Metals In Soils Research Articles

Identifying driving factors and their interacting effects on accumulation of heavy metals in cultivated soils based on optimal parameter geographic detector model

Identifying the factors and their interactive effects on soil heavy metals (HMs) accumulation in karst areas is a significant challenge in preventing and controlling soil contamination by HMs. A total of 1043 topsoil (0–20 cm) samples were collected from northwestern Guizhou to determine the concentrations of HMs (Cd, Pb, Zn, Cr, Cu, and Ni). Then, the optimal parameter based geographic detector (OPGD) model was used to identify the driving factors and interactions of natural variables (such as strata, soil organic matter, terrain, etc.) and human activity variables (such as distance from mining sites (DFM), distance from road (DFR), population density (DOP), etc.) on the spatial accumulation of soil HMs in the region. The findings revealed that the average concentrations of all HMs exceeded the corresponding background values of soil in Guizhou Province. Cd had the highest accumulation, followed by Cu, Ni, and Cr. Moran's I and inverse distance interpolation results showed clear clustering trends in the spatial distribution of HMs. The high-high clusters of Cd, Pb, and Zn were concentrated in the northern and southern parts of the study area, while the high-high clusters of Ni, Cr, and Cu were distributed mainly in the eastern and western parts of the study area. OPGD analysis results indicated that soil Cd, Pb, and Zn accumulation was influenced primarily by SOM, DFM, and stratigraphic distribution, followed by pH and soil type. Whereas Ni, Cr, and Cu were mainly affected by stratigraphic distribution. Additionally, DOP, terrain, and soil type were secondary factors affecting the accumulation of these three types of HMs. Notably, the interactive effects among these factors were found to have a more significant impact on HMs accumulation than individual factors alone. Overall, this study provides valuable insights into the main factors influencing the spatial distribution of HMs and their interactive relationships, contributing to the theoretical basis for preventing and controlling HMs pollution in the study area.

Discarded substrates from soilless hydroponic horticulture as potential amendments for metal-contaminated soils

Soil contamination with metals is a major threat for the environment and public health since most metals are toxic to humans and to non-human biota, even at low concentrations. Thus, new sustainable remediation approaches are currently needed to immobilize metals in soils to decrease their mobility and bioavailability. In this work, we explore the application of discarded substrates from hydroponic cultivation, namely coconut shell and a mixture of coconut shell and pine bark, for immobilization of metals (Cd, Cr, Ni, Cu, Pb, Hg, Sb and As) in a naturally contaminated soil from a mining region in Portugal. The immobilization capacity of substrates (added to the soil at 5% mass ratio) was assessed both individually and also combined with other traditional agriculture soil additives (limestone and gypsum, at 2% mass ratio) and nanoparticles of zero-valent iron (nZVI) at 1–3% mass ratio. The overall results obtained after a 30-d incubation showed that the discarded substrates are a viable, economic, and environmental-friendly solution for metal remediation in soils, with the capacity of immobilization ranging from 20 to 91% for the metals and metalloids studied. Furthermore, they showed the capacity to reduce the soil toxicity (EC50 ∼ 6000 mg/L) to non-toxic levels (EC50 > 10000 mg/L) to the bacteria Aliivrio fischeri.

Enhancing chromium resistance and bulb quality in onion (Allium cepa L.) through copper nanoparticles and possible health risk

Chromium (Cr) is a toxic metal in soil–plant system, hence causing possible health risks prominently in the areas with forgoing industrial activities. Copper nanoparticles (Cu NPs) have been reported as an excellent adsorbent for pollutants. Therefore, this study investigates how copper nanoparticles enhance onion growth while decreasing chromium uptake in onion plants. Additionally, it examines the potential health risks of consuming onion plants with elevated chromium levels. The results demonstrated that the addition of CuNPs at 15 mg kg−1 significantly improved the plant height (48%), leaf length (37%), fresh weight of root (61%), root dry weight (70%), fresh weight of bulb (52%), bulb dry weight (59%), leaves fresh weight (52%) and dry weight of leaves (59%), leaf area (72%), number of onion leaves per plant (60%), Chl. a (42%), chl. b (36%), carotenoids (40%), total chlorophyll (40%), chlorophyll contents SPAD value (56%), relative water contents (35%), membrane stability index (16%), total sugars (25%), crude protein (21%), ascorbic acid (19%) and ash contents (64%) at 10 mg kg−1 Cr. Whereas, maximum decline of Cr by 46% in roots, 68% in leaves and 92% in bulb was found with application of 15 mg kg−1 of Cu NPs in onion plants under 10 mg kg−1 Cr toxicity. The health risk assessment parameters of onion plants showed minimum values 0.0028 for average daily intake (ADI), 0.001911 for Non-cancer risk (NCR), and 0.001433 for cancer risk (CR) in plants treated with Cu NPs at 15 mg kg−1 concentration grown in soil spiked with 10 mg kg−1 chromium. It is concluded that Cu NPs at 15 mg kg−1 concentration improved growth of plants in control as well as Cr contaminated soil. Therefore, use of Cu NPs at 15 mg kg−1 concentration is recommended for improving growth of plants under normal and metal contaminated soils.

Nitrogen fertilization and soil nitrogen cycling: Unraveling the links among multiple environmental factors, functional genes, and transformation rates

Anthropogenic nitrogen (N) inputs substantially influence the N cycle in agricultural ecosystems. However, the potential links among various environmental factors, nitrogen functional genes, and transformation rates under N fertilization remain poorly understood. Here, we conducted a five-year field experiment and collected 54 soil samples from three 0–4 m boreholes across different treatments: control, N-addition (nitrogen fertilizer) and NPK-addition (combined application of nitrogen, phosphorus and potassium fertilizers) treatments. Our results revealed pronounced variations in soil physiochemical parameters, metal concentrations and antibiotic levels under both N and NPK treatments. These alternations induced significant shifts in bacterial and fungal communities, altered NFG abundance and composition, and greatly enhanced rates of nitrate reduction processes. Notably, nutrients, antibiotics and bacteria exerted a more pronounced influence on NFGs and nitrate reduction under N treatment, whereas nutrients, metals, bacteria and fungi had a significant impact under NPK treatment. Furthermore, we established multidimensional correlations between nitrate reduction gene profiles and the activity rates under N and NPK treatments, contrasting with the absence of significant relationships in the control treatment. These findings shed light on the intricate relationships between microbial genetics and ecosystem functions in agricultural ecosystem, which is of significance for predicting and managing metabolic processes effectively.

Unravelling the influence of microplastics with/without additives on radish (Raphanus sativus) and microbiota in two agricultural soils differing in pH

Here we investigated the effects of three types of microplastics (MPs), i.e., PS (P), ABS (B), PVC (V), and each with additive (MPAs) (PA, BA, and VA), on soil health, microbial community, and plant growth in two acidic and slightly alkaline soils. Incubation experiment revealed that although MPs and MPAs consistently stimulated soil nutrients and heavy metals (e.g., Mn, Cu) in weakly alkaline soils, only BA and VA led to increase in soil nutrients and heavy metals in acidic soils. This suggests distinct response patterns in the two soils depending on their initial pH. Concerning microorganisms, MPs and MPAs reduced the assembly degree of bacteria in acidic soils, with a reduction of Chloroflexi and Acidobacteriota but an increase of WPS-2 in VA. Culture experiment showed consistent positive or negative responses in radish seed germination, roots, and antioxidant activity across MPs and MPAs types in both soils, while the responses of seed heavy metals (e.g., Cr, Cd) were consistent in acidic soils but dependent on MPs and MPAs types in alkaline soils. Therefore, our study strongly suggests that the effects of MPs on soil-microbial-plant systems were highly dependent on initial soil characteristics and the types of MPs with plastic additives.

Research Progress on the Physiological Mechanism by Which Selenium Alleviates Heavy Metal Stress in Plants: A Review

Human activities, such as mining, industrialization, industrial waste emissions, and agricultural practices, have caused heavy metals to become widespread and excessively accumulated in soil. The high concentrations of heavy metals in soil can be toxic to plants, severely affecting crop yield and quality. Moreover, these heavy metals can also enter the food chain, affecting animals and humans and leading to various serious illnesses. Selenium (Se) is not only an essential element for animals and humans but is also beneficial for plants, as it promotes their ability to respond actively to biotic and abiotic stresses. The global issue of Se deficiency in diets has made plants the primary source for human Se supplementation. This paper comprehensively reviews the effects of heavy metal stress on plant growth and development, physiological responses of plants to such stress, and the intracellular transport processes of heavy metals within plants. It particularly focuses on the mechanisms by which Se alleviates heavy metal stress in plants. Additionally, the study delves into how Se significantly enhances plant tolerance mechanisms against typical heavy metals, such as cadmium (Cd), lead (Pb), and mercury (Hg). This integrative research not only expands the boundaries of research in the field of plant heavy metal stress and Se application but also provides new perspectives and solutions for understanding and addressing complex environmental heavy metal pollution issues. By integrating these aspects, this paper not only fills existing gaps in the literature but also offers comprehensive scientific basis and strategic recommendations for environmental protection and sustainable agriculture development.

Comprehensive Perspective on Contamination Identification, Source Apportionment, and Ecological Risk Assessment of Heavy Metals in Paddy Soils of a Tropical Island

Comprehensive Perspective on Contamination Identification, Source Apportionment, and Ecological Risk Assessment of Heavy Metals in Paddy Soils of a Tropical Island

GLDA exhibits advantages in the phytoextraction of Cd and Ni in land-applied municipal sludge.

Landscape utilization is a green and environment-friendly way of disposing of compost sludge. Garden plants can extract heavy metals from the sludge of land use, but the effect is not enough to be widely used. Chelating agents have been found to facilitate the extraction of heavy metals from plants and are expected to be popularized if they are also environmentally friendly. In this study, the effects of methylglycinediacetic acid trisodium salt (MGDA), tetrasodium glutamate diacetate (GLDA), and ethylene diamine tetraacetate (EDTA) on the extraction of Ni and Cd from compost sludge by SymphytumofficinaleL. were studied through the pot experiment. Compared with the control group, the application of 5-10 mmol kg-1 MGDA and 1-9 mmol kg-1 GLDA promoted plant growth, while the application of 3-4 mmol kg-1 EDTA inhibited plant growth. The highest Ni content in shoots appeared in 4 mmol kg-1 GLDA treatment, which was 4.2 times that of the CK group. The highest shoot Cd concentration appeared in 4 mmol kg-1 EDTA treatment, 6.5 times that of CK. The promotion effects of the three reagents on the acid-extractable state of Cd were similar, while that of GLDA on the acid-extractable state of Ni was outstanding. The results of this study suggested that S. officinale could be a potential phytoextraction plant for Cd and Ni, and GLDA could friendly promote the Ni phytoextraction ability of the plant. The study provides a new and efficient method for phytoremediation of heavy metals in soil.

Variations of soil metal content, soil enzyme activity and soil bacterial community in Rhododendron delavayi natural shrub forest at different elevations

BackgroundRhododendron delavayi is a natural shrub that is distributed at different elevations in the karst region of Bijie, China, and that has an important role in preventing land degradation in this region. In this study, we determined the soil mineral element contents and soil enzyme activities. The composition of the soil bacterial community of R. delavayi at three elevations (1448 m, 1643 m, and 1821 m) was analyzed by high-throughput sequencing, and the interrelationships among the soil bacterial communities, mineral elements, and enzyme activities were determined.ResultsThe Shannon index of the soil bacterial community increased and then decreased with increasing elevation and was highest at 1643 m. Elevations increased the number of total nodes and edges of the soil bacterial community network, and more positive correlations at 1821 m suggested stronger intraspecific cooperation. Acidobacteria, Actinobacteria and Proteobacteria were the dominant phyla at all three elevations. The Mantel test and correlation analysis showed that Fe and soil urease significantly affected bacterial communities at 1448 m; interestingly, Chloroflexi was positively related to soil urease at 1448 m, and Actinobacteria was positively correlated with Ni and Zn at 1821 m. Fe and soil urease significantly influenced the bacterial communities at lower elevations, and high elevation (1821 m) enhanced the positive interactions of the soil bacteria, which might be a strategy for R. delavayi to adapt to high elevation environments.ConclusionElevation significantly influenced the composition of soil bacterial communities by affecting the content of soil mineral elements and soil enzyme activity.

Impact of agricultural inputs on the abundance of heavy metals (Cu, Zn) in soil, water, and plants in the south of Algeria

he aim of our study is to assess the impact of agricultural inputs on the levels of heavy metals, specifically copper (Cu) and zinc (Zn), in soil, water, and plants in the oasis of El Ghrous, Branis, and Sidi Okba in Algeria. The existence of perilous substances in the surroundings is a significant ecological issue, endangering both human well-being and agricultural output. The overuse of fertilizers and pesticides may be causing heavy metals build-up. The aim will be to highlight a better understanding of the concentrations of copper (Cu) and zinc (Zn), considering as detrimental contaminants, after extensive utilization of agricultural inputs. In order to examine the levels of trace metals (TMs), we performed additional tests by comparing field samples using metal analysis techniques that involved ammonium acetate and EDTA, and detection by atomic absorption spectrophotometry. Our findings suggest that in soils affected by fertilizers and phytosanitary agents, the concentrations of Cu++ and Zn++ are below levels that would cause toxicity. Indeed, the levels of Cu++ are measured at 6.14 µg/g and the levels of Zn++ are measured at 4.97 µg/g. Nevertheless, the copper contents in irrigation waters from sites 01 and 02 beyond the levels that are considered dangerous. Similarly, copper levels in plants are categorized as hazardous. The findings emphasize the significance of implementing integrated pest management strategies in order to reduce the negative consequences of excessive use of agricultural inputs. Additionally, our study imposes the need to closely monitoring agricultural practices in order to mitigate environmental and public health hazards. Implementing sustainable farming practices and employing effective resource management strategies is crucial for safeguarding agricultural ecosystems and guaranteeing sustainable food production in the long run. Adopting an all-encompassing strategy is crucial for preserving the well-being of both the ecosystem and the populace.

Meta-analysis of Heavy Metal Pollution in Soil-crop Systems in China's Urban-Rural Fringe

Owing to the influence of human activities, the issue of heavy metal pollution in farmland soil at the urban-rural fringe has become increasingly prominent. An accurate understanding of the characteristics of soil-crop heavy metal pollution in these areas is of great significance for ensuring food safety and promoting social sustainable development. Most of the existing studies rely on small-scale field monitoring, but research at the national level has not effectively captured the unique pollution dynamics of this urban-rural interface. Based on the published literature, the present study investigated the status of heavy metal pollution in the soil-crop system within China's urban-rural fringe through Meta-analysis. On this basis, the study evaluated the risks to human health associated with heavy metals in major crops in a given region. The results showed that heavy metals were accumulated in farmland soil in the urban-rural fringe of China, especially in Cd （Igeo = 0.89） pollution, and its distinct spatial heterogeneity patterns emerged. When considering different types of cultivated land, paddy fields and irrigated land exhibited a higher tendency of heavy metal accumulation. From the varying urbanization levels, the accumulation of heavy metals in soils of small and medium-sized cities was more obvious. For crops in the urban-rural fringe, Cd and Pb had the highest exceedance rate in rice （28.25% and 39.64%） and wheat （27.72% and 42.72%）. The health risk assessment results of heavy metals in crops showed that Cd was the main element that posed human health risks, which had some degree of non-carcinogenic risk and unacceptable carcinogenic risk to both children and adults.

Distribution Characteristics and Ecological Risk Assessment of Heavy Metals in Roadside Soil of Important National Highways on the Qinghai-Xizang Plateau

To clarify the impact of transportation on the sensitive and fragile ecosystems of the Qinghai Tibet Plateau and major ecological safety barrier functions, soil samples within 0-25 m on the roadside were collected from sections of national highways such as G214, G213, G345, G109, G316, and G317, and the contents of six heavy metals were analyzed. Then, the degree of heavy metal pollution and the risk of ecological hazards were evaluated using the single-factor pollution index method （Pi）, Nemero comprehensive index method （PN）, and potential ecological risk index method （RI）. The results showed that the heavy metal contents of As, Cd, Hg, Ni, Pb, and Zn in the soil of important transportation national roads on the Qinghai Tibet Plateau ranged from 5.65 to 176.00, 0.04 to 0.27, 0.01 to 0.14, 9.52 to 113.00, 9.16 to 54.50, and 24.70 to 109.00 mg·kg-1, respectively, showing high variability. In some sections of the soil, the values of the elements As, Cd, and Hg were higher than the local soil background values. The single-factor pollution index of heavy metals in roadside soil was Pi （As） > Pi （Hg） > Pi（Cd） > Pi （Pb） > Pi （Ni） > Pi （Zn）. The Nemero comprehensive pollution index ranged from 0.41 to 9.20, with an average value of 1.53, indicating clean and mild pollution. Some areas showed a moderate or severe pollution. The average potential ecological risk index of the research section was 106.2, and the soil was generally in a state of no pollution and light pollution. Only two road sections had soil heavy metal enrichment reaching moderate and strong ecological hazards. The comprehensive potential risk of the G213a road section indicated moderate to severe ecological risk, mainly contributed by Hg, As, and Cd. The comprehensive pollution risk of the G317 road section indicated mild to moderate ecological risk, mainly contributed by Hg and Cd. The heavy metal content in the soil of the Qinghai Tibet Plateau road area was not significantly correlated with the roadside distance and soil depth but was significantly positively correlated with the annual average temperature （P < 0.05）. In all, there was a trend of heavy metal input into the soil environment in areas with intense human activities and high traffic flow during road construction on the Qinghai Tibet Plateau.

Assessment and Source Analysis of Heavy Metal Pollution in Farmland Soil Around Tin Mine

Studying the status and source analysis of heavy metal pollution in farmland in typical mining and processing areas is an important prerequisite for promoting farmland soil ecological restoration and farmland protection in concentrated mining areas. In this study, the heavy metal content of farmland soil around a mining area in southwest China was detected, and the pollution status, distribution law, health risks, and sources of heavy metals were studied by using the land accumulation index method, comprehensive pollution index method, kriging interpolation method, health risk assessment method, and PMF receptor model on the sampling data. The results showed that the mean values of eight heavy metals in farmland soil except Ni exceeded the local soil background values, and the results of the ground accumulation index evaluation showed that Cd and Hg were extremely polluted； Pb and As showed medium pollution-heavy pollution； and Cr, Zn, Ni, and Cu were lightly polluted. In the health risk assessment, oral ingestion was the main exposure route posing a health risk to the human body； the main element that constituted non-carcinogenic health risks was As, and the carcinogenic risks were from As and Cd. PMF model analysis showed that the contribution rate of weathering natural sources of iron-bearing ore was 28.02%, and the main factors were Ca and Fe. The contribution rate of agricultural sources was 3.02%, and the main factors were Pb and As. The contribution rate of industrial and atmospheric deposition composite sources was 33.09%, and the main factor was Hg. The contribution rate of the parent material source was 17.27%, and the main factor was Ca. The contribution rate of mining activities such as mining and smelting was 18.60%, and the main factors were Zn and Cd.

Enhancing cauliflower growth under cadmium stress: synergistic effects of Cd-tolerant Klebsiella strains and jasmonic acid foliar application.

The pollution of heavy metals (HMs) is a major environmental concern for agricultural farming communities due to water scarcity, which forces farmers to use wastewater for irrigation purposes in Pakistan. Vegetables grown around the cities are irrigated with domestic and industrial wastewater from areas near mining, paint, and ceramic industries that pollute edible parts of crops with various HMs. Cadmium (Cd) is an extremely toxic metal in arable soil that enters the food chain and damages the native biota, ultimately causing a reduction in plant growth and development. However, the use of microbes and growth regulators enhances plant growth and development as well as HM immobilization into the cell wall and hinders their entry into the food chain. Thus, the integrated use of bacterial consortium along with exogenously applied jasmonic acid (JA) mitigates the adverse effect of metal stress, ultimately reducing the metal mobility into roots by soil. Therefore, the current study was conducted to check the impact of Cd-tolerant bacteria and JA on the growth, nutrient status, and uptake of Cd in the cauliflower (Brassica oleracea). Our results demonstrated that increasing concentrations of Cd negatively affect growth, physiological, and biochemical attributes, while the use of a bacterial consortium (SS7 + SS8) with JA (40 μmol L-1) significantly improved chlorophyll contents, stem fresh and dry biomass (19.7, 12.7, and 17.3%), root length and root fresh and dry weights (28.8, 15.2, and 23.0%), and curd fresh and dry weights and curd diameter (18.7, 12.6, and 15.1%). However, the maximum reduction in soil Cd, roots, and curd uptake was observed by 8, 11, and 9.3%, respectively, under integrated treatment as compared to the control. Moreover, integrating bacterial consortium and JA improves superoxide dismutase (SOD) (16.79%), peroxidase dismutase (POD) (26.96%), peroxidase (POX) (26.13%), and catalase (CAT) (26.86%). The plant nitrogen, phosphorus, and potassium contents were significantly increased in soil, roots, and curd up to 8, 11, and 9.3%, respectively. Hence, a consortium of Klebsiella strains in combination with JA is a potential phytostabilizer and it reduces the uptake of Cd from soil to roots to alleviate the adverse impact on cauliflower's growth and productivity.

Characterization of Heavy Metal and Physico-chemical Profiling of Sewage Water Soil in Jaipur District, Rajasthan, India

Jaipur is the capital state of Rajasthan. During the year 2021, District Jaipur of 3 blocks (Chomu, Sanganer, and Shahpura) in 9 villages [Keshav Nagar (V1), Morija (V2), Nindola (V3), Goner (V4), Shrikishanpura (V5), Durgapura (V6), Shivpuri (V7), Manoharpur (V8), Nwalpura (V9)] were selected for estimation of physico-chemical properties and Heavy metal contamination in severage channels. A total of 9 samples were collected from 9 villages sewerage channels. This study aimed to analyze the physico-chemical properties of agricultural soil and irrigation water in three blocks of Jaipur, Rajasthan. The findings revealed significant variations in the physico-chemical properties of the agricultural soil and water in Chomu, Sanganer, and Shahpura. Standard methods were employed to assess the physico-chemical characteristics of soil samples contaminated with sewerage effluents in these regions, which exhibited considerable diversity. The pH levels of the soil samples were predominantly slightly acidic and alkaline ranging from 6.22 to 7.31. Electrical conductivity values varied between 0.41 to 0.62 mmhos/cm. The percentages of organic matter and organic carbon in the soil samples ranged from 0.17% to 0.25% and 0.29% to 0.43%, respectively. Additionally, the analysis included heavy metals such as zinc (Zn), manganese (Mn), iron (Fe), and copper (Cu). The soil samples were found to contain elevated levels of heavy metals, surpassing the permissible limits. The discharge of sewerage effluent into the environment, primarily originating from the textile industry, house, etc. constitutes are major source of pollution that can adversely impact the local flora and fauna. Therefore, it is imperative to implement effluent treatment measures before their release into the environment.

Heavy Metal Pollutants Or Contaminant In Soil Samples Obtained From Wash Boreholes Within Pantisawa, Yorro L.G.A. Of Taraba State

The problem of environmental pollution and its compartments due to an increase in contamination as a result of the accumulation of heavy metals and microorganisms from soil has raised wide-spread of concerns in different parts of the nations and this has compromised the ability of the environments to foster life and render them an intrinsic value. Hence the study aimed to ascertain the level of environmental pollution in soil from wash borehole within Pantisawa Yorro Local Government Area of Taraba State, Nigeria. A total of 45 samples for soil were collected aseptically from the five different zones (Pantisawa Main Market YM, Kapazang YG, Dola YD, Kallau YK and Zabi YZ) of Pantisawa. The levels of trace metals in soil samples were determined using Atomic Absorption Spectroscopy (AAS) PG-990. The results were analyzed using SPSS Version 20. The soil samples result for these metals revealed that iron concentration was between 3000-4010mg/kg most especially for site SD which is higher than all other elements analyzed. Zinc ranges from 2.54-6800mg/kg which is above the standard as prescribed by WHO and FEPA in soil and also exceeded the dutch target values of (Zn: 50mg/kg and Cu: 30mg/kg) in some of the sampling sites. Nickel was between 8.47-19.09 mg/kg in soil samples, this is below the toxicity threshold limit of 35mg/kg for safe environment as stated by WHO. Arsenic ranges from 53.06mg/kg–141mg/kg, which is higher than the admissible limit of 50mg/kg in soil recommended by UNEP. The order of all the metal concentration in the areas was Fe>Zn>Mn>As>Pb>Cu>Mn>Co and Cd respectively. Based on this study, the high concentration of the metals such as Zn, As, Cd, Pb, and Co in some of these sites most especially SK, SM and SD within Pantisawa revealed that some of the soil samples collected from these areas were contaminated with heavy metal pollutants which may have serious health risk to the people using it for various activities. The higher concentrations of these toxic metals in soils need to be monitored regularly for heavy metal enrichment.

Distribution of Heavy Metals in the Surrounding Mining Region of Kizhnica in Kosovo

This study investigated the distribution of heavy metals in agricultural soils in the vicinity of three large mining landfills of the Kizhnica mine in the Republic of Kosovo. The mining sector is one of the most important sectors of Kosovo’s economic development, and the Kizhnica mine is one of the most important ore producers in Kosovo. Besides the positive aspects, the development of production also has some negative side effects, such as the generation of industrial waste and the possible contamination of surrounding areas, including agricultural land. Therefore, ten sampling sites were selected in the vicinity of the Kizhnica mine. These sites were characterized and assessed as the most important due to the anthropogenic impact of mineral processing and open-tailing waste deposits in Kizhnica. The concentration of Pb, Zn, Cu, As, Cd, Ni, Mn and Sb in the selected samples was determined using inductively coupled plasma–optical emission spectrometry. The data obtained were used to create geochemical maps and calculate the contamination factor, pollution load index and geoaccumulation index. Cluster analysis, Pearson correlation coefficient and air spatial distribution patterns using the air dispersion model were used to evaluate within the area. The results showed that heavy metal levels are influenced by the anthropogenic nature of pollution, confirming a current ecological threat from mining activities in the region. In order to improve waste management, reduce the hazardous impacts of mining and contribute to the sustainable development of the region, the potential reuse of the deposited waste material in the construction industry is proposed.

Effect of AC electric field on enhancing phytoremediation of Cd-contaminated soils in different pH soils

To increase the efficiency of phytoremediation to clean up heavy metals in soil, assisted with alternating current (AC) electric field technology is a promising choice. Our experiments utilized the hyperaccumulator Sedum alfredii Hance and the fast-growing, high-biomass willow (Salix sp.). We investigated the efficiency of AC field combined with S. alfredii—willow intercropping for removing Cd from soils with different pH values. In the AC electric field treatment with S. alfredii—willow intercropping, the available Cd content in acidic soil increased by 50.00% compared to the control, and in alkaline soil, the increase was 100.00%. Furthermore, AC electric field promoted Cd uptake by plants in both acidic and alkaline soils, with Cd accumulation in the aboveground increased by 20.52% (P < 0.05) and 11.73%, respectively. In conclusion, the integration of AC electric fields with phytoremediation demonstrates significant favorable effectiveness.

Improved mapping of heavy metals in agricultural soils using machine learning augmented with spatial regionalization indices

The accurate spatial mapping of heavy metal levels in agricultural soils is crucial for environmental management and food security. However, the inherent limitations of traditional interpolation methods and emerging machine-learning techniques restrict their spatial prediction accuracy. This study aimed to refine the spatial prediction of heavy metal distributions in Guangxi, China, by integrating machine learning models and spatial regionalization indices (SRIs). The results demonstrated that random forest (RF) models incorporating SRIs outperformed artificial neural network and support vector regression models, achieving R2 values exceeding 0.96 for eight heavy metals on the test data. Hierarchical clustering for feature selection further improved the model performance. The optimized RF models accurately predicted the heavy metal distributions in agricultural soils across the province, revealing higher levels in the central-western regions and lower levels in the north and south. Notably, the models identified that 25.78 % of agricultural soils constitute hotspots with multiple co-occurring heavy metals, and over 6.41 million people are exposed to excessive soil heavy metal levels. Our findings provide valuable insights for the development of targeted strategies for soil pollution control and agricultural soil management to safeguard food security and public health.

Biochar from Co-Pyrolyzed Municipal Sewage Sludge (MSS): Part 2: Biochar Characterization and Application in the Remediation of Heavy Metal-Contaminated Soils.

The disposal of municipal sewage sludge (MSS) from wastewater treatment plants poses a major environmental challenge due to the presence of inorganic and organic pollutants. Co-pyrolysis, in which MSS is thermally decomposed in combination with biomass feedstocks, has proven to be a promising method to immobilize inorganic pollutants, reduce the content of organic pollutants, reduce the toxicity of biochar and improve biochar's physical and chemical properties. This part of the review systematically examines the effects of various co-substrates on the physical and chemical properties of MSS biochar. This review also addresses the effects of the pyrolysis conditions (temperature and mixing ratio) on the content and stability of the emerging pollutants in biochar. Finally, this review summarizes the results of recent studies to provide an overview of the current status of the application of MSS biochar from pyrolysis and co-pyrolysis for the remediation of HM-contaminated soils. This includes consideration of the soil and heavy metal types, experimental conditions, and the efficiency of HM immobilization. This review provides a comprehensive analysis of the potential of MSS biochar for environmental sustainability and offers insights into future research directions for optimizing biochar applications in soil remediation.