Spatial Distribution Characteristics and Risk Assessment of Heavy Metals in Cultivated Land in Small Watersheds

doi:10.11924/j.issn.1000-6850.casb2025-1029

Abstract

Abstract:

To investigate the distribution patterns and ecological risks of heavy metals (Pb, Cr, Cd, Hg, As, Zn, Cu, Ni) in agricultural watersheds and to identify the sources of these heavy metals related to contemporary agricultural practices, spatial interpolation methods were employed to analyze the spatial distribution characteristics of heavy metal concentrations at the small watershed scale. Ecological risk assessment was conducted using the geo-accumulation pollution index and the potential ecological hazard index, supplemented by health risk assessment and source apportionment analysis. The results showed that cadmium (Cd) was the major pollutant, 6% of the soil samples posed serious ecological risks, and 82% posed moderate ecological risks. Hg and As exhibited relatively high ecological hazards at local sites. The high-value areas of heavy metals were mainly concentrated in the town centers and the confluence areas of rivers, presenting an overall spatial distribution that spread from the town center to the periphery. Furthermore, based on health risk assessment, heavy metals in soil conducted a non-carcinogenic risk to children, while there was no obvious risk to adults. As, Cr, Ni and Cd posed potential carcinogenic risks to children, and As and Cr posed potential carcinogenic risks to adults. Cr and Ni mainly originated from soil parent material, while Pb, Cd, Cu, Zn and As might be closely related to historical agricultural inputs, especially long-term fertilization behavior. In conclusion, heavy metal pollution in cultivated land is not a continuous and intensifying input process, but is dominated by the superimposition of historical agricultural activities and natural background. There is still room for improvement in the control of heavy metal pollution in cultivated land.

Key words: agricultural soil, heavy metals, spatial distribution, ecological risk, source apportionment

CLC Number:

X53土壤污染及其防治

XU Zhuo, LIANG Jiecong, HUANG Xurong, LI Xiang, HUANG Zulyu, JIANG Shaojun, CHEN Huayi. Spatial Distribution Characteristics and Risk Assessment of Heavy Metals in Cultivated Land in Small Watersheds[J]. Chinese Agricultural Science Bulletin, 2026, 42(16): 127-140.

Figures/Tables 14

References 54

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参数含义	符号/单位	儿童参考值	成人参考值
土壤摄入量	IR_ing/(mg/d)	200	100
呼吸摄入量	IR_inh/(mg/d)	7.5	14.5
暴露频率	EF/(d/a)	350	350
暴露持续时间	ED/a	6	24
体重	BW/kg	16	60
平均暴露时间	AT/d	ED×365	ED×365
暴露皮肤表面积	SA/(cm²)	2800	5700
皮肤粘附因子	SL/(mg/cm²)	0.2	0.07
皮肤吸附因子	ABF	0.001	0.001
颗粒物释放因子	PEF/(m³/kg)	1.36×10⁹	1.36×10⁹

参数含义	符号/单位	儿童参考值	成人参考值
土壤摄入量	IR_ing/(mg/d)	200	100
呼吸摄入量	IR_inh/(mg/d)	7.5	14.5
暴露频率	EF/(d/a)	350	350
暴露持续时间	ED/a	6	24
体重	BW/kg	16	60
平均暴露时间	AT/d	ED×365	ED×365
暴露皮肤表面积	SA/(cm²)	2800	5700
皮肤粘附因子	SL/(mg/cm²)	0.2	0.07
皮肤吸附因子	ABF	0.001	0.001
颗粒物释放因子	PEF/(m³/kg)	1.36×10⁹	1.36×10⁹

元素	RfD			SF
元素	经口摄入	呼吸摄入	皮肤接触	经口摄入	呼吸摄入	皮肤接触
Cd	1×10^-3	1×10^-3	1×10^-5	6.1	6.4	6.1
As	3×10^-4	3×10^-4	1.23×10^-4	1.5	1.5	7.5
Cr	3×10^-3	3×10^-4	6×10^-5	0.5	42.0	20.0
Ni	2×10^-2	2×10^-2	5.4×10^-3	0.84	0.84	0.84
Hg	3×10^-4	3×10^-4	2.1×10^-5
Pb	3.5×10^-3	3.5×10^-3	5.25×10^-4
Cu	4×10^-2	4×10^-2	1.2×10^-2
Zn	3×10^-1	3×10^-1	6×10^-2

元素	RfD			SF
元素	经口摄入	呼吸摄入	皮肤接触	经口摄入	呼吸摄入	皮肤接触
Cd	1×10^-3	1×10^-3	1×10^-5	6.1	6.4	6.1
As	3×10^-4	3×10^-4	1.23×10^-4	1.5	1.5	7.5
Cr	3×10^-3	3×10^-4	6×10^-5	0.5	42.0	20.0
Ni	2×10^-2	2×10^-2	5.4×10^-3	0.84	0.84	0.84
Hg	3×10^-4	3×10^-4	2.1×10^-5
Pb	3.5×10^-3	3.5×10^-3	5.25×10^-4
Cu	4×10^-2	4×10^-2	1.2×10^-2
Zn	3×10^-1	3×10^-1	6×10^-2

统计值	pH	重金属/(mg/kg)
统计值	pH	Pb	Cr	Cd	Hg	As	Zn	Cu	Ni
平均值	5.32	59.40	44.07	0.46	0.22	27.95	80.66	27.89	13.37
最大值	8.42	164.85	79.28	5.44	0.60	66.52	391.93	144.01	26.94
最小值	3.17	14.35	14.34	0.04	0.04	3.14	24.13	7.72	5.31
中位数	5.34	49.59	43.81	0.17	0.19	26.82	61.72	21.23	12.44
变异系数/%	0.17	52.45	33.02	215.85	62.71	51.98	85.19	90.41	36.27