Cd Threshold Research Articles

Classification and regression tree (CART) for predicting cadmium (Cd) uptake by rice (Oryza sativa L.) and its application to derive soil Cd threshold based on field data

The entry of Cd into soil-rice systems is a growing concern as it can pose potential risks to public health. To derive regional soil Cd threshold, a total of 333 paired soil and rice samples was collected in Anhui Province, Eastern China. The results showed that the total soil Cd and soil Zn/Cd were the most significant variables contributing to Cd content in polished rice. The Chinese Soil Quality Standards might overestimate risk posed by Cd-contaminated soil for rice production in the mining area due to high Zn/Cd values of some mining-associated soils. Cd levels in polished rice can be predictable using stepwise multiple linear regression (MLR) model. However, the derived soil Cd threshold based on the MLR model would be unrealistically high. The classification and regression tree method (CART) performed well in simulating Cd levels in polished rice and can be used to derive soil Cd threshold instead of MLR to minimize the uncertainty.

Sanitary Problems and Trace Metals Bioaccumulation during Drip Irrigation with Treated Wastewater in Okra

Water scarcity, mainly in arid and semi-arid zones, has encouraged efforts to adopt non-conventional waters for food production and agricultural development. Treated Wastewater (TWW) is one of the most continuously produced, accessible, and inexpensive water resources, with great potential for use in irrigation. The aim of this study was to investigate the combined effect of drip irrigation methods (surface vs. subsurface at 15 cm depth) and water quality (borehole water vs. treated wastewater) on soil water content, morphological and physiological traits, and nutrient content in the plant and fruit of okra grown in the Nabeul region of north-west Tunisia, a semi-arid zone. The results indicated that Okra yield was significantly affected by water quality rather than irrigation technique. Irrigation with TWW significantly increased the Okra plant height; leaf number; total fruit/m²; final yield and leaf area compared with borehole water. Nutrient levels (Fe, Cu, Zn, and Mn) in Okra plant parts (root, stem, leaf, and fruit) were also significantly increased with TWW in subsurface drip irrigation. Apart from these increased parameters were related to better soil moisture and increased available nutrients in the root zone. In terms of bioaccumulation, apart from Ni, the elements analyzed (Zn, Mn, Cu, Pb, Co, Cd) in plant and fruits showed higher values in treated wastewater than in borehole water with fruit values exceeding the toxicity threshold for Cd and Pb. Furthermore, the increase in the content of trace metal elements analyzed in the fruit following irrigation with TWW did not affect the human Health Risk Index (HRI), which remained below 1 for all treatments. Furthermore, with regard to bacterial and fungal contamination of fruit, we note that although these parameters are significantly higher in Irrigation with TWW, they remain below the toxicity thresholds. Thus, the long-term effect and continuous monitoring of the water and fruit quality in wastewater-irrigated areas to take remedial actions for sustainable agriculture development and protect ecosystems are recommended.

Cadmium accumulation in wastewater-irrigated vegetables: Exploring factors, thresholds, health implications, and transfer modeling

The Introduction of cadmium (Cd) into the soil-crop system through wastewater (WW) irrigation poses a significant challenge to environmental safety. However, the understanding of the relationship between Cd phytoavailability in WW-irrigated soil and its uptake characteristics in edible vegetables remains largely unknown. This study aims to analyze the influence of WW irrigation on the accumulation characteristics and health risks associated with Cd in the soil-vegetables system. Soil and corresponding vegetable samples were collected from 12 vegetable farms including cabbage, lettuce, green beans, and pepper were studied under wastewater (WW) and freshwater (FW) irrigation. WW irrigation led to a significant increase in soil Cd levels, with enrichment factor, and contamination factor values ranging from 2.9 to 3.1 and 2.7 to 3.3 times higher, respectively, compared to the control. Across the study farms, WW irrigation increased Cd concentrations in cabbage, green beans, lettuce, and pepper by 62–220%, 55–100%, 25–68%, and 29–80%, respectively, compared to FW-irrigated farms. The average hazard quotient (HQ) and carcinogenic risk (CR) scores for Cd in WW-irrigated vegetables indicated low risk (0.1 < HQ) and fell within the permissible range (1.00E-06 < CR < 1.00E-04) for children and adults. The soil DTPA-extractable Cd thresholds for WW-irrigated farms cultivating cabbage, lettuce, green beans, and pepper were 0.62, 0.72, 0.85, and 0.83 mg kg−1, respectively. The results provide insight into the management strategies along with developing sustainable production practices for common leafy vegetables in Cd-enriched soil resulting from WW irrigation.

Heavy metal concentrations in sharks, rays and chimaeras from the western Mediterranean Sea

The potential bioaccumulation of pollutants, such as heavy metals, may pose a threat to the western Mediterranean chondrichthyans and human consumers. Therefore, the first extensive assessment of cadmium (Cd), lead (Pb), and copper (Cu) concentrations in the muscle tissue of 17 species of sharks, rays, and chimaeras in this region was conducted via Microwave Assisted Extraction (MAE) and Graphite Furnace Atomic Absorption Spectrometry (GFAAS). Significant differences between species were observed, particularly related to the rabbit fish (Chimaera monstrosa) and the velvet belly lantern shark (Etmopterus spinax), which exceeded the European Union (EU) Commission Regulation 2023/915 threshold of Cd. Overall, heavy metal concentrations correlated negatively with size and trophic level but positively with depth. Although the consumption of these species may entail minimal risk to adult humans, caution is advised, especially for children. These findings are important due to the widespread consumption of chondrichthyans in many western Mediterranean regions.

Estimation of the Cadmium Nephrotoxicity Threshold from Loss of Glomerular Filtration Rate and Albuminuria.

Cadmium (Cd) is a pervasive, toxic environmental pollutant that preferentially accumulates in the tubular epithelium of the kidney. Current evidence suggests that the cumulative burden of Cd here leads to the progressive loss of the glomerular filtration rate (GFR). In this study, we have quantified changes in estimated GFR (eGFR) and albumin excretion (Ealb) according to the levels of blood Cd ([Cd]b) and excretion of Cd (ECd) after adjustment for confounders. ECd and Ealb were normalized to creatinine clearance (Ccr) as ECd/Ccr and Ealb/Ccr. Among 482 residents of Cd-polluted and non-polluted regions of Thailand, 8.1% had low eGFR and 16.9% had albuminuria (Ealb/Ccr) × 100 ≥ 20 mg/L filtrate. In the low Cd burden group, (ECd/Ccr) × 100 < 1.44 µg/L filtrate, eGFR did not correlate with ECd/Ccr (β = 0.007) while an inverse association with ECd/Ccr was found in the medium (β = -0.230) and high burden groups (β = -0.349). Prevalence odds ratios (POR) for low eGFR were increased in the medium (POR 8.26) and high Cd burden groups (POR 3.64). Also, eGFR explained a significant proportion of Ealb/Ccr variation among those with middle (η2 0.093) and high [Cd]b tertiles (η2 0.132) but did not with low tertiles (η2 0.001). With an adjustment of eGFR, age and BMI, the POR values for albuminuria were increased in the middle (POR 2.36) and high [Cd]b tertiles (POR 2.74) and those with diabetes (POR 6.02) and hypertension (2.05). These data indicate that (ECd/Ccr) × 100 of 1.44 µg/L filtrate (0.01-0.02 µg/g creatinine) may serve as a Cd threshold level based on which protective exposure guidelines should be formulated.

Identification of cadmium phytoavailability in response to cadmium transformation and changes in soil pH and electrical conductivity

Owing to complex changes in the soil environment, determining cadmium (Cd) phytoavailability is challenging. We devised a soil-wheat system to monitor alterations in soil pH, electrical conductivity (EC), and Cd transformation under various rates of calcium chloride and/or low-molecular-weight organic acids (LMWOAs) addition. The findings indicate that decreasing soil pH value, increasing soil EC value, and Cd transformation affect the phytoextraction of Cd. The exchangeable Cd and transformation of Cd under shifts in soil pH and EC contribute differentially to the phytoextracted Cd. The level of potentially phytoavailable Cd was identified through complete wheat cultivation in which the soil pH decreased by 0.47 unit and soil EC increased by 600-1000 μS cm−1, resembling the concentration of 0.01 M LMWOAs extractable Cd, when transitioning from paddy to dryland soil. Based on considering the phytoextracted Cd as the phytoavailable Cd throughout a complete wheat growth term, the threshold for phytoavailable Cd in soil, ensuring the safety of wheat grain (limit: 0.1 mg kg−1), is determined to be 2.90 μg kg−1. Maintaining control over Cd phytoavailability in soil emerges as the key factor in ensuring the safety of wheat grain cultivation.

Screening for Low-Cadmium Accumulation in Maize Varieties Based on Species Sensitivity Distribution and Research on Soil Environmental Thresholds

Screening for low-accumulation varieties is an effective way to reduce the cadmium (Cd) content in crops and decrease human Cd intake. In this study, a field experiment was conducted to analyze the characteristics of Cd absorption and accumulation in 24 maize varieties at maturity in farmland with different levels of Cd pollution. Cluster analysis and Pareto analysis methods were used to screen for maize varieties with low Cd absorption. In addition, the environmental threshold of Cd in farmland in the study area was estimated based on the Species Sensitivity Distribution (SSD) characteristics of different maize Cd enrichment coefficients (1/BCF). The results showed that maize in the study area was subject to varying degrees of Cd pollution, with total soil Cd content ranging from 1.81 to 2.71 mg·kg−1 at test site 1 and from 0.95 to 1.76 mg·kg−1 at test site 2. Only the Cd content of heavy metals in maize kernels at test site 2 did not exceed China’s national food safety standard (GB 2762-2022, 0.1 mg·kg−1), with the Cd content of different maize varieties at test site 2 ranging from 0.008 to 0.073 mg·kg−1 and the bioconcentration factor (BCF) of maize kernels for Cd ranging from 0.004 to 0.054. According to cluster analysis and Pareto analysis, the low-Cd accumulation maize varieties suitable for local planting were identified as Yufeng 303, Nongda 372, Jingnongke 728, MC121 (Fengda Seed Industry), and Jinyu 1233. In addition, the soil Cd environmental threshold for ensuring that 95% of maize would not be polluted by Cd in soil was derived as 1.39 mg·kg−1.

Prediction of the cadmium content in grains of low-accumulating wheat cultivars and soil cadmium threshold for safe production

Wheat cultivars with low cadmium (Cd) accumulation (WCCA-Cd) are widely used on Cd-contaminated farmland and can effectively reduce the grains Cd content to achieve the clean production in agriculture. However, there is a lack of soil Cd content thresholds specifically for the WCCA-Cd. To achieve safer production of wheat grains, a prediction model for WCCA-Cd was developed based on total Cd content in wheat grains (Grain-Cd) and soil factors using 379 soil‒wheat datasets from 10 field experiments in this research. The adaptability of the prediction model was tested using 312 pairs of data. Descriptive statistics (N = 379) showed that soil pH ranged from 4.28 to 8.76, the total Cd content in soil (Soil-Cd) ranged from 0.09 to 10.25 mg kg−1, and Grain-Cd ranged from 0.002 to 1.35 mg kg−1. Correlation analysis showed that Grain-Cd had a highly significant negative correlation with soil organic matter (SOM), soil pH, and soil conductivity (EC) and a highly significant positive correlation with Soil-Cd and Cd content in the diethylenetriaminepentaacetic acid extraction state (DTPA-Cd) (P < 0.001). The bioconcentration factor (BCF) decreased with increaseing soil pH. Both random forest and stepwise regression equations indicated that the most important factors affecting Cd bioeffectiveness were Soil-Cd and soil pH, explaining 80% of the variation in Grain-Cd. The prediction model indicated a soil Cd threshold (0.23–1.25 mg kg−1) for the safe production of WCCA-Cd at soil pH (4–9), which has a wider range of applicability compared with the Chinese Soil Safety Standards. Therefore, these results can quantify the grain Cd content of WCCA-Cd and guide the safe and clean production of WCCA-Cd on different Cd contaminated farmlands.

Effects of Different Trace Elements on Ecophysiological Characteristics of Ligustrum obtusifolium Saplings

Phytoremediation is becoming more prevalent globally. Literature on phytoremediation strategies in western China is relatively scarce. The present research sought to fill this gap by examining the effects of trace elements such as Cd, Cr, Pb, and Zn on growth, physiological traits, tolerances, and accumulation characteristics in 2-year-old saplings of Ligustrum obtusifolium. The gradient of trace element concentration was determined by adding exogenous trace elements to the soil in a pot experiment: CK (no exogenous trace element), T1, T2, and T3 (Cd 0, 2, 5, and 10 mg/kg; Cr 0, 300, 500, and 700 mg/kg; Pb 0, 400, 800, and 1200 mg/kg; and Zn 0, 300, 500, and 1000 mg/kg, respectively). The results indicated that Chla, Chlb, and total Chls significantly decreased (p &lt; 0.05) in the leaves of L. obtusifolium, with the lowest value obtained during soil treatment with T3. Along with the increase in trace element concentration, the net increase in height, root biomass, aerial biomass, and total biomass was reduced significantly. The net growth of L. obtusifolium under Cr stress did not differ significantly from that of CK at T1; however, the net growth of L. obtusifolium under Cr stress was considerably reduced at T2 and T3. The antioxidant enzyme activity of L. obtusifolium increased under different trace element stresses and first increased and then decreased as trace element levels increased. It was found that the SOD, POD, CAT, and APX activity of L. obtusifolium peaks at T2 under Cd and Zn stress in contrast to a peak at T1 under Cr and Pb stress. The contents of trace elements in L. obtusifolium roots, stems, and leaves increased along with the increase in soil trace element levels. Cr, Pb, and Zn threshold values can be set at 300 mg/kg, 400 mg/kg, and 300 mg/kg, respectively. This is carried out by using a reference index of the biomass of L. obtusifolium decreased by 10%, while the Cd threshold value needs to be further studied. L. obtusifolium would be an appropriate plant for phytoremediation of Cr-polluted soil, compared to Cd, Pb, and Zn absorption and accumulation. It showed optimal antioxidant enzyme activity and transfer ability under soil Cr contents of 300 mg/kg, and the growth of L. obtusifolium was not restricted. Therefore, L. obtusifolium was particularly suitable for phytoremediation of Cr pollution in areas in western China.

Derivation and validation of soil cadmium thresholds for the safe farmland production of vegetables in high geological background area

Excessive dietary intake of cadmium (Cd) poses toxicity risks to human health, and it is therefore essential to establish accurate and regionally appropriate soil Cd thresholds that ensure the safety of agricultural products grown in different areas. This study investigated the differences in the Cd accumulation in 32 vegetable varieties and found that the Cd content ranged from 0.01 to 0.24 mg·kg−1, and decreased in the order of stem and bulb vegetables > leafy vegetables > solanaceous crops > bean cultivars. A correlation analysis and structural equation model showed that pH, soil organic matter, and the cation exchange capacity had significant effects on Cd accumulation in the vegetables and explained 72.1 % of the variance. In addition, species sensitivity distribution (SSD) curves showed that stem and bulb vegetables were more sensitive to Cd than other types of vegetables. Using the Burr Type III function for curve fitting, we derived Cd thresholds of 6.66, 4.15, and 1.57 mg·kg−1 for vegetable soils. These thresholds will ensure that 20 %, 50 %, and 95 % of these vegetable varieties were risk–free, respectively. The predicted threshold of soil Cd was more than twice that of China's current National Soil Quality Standard (GB 15618–2018) for Cd values. Therefore, soil scenarios and cultivars should be considered comprehensively when determining farmland soil thresholds. The present results provide a new model for setting soil Cd criteria in high geological background areas.

Do tillage systems affect the cadmium threshold in farmland soil for environmental quality standard setting?

Tillage systems may change the cadmium (Cd) threshold of farmland soil. However, there have been few studies on this topic. Therefore, this study aimed to explore the influence of tillage systems on Cd threshold. The study conducted 2-year field experiments under different tillage systems (early rice-fallow, early rice-late rice and early rice-vegetable) at three typical Cd-polluted sites in China. The species sensitivity distribution (SSD) method was used to construct the SSD curves for the calculation of the Cd threshold by analyzing the experimental data. The sensitivity analysis results based on the SSD curves revealed that the sensitivities to Cd in rice varieties under the same tillage system were substantially different but almost the same under different tillage systems. These results can help select rice varieties with low Cd sensitivity for crop safety. Different tillage systems at the same site varied in their influence on Cd threshold values. Cd threshold values under early rice-late rice (e.g., 0.27, 0.28 mg/kg in Xiangtan City) and early rice-vegetable (e.g., 0.26, 0.31 mg/kg in Xiangtan City) tillage systems were roughly lower than that under the early rice-fallow tillage system (e.g., 0.33, 0.35 mg/kg in Xiangtan City). Notably, the influence of tillage systems resulted in Cd threshold values being generally lower than the Cd risk screening values of the current Chinese soil environmental quality standard. Analysis of the influence of different tillage systems on the Cd threshold is beneficial for the optimization of farmland soil environmental quality standards.

Determination of Soil Cadmium Safety Thresholds for Food Production in a Rice-Crayfish Coculture System.

Previous studies have mainly focused on cadmium (Cd) contamination in conventional rice monocultures, and no research on rice-crayfish coculture has been reported. In this study, a Cd-contaminated (0-30 mg kg-1) rice-crayfish co-culture system was established by adding exogenous Cd. The results showed that the Cd concentration in each tissue of rice and each organ of crayfish increased with increasing soil Cd concentration. Specifically, the Cd concentration in each rice tissue was as follows: root &gt; stem &gt; leaf ≈ panicle &gt; grain &gt; brown rice, and the jointing and heading stages were critical periods for the rapid enrichment of Cd in the aboveground tissues of rice. The Cd concentration in each organ of crayfish was as follows: hepatopancreas &gt; gut &gt; gill ≈ exoskeleton &gt; abdominal muscle. Cd was gradually enriched in the abdominal muscle after 30 days of coculture between crayfish and rice. Pearson's correlation analysis showed that the soil's total Cd concentration, available Cd concentration, and water Cd concentration were positively correlated with Cd content in various tissues of rice and various organs of crayfish, whereas EC and TDS in water were markedly related to rice stems, leaves, stalks, and small crayfish. According to the maximum limit of Cd in grain (0.2 mg kg-1) and crustacean aquatic products (0.5 mg kg-1) in China, the safe threshold of soil Cd for rice and crayfish under the rice-crayfish coculture system is 3.67 and 14.62 mg kg-1, respectively. Therefore, when the soil Cd concentration in the rice-crayfish coculture system exceeds 3.67 mg kg-1, the safety risk to humans through the consumption of food from this coculture system will increase. This study provides a theoretical basis for safe food production in a rice-crayfish coculture system using the established Cd pollution model.

Vitiligo and Crohn′s disease form an autoimmune cluster: insights from a population-based study

Background While the coexistence of vitiligo and Crohn′s disease (CD) has been reported in individual patients, the epidemiological association between these autoimmune conditions remains inconclusive. Objective To assess the bidirectional association between vitiligo and CD. Methods A population-based study was performed to compare vitiligo patients (n = 20,851) with age-, sex- and ethnicity-matched control subjects (n = 102,475) regarding the incidence of new-onset and the prevalence of preexisting CD. Adjusted hazard ratios (HRs) and adjusted odds ratios (ORs) were calculated by multivariable Cox regression and logistic regression, respectively. Results The incidence rate of new-onset CD was evaluated at 3.6 (95% CI, 2.7–4.9) cases per 10,000 person-years (PY) in patients with vitiligo and 2.4 (95% CI, 2.0–2.9) cases per 10,000 PY in controls. Patients with vitiligo experienced an elevated risk of CD (fully adjusted HR, 1.60; 95% CI, 1.10–2.34; p = 0.015). Congruently, a history of preexisting CD predicted elevated odds of having subsequent vitiligo (fully adjusted OR, 1.49; 95% CI, 1.15–1.93; p = 0.002). Compared to other patients with vitiligo, those with vitiligo and comorbid CD were older and had a higher prevalence of diabetes mellitus, hyperlipidemia, and hypertension but a comparable all-cause mortality rate. Conclusions The current study depicts a robust bidirectional association between vitiligo and CD. This knowledge is of clinical implication for physicians managing patients with both conditions. The diagnostic threshold for CD should be lowered in vitiligo patients with compatible symptoms.

Study on Safe Usage of Agricultural Land in Typical Karst Areas Based on Cd in Soil and Maize: A Case Study of Northwestern Guizhou, China

Cadmium (Cd) is an unnecessary dietary toxin that is harmful to human health. The Cd translocation in soil-crops system varies greatly depending on different soil matrices; therefore, a valuable method that could accurately evaluate soil Cd thresholds needs to be proposed immediately. In the southwestern part of China, a typical karst mountainous area of east Asia, the results of our survey of 492 soil-maize samples in the region showed high Cd accumulation in the soil, with concentrations ranging from 0.07 to 31.95 mg kg−1. The Cd concentrations in maize kernels planted in those fields, however, were quite low, and only 4 samples exceeded the national standard. A comparative study with nonkarst areas revealed a low bioaccumulation factor for soil Cd. This may be interpreted as the weathering soil-forming process of mineral-bearing rock systems, leading to high accumulation as well as low bioavailability of Cd in karst soils. A total of 172 soil-maize samples were evaluated inaccurately by the national standard evaluation procedure, accounting for 34.96% of the total. Therefore, we proposed the species sensitivity distribution model to address this inaccurate assessment. The results show that the hazardous concentrations of 95% and 5% in maize fields were 2.2 and 85.1 mg kg−1 for soil pH ≤ 5.5, 2.5 and 108.5 mg kg−1 for 5.5 &lt; pH ≤ 6.5, and 3.0 and 161.8 mg kg−1 for 6.5 &lt; pH ≤ 7.5, respectively. The total number of unsuitable samples according to the evaluation results decreased from 172 to 2 after modification. Therefore, this result could be considered a more accurate assessment threshold.

Exploring the Risk Thresholds of Soil Heavy Metals in Carbonate and Non-carbonate Rock Areas: The Case of Qianjiang District in Chongqing, China.

To determine whether the national soil heavy metal standards (GB 15618-2018) are applicable to some carbonate and non-carbonate zones in Southwest China, rice and rhizosphere soil samples were collected in Chongqing and analyzed for heavy metal contents, pH, and other chemical parameters. In addition, regression analysis was also used to predict the risk threshold of soil heavy metals. The Cd risk screening value in GB 15618-2018 was strict for alkaline soils (pH > 7.5) as compared to those revealed in carbonate and non-carbonate areas, while the calculated pollution threshold for Cd in acidic soils (pH ≤ 5.5) in the non-carbonate area was lower than that in GB 15618-2018. Therefore, to improve the applicability of the evaluation results, a soil-crop system evaluation is recommended.

Determination of Soil Cadmium Threshold for Potato

In this study, pot experiments were conducted to investigate the characteristics of Cd transfer to potato tubers from two types of soil. The results showed that the Log-normal and Burr III functions can be used to determine the sensitivity of different potato varieties to Cd as well as the soil Cd threshold. With regard to the prediction accuracy, the root mean squared error (RMSE) values for the total Cd biaoaccumulation factor (BAFtotal) calculated with both functions were smaller than those for exogenous Cd biaoaccumulation (BAFadd) in acidic and alkaline soils, indicating that BAFtotal is more appropriate for the calculation of the soil Cd threshold. The average Cd threshold values in acidic soil calculated with the Log-normal and Burr III functions were 0.411 and 0.461 mg kg−1, and the average values in alkaline soil were 0.716 and 0.888, respectively. The Log-normal function can also be applied to fit the sensitivity distributions of different species for the development of appropriate soil Cd threshold values for conservation purposes.

Technical solutions for minimizing wheat grain cadmium: A field study in North China

The minimization of Cd pollution in wheat is urgently needed in many parts of the world. Thus, the aims of the present study were to evaluate the feasibility of popular technologies (i.e., soil amendment and low-Cd wheat cultivar) at sites with different Cd risk levels (high and low) and to propose a risk-based strategy for safe grain production. At a high-Cd site, wheat variety JM22 yielded significantly lower grain Cd than SX828, regardless of soil amendment (biochar, sepiolite, and microbial agent YZ1). Neither biochar nor sepiolite amendment reduced grain Cd, DTPA-Cd, or bioconcentration factors, possibly due to low dosage. Metagenomic sequencing and quantitative PCR showed that YZ1 colonization had little effect on rhizospheric fungal community structure and could not be sustained through winter. At a low-Cd site, significantly lower grain Cd was observed in JM22, LX99, and JM262, which could be used as low-Cd cultivars in the study area. Interestingly, the grain Cd of JM22 was linearly correlated with soil Cd (R2 = 0.84), which allowed the inference of a soil Cd threshold of 1.55 mg·kg−1, below which JM22 alone was capable of producing safe grain. Cost-benefit analysis also indicated that the use of low-Cd cultivars is promising for pollution control. This study provides viable technical solutions for minimizing the grain Cd of wheat grown in northern China.

Information on the Distribution of Cadmium in Agricultural Land in the Middle of the Serayu Watershed

&#x0D; &#x0D; &#x0D; Cadmium (Cd) is a heavy metal that is prohibited in food products. In the long term, consumption of food containing Cd can cause cancer (it is a direct carcinogen in humans). Poor management of the Serayu watershed has resulted in pollution of the surrounding land. Meanwhile, trust in management must be built within the framework of trade in the Industrial Era 4.0, which is developing continuously in world trade relations. This study aimed to obtain information on the distribution of Cd in agricultural soils in the middle of the Serayu watershed in March-August 2017. A total of 220 soil samples were taken using the GRID method, and the analysis of Cd concentration was determined by atomic absorption spectrofotometry (AAS). The results showed that Cd was detected in 142 soil samples in the range of 1.0-&lt;1.5 mg kg−1 and detected in the range of 0.5-&lt;1.0 mg kg−1 in 78 soil samples. The results were non-normally distributed with a clustered distribution pattern. The average value of the distribution of Cd in agricultural land in the middle of Serayu watershed was 1.21 mg kg−1, and the highest Cd concentration was 2.18 mg kg−1. The Cd concentration in the middle of the Serayu watershed is classified within the safe category because the concentration is still below the critical Cd threshold value of 3-8 mg kg−1.&#x0D; &#x0D; &#x0D; &#x0D; Keywords: agricultural land, cadmium, distribution, the middle of Serayu watershed&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D;

Human Health Risk Distribution and Safety Threshold of Cadmium in Soil of Coal Chemical Industry Area

Cadmium (Cd) is a highly carcinogenic metal that plays an important role in the risk management of soil pollution. In this study, 153 soil samples were collected from a coal chemical plant in northwest China, and the human health risks associated with Cd were assessed through multiple exposure pathways. Meanwhile, by the Kriging interpolation method, the spatial distribution and health risks of Cd were explored. The results showed that the average concentration of Cd in the soil was 0.540 mg/kg, which was 4.821 and 5.567 times that of the soil background value in Ningxia and China, respectively. In comparison, the concentration of Cd in the soil was below the national soil environmental quality three-level standard (1.0 mg/kg). In addition, health risk assessment results showed that the total carcinogenic risk of Cd was 1.269 × 10−6–2.189 × 10−6, both above the acceptable criteria (1 × 10−6), while the hazard quotient was within the acceptable level. Oral intake and ingestion of soil particles were the main routes of exposure, and the carcinogenic risk control value of oral intake was the lowest (0.392 mg/kg), which could be selected as the strict reference of the safety threshold for Cd in the coal chemical soil. From Kriging, a prediction map can be centrally predicted on heavy metal pollution in the area surrounding the coal entrance corridor and pedestrian entrance. This study can provide a theoretical basis for the determination of the heavy metal safety threshold of the coal chemical industry in China.

Ecological Risk Assessment of Cadmium in Karst Lake Sediments Based on Daphnia pulex Ecotoxicology

The background value of cadmium (Cd) in soil and water sediments in the karst area is 0.31 mg kg−1, with a typical high background of cadmium geochemistry. It is well-known that Cd is classified as a highly toxic metal. Therefore, at the Yelang reservoir in Guizhou province, eco-toxicological tests were carried out using Daphnia pulex. The Geo-Accumulation Index and Potential Ecological Risk Index were used to assess the environmental risk of Cd in sediments. The Cd contents in the sediments of Yelang reservoir ranged from 2.51 to 5.23 mg kg−1, while the LC50 values of the acute toxicity test of Daphnia pulex and Cd at 24, 48, 72, and 96 h were 1.17, 0.50, 0.24, and 0.12 mg L−1, respectively, giving a Safe Concentration threshold of Cd of 1.20 × 10−3 mg L−1 in the water body. Based on curve fitting the solid–liquid two-phase distribution model of cadmium in Yelang reservoir was Y = 7.59 × 10−9 × X2.58 (R2 = 0.9995). The safety threshold sediment Cd concentration was 103 mg kg−1, and was much higher than the Cd content in the sediment of the Yelang reservoir. The Geo-Accumulation Index (Igeo 2.432–3.491) results show that the sediments had reached medium-strong or strong risk levels. The Potential Ecological Risk Index (Eri 242.8–505.9) reached a very high or extremely high-risk level. However, due to high concentrations of Ca2+ and Mg2+, and the pH being in the neutral–alkaline range of water body in karst areas, the Daphnia ecotoxicology evaluation method showed slight ecological risk, quite different from other assessment results, thus this method could be considered to use in such areas.