulated conditions of continuous soaking and a high water table, residual Cd and Pb in soil are transformed into more active acid-extractable forms. The redox potential (Eh) in the soil solution decreases, promoting the reduction of Fe³⁺, the decomposition of soil organic matter, and the release of Cd and Pb into the system. The adsorption and co-precipitation of amorphous ferric oxide with heavy metals in soil reduce their migration risk. However, in areas with frequent water table fluctuations, particularly in oxygen-limited and organic-rich vadose zones, the potential risk of heavy metal release into groundwater is significantly elevated. These findings highlight the importance of controlling water table fluctuations to prevent and mitigate the potential risks of heavy metal pollution in mining areas.

Key words: tailings, water table, soil contamination, heavy metals, fractionation

中图分类号:

X705

钟林健, 郭朝晖, 谢慧民, 黄驰岳, 高梓伦, 梁学超, 徐锐. 地下水位对尾矿中重金属释放及其在土壤中吸附的影响研究[J]. 地学前缘, 2025, 32(2): 484-494.

ZHONG Linjian, GUO Zhaohui, XIE Huimin, HUANG Chiyue, GAO Zilun, LIANG Xuechao, XU Rui. The influence of water table on the release of heavy metals from tailings and their adsorption in soil[J]. Earth Science Frontiers, 2025, 32(2): 484-494.

图/表 11

表1 供试尾矿及其周边土壤重金属含量及主要理化性质

Table 1 Heavy metal content and main physical and chemical properties of tested tailings and surrounding soil

样品	pH	有机质含量/%	CEC/ (cmol·kg^-1)	重金属含量/(mg·kg^-1)
样品	pH	有机质含量/%	CEC/ (cmol·kg^-1)	As	Cr	Cd	Pb	Zn
尾矿	3.51	—	—	5	29	220	8 700	10 400
土壤	4.50	2.70	12.5	22	210	2	48.5	235

图1 实验装置示意图 (a)—LW和DW;(b)—HW和CK。

Fig.1 Schematic diagram of experimental setup (a) LW and DW, (b) HW and CK

图2 土壤水pH值(a)、Eh(b)和EC (c)随处理时间的变化

Fig.2 The changes of pH value (a), Eh (b) and EC (c) of soil water with treatment time

图3 土壤水中Cd (a)、Pb (b)和Zn (c)浓度变化

Fig.3 The concentration changes of Cd (a), Pb (b) and Zn (c) in soil water

图4 不同地下水位处理56 d后剖面土壤Cd (a)、Pb (b)和Zn (c)含量

Fig.4 The concentration of Cd (a), Pb (b) and Zn (c) in soil profile after 56 days’ different water table treatment

表2 不同地下水位处理56 d后剖面土壤Cd、Pb和Zn变化率

Table 2 The change rate of Cd, Pb and Zn in soil profile after 56 days’ different water table treatment

重金属	处理	实验后土壤中重金属变化率/%
重金属	处理	0~5 cm	5~10 cm	10~15 cm
Cd	HW	90.63	28.13	-15.63
	LW	59.83	0	-31.25
	DW	56.25	3.13	3.13
	CK	25	-9.38	-34.38
Pb	HW	1096.13	438.79	6.25
	LW	548.45	169.72	-36.02
	DW	942.07	675	30.41
	CK	29.51	17.53	-8.38
Zn	HW	393.96	238.50	79.80
	LW	263.11	79.02	68.70
	DW	272.19	133.52	91.60
	CK	331.62	77.01	32.47

图5 土壤中Cd (a)、Pb (b)和Zn (c)含量的变化

Fig.5 The concentration changes of Cd (a), Pb (b) and Zn (c) in soil

图6 处理56 d后Cd、Pb和Zn在剖面土壤中的形态分布 a—0~5 cm;b—5~10 cm;c—10~15 cm。

Fig.6 The chemical forms of Cd, Pb and Zn in soil profile after 56 days’ experiment: (a)0-5 cm; (b)5-10 cm; (c)10-15 cm

图7 处理56 d后剖面土壤有机质含量

Fig.7 The organic matter content in soil profile after 56 days’ experiment

图8 处理56 d后剖面土壤中铁氧化物含量 a—游离态氧化铁;b—无定形态氧化铁;c—晶体态氧化铁。

Fig.8 The iron oxide content in soil profile after 56 days’ experiment: (a) free iron oxide; (b) amorphous iron oxide; (c) crystalline iron oxid

图9 实验结束后不同地下水位条件下土壤SEM和XRD图谱

Fig.9 SEM and XRD spectra of soil under different water table after the experimet

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