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Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment

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A special issue of International Journal of Environmental Research and Public Health (ISSN 1660-4601). This special issue belongs to the section "Environmental Earth Science and Medical Geology".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 27660

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Special Issue Editors

Prof. Dr. Jinling Liu

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Guest Editor

School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
Interests: interaction between microbes and heavy metal/trace element; biogeochemistry of trace element in environment; isotopic geochemisty in environment; environmental pollution and human health

Dr. Jun Zhou

E-Mail Website
Guest Editor

Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts Lowell, Lowell, MA 01854, USA
Interests: mercury exchange fluxes between terrestrial surface and atmosphere

Special Issue Information

Dear Colleagues,

Surface earth environmental pollution by heavy metals has been a global issue due to their adverse effects on public health. These inorganic pollutants occur naturally in the environment from geogenic processes such as weathering of parent material, volcanic emissions and from anthropogenic sources such as agriculture and metal industries, improper waste disposal, fertilizers and pesticides, vehicle exhaust as well as coal and fuel combustion. The overlapping effects of human activities and the original environment, as well as the overlapping effects of historical discharge and later re-release, make it more challenging to quantitatively identify the pollution sources of heavy metals in the environment. On the surface environment of the earth, heavy metals could be interacted with mineral particles, organic matters, microbes, organic pollutants, plastics or other emerging pollutants, making their geochemical behavior in the surface environment more complicated and making their risks difficult to predict and assess. In order to prevent and control heavy metal pollution on the surface earth environment, it is important to provide novel insights for source apportionment of heavy metals, the behaviors and risks of heavy metals influenced by environmental factors, microbes and other pollutants.

This Special Issue of the International Journal of Environmental Research and Public Health (IJERPH) aims to solicit high-quality original research papers, which address the novel methods for source apportionment of heavy metals on the surface earth environment, and the new insight of behaviors and risks of heavy metals influenced by environmental factors, microbes and other pollutants.

New research papers, reviews, case reports, and conference papers are welcome to this issue.

Here are some examples of topics that could be addressed in this Special Issue:

Source discrimination and apportionment of heavy metal
Geochemical behavior of heavy metal in environment
Interaction of heavy metal and minerals in soils
Interaction of heavy metal and organic matters
Interaction of heavy metal and microplastics
Interaction of heavy metal and microbes
Risk of heavy metal in air, water, and soil.

Prof. Dr. Jinling Liu
Dr. Jun Zhou
Guest Editors

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Keywords

heavy metal
microbes
organic matter
source
microplastic
risk
behavior
adsorption
transformation

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Published Papers (12 papers)

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12 pages, 7117 KiB

Open AccessArticle

Reduction of Hexavalent Chromium from Soil of the Relocated Factory Area with Rice Straw Hydrothermal Carbon Modified by Nano Zero-Valent Iron (nZVI)

by Wei Zhong, Weiyang Bai and Gang Li

Int. J. Environ. Res. Public Health 2023, 20(4), 3089; https://doi.org/10.3390/ijerph20043089 - 10 Feb 2023

Cited by 3 | Viewed by 1740

Abstract

In order to reduce the content of Cr(VI) in the soil of the relocated chromium salt factory, the rice straw-derived hydrothermal carbon was prepared by hydrothermal method and loaded with nano zero-valent iron generated by liquid phase reduction, which effectively alleviated the self-aggregation problem of nano zero-valent iron (nZVI) in the treatment of Cr(VI) and improved the Cr(VI) reduction rate without changing the soil structure. The reduction effect of Cr(VI) in soil by key influencing factors such as carbon-iron ratio, initial pH value, and initial temperature was investigated. The results showed that nZVI modified hydro-thermal carbon composite (named RC-nZVI) had a good reduction effect on Cr(VI). Scanning electron microscope (SEM) and energy spectrum analysis showed that nZVI was evenly distributed on the surface of hydrothermal carbon, which effectively reduced the agglomeration of iron. Under the conditions of C/Fe = 1:2, 60 °C, with pH of 2, the average Cr(VI) content in soil decreased from 182.9 mg kg⁻¹ to 21.6 mg kg⁻¹. Adsorption kinetics of Cr(VI) by RC-nZVI fit well with the pseudo-second-order model, and the kinetic velocity constant revealed that Cr(VI) reduction rate decreased with increasing initial Cr(VI) concentration. Cr(VI) reduction by RC-nZVI was mainly dominated by chemical adsorption. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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13 pages, 2588 KiB

Open AccessArticle

Spatial Distribution, Pollution, and Ecological Risk Assessment of Metal(loid)s in Multiple Spheres of the Shennongjia Alpine Critical Zone, Central China

by Xiannong Song, Yongqiang Ning, Shaochen Yang, Jiaxin Ye and Jinling Liu

Int. J. Environ. Res. Public Health 2023, 20(2), 1126; https://doi.org/10.3390/ijerph20021126 - 8 Jan 2023

Viewed by 1775

Abstract

The development of Earth’s critical zone concept has strengthened the capacity of environmental science to better solve real-world problems, such as metal(loid) pollution in the remote alpine areas. The selected metal(loid) contents in soil, moss, and water were investigated to explore the geochemical distribution patterns, pollution levels, and potential ecological risks of metal(loid)s in the Shennongjia (SNJ) alpine critical zone of central China. The distribution of metal(loid)s in different spheres had horizontal and vertical differences. The maximum V, Ni, and Zn contents in water occurred at the sampling sites close to the Hohhot–Beihai Highway, while Dajiuhu Lake had the maximum Cu, Cr, and Mn contents. Most metal(loid) contents in the mosses showed an increasing trend from the northeast low-altitude area to the southwest high-altitude area, while As, Co, V, Ni, Cr, and Zn in soil decreased significantly with altitude and were enriched near the service areas and the highway. The contents of water Co and Ni, soil Cu and Mn, and moss As were evenly distributed and showed no significant differences with altitude. The enrichment factors, pollution index, Nemerow integrated pollution index, geo-accumulation index, heavy metal pollution index, contamination factor, and potential ecological risk index (PERI) were used to assess the pollution levels and ecological risks of SNJ soil, water, and atmosphere. The overall pollution levels of SNJ soil, moss, and water were low to moderate, low, and low, respectively. Soil V, Cu, Zn, moss As, Co, V, and Dajiuhu Lake water Mn were the main pollution factors. The ecological risks in the three spheres of the SNJ alpine critical zone were low to moderate, and As, Co, and V were the most critical potential ecological risk factors. The metal(loid)s pollution problem caused by the continuous development of tourism needs further attention. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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19 pages, 3964 KiB

Open AccessArticle

Enhanced Adsorption of Cd on Iron–Organic Associations Formed by Laccase-Mediated Modification: Implications for the Immobilization of Cadmium in Paddy Soil

by Weilin Yang, Chunlei Huang, Xiang Wan, Yunyun Zhao, Zhengyu Bao and Wu Xiang

Int. J. Environ. Res. Public Health 2022, 19(23), 15650; https://doi.org/10.3390/ijerph192315650 - 25 Nov 2022

Cited by 1 | Viewed by 1620

Abstract

The objectives of this study were to evaluate the cadmium adsorption capacity of iron–organic associations (Fe-OM) formed by laccase-mediated modification and assess the effect of Fe-OM on the immobilization of cadmium in paddy soil. Leaf organic matter (OM) was extracted from Changshan grapefruit leaves, and then dissolved organic matter (Lac-OM) and precipitated organic matter (Lac-P) were obtained by laccase catalytic modification. Different Fe-OM associations were obtained by co-precipitation of Fe with OM, Lac-OM, and Lac-P, respectively, and the adsorption kinetics, adsorption edge, and isothermal adsorption experiments of Cd on Fe-OM were carried out. Based on the in situ generation of Fe-OM, passivation experiments on Cd-contaminated soils with a high geological background were carried out. All types of Fe-OM have a better Cd adsorption capacity than ferrihydrite (FH). The theoretical maximum adsorption capacity of the OM-FH, Lac-OM-FH, and Lac-P-FH were 2.2, 2.53, and 2.98 times higher than that of FH, respectively. The adsorption of Cd on Fe-OM is mainly chemisorption, and the -OH moieties on the Fe-OM surface form an inner-sphere complex with the Cd ions. Lac-OM-FH showed a higher Cd adsorption capacity than OM-FH, which is related to the formation of more oxygen-containing groups in the organic matter modified by laccase. The immobilization effect of Lac-OM-FH on active Cd in soil was also higher than that of OM-FH. The Lac-OM-FH formed by laccase-mediated modification has better Cd adsorption performance, which can effectively inactivate the activity of Cd in paddy soil. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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16 pages, 4052 KiB

Open AccessArticle

Spatial Pattern, Sources Identification, and Risk Assessment of Heavy Metals in a Typical Soda Soil from Bayannur, Northwestern China

by Shuncun Zhang, Tao Wang, Hao Wang, Qiangqiang Kang, Qian Zhou and Bo Chen

Int. J. Environ. Res. Public Health 2022, 19(21), 13880; https://doi.org/10.3390/ijerph192113880 - 25 Oct 2022

Cited by 3 | Viewed by 2443

Abstract

Soil is an important natural resource in the agricultural areas of northwest China. The heavy metal concentration and ecological risk assessments are crucial for food safety and human health. This work collected 35 surface soil samples and focused on a typical soda soil quality of the Hetao Plain in Bayannur, which is an important grain production base in northern China. The concentration and composition of heavy metal (arsenic (As), cobalt (Co), copper (Cu), lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg), nickel (Ni), zinc (Zn)), soluble salts, total organic carbon (TOC), and minerals of the surface soils were analyzed to assess the biotoxicity, ecological risk, sources, and influencing factors of heavy metals in these soda soil from this region. The enrichment factors (EF) showed that As, Co, Cu, and Pb were not contaminated in these soils, while Cd, Cr, Hg, Ni, and Zn were lightly contaminated. The index of geoaccumulation (I_geo) for the soda soils indicated that Co and Pb were uncontaminated, and Cr, Cd, Ni, Zn, Hg, Cu, and As were lightly contaminated. The potential ecological risk index (RI) indicated there were no or low risks for As, Co, Cr, Cu, Ni, Pb, and Zn. Although the concentrations of Cd and Hg in the soil were low, the two heavy metals exhibited moderate–high ecological risk because they have high biological toxicity. Cd in the soils from Hetao Plain in Bayannur is mainly exchangeable and reducible fractions. The other heavy metals in these soda soils are mainly in residue fraction, implying that their mobility is low and not easily absorbed and used by plants. Heavy metal fractions, principal component analysis (PCA), and correlation analysis showed that As, Co, Cr, Cu, and Pb were mainly from natural sources, while Ni, Cd, and Zn were mainly from anthropogenic discharge-related irrigation, fertilizers, and pesticide application, and Hg was mainly from winter snowfall in the study area. Naturally sourced metal elements have obvious sediment properties, and their adsorption by clay minerals and coupling with organic matter along with sediment transport sorting. The salinity and pH of soda soils in the study area have a highly positive correlation, hence the influence of factors on the concentrations of soil heavy metals are consistent. For anthropogenically imported heavy metals, increasing salinity and pH promote the precipitation of metallic elements in water. Cd is present as an exchangeable and reducible fraction, while Ni and Zn are mainly sequestered by organic matter and clay minerals. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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17 pages, 4299 KiB

Open AccessArticle

Concentrations, Speciation, and Potential Release of Hazardous Heavy Metals from the Solid Combustion Residues of Coal-Fired Power Plants

by Yiming Huang, Jinling Liu, Guan Wang, Xiangyang Bi, Guangyi Sun, Xian Wu, Qingfeng Wang and Zhonggen Li

Int. J. Environ. Res. Public Health 2022, 19(19), 12617; https://doi.org/10.3390/ijerph191912617 - 2 Oct 2022

Cited by 4 | Viewed by 1878

Abstract

Hazardous heavy metal-laden coal combustion byproducts exposed to precipitation or surface/groundwater are of environmental concern. This study analyzed fly ash (FA) and desulfurization gypsum (FGD gypsum) samples obtained from 16 coal-fired power plants in Guizhou Province, China. A combination of field and laboratory studies was used to investigate the binding forms of lead (Pb), cadmium (Cd), and chromium (Cr) and their leaching characteristics under natural storage conditions. The results showed that there were significant proportions of residual states of these elements in FA (84–99% for Pb, 83–91% for Cd, and 73–97% for Cr), indicating a lack of migration to other environmental media. FGD gypsum contained high proportions of metals in migratable states, but the environmental risks were low due to their very low concentrations. The release of Pb, Cd, and Cr from FA and FGD gypsum into extracts varied according to pH. This is related to the form of each element in the solid and the series of reactions that occurs during the leaching process. However, aside from Cr in FA, all heavy metals in FA and FGD gypsum samples were present in concentrations below the relevant standards for landfill leachate, indicating very low release rates. The Cr levels (206–273 μg/L) in some of the FA extracts were higher than the limits for water pollution from domestic landfill, indicating that Cr in FA poses a leaching risk. The results of field leachate sampling and indoor simulated rainfall experiments further validated these findings, indicating that the release of Cr from stockpiled coal FA is a cause for concern. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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15 pages, 1826 KiB

Open AccessArticle

Comparison of Pollution Levels, Biomagnification Capacity, and Risk Assessments of Heavy Metals in Nearshore and Offshore Regions of the South China Sea

by Shaochen Yang, Kaifeng Sun, Jinling Liu, Nan Wei and Xing Zhao

Int. J. Environ. Res. Public Health 2022, 19(19), 12248; https://doi.org/10.3390/ijerph191912248 - 27 Sep 2022

Cited by 4 | Viewed by 1757

Abstract

Seawater and fish were collected from nearshore (Pearl River Estuarine, PRE) and offshore (middle of the South China Sea, MSCS) regions of the South China Sea (SCS) to determine the heavy metals (HMs) pollution status and biomagnification characteristics. Results show that Cu in PRE seawater was moderately contaminated. Overall pollution risk of seawater were PRE (3.32) > MSCS (0.56), whereas that of fish was MSCS (0.88) > PRE (0.42). δ¹³C and δ¹⁵N exhibited distinguished characteristics for PRE and MSCS fish, indicating the diverse energy sources, nitrogen sources, and food web structures of nearshore and offshore regions. Cu was biomagnified whereas Pb and Ni were biodiluted in offshore fish. Hg presented significant biomagnification in both of nearshore and offshore fish. Finally, the target hazard quotient of Hg (1.41) in MSCS fish exceeded the standard limit, which was posed by high Hg concentration and consumption rate of offshore fish. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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12 pages, 4109 KiB

Open AccessArticle

Distribution of Mercury and Methylmercury in Farmland Soils Affected by Manganese Mining and Smelting Activities

by Yongjiang Zhang, Xian Zhou, Weibin Ma, Deliang Yin, Yongmin Wang, Cheng Zhang and Dingyong Wang

Int. J. Environ. Res. Public Health 2022, 19(16), 10288; https://doi.org/10.3390/ijerph191610288 - 18 Aug 2022

Cited by 3 | Viewed by 1387

Abstract

Manganese (Mn)-related activities would affect the mercury (Hg) cycling in farmlands, whereas this was not well understood. Here, one of the largest Mn ores in China was selected to study the effects of Mn-related activities on the accumulation and distribution of total Hg (THg) and methylmercury (MeHg) in farmland soils. The soil THg concentrations in the mining area were 0.56 ± 0.45, 0.56 ± 0.45, 0.53 ± 0.44, and 0.50 ± 0.46 mg kg⁻¹ in the 0–10, 10–20, 20–30, and 30–40 cm layers, respectively, while they were increased to 0.75 ± 0.75, 0.72 ± 0.60, 0.62 ± 0.46, and 0.52 ± 0.38 mg kg⁻¹ in the smelting area. Similarly, the soil MeHg concentrations in the smelting area were also elevated by 1.04–1.34 times as compared to those in the mining area. Concentrations of THg (0.59 ± 0.50 mg kg⁻¹) and MeHg (0.64 ± 0.82 μg kg⁻¹) in soils were higher than the regional background value but lower than in vicinal Hg-mining areas, while they were largely elevated at the intersection of two rivers in the smelting area. Significant positive Mn-THg relationship (p < 0.01) and negative Mn-MeHg relationship (p < 0.01) favored the conclusion that soil Mn could promote Hg accumulation while inhibiting MeHg production. Approximately 70% of soil Hg was distributed in the residual phase, and the environmental hazard was not elevated according to a geochemical model. Overall, mining and smelting activities of Mn ores have resulted in obvious and distinct effects on the accumulation and methylation of Hg in farmland soils, but the environmental hazards are currently manageable. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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12 pages, 1994 KiB

Open AccessArticle

Accumulation of Co, Ni, Cu, Zn and Cd in Aboveground Organs of Chinese Winter Jujube from the Yellow River Delta, China

by Zaiwang Zhang, Qiong Zhang, Guoli Liu, Jian Zhao, Wenjun Xie, Shuai Shang, Jie Luo, Juanjuan Liu, Wenwen Huang, Jialiang Li, Yanpeng Zhang, Jikun Xu and Jiqiang Zhang

Int. J. Environ. Res. Public Health 2022, 19(16), 10278; https://doi.org/10.3390/ijerph191610278 - 18 Aug 2022

Viewed by 1596

Abstract

In the present study, winter jujube organs including fruit, fruiting leaf and foliage leaf, and associated soils in 14 typical orchards in Binzhou City, Shandong Province, China were collected and determined for the mass fractions of Co, Ni, Cu, Zn, and Cd. The mass fractions of Co, Ni, Cu, Zn, and Cd in plant tissues generally showed an order of Cu > Zn > Ni > Co > Cd as well as those in the soils decreased as Zn > Cu > Ni > Co > Cd. The values of single factor index and Nemerow pollution index suggested the jujube fruits were not polluted by heavy metals. Values of estimated daily intake for all the elements were far below their associated acceptable reference values, indicating no health risks would be caused by a single trace element. The results of targeted hazard quotient (THQ) of the metals in the fruits decreased as Cu > Ni > Zn > Cd accompanying total THQ (TTHQ) lower than 1 showing no hazard would be caused by those metals. Correlation analysis showed soil might not be the main source of heavy metals in winter jujube organs. Bioaccumulation factors (BAFs) for Co, Ni, Zn and Cd in fruits and leaves were far below 1 suggesting their low bioavailablities. The relatively great BAFs of Cu in the leaves might be due to the application of fertilizers and pesticides containing great amounts of Cu through soil and foliar spraying. To sum up, heavy metals tended not to be a major threat to winter jujube cultivation, and winter jujube had great edible safety. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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17 pages, 3059 KiB

Open AccessArticle

Distribution, Assessment, and Source of Heavy Metals in Sediments of the Qinjiang River, China

by Shuncun Zhang, Bo Chen, Junru Du, Tao Wang, Haixin Shi and Feng Wang

Int. J. Environ. Res. Public Health 2022, 19(15), 9140; https://doi.org/10.3390/ijerph19159140 - 26 Jul 2022

Cited by 24 | Viewed by 2647

Abstract

Heavy metals are toxic, persistent, and non-degradable. After sedimentation and adsorption, they accumulate in water sediments. The aim of this study was to assess the extent of heavy metal pollution of Qinjiang River sediments and its effects on the ecological environment and apportioning sources. The mean total concentrations of Mn, Zn, Cr, Cu, and Pb are 3.14, 2.33, 1.39, 5.79, and 1.33 times higher than the background values, respectively. Co, Ni, and Cd concentrations are lower than the background values. Fe, Co, Ni, Cd, Cr, Cu, and Pb are all primarily in the residual state, while Mn and Zn are primarily in the acid-soluble and oxidizable states, respectively. Igeo, RI, SQGs, and RAC together indicate that the pollution status and ecological risk of heavy metals in Qinjiang River sediments are generally moderate; among them, Fe, Co, Ni, Cd, Cr, and Pb are not harmful to the ecological environment of the Qinjiang River. Cu is not readily released because of its higher residual composition, suggesting that Cu is less harmful to the ecological environment. Mn and Zn, as the primary pollution factors of the Qinjiang River, are harmful to the ecological environment. This heavy metal pollution in surface sediments of the Qinjiang River primarily comes from manganese and zinc ore mining. Manganese carbonate and its weathered secondary manganese oxide are frequently associated with a significant amount of residual copper and Cd, as a higher pH is suitable for the deposition and enrichment of these heavy metals. Lead–zinc ore and its weathering products form organic compounds with residual Fe, Co, Cr, and Ni, and their content is related to salinity. The risk assessment results of heavy metals in sediments provide an important theoretical basis for the prevention and control of heavy metal pollution in Qinjiang River. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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15 pages, 3403 KiB

Open AccessArticle

Arbuscular Mycorrhizal Fungi and Glomalin Play a Crucial Role in Soil Aggregate Stability in Pb-Contaminated Soil

by Yinong Li, Jiazheng Xu, Jin Hu, Tianyu Zhang, Xuefeng Wu and Yurong Yang

Int. J. Environ. Res. Public Health 2022, 19(9), 5029; https://doi.org/10.3390/ijerph19095029 - 21 Apr 2022

Cited by 18 | Viewed by 3062

Abstract

With the rapid development of industrialization and urbanization, soil contamination with heavy metal (HM) has gradually become a global environmental problem. Lead (Pb) is one of the most abundant toxic metals in soil and high concentrations of Pb can inhibit plant growth, harm human health, and damage soil properties, including quality and stability. Arbuscular mycorrhizal fungi (AMF) are a type of obligate symbiotic soil microorganism forming symbiotic associations with most terrestrial plants, which play an essential role in the remediation of HM-polluted soils. In this study, we investigated the effects of AMF on the stability of soil aggregates under Pb stress in a pot experiment. The results showed that the hyphal density (HLD) and spore density (SPD) of the AMF in the soil were significantly reduced at Pb stress levels of 1000 mg kg⁻¹ and 2000 mg kg⁻¹. AMF inoculation strongly improved the concentration of glomalin-related soil protein (GRSP). The percentage of soil particles >2 mm and 2–1 mm in the AMF-inoculation treatment was higher than that in the non-AMF-inoculation treatment, while the Pb stress increased the percentage of soil particles <0.053 mm and 0.25–0.53 mm. HLD, total glomalin-related soil protein (T-GRSP), and easily extractable glomalin-related soil protein (EE-GRSP) were the three dominant factors regulating the stability of the soil aggregates, based on the random forest model analysis. Furthermore, the structural equation modeling analysis indicated that the Pb stress exerted an indirect effect on the soil-aggregate stability by regulating the HLD or the GRSP, while only the GRSP had a direct effect on the mean weight diameter (MWD) and geometric mean diameter (GMD). The current study increases the understanding of the mechanism through which soil degradation is caused by Pb stress, and emphasizes the crucial importance of glomalin in maintaining the soil-aggregate stability in HM-contaminated ecosystems. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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12 pages, 833 KiB

Open AccessArticle

Racial Disparities in the Heavy Metal Contamination of Urban Soil in the Southeastern United States

by Daleniece Higgins Jones, Xinhua Yu, Qian Guo, Xiaoli Duan and Chunrong Jia

Int. J. Environ. Res. Public Health 2022, 19(3), 1105; https://doi.org/10.3390/ijerph19031105 - 19 Jan 2022

Cited by 26 | Viewed by 4082

Abstract

(1) Background: Field monitoring data for addressing the disproportional burden of exposure to soil contamination in communities of minority and low socioeconomic status (SES) are sparse. This study aims to examine the association between soil heavy metal levels, SES, and racial composition. (2) Methods: A total of 423 soil samples were collected in the urban areas of eight cities across six Southern states in the U.S., in 2015. Samples were analyzed using inductively coupled plasma–mass spectrometry (ICP–MS) for eight heavy metals. The association was examined with mixed models with the log-transformed metal concentrations as the dependent variables and rankings of low-income or minority percentages as the explanatory variables. (3) Results: Model results showed that soil metal concentrations were significantly associated with rankings of poverty and minority percentages. The cadmium concentration significantly increased by 4.7% (p-value < 0.01), for every 10 percentiles of increase in poverty rank. For every 10 percentiles of increase in minority rank, the soil concentrations were significantly up (p-values < 0.01) for arsenic (13.5%), cadmium (5.5%), and lead (10.6%). Minority rank had significant direct effects on both arsenic and lead. (4) Conclusions: The findings confirmed elevated heavy metal contamination in urban soil in low-income and/or predominantly minority communities. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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12 pages, 2083 KiB

Open AccessReview

Bibliometric Analysis of the Influencing Factors, Derivation, and Application of Heavy Metal Thresholds in Soil

by Zhaolin Du, Dasong Lin, Haifeng Li, Yang Li, Hongan Chen, Weiqiang Dou, Li Qin and Yi An

Int. J. Environ. Res. Public Health 2022, 19(11), 6561; https://doi.org/10.3390/ijerph19116561 - 27 May 2022

Cited by 2 | Viewed by 2487

Abstract

The study of threshold levels of heavy metals in soil is essential for the assessment and management of soil environmental quality. This study reviewed the influencing factors, the derivation, and application aspects of heavy metals’ threshold values comprehensively by a combination of bibliometric analysis and scientific knowledge mapping. A total of 1106 related studies were comprehensively extracted from the Web of Science database during the period from 2001 to 2020. The results showed that the publication output has been growing strongly. An analysis on the subject, journal, country, and institution was carried out to demonstrate the development and evolution of this research branch during the two decades. According to high-frequency keywords analysis, external factors (e.g., soil physicochemical properties) and internal factors (e.g., crop genotype) can affect heavy metal threshold values in the soil–crop system. The current methods mainly include the Point model (e.g., evaluation factor method), the Probability model (e.g., species sensitivity distribution method), and the Empirical model (e.g., ecological environment effect method). A threshold study can be applicable to the risk assessment for soil heavy metal contamination in order to determinate the soil pollution degree and its spatial and temporal distribution characteristics. Moreover, challenges and prospects of the study of heavy metal threshold values are proposed, indicating that research should focus on the relationships between human health risks and the established threshold values of heavy metals in the soil, long-term field trials and bioavailability of heavy metals for the derivation of the thresholds, and the establishment of more scientific and rational soil environmental benchmarks. Full article

(This article belongs to the Special Issue Sources, Behavior and Risk of Heavy Metal in the Surface Earth Environment)

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