Ecological Risk Assessment of Heavy Metals in Farmland System from an Area with High Background of Heavy Metals, Southwestern China

doi:10.19657/j.geoscience.1000-8527.2020.068

Abstract

Abstract:

Southwestern China contains high metals (HMs) background, and ecological risk assessment on HMs is important to ensure food security.A total of 242 soil samples (0-20 cm) and 74 sets of rhizosphere soil and crop samples were collected from high-HM background area in Yunnan Province. We analyzed the concentrations of Cd, Hg, Pb, As, Cu, Zn, Ni and Cr in the soil and crop samples, as well as the chemical forms of heavy metals in soil. The results show that most soil samples are acidic (low pH) and low organic matter (OM) content, and the mean Cd, Cr, Cu, Hg, Ni, and Zn contents in the topsoil all exceed the soil background value in Yunnan Province. The average Cd, Cu, and Ni contents are remarkably higher than the screening value specified in the soil contamination risk in agricultural land (GB 15618-2018). Speciation analysis indicates that the HMs (Cr, As, Pb, Cu, Zn, and Ni) mainly exist in the residual form, with low bioavailability and source from the background geology. Cd has a high bioavailability ratio. Distribution of geo-accumulation index (I_geo) of Cd shows that Cd is affected by the superposition of anthropogenic pollution and background geology, and represents the highest pollution risk in the study area. Mercury has a complex source with a low volume and low pollution risk. The HMs concentrations of the staple crops in the study area do not exceed the standard, and the bioconcentration factor (BCF) is below 0.03, thus the food crops are safe for consumption and ecological risks are low. The Cd concentration in tobacco far exceeds the preliminary safety limit standard, and the BCF is 3.13, indicating that tobacco can concentrate much Cd, and affect human health and pose ecological risks. The potential ecological risk index (RI) shows that the descending order of Cd>Hg>Cu>Ni>As>Cr>Pb>Zn, with the contribution ratios of 40.33%, 31.41%, 13.81%, 4.79%, 4.04%, 2.27%, 2.21%, and 1.13%, respectively. Mercury and Cd are the main source of risk because of their high toxicity coefficient.Both Hg and Cd present moderate risk, and the strong risk area is small. The overall ecological risk is low and the risk is controllable in the study area.

Key words: soil heavy metal, crops, farmland system, ecological risk assessment, high background area

CLC Number:

P595
P632

TANG Ruiling, WANG Huiyan, LÜ Xupeng, XU Jinli, XU Renting, ZHANG Fugui. Ecological Risk Assessment of Heavy Metals in Farmland System from an Area with High Background of Heavy Metals, Southwestern China[J]. Geoscience, 2020, 34(05): 917-927.

Figures/Tables 10

References 51

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元素	土壤样品分析方法及仪器	检出限	元素	农作物样品分析方法及仪器	检出限
As	原子荧光光谱法(XGY-1011A)	0.2	As	氢化物-原子荧光光谱法(XGY-2010A)	0.1
Cd	等离子体质谱法(Element XR)	0.02	Cd	等离子体发射光谱法(IRIS Intrepid II)	0.01
Cr	等离子体质谱法(Element XR)	1.5	Cr	等离子体发射光谱法(IRIS Intrepid II)	0.2
Cu	等离子体质谱法(Element XR)	0.1	Cu	等离子体发射光谱法(IRIS Intrepid II)	0.1
Hg	原子荧光光谱法(XGY-1011A)	0.000 5	Hg	氢化物-原子荧光光谱法(XGY-2010A)	0.000 5
Ni	等离子体质谱法(Element XR)	0.2	Ni	等离子体发射光谱法(IRIS Intrepid II)	0.2
Pb	等离子体质谱法(Element XR)	0.2	Pb	等离子体发射光谱法(IRIS Intrepid II)	0.2
Zn	等离子体质谱法(Element XR)	1	Zn	等离子体发射光谱法(IRIS Intrepid II)	1
pH	电位法(PHS-3C)	0.01

元素	土壤样品分析方法及仪器	检出限	元素	农作物样品分析方法及仪器	检出限
As	原子荧光光谱法(XGY-1011A)	0.2	As	氢化物-原子荧光光谱法(XGY-2010A)	0.1
Cd	等离子体质谱法(Element XR)	0.02	Cd	等离子体发射光谱法(IRIS Intrepid II)	0.01
Cr	等离子体质谱法(Element XR)	1.5	Cr	等离子体发射光谱法(IRIS Intrepid II)	0.2
Cu	等离子体质谱法(Element XR)	0.1	Cu	等离子体发射光谱法(IRIS Intrepid II)	0.1
Hg	原子荧光光谱法(XGY-1011A)	0.000 5	Hg	氢化物-原子荧光光谱法(XGY-2010A)	0.000 5
Ni	等离子体质谱法(Element XR)	0.2	Ni	等离子体发射光谱法(IRIS Intrepid II)	0.2
Pb	等离子体质谱法(Element XR)	0.2	Pb	等离子体发射光谱法(IRIS Intrepid II)	0.2
Zn	等离子体质谱法(Element XR)	1	Zn	等离子体发射光谱法(IRIS Intrepid II)	1
pH	电位法(PHS-3C)	0.01

元素	As	Cd	Cr	Cu	Hg	Ni	Pb	Zn	pH
最小值	2.90	0.05	59.60	20.60	0.03	14.30	17.20	31.40	4.26
最大值	87.70	4.12	549.50	400.70	0.44	135.00	73.60	287.90	7.74
平均值	13.60	1.62	135.20	233.80	0.09	74.50	32.80	185.70	6.12
中值	10.40	1.16	113.10	242.10	0.08	73.10	31.50	189.20	5.75
标准差	11.27	1.02	73.06	52.16	0.04	14.36	8.34	33.95	0.95
变异系数/%	82.87	62.96	54.04	22.31	44.44	19.28	25.43	18.28	15.52
云南省土壤背景值^[37]	18.40	0.66	65.20	46.30	0.06	42.50	40.60	89.70	4.26
表层土壤筛选值^[5]	40	0.2	150	050	1.8	070	090	200	< 6.5
	30	0.3	200	100	2.4	100	120	250	6.5~7.5
	25	0.6	250	100	3.4	190	170	300	>7.5

元素	As	Cd	Cr	Cu	Hg	Ni	Pb	Zn	pH
最小值	2.90	0.05	59.60	20.60	0.03	14.30	17.20	31.40	4.26
最大值	87.70	4.12	549.50	400.70	0.44	135.00	73.60	287.90	7.74
平均值	13.60	1.62	135.20	233.80	0.09	74.50	32.80	185.70	6.12
中值	10.40	1.16	113.10	242.10	0.08	73.10	31.50	189.20	5.75
标准差	11.27	1.02	73.06	52.16	0.04	14.36	8.34	33.95	0.95
变异系数/%	82.87	62.96	54.04	22.31	44.44	19.28	25.43	18.28	15.52
云南省土壤背景值^[37]	18.40	0.66	65.20	46.30	0.06	42.50	40.60	89.70	4.26
表层土壤筛选值^[5]	40	0.2	150	050	1.8	070	090	200	< 6.5
	30	0.3	200	100	2.4	100	120	250	6.5~7.5
	25	0.6	250	100	3.4	190	170	300	>7.5

形态	As	Cd	Cr	Cu	Hg	Ni	Pb	Zn
F₁+F₂+F₃	0.08	38.41	1.45	0.08	3.27	0.78	0.11	0.12
F₄+F₅+F₆	3.17	34.79	17.20	2.87	42.05	10.19	3.76	4.11
F₇	96.75	26.80	81.35	97.13	54.68	89.03	96.13	95.77