Management Of Heavy Metal Pollution Research Articles

Stepwise extraction of Fe, Si from copper slag and self-assembly synthesis of microspheres for As(V) removal: Resource transformation and environmental governance

Heavy metal pollution control and industrial solid waste management have always been urgent environmental issues. The management of heavy metal pollution through industrial solid waste may be a solution to both problems. In this paper, copper slag (CS) is used as a base material to separate the iron and silicon with a relatively high percentage of content. The Fe-mSiO2/SA (FSA), a microsphere (Φ = 2–3 mm) adsorbent with specific adsorption capacity for As(Ⅴ), was finally synthesized by “Acid leaching & Alkaline extraction & Template synthesis & Gelatinization”. The optimal adsorption conditions were explored using response surface methodology. FSA has a wide range of pH applicability (3–9) and the maximum adsorption capacity is 140.45 mg/g by theoretical calculation. The adsorption process follows pseudo-second-order kinetic model, which indicates that the adsorption process is a surface homogeneous monolayer adsorption controlled by chemisorption mechanism. The synthesis mechanism of FSA was explored by systematic characterization of FSA, and the mechanism of As(Ⅴ) adsorption was elucidated. The −OH and FeOOH formed stable single-tooth or double-tooth complexes with As(Ⅴ) on the surface of FSA. Moreover, the unique spherical structure of FSA facilitates subsequent solid–liquid separation. This study is in line with the concept of economic applicability and “waste for waste”.

Numerical simulation of heavy metal migration in stabilized soils under multi-field coupling

Heavy metal contamination of soils has become a global issue. In pursuit of a reference for the management of heavy metal pollution, numerical simulations were used here to investigate the migration pattern of heavy metals in soil under multi-field coupling of rainfall, temperature, and hydraulic conductivity. Models were built using TOUGHREACT, and measured and simulated values were compared with those of existing studies to verify the accuracy of the software in simulating coupled water vapor-thermal transport and rainfall infiltration. Taking Nanjing rainfall data as an example, the transport pattern of zinc in soil under multi-field coupling was explored. Although evaporation and rainwater infiltration were found to increase with the temperature, the effects of evaporation and temperature counteracted each other, resulting in a weak influence of temperature on heavy metal transport. The hydraulic conductivity of stabilized soil was the main factor controlling zinc migration, with the saturation and heavy metal concentration clouds of soil columns tending to stabilize when the hydraulic conductivity of solidified soil was under 1 × 10-11 m/s.

Analysis of the Source Apportionment and Pathways of Heavy Metals in Soil in a Coal Mining Area Based on Machine Learning and an APCS-MLR Model

Long-term coal mining activities have led to severe heavy metal pollution in the soil environment of coal mining areas, posing significant threats to both ecological environments and human health. In this study, surface soil samples were collected from the overlying soil of coal gangue and the surrounding areas of the Panyi coal mine in Huainan. The concentrations of Cd, Zn, Cu, Ni, and Pb elements were determined. A self-organizing map (SOM) and an absolute principal component score multiple linear regression (APCS-MLR) receptor model were employed for the quantitative analysis of the soil’s heavy metal pollution sources and contributions. Additionally, this study focused on the analysis of the pathways of the relatively serious pollution of Cd. The results revealed that the average concentrations of heavy metals (Cd, Pb, Zn, Cu, Cr, and Ni) in the study area were 4.55, 0.59, 1.54, 0.69, 0.59, and 0.71 times the local soil background values, respectively. The concentrations of Cd and Zn exceeded the risk screening values at some sampling points, with exceedance rates of 44% and 8%, respectively, indicating a relatively serious Cd contamination. The sources of heavy metals in the soil in the study area were classified into four categories: mining activities, agricultural activities, weathering of natural matrices, and other unknown sources, with average contributions of 55.48 percent, 24.44 percent, 8.91 percent and 11.86 percent, respectively. Based on the spatial distribution of Cd, it was inferred that atmospheric deposition is one of the important pollution pathways of Cd in the study area. Cd profile distribution patterns and a surface water pollution survey showed that the farmland areas were affected by the irrigation water pathway to some extent. The vertical distribution of heavy metal content in the forest area showed a strong disorder, which was related to the absorption function of plant roots. The results of this study can help to improve the environmental management of heavy metal pollution so as to protect the ecological environment and human health.

Characteristics and Sources of Heavy Metal Pollution in Cropland near a Typical Lead–Zinc Processing Plant in Xieping Village, Hui County, China

Metal beneficiation activities may cause soil pollution in the surrounding cropland, making it crucial to conduct heavy metal pollution assessment and source analysis of the cultivated land in mining areas for the protection of the ecological environment and human health. In this study, a total of 205 surface soil samples (0–20 cm) were collected on site from the Tianheba cropland near the lead–zinc concentrator in Xieping Village, Huixian County, Gansu Province, China; their pH values and their SOM, Zn, As, Cd, Cr, Hg, and Pb contents were determined. Based on the data, we used the Kriging spatial interpolation, the Nemero index, the index of geoaccumulation, and the PMF model to analyze the characteristics of the spatial distribution of soil heavy metals in the region, the degree of contamination, the sources, and the contribution rate. The results indicated that the heavy metals with contamination levels in the Tianheba cropland were Cd, Zn, Pb, Hg, As, and Cr in descending order, with the average concentrations of Cd (0.39 mg/kg), Zn (122 mg/kg), Pb (30.4 mg/kg), and Hg (0.07 mg/kg) being significantly higher than the background values of the Gansu soils. The soil in the region as a whole was heavily polluted; it was heavily polluted with Cd, moderately polluted with Zn, and mildly polluted with Pb. Hg had a larger value in the index of geoaccumulation. By analyzing the spatial distribution and sources of the soil metals, it was found that the cropland contaminated with heavy metals in Tianheba was distributed around the mineral processing plant and the infiltration area of the canal. The PMF model revealed three pollution sources: the industrial source related to mining activities, the fertilizer application source, and the natural source. This study provides a scientific basis for the precise management of heavy metal pollution in the area.

Mechanisms of lead-containing pigment discoloration caused by Naumannella cuiyingiana AFT2T isolated from 1500 years tomb wall painting of China

Biodeterioration of ancient wall paintings is a ubiquitous phenomenon that threatens the long-term survival of invaluable cultural heritage. In this study, the Naumannella cuiyingiana AFT2T, isolated from the surface of tomb paintings dating back 1500 years, was observed to be capable of altering the appearing colors of Pb-containing pigments. By a combination of physiological and biochemical measurements and transcriptomic analysis of strain AFT2T under Pb amendment treatments, the discoloration mechanisms were investigated further in depth. Incubation experiments showed that the discoloration reaction resulted from an interaction between Pb-containing pigments and strain AFT2T cells. Subsequently, we found that strain AFT2T had ability to assimilate Pb ions from pigments by using EDX mapping. Finally, after comparing to the controls, it is speculated that the observed discoloration is the formation of cellular product PbS and a series of additional tests were conducted to verify this. In addition, controlling the chemical composition in the culture medium was utilized to confirm the source of S which might be related to the sulfur-containing amino acids of animal proteins in the medium. Transcriptomic analysis exhibited that Pb stress strongly affected the expression of some genes in strain AFT2T, such as metal ion transport and metabolism genes and genes related to the TlpA family protein disulfide reductases. Among them, the gene of the enzyme with disulfide-bond reducing properties and the gene encoding the divalent Pb ion uptake transporter are the key genes in the process of discoloration. A combination of biochemical reactions and transcriptomic analysis was utilized to reveal the key genes involved in the discoloration of Pb-containing pigments by strain AFT2T. These results provide not only new insights and a theoretical basis for the conservation of cultural relics but also a new means for the management of heavy metal pollution in the environments.

Distribution, Sources, and Ecological Risk Evaluation of Heavy Metals in Surface Sediments of Taihu Lake

For the surface sediment samples of Taihu Lake in 2010, the eight physicochemical indices of pH, temperature, Eh, water content, porosity, grain size, total phosphorus, and Loss-on-ignition were measured and analyzed, along with the contents of nine heavy metals:Cu, Zn, Ni, Cr, Pb, Ba, Mn, Co, and V. The order of magnitudes of heavy metal content of surface sediments in Taihu Lake was:Mn>Ba>Zn>Cr>V>Ni>Pb>Cu>Co. This suggested that the contents of the nine heavy metals were beyond the background value, which had a close connection to the geology of the Taihu Lake Basin and were influenced by human activity to varying degrees. The clustering analysis and the spatial distribution of the heavy metals revealed that the concentrations of heavy metals in the North and South Taihu Lake sections decreased from the lake shore to the lake center, the concentrations of heavy metals in the West Taihu Lake section increased from the lake shore to the lake center, and the distribution of heavy metals in the center of the lake remained relatively uniform. According to the correlation study, the metal elements were positively correlated with one another to varying degrees, indicating that they originate from the same source of pollution. According to the PCA and PMF analyses, there were some different sources of heavy metals in Taihu Lake, in which the transportation and industrial complex source were the most important sources, the diagenesis was the second major source, and agriculture was the third major source. Furthermore, the heavy metal pollution was evaluated using the geoaccumulation and the potential ecological risk indices. This offers a solid theoretical backing for the future management of heavy metal pollution in Taihu Lake.

Assessment of soil quality in hanzhong city based on risk management of heavy metal pollution

In the present study, Hanzhong City was taken as an example, and the classification of soil heavy metal pollution risks was performed based on the evaluation of soil fertility status with soil physical and chemical properties as the main indicators. Results showed that the coefficients of variation of soil physical and chemical indicators in the study area were in the descending order: the soil fertility status showed a trend of increasing with decreasing terrain and increasing rivers. The high fertility areas were mainly distributed in the northwest and northeast of the plain area, while the low fertility areas were mainly distributed in the southeastern hilly and mountainous areas and in the western low-lying areas, and the transitional areas surrounded the low-fertility areas. At least 88.89% of the Cd samples and 98.61% of the Cr samples out of the eight heavy metals, Cd, Hg, As, Pb, Cr, Ni, Cu, and Zn, belonged to the priority protection class, while 11.11% of the Cd samples and 1.39% of the Cr samples belonged to the safe use class. The overall distribution of soil quality was similar to that of soil fertility status, while the distribution range of low-quality soil in the southeastern part was smaller and more concentrated. The above research results indicate that the introduction of the classification results of soil pollution risk control types generally reduces the soil fertility status correction and changes the spatial distribution pattern of the original soil fertility status to some extent. Bangladesh J. Bot. 52(2): 659-669, 2023 (June) Special

Assessment of soil quality in hanzhong city based on risk management of heavy metal pollution

In the present study, Hanzhong City was taken as an example, and the classification of soil heavy metal pollution risks was performed based on the evaluation of soil fertility status with soil physical and chemical properties as the main indicators. Results showed that the coefficients of variation of soil physical and chemical indicators in the study area were in the descending order: the soil fertility status showed a trend of increasing with decreasing terrain and increasing rivers. The high fertility areas were mainly distributed in the northwest and northeast of the plain area, while the low fertility areas were mainly distributed in the southeastern hilly and mountainous areas and in the western low-lying areas, and the transitional areas surrounded the low-fertility areas. At least 88.89% of the Cd samples and 98.61% of the Cr samples out of the eight heavy metals, Cd, Hg, As, Pb, Cr, Ni, Cu, and Zn, belonged to the priority protection class, while 11.11% of the Cd samples and 1.39% of the Cr samples belonged to the safe use class. The overall distribution of soil quality was similar to that of soil fertility status, while the distribution range of low-quality soil in the southeastern part was smaller and more concentrated. The above research results indicate that the introduction of the classification results of soil pollution risk control types generally reduces the soil fertility status correction and changes the spatial distribution pattern of the original soil fertility status to some extent. Bangladesh J. Bot. 52(2): 659-669, 2023 (June) Special

Impact of different industrial activities on heavy metals in floodplain soil and ecological risk assessment based on bioavailability: A case study from the Middle Yellow River Basin, northern China

Understanding the impact of different industrial activities on heavy metals and conducting scientific ecological risk assessments are critical to the management of heavy metal pollution. The present study compared soils affected by different industrial activities in three types of industrial cities (coal city, oil-gas city, and economic city) to control samples and examined the ecological risk based on bioavailability in the Middle Yellow River Basin. The findings revealed that the impact characteristics of different industrial activities on soil heavy metals in the research area were different. Both coal-based and oil-gas industry activities had a minor impact on soil heavy metals, whereas economic industry activities in the southern part had a major impact, as evidenced by significant enrichment of Cd, Hg, Cu, Pb, and Zn. In principal component analysis, the soil heavy metals affected by economic industry activities designated a distinct source from the control samples, particularly the anthropogenic sources represented by Hg and Cd. In the context of heavy metals in chemical form, three types of industrial activities all had an effect on bioavailability (0.72–24.27%) and could increase migratory activity in the environment. Furthermore, both traditional and improved assessments, based on total content and bioavailability, showed a low ecological risk near coal cities and oil-gas cities in the middle and northern parts, while there was a medium-high ecological risk near economically developed cities in the south, particularly Tianshui, Baoji, Qishan, Xianyang, Xi'an, and Tongchuan. In comparison, improved risk assessment based on bioavailability tends to not only compensate for an overestimation in traditional risk assessment from the perspective of total content, but additionally achieve a more reasonable, effective, and advanced assessment of heavy metal risks in scientific research. The outcome of this study has significance for the ecological conservation and high-quality development of the Yellow River Basin.

Study on the Combined Behaviour of Montmorillonite and Carbonate Mineralizing Bacteria on Lead Retention and Fixation

Heavy metal pollution management is a global environmental problem that poses a great threat to the ecological environment. Adsorption and biomineralization are considered to be the two most promising heavy metal pollution remediation techniques among the numerous available ones. In this work, a combined heavy metal removal system was constructed employing the adsorption of montmorillonite and the mineralization of carbonate mineralizing bacteria to expand their application potential for controlling heavy metal water pollution. Analysis of changes in pH, CO32− concentration, Pb2+ concentration in the liquid phase, and changes in microscopic morphology, mineral phase, and functional group on sedimentary minerals was done to study the retention and fixation behaviour of montmorillonite and carbonate mineralizing bacteria on Pb2+. The results show that the liquid phase pH may be slightly altered by the ions dissolved in montmorillonite. Based on the conditions of montmorillonite and carbonate mineralizing bacteria functioning separately, the elimination of Pb2+ may reach 35.31% and 45.75%, respectively. However, when montmorillonite is combined with carbonate mineralizing bacteria, which is the heavy metal removal system constructed in this study, montmorillonite can buffer part of the Pb2+ rapidly and reduce its biotoxicity. Subsequently, these buffered Pb2+ are gradually desorbed by carbonate mineralizing bacteria and removed by the effect of mineralized deposition. Results from SEM, FTIR, and XRD indicate that Pb2+ is primarily removed from the liquid phase as rod-shaped PbCO3. It is worth noting that this process is able to significantly increase the removal of Pb2+ up to 90.06%. In addition, the presence of carbonate mineralizing bacteria can increase montmorillonite’s desorption rate to over 81%, greatly enhancing its capacity for reuse. Therefore, our research work contributes to expanding the potential of montmorillonite and carbonate mineralizing bacteria in the treatment of heavy metal-polluted waters.

Diversity and Heavy Metal Tolerance of Fungi Associated with Different Coal Overburden Strata of Tikak Colliery, Assam.

Coal mine overburdens are generally highly acidic and contaminated with toxic heavy metals. Here, we studied the culturable fungal diversity associated with different coal overburden strata (OBS) of Assam, India, and assessed their heavy metal tolerance ability against five different heavy metals viz., As3+, Cd2+, Cr6+, Cu2+, and Ni2+. Among 15 distinct coal OBS considered in this study which spans a depth of ~ 35m from the ground surface, the isolation of fungi was successful only from 11 OBS samples and the colony-forming unit (CFU) counts were highly variable among the samples. A total of 66 fungal pure cultures were isolated which belong to 18 genera (17 known and 1 unknown) under 15 families and two divisions i.e., Ascomycota (89.4%) and Basidiomycota (10.6%). Acidiella bohemica was found relatively the most abundant species followed by Rhodotorula toruloides. A good number of fungal isolates was found tolerant to the test heavy metals at concentrations ≥ 1mM. Findings of some multi-metallotolerant fungal isolates along with a tolerance up to 5mM concentration of As3+, and up to 10mM each of Cu2+, Cr6+, Ni2+ and Cd2+ were noteworthy in the present study that could be useful in the management of heavy metal pollution or stress. Cultivable fungal diversity of coal mine overburden strata of Tikak colliery, Margherita, Assam, India. It shows a photograph of the coal mining site as the background, front view of the fungal colonies in the upper section, and a graphical representation of heavy metal tolerance of the isolates at different concentrations of As, Cd, Cr, Cu, and Ni in the lower section.

Identification and hazard analysis of heavy metal sources in agricultural soils in ancient mining areas: A quantitative method based on the receptor model and risk assessment,

Industry in ancient mining areas caused significant heavy metal pollution (HMP) in agricultural soils. This study measured the hazards of specific sources of heavy metals (HMs) in an ancient mining areas agricultural soil. Firstly, we identified the major pollution sources based on the PMF model. Then, the proposed single-factor pollution load index (SPLIzone) and ecological load index (SELIzone) analyzed the integrated pollution and ecological risks of various elements. Finally, the source-specific soil contamination levels and ecological risks were quantified by combining the source assignment and single-factor assessment processes. SPLIzone and SELIzone showed that Cu and Cd were the most contaminated elements. Five factors were determined as the major sources of HMs, including mining, natural, smelting industry, agricultural and traffic sources. The mining sources contributed the most soil contamination (33.73%). However, the largest contributor to ecological risk was the smelting industrial (42.18%). Lower soil contamination may contain higher ecological risk. Smelting industrial and traffic are the most critical sources that need to be controlled at present. This study proposes a quantitative method for assessing the hazards of HM sources, which provides a beneficial reference for the study and management of HMP.

Spatial analysis and risk assessment of heavy metal pollution in rice in Fujian Province, China

To comprehensively understand the spatial characteristics and pollution hazards of heavy metals in rice in Fujian Province, the contents of Cd, Hg, As, Pb, Cr, Ni, Cu, and Zn in 260 rice samples were measured based on the field investigation. Their spatial distribution patterns and clustering characteristics were explored by geostatistical methods, and their pollution-health risks were revealed by the pollution index method and exposure evaluation model. The results showed that the average contents of eight heavy metals in rice were below the food safety limits, but the excess rates of As, Cu, and Cd samples reached 33.08%, 22.69%, and 18.85%, respectively. In terms of spatial characteristics, the contents of Cd, Hg, and Ni were higher in the southeastern and northwestern regions, while the contents of As, Cu, and Cr were higher in the southwestern parts of Fujian Province. The hotspots of the corresponding heavy metals were also concentrated in the above-mentioned areas, showing an obvious spatial clustering effect. The pollution risk assessment showed that the single factor pollution index of heavy metals in rice decreased in the order of As (0.536) > Hg (0.505) > Cu (0.421) > Cd (0.378) > Cr (0.318) > Zn (0.304) > Pb (0.286) > Ni (0.116), and the Nemerow comprehensive pollution index was 0.623, which was generally at a safe level with low pollution risk. Furthermore, the non-carcinogenic risk index of heavy metals for adults and children were 3.558 and 6.014, and the carcinogenic risk index were 0.0050 and 0.0084, respectively, with extremely serious health hazards. In contrast, the health damage of heavy metals was higher in children than that in adults, with As and Cd in rice as the pivotal elements. Therefore, attention should be paid to the future monitoring and agricultural management of heavy metal pollution in rice in the region.

Characteristics of Heavy Metal Pollution in Farmland Soil of the Yangtze River Economic Belt Based on Bibliometric Analysis

The Yangtze River Economic Belt is one of the major strategic development regions in China. It is of great significance to clarify the characteristics and sources of heavy metal pollution in farmland soil of the Yangtze River Economic Belt for the prevention and control of heavy metal pollution and to ensure safe agricultural production. After collecting extensive literature data, we analyzed the pollution characteristics, environmental risk, and potential sources of heavy metals (Cd, Cr, Hg, As, Pb, Cu, Zn, and Ni) in farmland soil of the Yangtze River Economic Belt through the integrated use of spatial and geo-accumulation index analyses. The results showed that:① the proportion of soil samples exceeding the risk screening values for soil contamination of agricultural land of Cd, Cu, Pb, Hg, Zn, and As were 39.8%, 18.5%, 8.3%, 6.9%, 6.9%, and 6.4%, respectively. Compared with the risk standard, soil Cd had the highest rate of exceeding the standard. ② The contents of Cr, Cu, Zn, and Ni in the upper reaches were higher than those in the middle and lower reaches, and the contents of Cd, As, and Pb in the middle reaches were higher than those in the upper and lower reaches. ③ The results of the geo-accumulation index analysis showed that the contamination degree of the eight heavy metals decreased in the order of Cd(0.42)>Hg(-0.28)>Pb(-0.32)>Zn(-0.39)>Cu(-0.42)>Cr(-0.7)>As(-0.81)>Ni(-0.73), where the accumulation risk of soil Cd and Hg was relatively higher. ④ Higher environmental background and mining activities were the main factors affecting the accumulation of heavy metals in soils in the upper and middle reaches. By contrast, rapid urbanization, industrial production, and intensive agricultural activities were the main factors affecting the heavy metal accumulation in soils in the middle and lower reaches. In view of the current status and control needs of heavy metal pollution in the Yangtze River Economic Belt, it is recommended to strengthen source prevention and control and to also carry out hierarchical control and regional classification management of heavy metal pollution in farmland soils according to the degree of heavy metal pollution, geological background, and quality of agricultural products. The ultimate objective of this research was to archive the farmland soil environmental quality safety and agricultural green sustainable production in the Yangtze River Economic Belt.

A Monitoring System for Air Quality and Soil Environment in Mining Areas Based on the Internet of Things

In order to solve the intensifying problem of heavy metal pollution of soil in mining areas, a method for monitoring air quality and soil environment in mining areas based on the Internet of Things is proposed. Using meta-analysis method and health risk assessment method, the impact of mining on soil heavy metal content in Southwest China was quantitatively analyzed, and the relationship between soil heavy metal value and its potential influencing factors was discussed, as well as the heavy metal pollution, ecological risk, and health caused by soil mining activities. Risks were assessed. The results showed that artificial and oral intake were the main modes of soil heavy metal exposure, with the highest daily intakes for noncarcinogenic risk children and the highest daily intakes for carcinogenic risk adult females. The noncarcinogenic risk (HQ>1) of soil As and Pb exposure to children was 3.74 and 1.44, respectively. The carcinogenic risk values of As, Cd, Cr, and Ni in soil were all higher than 10-6, indicating that the carcinogenic risk was within the tolerance range of human body. Children were exposed to the combined noncarcinogenic risk ( HI = 3.83 ), and the risk values of the three types of recipients were 1.19 × 10 − 4 , 1.21 × 10 − 4 , and 1.06 × 10 − 4 , respectively. The correlation between heavy metal content and environmental factors was obtained. It is verified that the system in this paper can effectively monitor the meteorological environment and soil environment, and at the same time, it reveals the pollution law of heavy metals in the soil of the mining area, which provides supporting conditions for future mining and heavy metal pollution management.

Meta-analysis of the Effects of Metal Mining on Soil Heavy Metal Concentrations in Southwest China

Metal mining is one of the main contributors of soil heavy metals. Previous studies examining the impact of metal mining on surrounding soil have mainly focused on one or a few metal mining areas. However, such studies cannot effectively inform the management of heavy metal pollution in soil at an inter-provincial scale. As part of this study, literature was collected on soil heavy metals (i.e., As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) affected by metal mining in regions of Southwest China (i.e., Yunnan Province, Sichuan Province, Guizhou Province, Chongqing Municipality, and Tibet Autonomous Region); Next, the impact of metal mining on the soil concentrations of these metals was quantified through meta-analysis, and the relationships between the selected factors (i.e., different sub-regions, metal minerals, and land-use types) and soil heavy metal concentrations were explored. Finally, the literature data was tested for publication bias. The results showed that metal mining in Southwest China has significantly increased the concentrations of heavy metals in topsoil. The different metals were ranked according to their weight effect sizes (ES+) in the following order Cd > Pb > Hg > Zn > As > Cu > Ni > Cr. Metal mining in both Sichuan and Yunnan led to higher effect sizes of soil Cd (ES+Sichuan=4.16, ES+Yunnan=3.20) and Pb (ES+Sichuan=3.47, ES+Yunnan=2.54) than those of the other heavy metals, while metal mining in Guizhou led to a higher effect size of soil Hg (ES+=2.80). The effect size of metal mining on soil heavy metals was higher in cultivated soil (ES+=1.42) than in forested soil (ES+=0.50). The mining of lead-zinc and tin significantly increased the concentrations of soil Cd, Pb, and Zn, and the mining of copper significantly increased the concentrations of soil Cu, Cd, and Pb. Of the investigated soil heavy metals in Southwest China, Pb and Zn showed slight potential publication biases (P<0.05). The above results can provide more effective information for the environmental protection of soil in metal mining areas of Southwest China.

Understanding the sorption behaviors of heavy metal ions in the interlayer and nanopore of montmorillonite: A molecular dynamics study

The molecular-scale adsorption mechanism of heavy metal ions in the interlayer and nanopore regions of montmorillonite (MMT) were investigated by molecular dynamics simulations. Three typical heavy metals (zinc, cadmium, and lead) were selected as the model ions, and two types of MMT (Arizona and Wyoming) were considered. The results showed that Cd2+ and Pb2+ can form both inner- and outer-sphere complexes on Wyoming MMT, while Zn2+ only formed outer-sphere complex due to the stronger hydration interaction of Zn2+ than Cd2+ and Pb2+. For Arizona MMT, all of the three ions only formed outer-sphere complexes on its interlayer and external basal surface in which the cations remained a fully hydrated state. The calculated diffusion coefficients of three cations in interlayer and nanopore indicated that their diffusion abilities were significantly impaired, implying that MMT adsorbents have a strong ability to fix and retard heavy metal ions. The derived results and mechanisms are instrumental to a profound understanding of the transport and retention of heavy metal elements in subsurface environments, and provide guidance for the management of heavy metal pollution.

Productivity and heavy metal pollution management in a silage maize field with reduced recycled wastewater applications with different irrigation methods

Using wastewaters in irrigated agriculture can cause heavy metal accumulation as well as salinity in soil. A practical way of minimizing accumulation in soil is to use irrigation techniques that require less water and consequently introduce less heavy metals into the feeding chain in silage maize cultivation with wastewater irrigation. The objective of this study is to address this issue. A factorial field experiment was carried out for two years in a completely randomized design with three replicates. Experimental plots were irrigated with three different irrigation methods (subsurface and surface drip, and furrow) applying three different levels (full irrigation and 33 and 67% deficit irrigations) of recycled wastewater and freshwater. The results showed that soil heavy metal contents, salinity, macro nutrients, organic matter, cation exchange capacity, porosity and wet aggregate stability were significantly higher in full irrigation with wastewater, while pH, carbonates, bulk and particle densities were significantly lower. Drip methods reduced salinity and heavy metal contents significantly. Heavy metal pollution indexes also indicated that drip methods are more effective in reducing metal pollution in soil. However, considerable accumulations of Cd and Ni were found with all methods while deficit irrigation decreased accumulations. The highest cation exchange capacity and K2O contents and the lowest exchangeable sodium percentage were determined with the subsurface drip method. The subsurface drip method saved 20.7 and 49% more irrigation water than the surface drip and furrow methods under fully irrigated conditions. Therefore, it can be concluded that using the subsurface drip method with recycled wastewater can be used in silage maize cultivation because soil productivity and water savings increased while metal pollution and salinity in soil decreased. Moreover, using 33% less wastewater can be a useful practice to decrease Cd and Ni accumulation.

Studies on heavy metals and fish health indicators in Malapterurus electricus from Lekki Lagoon, Lagos, Nigeria

The aquatic ecosystem is constantly being disturbed by rising levels of different classes of pollutants of human origin in the form of urban, agricultural and industrial discharges. In this study, the health of fish Malapterurus electricus was examined, to serve as a reflection of the impact of anthropogenic disturbances in the Lekki lagoon. Eighty six samples of the fish were analysed for parasitic infections, heavy metals, microorganisms in their internal and external body parts while the proximate composition and fish condition factor were also determined using conventional methods. One parasite species, a cestode Electrotaenia malapteruri was found to infect the fish. Total parasite load was eighty five with a total prevalence of infection of 36%. Elements detected in sediment were of the order of Al>Fe>Mn>Pb>Cr>Zn>Cd>Ba>Cu>Ni while in water, it is Mn>Fe>Zn>Ba>Cd>Cr>Al>Cu>Ni>Pb. Metals analysed in the fish tissues were generally low and below regulatory limits. In the proximate analysis, moisture content has a value of 80.7%, while ash content had a value of 1.26%. Eight bacterial and two fungal species were isolated from the fish. The condition factor of fish varied between 1 and 2. The study provides valuable information for monitoring and management of heavy metal pollution in the aquatic ecosystem.

Cause Analysis for the Different Change Profiles of Sedimentary Heavy Metals in Qilu Lake (Yunnan–Guizhou Plateau, China) over the Past Century

The causes of the changes in different heavy metals in the hypereutrophic Qilu Lake were investigated by reconstructing the change history of heavy metal contamination in the past century, combined with land-use change and meteorological data. The results indicated that Qilu Lake was one of the lakes with the most serious risk of heavy metal pollution in China. The potential ecological risk index (RI) has remained at a very high level, and Cd and Hg were the main ecological risk factors. Four types of the sedimental content profiles of the heavy metals were observed, i.e. increase (Cd, Pb, and As), decline (Fe, Al, Zn, Ni, and Cr), unchanged (Hg), and first increase and then decrease (Cu). The results suggested that Fe, Al, Zn, Ni, and Cr were mainly originated from natural sources, while Cd, Pb, As, Cu, and Hg were related to anthropogenic sources. The EF profiles of Cd, Pb, Hg, Cu, and As showed increasing trend implying that the anthropogenic input of those heavy metals was increasing. By analysis of the human activities in the catchment, the reduction of soil loss by interception effect of water conservancy facility development and the expansion of built-up land were the main causes for the decline in sedimental contents of Fe, Al, Zn, Ni, and Cr. The development of industry of ferrous metal smelting and manufacturing in recent decades may be the main sources of the anthropogenic heavy metals in Qilu Lake catchment. Additionally, the discharge of waste and fallouts from local cement plants and application of chemical fertilizers were possibly the main contributors of Cd and Pb. Long-distance atmospheric transportation from outside the catchment may also contribute to the enrichment of Hg in Qilu Lake. The results of this study provided insights for the management of heavy metal pollution in Qilu Lake catchment, as well as for the other lakes in Yunnan–Guizhou Plateau.