Soil Pb Concentrations Research Articles

Zeolite-Assisted Immobilization and Health Risks of Potentially Toxic Elements in Wastewater-Irrigated Soil under Brinjal (Solanum melongena) Cultivation

Application of wastewater to agricultural soils not only enhances economic benefits but is also considered as a safe disposal option by the administrators. Worldwide, peri-urban horticulture is a common practice for growing vegetables. When agricultural soils are irrigated with wastewater, numerous potentially toxic elements (PTEs) contained therein are bioaccumulated and pose health risks. The presented study aimed to reveal the PTEs, i.e., copper (Cu), cadmium (Cd), nickel (Ni) and lead (Pb) concentration in the agricultural soils irrigated with wastewater for longer times. Zeolite, a natural mineral was used to immobilize these in contaminated soils to reduce its availability to brinjal (Solanum melongena L.). During a pot study, zeolite was applied at four different levels, i.e., 0.25, 0.50, 1.00 and 2.00% in contaminated soil, keeping one control. The results revealed that growth as well as biochemical and physiological characters were found best with treatment receiving zeolite at 2.00%. In edible parts (fruit), PTE contents were found lowest in the same treatment. Relative to the control, ~121, 87, 120 and 140% less DTPA-extracted Cu, Cd, Ni and Pb in soil was found with this treatment. Based on the results, it was revealed that zeolite effectively immobilized Cu, Cd, Ni and Pb in the soil. Although all the applied levels of zeolite had positive potential to immobilize PTEs in wastewater-contaminated soil, zeolite applied at 2.00% proved most effective.

Soil heavy metal Pb concentration quantitative inversion method based on hyperspectral remote sensing

Taking a mining area in the Liangshan section of the Anning River Basin as the research area, soil samples were collected, and the collected soil samples were respectively measured for Pb concentration and soil spectral reflectance, and the correlation between soil Pb concentration and soil spectral reflectance was analyzed, using the partial least squares regression method to construct the soil Pb concentration estimation model and carry out the accuracy test. The results show that: (1) The correlation between the original soil spectral curve and the measured value of soil Pb concentration is greatly improved after the first-order differential(FD), second-order differential(SD), reciprocal first-order differential(RTFD) and inverse second-order differential(RTSD) transformation, and there are many characteristic bands. (2) The best model for estimating soil Pb concentration is the model established by second-order differential, whose coefficient of determination (R2) is 0.56 and root mean square error (RMSE) is 1.28. It provides a reference for the retrieval of remote sensing hyperspectral soil Pb concentration in this area.

Uptake of lead and zinc from soil by blackberry plants (Rubus fruticosus L. agg.) and translocation from roots to leaves

• Pb and Zn in soil ofa the Innerste floodplain exceed precautionary limits. • Concentrations of Pb and Zn in soils and blackberries are positively correlated. • Uptake and translocation of Pb and Zn are reduced at higher soil levels. • R. fruticosus is a useful bioindicator but unsuited for phytoremediation. Heavy metals transported by rivers are deposited in sediments and floodplains, and floodplain soils act as both sinks and sources of these metals. The Innerste River is contaminated by historical metal ore mining, processing, and smelting in the Harz Mountains (Germany). Our study compared the uptake of lead (Pb) and zinc (Zn) in wild blackberries ( Rubus fruticosus L. agg.) growing within and outside the Innerste floodplain in a downstream area. The potential of blackberries as bioindicators and for phytoremediation of soils polluted by Pb and Zn was assessed based on bioconcentration factors (BCF) and the intra-plant mobility of the two metals based on translocation (TF) factors. Concentrations of Pb and Zn were significantly higher in soils and blackberry plants from the Innerste floodplain compared to adjacent non-flooded area, while soil pH and organic matter content did not differ significantly between the two zones. Mean concentrations (mg/kg d.w.) of Pb (1457.2) and Zn (1365.2) in the regularly flooded soils far exceeded the precautionary limits of the German Federal Soil Protection and Contaminated Sites Ordinance. Concentrations of both heavy metals in blackberry roots and leaves increased with their levels in soil. Except for BCF Root Pb, BCFs and TFs decreased exponentially with increasing heavy metal concentration in soil and roots, respectively. This indicates that the uptake of Pb and Zn by R. fruticosus and their translocation within the plant are reduced at higher soil levels of both heavy metals. BCF < 1 were determined for both heavy metals and a TF < 1 for Pb. Only blackberries growing outside the floodplain showed a TF > 1 for Zn. Our results indicate that blackberries can be used as bioindicators of soil contamination by Pb and Zn. Regarding their uptake characteristics, blackberries constitute excluders rather than accumulators, and are thus unsuited for phytoremediation.

Heavy Metal Pollution and Source Contributions in Agricultural Soils Developed from Karst Landform in the Southwestern Region of China.

Heavy metal pollution of soil in agricultural areas is the most prominent environmental pollution problem in China, seriously affecting human health and food security. It has become one of the environmental problems to which all sectors of society attach great importance. Soil heavy metals in the weathering area of hazardous geological bodies in southwest China have naturally high background attributes. Therefore, ecological risk assessment and analysis of potential sources of soil heavy metals in southwest China is of great significance for soil health management, soil heavy metal pollution control and territorial spatial planning. In this study, we collected 787 soil samples (0–20 cm) in Xuanwei County in China and analyzed the concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in soils. Igeo, RI, HI and CR were used to calculate the pollution levels, ecological risks and human health risks. Additionally, the PMF model and one-way ANOVA were used to identify the potential sources and discuss the factors affecting the enrichment of heavy metals. The results showed that the mean contents of the surface soils were 1.190 (Cd), 139.4 (Cr), 96.74 (Cu), 0.081 (Hg), 56.97 (Ni), 46.66 (Pb) and 130.1 (Zn) mg/kg. All heavy metals exceeded the background values of the A layer soil in Yunnan Province. The Igeo showed that Cd was the most hazardous element in the study area, followed by Cu, Cr, As, Ni and Pb. The RI showed that low ecological risks, moderate ecological risks, considerable ecological risks and strong ecological risks accounted for 3.81%, 55.27%, 37.74% and 3.18%, respectively, of the total samples, and Cd was the main dominant element. The HI values of the As element in children were greater than 1, indicating a non-carcinogenic risk, and other elements’ risks were acceptable. The CR values of Cr and Ni were higher than their limits (1 × 10−4), and both had carcinogenic risks in children and adults, as did As in children. According to the PMF model, four heavy metals sources were identified: geological sources (32%), sources from mining activities (19.38%), atmospheric deposition sources (17.57%) and agricultural sources (31.05%). Thereinto, As and Pb were mainly derived from agricultural sources, Cd and Cr were mainly associated with geological sources, Cu was largely from mining activity sources, Hg was mainly from atmospheric deposition sources and Ni and Zn were mainly from geological sources, mining activities and agricultural activities. The parent material has a significant influence on the enrichment of heavy metals in the soil, and the heavy metals are significantly enriched in the carbonate parent material and quaternary parent material. Topography also plays a role in heavy metal accumulation; Cd, Cr, Cu, Ni and Zn gradually decreased with the increase in altitude, and As and Pb increased with the increase in altitude. Mn-oxide played a crucial part in the enrichment of Cu and Zn, while SOC, K2O and pH had little influence on the accumulation of heavy metals.

Ecological and health risks assessment of lead in environmental and plants in an artisanal mining area in Nigeria

Background and Aim: The emission of persistent toxic metals into the environment from artisanal mining remains a major challenge to the environment and risk to public health. Thereby causing severe diseases and eventual death amongst adults and children. The study determined the ecological and health risk assessment of lead emission from gold mining in Arufu, Northeast, Nigeria. Methods: Fifty-sixty (56) samples, comprising 30 soils, 10 stream sediments, 6 rocks, 5 mine tailings and 5 plants were collected in areas close to mining excavation. All samples were air-dried and pulverized while rock samples was crushed and pulverized. Samples were analysed for Lead (Pb) using High Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry. Statistical evaluations of rate of bioaccumulation of metals in plant and health risk assessment for carcinogenic and non-carcinogenic effect were also assessed. Results: Mean concentration of Pb in soils, sediments, tailings, rocks and plants are: 1,100 mg/kg, 15,800 mg/kg, 110 mg/kg, 12,756 mg/kg, 7,105 mg/kg and 50 mg/kg, respectively. Bioaccumulation factor showed metal mobility from soil to plant. Ecological risk assessment revealed that Pb poses threat to the environment and metals in all the media pose high carcinogenic and non-carcinogenic health risk especially in children. Pollution load index (PLI) revealed all samples to be highly polluted with Pb due to mining. Conclusion: Mining and geogenic activities contributes significantly to the contamination of media in the area. Lead in the samples poses both carcinogenic and non-carcinogenic health diseases. It is recommended from this study that artisanal mining in the area should be regularly monitored to forestall future epidemic. Keywords: Artisanal, Bioaccumulation factor, Ecological risk, Diseases, Mining

Effects of bentonite and zeolite minerals on mobility of lead in paddy soil in Chi Dao commune, Van Lam district, Hung Yen province, Vietnam

Used lead-acid battery recycling activities in Minh Khai handicraft village, Chi Dao commune, Van Lam district, Hung Yen province, Vietnam has markedly increased the lead (Pb) content in paddy soil. Reducing the mobility of lead and lead accumulation in rice plants/plain rice are major priorities to reduce the impacts of lead in paddy soil. Application of the minerals zeolite (4A and Faujasite) and bentonite (natural and modified) to lead-contaminated soil has been carried out in lab scale for three years. The results showed the efficiencies in reducing accumulated lead in rice were 58 and 56% after adding the artificial additives zeolite 4A and zeolite Faujasite, respectively. These results were better than those of modified bentonite and natural bentonite, which were only 44 and 24%, respectively. The control efficiency of Pb accumulated in rice plants between the supplemented samples of zeolite Faujasite, zeolite 4A, modified bentonite, and natural bentonite were 69, 56, 42, and 40%, respectively, compared with the control samples. The addition of minerals to the soils has also resulted in decreases of the growth and yield of the experimental rice plants compared with the control samples. In this research, 0.1 to 0.2% of zeolite Faujasite showed the best results in terms of reducing Pb content in soil as well as low effect on plant growth. This research opens up on-site pollution control solutions for lead-contaminated agricultural soils.

Source Identification and Superposition Effect of Heavy Metals (HMs) in Agricultural Soils at a High Geological Background Area of Karst: A Case Study in a Typical Watershed.

Exogenous sources and the superposition effect of HMs in agricultural soils made the idenfication of sources complicated in a karst area. Here, a typical watershed, a research unit of the karst area, was chosen as the study area. The smaller-scale study of watersheds allowed us to obtain more precise results and to guide local pollution control. In this study, sources of HMs in agricultural soil were traced by a CMB model. Superposition effects were studied by spatial analysis of HMs and enrichment factor (EF) and chemical fraction analysis. The average concentrations of Cd, Pb, Cr, Cu, Ni and Zn in surface soils were 8.71, 333, 154, 51.7, 61.5 and 676 mg∙kg−1, respectively, which exceeded their corresponding background values. The main sources of Cd, Pb and Zn in agricultural soil were rock weathering, atmospheric deposition and livestock manure, and their contributions were 47.7%, 31.0% and 21.2% for Cd; 7.63%, 78.7% and 13.4% for Pb; and 17.0%, 52.3% and 28.1% for Zn. Cr mainly derived from atmospheric deposition (73.8%) and rock weathering (20.0%). Cu and Ni mainly came from livestock manure (81.3%) and weathering (87.5%), respectively, whereas contributions of pesticides and fertilizers were relatively limited (no more than 1.04%). Cd, Pb, Zn and Cu were easily enriched in surface soils near the surrounding pollution sources, whereas Cr and Ni were easily enriched in the high-terrain area, where there was less of an impact of anthropogenic activities. The superposition of exogenous sources caused accumulation of Cd, Pb and Zn in topsoil, contaminated the subsoil through leaching and improved bioavailability of Cd and Pb, causing high ecological risk for agricultural production. Therefore, Cd and Pb should be paid more attention in future pollution control.

Distribution Characteristics and Risk Assessment of Heavy Metal Pollution in Farmland Soils and Crops in Luancheng, Shijiazhuang City

In order to explore the distribution characteristics of heavy metal contamination of farmland soil surrounding Luancheng town, Shijiazhuang City, Henan province, the concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the surface soil and crops were determined and assessed. The principal components were also analyzed for source apportionment. The heavy metal concentrations in crops were further detected, and the non-carcinogenic health risks in the study area were evaluated using the probabilistic risk assessment method, as to provide a theoretical basis for the treatment, prevention, and control of heavy metal pollution in farmland soil in Luancheng. According to the results, ω(Cd), ω(Cr), ω(Cu), ω(Pb), and ω(Zn) in the soils were 0.06-1.08, 22.14-473.47, 12.83-150.74, 10.75-577.72, and 62.23-652.78 mg·kg-1, which exceeded the standard with over-standard rates reaching 1.83%, 1.22%, 0.61%, 0.61%, and 1.22%, respectively. Further, Cd and Pb were transported into crops, in which Cd concentrations exceeded the standard in some corn samples, and Cd and Pb concentrations exceeded the standard in some wheat samples. The total non-carcinogenic health risks (TTHQ) to the human body caused by the consumption of heavy metals in corn grown in the study area were all less than 1, with no obvious negative effects, and TTHQ was higher than 1 in wheat, increasing the likelihood of negative impacts on the human body. With the influence of the distribution of pollution-related enterprises in the industrial zone, heavy metal concentrations were higher in the south, west, and middle directions of the study area. Among them, the study area soil was slightly contaminated by Cd (Level 1). Cd and Hg had a slight potential ecological risk (Level 2), whereas other heavy metals had low potential ecological risk (Level 1). In general, most of the surface cultivated soil was not obviously polluted by heavy metals in the study area. According to the PMF results and survey, we speculated that soil heavy metals mainly came from soil parent material (52.05%), artificial pollution sources (historical sewage irrigation and industrial manufacture) (32.98%), and atmospheric deposition (14.97%). To summarize, the study area should be divided into a priority protection category and safe utilization category. The input of pollution sources should be strictly controlled for the priority protection category, and alternative planting, rotating, and fallow should be implemented for the safe utilization category to reduce the risk of standard-exceeding agricultural products.

Combination of low-accumulation kumquat cultivars and amendments to reduce Cd and Pb accumulation in kumquat grown in contaminated soil

Kumquat, the main economic fruit of Guangxi, China was selected as the research object of this study. Pot and field experiments were conducted to systematically study the safe utilization of Cd- and Pb-contaminated orchard soil, which is a typical karst zone surrounding a historical Pb–Zn mining area in Yangshuo County, Guilin City, Guangxi Province. The pot experiment compared the Cd and Pb accumulation ability of different kumquat cultivars. The results showed that Cuipi (CP) had a lower Cd and Pb accumulation ability. Compared with Yingmu (YM), the Cd and Pb contents of CP leaves were reduced by 39.71% and 32.83%, respectively. In the field experiment (one year), CP with low accumulation was combined with 0.5% amendments including rice husk biochar (RB), pig manure (PB), soil conditioner (SC), and organic fertilizer (OF) in real Cd- and Pb-contaminated kumquat orchard soils. The results showed that all amendments reduced non-carcinogenic health risks and improved agricultural sustainability. In terms of health risk reduction, the amendments significantly reduced the accumulation of Cd and Pb in fruit of CP. In particular, RB decreased Cd and Pb by 76.90% and 25.59%, respectively, achieving the highest health risk reduction (37.16%). Moreover, RB is more advantageous owing to its low cost. To determine agricultural sustainability, the soil quality and kumquat production were evaluated. After adding amendments, the available Cd and Pb contents in soil decreased by 42.19–60.94% and 41.64–57.79%, respectively. SC and OF improved soil quality more effectively, while RB increased the fruit biomass and the basic quality of CP. Comprehensive analysis, RB has more advantages. The mechanism of immobilization by the different amendments was further analyzed. RB and OF primarily immobilized the heavy metals by adsorption, and that of SC and PB mainly due to adsorption and precipitation. This study provides a theoretical and practical basis for the remediation of heavy metal-contaminated orchard soil.

Assess long-term As, Pb and Cr contamination and uptake by Eriocaulon decangulare in the Apalachicola National Forest.

Phytoremediation is an effective remediation process for heavy metal contamination. The primary zone of phytoremediation is the rhizosphere where the plants uptake the heavy metals from the soil matrix. The bioavailability of the contaminants in the rhizosphere is affected by the physical, chemical, and biological conditions of the rhizosphere. In the study area of the Apalachicola National Forest, the concentrations of As, Pb and Cr in the bulk soil (n = 20) were 515.81, 220.77, and 2.02 mg/kg soil, respectively. Using a sequential extraction method, the bioavailability of heavy metals in the bulk soil (S-NR) and rhizosphere soil (S-R) was characterized. The results showed that the bioavailability of the three heavy metals had the order of Cr > Pb > As for S-NR and Pb > As > Cr for S-R. The bioavailability of these metals was affected by the nature of the heavy metals and the soil physicochemical properties. Native plant Eriocaulon decangulare could uptake a large number of heavy metals from the natural soil, demonstrating great phytoremediation potential for metal contamination. Energy Dispersive Spectroscopy (EDS) mapping successfully located the dominant accumulation of heavy metals in aerial parts of E. decangulare. E. decangulare was also found to be highly selective and Pb and As were both extensively accumulated in the shoots and roots. Cr was significantly immobilized in the rhizosphere soil, and also accumulated in the root of E. decangulare. This study not only correlated the phytoremediation potential with heavy metal bioavailability and soil physicochemical properties, but also demonstrated the important role of the nature of heavy metals played during the phytoremediation.

Application of Different Indices for Soil Heavy Metal Pollution Risk Assessment Comparison and Uncertainty: A Case Study of a Copper Mine Tailing Site

The concentrations of Cu, Zn, As, Pb, Cr, and Cd in soil were analyzed in a mining area in the Inner Mongolia Autonomous Region, China. The average metal concentrations in the soil samples were 204.07 mg/kg, 88.15 mg/kg, 14.47 mg/kg 88.52 mg/kg, 56.45 mg/kg, and 0.235 mg/kg, respectively. Based on the evaluation standards, background values of the soil heavy metals, multiple soil pollution assessment indices, such as the single factor index (Pi), the geological accumulation index (Igeo), the Nemerow index (Pn), the ecological risk index (ER), and the health risk index (HI) were applied to evaluate the soil environmental risks in the study area. It was found that in different soil layer depths (0–10 cm, 10–30 cm, and 30–50 cm), the evaluation result of each index showed that there were significant spatial differences in soil pollution levels, and the focus of different indices differed greatly from each other. The Pi put 18.14% of the area at high risk of soil contamination levels, due to the fact that this index highlights the Cu pollution factor more than other indices and relatively amplifies hazards in some high-risk areas. While the Pn indicated that 61.36% of the study area was at a safe level of soil contamination, it can underestimate the regional soil heavy metal pollution risk. In order to scientifically carry out soil-pollution-risk prevention and control, it is necessary to comprehensively compare and analyze the information disclosed by different indices.

A field study of nano-FeS loaded lignin hydrogel application for Cd reduction, nutrient enhancement, and microbiological shift in a polluted paddy soil

Cadmium (Cd) pollution in paddy soil has caused serious harm to human health. Nano-ferrous sulfide@lignin hydrogel (FeS@LH) composites could be an ideal material for paddy soil Cd removal due to the excellent adsorption performance and mechanical strength. But the FeS@LH’s performance in a paddy field remains unclear. In this study, FeS@LH was applied to a Cd-contaminated paddy field when planting water spinach (Ipomoea aquatica Forssk). The results showed that FeS@LH effectively removed Cd from the soil (37.6 %) and water spinach (34.5 %) after 30 days. The concentrations of Pb, Zn, Cu, and other metals in soil and water spinach were co-reduced. When the FeS@LH dosage was 30 g·m−2, the effective functional distance was within 30 cm. FeS@LH application had a positive effect on soil nutrients. The soil nitrogen and organic matter contents increased by 16.1 % and 13.8 %, respectively. No significant effect on soil total phosphorus and potassium contents was presented. The survival rate of zebrafish in the acute toxicity test of FeS@LH was 98.9 %, indicating its biosafety. In addition, FeS@LH application decreased soil microbial community diversity probably due to the decreased pH. The microbial metabolism tended to enhance, suggesting a restoration of soil microbial community function after Cd removal.

Occurrence and Uptake of Heavy Metals in Soil and Plant (Tomato) Associated with Crude Oil Contamination

The general increase of heavy metal content in the soil has been largely caused by crude oil spillage. This study investigates the possibility of tomato (Lycopersicon esculentum Miller) to sorb heavy metals present in crude oil. Crude oil of 0 mL (control), 75 and 150 mL were mixed thoroughly with 15 kg of loamy soil (dry weight) in perforated plastic buckets, as the experimental pots and left for 4 days before transplanting tomato seedlings. After 12 weeks of transplanting, heavy metals analysis was carried out on plant’s fruits, leaves, stems and roots. Physicochemical analyses show that control soil had the lowest organic carbon (3.07 %) while 150 mL had the highest mean organic carbon content (8.24 %). The silt, clay and sand constituents were not significantly different (p &gt; 0.05) in both treated and untreated soil. The control had the least pH value (6.1) while the lead (Pb) content in soil was highest in 150 mL (0.33 mg/kg) but was not significantly different (p &gt; 0.05) from control (0.26 ) and 75 mL (0.30 mg/kg). Lead (Pb) and Cadmium (Cd) were not detected in leaves and fruits. However, bioaccumulation factor (BAF) of Cd and Ni in stem were greater than 1. Although, the concentrations of these heavy metals falls below toxic levels, its consumption could lead to adverse health effects in both man and animals through bioaccumulation or biomagnification.&#x0D; HIGHLIGHTS&#x0D; &#x0D; Countries with poor hydrocarbon pollution regulation are more challenging with oil spills, either through accidental discharges or indiscriminate disposal of hydrocarbon waste&#x0D; Plants essentially need some metals such as iron, copper among others, for their growth and other metabolic activities. However, at excess of specific limits, these metals adversely affect plant growth&#x0D; In this study, bioaccumulation factors (BAF) of Cd and Ni in the stem were greater than 1, this shows that the tomato plant is a hyperaccumulator of Cd and Ni from the soil&#x0D; &#x0D; GRAPHICAL ABSTRACT

Effect of biochar amendment on metal mobility, phytotoxicity, soil enzymes, and metal-uptakes by wheat (Triticum aestivum) in contaminated soils

The use of low-cost substances such as biochar could be a sustainable approach to reduce the mobility, accumulation, and toxic impact of heavy metals in crop systems. This study investigates the effect of biochar amendment on heavy metal (Cr, Cd, Cu, Pb, Ni, Zn, Mg and Fe) mobility, bioaccumulation factor (BAF), plant (wheat) metal-uptake, plant oxidative stress, and soil enzymatic profile in contaminated industrial soil. Biochar was obtained from slow pyrolysis of Lantana (LBC), and Parthenium (PBC) biomass, and applied at 3% rates in contaminated soils for wheat crop study under a greenhouse experimental setup. Results show in comparison with control setups, low mobility of Cr (14.15–16.35%), Cd (7.17–15.24%), Cu (9.81–12.97%), Pb (7.99–15.23%), Ni (1.52–2.38%), Zn (10.47–14.42%), Mg (48.85–52.89%), and Fe (19.13–19.90%) contents in soils. The heavy metal uptake rates were 63.08% (Cr), 78.07% (Cd), 74.61% (Cu), 78.11% (Pb), 75.73% (Ni), 69.71% (Zn), 28.78% (Mg), and 49.26% (Fe) lower in biochar amendments, compared with the control treatments. Similarly, the biochar amended treatments exhibited low oxidative stress in wheat plants than control setups. In addition, soil enzymes (dehydrogenase, β-glucosidase, alkaline phosphatase, and urease) alleviated in biochar amended soils indicating reduced toxicity of metals in experimental soils. In summary, this study indicates that biochar amendment in contaminated soils not only improves plant growth but also lowers the rates of soil and plant toxicity and metal bioavailability as well.

Spatial variation, sources identification and risk assessment of soil heavy metals in a typical Torreya grandis cv. Merrillii plantation region of southeastern China

Torreya grandis (Torreya grandis cv. Merrillii) is a unique nut tree species in China. Currently, researches on Torreya grandis focus on nuts quality and yield, while few works are related to the soil quality of Torreya grandis plantation. In this study, the typical Torreya grandis production areas of Zhuji, Shengzhou, Keqiao and Dongyang cities along the Kuaiji Mountain were selected. A total of 121 topsoil samples (0–20 cm) were collected based on a grid of 1 km × 1 km. The results indicated that the average concentrations of Cd, Cr, Cu, As, Ni and Pb in soils were 0.12, 49.01, 27.95, 14.28, 26.97 and 40.28 mg kg−1, respectively. The concentrations of six heavy metals all exceeded the background values, and there were different degrees of pollution levels. The results of Moran's I indicated that the spatial high-high clusters of soil heavy metals were mainly distributed in Zhuji and the junction of Shengzhou and Keqiao. The partial least squares path analysis of structural equation modeling (PLS-SEM) showed that OM and soil nutrients had extremely significant effects on soil heavy metals. Sources identification of principle component analysis (PCA) and positive matrix factorization model (PMF) revealed that agricultural activities, natural factors and mining were the main sources of soil heavy metals. The human health risks caused by soil heavy metals pollution were generally acceptable based on Monte Carlo simulation method. For the heavy-metal polluted area, management measures should be considered in order to protect human health.

Nitrogen and sulfur fertilizers promote the absorption of lead and cadmium with Salix integra Thunb. by increasing the bioavailability of heavy metals and regulating rhizosphere microbes.

Fertilization is an effective agronomic strategy to improve the efficiency of phytoextraction by Salix integra Thunb. However, the specific effects of the simultaneous application of nitrogen (N) and sulfur (S) fertilizers in the rhizosphere remain unclear. We investigated the bioavailability of lead (Pb) and Cadmium (Cd) along with the microbial metabolic functions and community structure in the rhizosphere soil of S. integra after the application of N (0, 100, and 200 kg·ha−1·year−1) and S (0, 100, and 200 kg·ha−1·year−1) fertilizers for 180 days. The simultaneous application of N and S fertilizers significantly enhanced the absorption of Pb and Cd by S. integra, whereas this effect was not observed for the single application of N or S fertilizer. The contents of acid-soluble Pb and Cd in the rhizosphere soil significantly increased after either single or combined fertilize applications. The microbial metabolic activity was enhanced by the N and S fertilizers, whereas the microbial diversity markedly decreased. The metabolic patterns were mainly affected by the concentration of N fertilizer. The dominant fungi and bacteria were similar under each treatment, although the relative abundances of the dominant and special species differed. Compared to the N200S100 and N200S200 treatments, the N100S100 and N100S200 treatments resulted in fewer pathogenic fungi and more rhizosphere growth-promoting bacteria, which promoted phytoremediation by S. integra. Redundancy analysis indicated that the pH and nitrate content were the key factors affecting the structure of the microbial community. Collectively, the results suggest interactive effects between N and S fertilizers on the rhizosphere soil, providing a potential strategy for plant-microbial remediation by S. integra.

REMEDIASI TANAH TERCEMAR TIMBAL (Pb) DAN AKUMULASINYA PADA TANAMAN GUMITIR (Tagetes erecta L.)

Lead (Pb) is a common pollutant found in agricultural soils and often contaminates the plants growing on the soil. One way to reduce the content of heavy metal contamination such as Pb in agricultural soil is through phytoremediation. The purpose of this study was to reduce the content of Pb in agricultural soils. The method used was remediation by planting gumitir (Tagetes erecta L.) plants on the soil added with various concentrations of Pb2+. The results showed that before planting with gumitir, the soil A, B, C added with Pb of 100; 200; and 400 mg Pb/kg soil, respectively, having the concentration of 108,97±2,25; 214,18±5,47; and 447,04±4.89 mg/kg, respectively, while on the harvesting time the concentration of Pb was 100,52±1,66; 170,04±2,88; and 397,98±2,24 mg/kg, respectively. The part of the plant that absorbed the highest Pb was the root, which was 47,01±4,52 mg/kg. The effectiveness of Pb absorption by gumitir plants in A, B, and C soils were &lt;50% with TF and BCF values ??&lt; 1, so the mechanism in accumulating lead metal is less effective or called phytostabilization.&#x0D; Keywords: adsorption, effectiveness, lead, remediation, Tagetes erecta L.

Lead and Zinc Uptake and Toxicity in Maize and Their Management

Soil contamination with heavy metals is a global problem, and these metals can reach the food chain through uptake by plants, endangering human health. Among the metal pollutants in soils, zinc (Zn) and lead (Pb) are common co-pollutants from anthropogenic activities. Thus, we sought to define the accumulation of Zn and Pb in agricultural soils and maize. Concentrations of Pb in agricultural soil (in Namibia) could reach 3015 mg/Kg, whereas concentrations of Zn in soil (in China) could reach 1140 mg/Kg. In addition, the maximum concentrations of Zn and Pb were 27,870 and 2020 mg/Kg in maize roots and 4180 and 6320 mg/Kg in shoots, respectively. Recent studies have shown that soil properties (such as organic matter content, pH, cation exchange capacity (CEC), texture, and clay content) can play important roles in the bioavailability of Zn and Pb. We also investigated some of the genes and proteins involved in the uptake and transport of Zn and Pb by maize. Among several amendment methods to reduce the bioavailability of Zn and Pb in soils, the use of biochar, bioremediation, and the application of gypsum and lime have been widely reported as effective methods for reducing the accumulation of metals in soils and plants.

Comprehensive assessment of heavy metals in soil-crop system based on PMF and evolutionary game theory

The traditional assessment of farmland environmental quality usually focuses on soil heavy metals, but ignores agricultural produce safety. It is urgent to comprehensively assess the effects of farmland environmental quality based on soil quality and produce safety. To fill this gap, the comprehensive assessment method was improved based on previous studies, which was used to assess the pollution level of heavy metals in soil-crop system of Shenyang, Liaoning Province, Northeast China. In addition, this study also made a comprehensive analysis of pollution sources based on positive matrix factorization (PMF) model, and discussed soil-crop system income stability by evolutionary game theory. The mean concentrations of As, Cd, Cr, Hg, Pb, Cu, Zn, and Ni in soil exceeded the corresponding Shenyang soil background values (5.68 %, 14.36 %, 57.61 %, 7.86 %, 30.32 %, 5.21 %, 211.72 %, 171.88 %). The results showed that about 28.28 % of paired soil-crop points were polluted by heavy metals, especially rice-soil points. Furthermore, heavy metals in crops may be transmitted less from soil and more from other environmental media. The PMF analysis results showed that there were six pollution sources in study area, and the major contributor of pollution were agricultural activities, traffic-related activities, and industrial activities. In farmland environment protection, the only stable strategy is soil-crop system, and soil-crop system is better than the benefits of single soil or crop from the perspective of benefits. This study provides a scientific and reliable method to combine soil quality with produce safety to assess the risk of heavy metals in farmland.

Monitoring the concentrations of Cd, Cu, Pb, Ni, Cr, Zn, Mn and Fe in cultivated Haplic Luvisol soils using near-infrared reflectance spectroscopy and chemometrics

This study illustrates the successful application of near-infrared reflectance spectroscopy extended with chemometric modeling to profile Cd, Cu, Pb, Ni, Cr, Zn, Mn, and Fe in cultivated and fertilized Haplic Luvisol soils. The partial least-squares regression (PLSR) models were built to predict the elements present in the soil samples at very low contents. A total of 234 soil samples were investigated, and their reflectance spectra were recorded in the spectral range of 1100–2500 nm. The optimal spectral preprocessing was selected among 56 different scenarios considering the root mean squared error of prediction (RMSEP). The partial robust M-regression method (PRM) was used to handle the outlying samples. The most promising models were obtained for estimating the amount of Cu (using PRM) and Pb (using the classic PLS), leading to RMSEP expressed as a percentage of the response range, equal to 9.63% and 11.5%, respectively. The respective coefficients of determination for validation samples were equal to 0.86 and 0.58, respectively. Assuming similar variability of model residuals for the model and test set samples, coefficients of determination for validation samples were 0.94 and 0.89, respectively. Moreover, the favorable PLS models were also built for Zn, Mn, and Fe with coefficients of determinations equal to 0.87, 0.87, and 0.79.