Distribution characteristics, pollution assessment, and source identification of heavy metals in soils around a landfill-farmland multi-source hybrid district

doi:10.21203/rs.3.rs-329478/v1

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Distribution characteristics, pollution assessment, and source identification of heavy metals in soils around a landfill-farmland multi-source hybrid district

https://doi.org/10.21203/rs.3.rs-329478/v1

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Heavy metal pollution is one of the negative impacts deriving from municipal solid waste landfills. Due to the multiple pollution transport pathways (including leachate, runoff, and waste gas) and complex and co-existing potential pollution sources (such as agricultural activities) around landfills, a combination of different pollution assessment methods and source identification tools are required to address pollution distribution and potential risks. In this study, the distribution of eight heavy metals (chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), arsenic (As), cadmium (Cd), and mercury (Hg)) around a landfill were analyzed using 60 topsoil samples. There are no environmental pollution and human carcinogenic risk posed by the heavy metals for the time being. However, high concentration of Cr in soil would cause non-carcinogenic risk for adults in the study area. Besides, the geo-accumulation indices of Cr, Cu, Ni, Zn, As, and Hg confirmed anthropogenic accumulation of these heavy metals in soils. Additionally, the potential ecological risk index indicated that Hg posed considerable risk to the eco-environment around the landfill. Sources of the heavy metals in the study area were attributed to natural sources (22.1%), agricultural activities (27.6%), and the landfill (50.3%). As the greatest contributor, the landfill affected heavy metal distribution in nearby surface soils mainly via surface runoff and waste gas. The continuous accumulation of heavy metals and non-carcinogenic risk for adults suggests the necessity for continuous monitoring of heavy metal content and migration around the landfill. This study provides a reference for local authorities in the study area.

Environmental Engineering

Environmental Policy

Soil

Heavy metals

Landfill

Distribution characteristics

Pollution assessment.

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Table 1. Summary statistics of heavy metal concentrations (mg kg^-1) in the soils around the landfill and comparison landfills.

				Cr	Cu	Ni	Pb	Zn	As	Cd	Hg
Min				53.58	16.69	12.82	20.41	47.87	7.46	0.07	0.03
Mean ± SE^a				67.77±1.35	23.31±0.54	27.62±0.83	24.71±0.29	63.07±1.41	10.77±0.24	0.10±0.00	0.05±0.00
Max				123.76	30.71	53.79	29.71	109.98	15.99	0.14	0.12
SD^b				10.48	4.15	6.46	2.22	10.92	1.88	0.02	0.01
CV^c				0.15	0.18	0.23	0.09	0.17	0.18	0.15	0.29
Background value				47.48	18.50	18.63	29.63	56.69	5.76	0.14	0.035
Chinese soil guideline^d (pH ≤ 5.5)				150	50	60	70	200	40	0.3	1.3
Chinese soil guideline^d (5.5 ≤ pH ≤ 6.5)				150	50	70	90	200	40	0.3	1.8
Chinese soil guideline^d (6.5 ≤ pH ≤ 7.5)				200	100	100	120	250	30	0.3	2.4

Landfill	Country	Operation time (years)	Disposal capacity (t/d)
Reference [1]	Laos	12	300	14.68	13.65	7.63	18.75	4.59	-	1.04	-
Reference [2]	Czech	21	37.5	77.16	48.41	41.47	4.87	35.25	-	-	0.04
Reference [3]	China	23	5000	86.00	34.00	-	11.60	99.50	-	0.20	-
Reference [4]	Italy	22	-	89.90	25.50	54.80	22.70	87.20	5.60	0.31	0.03

^a Standard error

^b Standard deviation

^c Coefficient of variation

^d Soil environment quality Risk control standard for soil contamination of agricultural land

[1] (Vongdala et al., 2019), [2] (Adamcova et al., 2017), [3] (Liu et al., 2013), [4] (Nannoni et al., 2017)

Table 2. Non-carcinogenic risks and carcinogenic risks posed to adults and children for each element and exposure pathway in the study area.

Element	Adults					Children
Element	HQ_ing	HQ_dermal	HQ_inh	HI=ΣHQ_i	Cancer risk	HQ_ing	HQ_dermal	HQ_inh	HI=ΣHQ_i	Cancer risk
Cr	5.57E+00	1.29E-03	2.37E-04	5.57E+00	2.56E-07	1.31E+01	6.33E-04	2.08E-04	1.31E+01	1.57E-07
Cu	6.32E-02	1.11E-04	1.22E-07	6.33E-02		1.48E-01	5.44E-05	1.07E-07	1.48E-01
Ni	1.57E-01	2.92E-04	2.82E-07	1.57E-01	2.09E-09	3.68E-01	1.43E-04	2.47E-07	3.68E-01	1.28E-09
Pb	1.04E-01	2.68E-04	1.48E-06	1.05E-01		2.45E-01	1.32E-04	1.29E-06	2.45E-01
Zn	6.22E-02	5.99E-05	4.42E-08	6.22E-02		1.46E-01	2.94E-05	3.86E-08	1.46E-01
As	3.54E-01	4.99E-03	7.30E-06	3.59E-01	1.46E-08	8.31E-01	2.45E-03	6.39E-06	8.33E-01	8.97E-09
Cd	2.85E-01	5.69E-04	2.10E-08	2.86E-01	5.66E-11	6.70E-01	2.79E-04	1.83E-08	6.70E-01	3.47E-11
Hg	4.75E-03	1.31E-04	1.18E-07	4.89E-03		1.12E-02	6.43E-05	1.03E-07	1.12E-02

Table 3. Comparison of three groups of sampling sites based on the mean values of heavy metal concentration (C_soil), pollution indices (PI and NIPI), geo-accumulation index (I_geo), and potential ecological risk indices (ER and PER).

	Cr	Cu	Ni	Pb	Zn	As	Cd	Hg	Integrated index
C_soil
Group 1	66.84	23.12	28.49	24.97	62.66	9.66	0.10	0.04
Group 2	67.26	23.46	26.81	25.00	61.87	12.25	0.09	0.06
Group 3	68.30	23.30	27.70	24.50	63.73	10.47	0.10	0.05

PI									NIPI
Group 1	0.45	0.46	0.44	0.31	0.31	0.24	0.34	0.03	0.41
Group 2	0.45	0.47	0.43	0.34	0.31	0.31	0.30	0.04	0.41
Group 3	0.43	0.40	0.38	0.28	0.30	0.28	0.34	0.03	0.39

I_geo
Group 1	-0.10	-0.29	0.00	-0.84	-0.46	0.14	-1.01	-0.45
Group 2	-0.09	-0.25	-0.07	-0.83	-0.47	0.48	-1.24	0.00
Group 3	-0.08	-0.28	-0.06	-0.87	-0.44	0.26	-1.03	-0.16

ER									PER
Group 1	2.82	6.25	7.65	4.21	1.11	16.78	22.33	44.91	106.05
Group 2	2.83	6.34	7.20	4.22	1.09	21.27	19.41	63.17	125.53
Group 3	2.88	6.30	7.43	4.14	1.12	18.18	22.22	54.88	117.15

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First submitted to journal
14 Mar, 2021

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Distribution characteristics, pollution assessment, and source identification of heavy metals in soils around a landfill-farmland multi-source hybrid district

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