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.

Environmental quality standards for agricultural land in China: What should be improved on derivation methodology?

Soil pollution has caused increasingly widespread attention in China. The environmental risk threshold of pollutants is a yardstick to measure soil environmental quality. For decades, plenty of research on soil environmental quality standards (SEQSs) has been carried out, providing scientific basis for the investigation and supervision of soil environmental quality. This paper summaries the development of SEQSs in China, the corresponding influencing factors and methodology of SEQSs derivation. In the current version of SEQSs (GB15618-2018), the thresholds of soil pollutants are derived by the methods of environmental risk assessment, which are more methodologically scientific than geochemical method and ecological effect method used in the previous version (GB15618-1995). Abundant toxicology data on related species is required for risk assessment of soil pollution using extrapolation; however, basic toxicological data is insufficient and few valid data is available at present. Besides, the inadequate consideration on influencing factors for the derivation of soil pollutant threshold would affect the scientificity and rationality of SEQSs, such as biotic factors (species type, test endpoint etc.) and abiotic factors (aging effect, leaching effect, synergistic or antagonistic effects of elements etc.). These problems should be paid close attention in future research on soil environmental quality standards. The contents summarized in this review may provide reference for decision-making on supervision of soil environmental quality and point out important directions for future studies.

Assessment of the Driving Pollution Factors of Soil Environmental Quality Based on China's Risk Control Standard: Multiple Bigdata-Based Approaches with Intensive Sampling.

Identifying the driving factors of soil environmental quality is critical in raising countermeasures for managing the soil environment efficiently and precisely. In 2018, China issued risk control standards to divide soil environmental quality into three classes to meet the demands of environment management. However, there is a lack of knowledge of this new standard. An intensive field-sampling research (2598 top-soil samples were analyzed) was conducted in the agricultural land of Hubei province, central China, to find the driving factors of pollutants based on this new standard. According to the standard, the proportion of classes 1, 2, and 3 in the overall quality grade was 57.3%, 41.7%, and 1%, respectively. The standardized index showed that the pollution levels of cadmium, arsenic, lead, and chromium were higher than that of mercury. The first component of the principal component analysis explained 56.4% of the total variance, and the loading of cadmium, arsenic and lead were -53.5%, -52.1%, and -51.2%, respectively. The general linear modeling found that cadmium and arsenic showed positive and significant effects (p < 0.001) on the grading results of soil environmental quality. Based on the random forest algorithm, cadmium showed the greatest importance on soil environmental quality (increase in mean squared error = 32.5%). Overall, this study revealed that cadmium, arsenic, and lead were driving pollutants affecting soil environment quality grade. The large data size increased the reliability and robustness of the study's conclusions, and it provided reference methods for future studies investigating China's new standard for assessing soil environmental quality.

Derived regional soil-environmental quality criteria of metals based on Anhui soil-crop systems at the regulated level.

Anhui province is a big agricultural province in China with regional heterogeneity, but there is still a lack of its regional soil-environmental quality standard for food safety and agricultural land protection. Herein, we collected 42 typical soil samples and 125 crop samples (roots, shoots and grains of wheat and rape) in the typical regions of northern, middle and southern Anhui province, and derived the regional criteria based on the current levels of eight metals (Cd, Cr, As, Pb, Hg, Cu, Zn, and Ni) as the basic items. Results showed that the metal concentrations in soil and crop samples varied with different Anhui regions and soil-crop systems. It was observed that there exists slight or moderate soil pollution (0.77-2.67), significantly higher concentrations (P < 0.05) in rape soils, generally higher concentrations (P > 0.05) in wheats, highest bioconcentration factor (BCF) in roots (0-9.570), and higher (P > 0.05) metal concentrations in the crops of southern and middle areas. The calculated regional soil-environmental quality criteria for Anhui province provided a new insight on developing regional soil-environmental quality criteria, which varied with different Anhui regions, and were ≥0.13-times lower than the screening values, except for Cd in the southern rape soil (0.351 mg/kg), but were generally higher for rape soils, except for Zn and As.

Evaluation of soil environmental quality of cultivated land in the Donghe River Basin of Chenzhou City, Hunan Province by three methods / 环境与职业医学

Background Heavy metal pollution in cultivated land will affect crop yield and quality, as well as groundwater quality, ecological security, and human health. Objective To analyze the pollution status of heavy metal elements such as chromium (Cr), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), and lead (Pb) in cultivated soils of the Donghe River Basin in Chenzhou City, and to evaluate the environmental quality of local cultivated soil. Methods A total of 16 samples of cultivated soil from the Donghe River Basin in Chenzhou City were collected, and the contents of Cr, Cu, Zn, As, Cd, and Pb in the samples were determined by inductively coupled plasma mass spectrometry. The Nemerow comprehensive pollution index method (the evaluation indicators included both Nemerow comprehensive pollution index and single pollution index), the geological accumulation index method, and the potential ecological risk index method were used to evaluate the soil environmental quality. Results The average levels of Cr, Cu, Zn, As, Cd, and Pb in the soil samples in the study area were 58.25, 49.50, 273.88, 137.76, 2.92, and 672.29 mg·kg−1, respectively. The average values of Cu, Zn, As, Cd, and Pb were all exceeded the background values of soil elements in Hunan Province. The single pollution indices of As, Cd, Pb, and Zn in soil were 4.40, 9.74, 5.85, and 1.15 respectively. The contamination of As and Pb reached 93.75% and 81.25% respectively. The geological accumulation indices of soil As, Cd, Pb, and Zn were 2.11, 3.71, 2.97, and 0.58, respectively, which showed heavy Cd pollution, moderate As and Pb pollution, and slight Zn pollution. The potential ecological hazard indices of soil Cr, Cu, Zn, As, Pb, and Cd were 1.63, 9.07, 2.90, 87.75, 113.18, and 695.76. 81.Twenty five percent of Cd samples showed heavy pollution and above, and 62.50% of Pb samples had moderate pollution and above. The Nemerow comprehensive pollution index was 7.72, which belonged to heavy pollution; and the comprehensive potential ecological risk index was 910.29, which belonged to high ecological risk. Conclusion There are certain differences in the results of different evaluation methods. The cultivated soils of the Donghe River Basin in Chenzhou City, is seriously polluted by heavy metals, and Cd, As, and Pb are the main polluting elements.

Quantitative analysis of soil sustainability after applying stabilizing amendments in long-term Cd-contaminated paddy soils.

Considering the biomagnification in food chains, cadmium (Cd) contamination in paddy fields has become concerning. The remediation of soil cadmium by the addition of amendments is a common agricultural practice. However, it remains ambiguous whether amendment use decreases soil environmental quality (SEQ) and sustainability. In this study, five compound amendments with different pH were utilized in long-term Cd-contaminated paddy soils. The SEQ of all treatments was quantitatively assessed according to a comprehensive evaluation mathematical model (Criteria Importance Through Inter-criteria Correlation (CRITIC)-Technique for Order Preference by Similarity to Ideal Solution (TOPSIS)), and the indicators involved in microbial functional gene (MFG) abundance, soil physicochemical and microbiological properties (CMP) and soil microbial function (N-related enzyme and transformation rate, N-ET) were measured. The results show that the SQE and remediation effect (expressed by the decrease in available Cd (ACd), %) in our treatments were alkaline > natural > acidic except for D alkaline treatment. The significant contradiction between soil SQE and remediation effect in D treatment attribute to its dose effects, which inhibiting microbial nitrogen assimilation and dissimilation and therefore counteracts the promoting effect of the decrease in ACd. Based on this discussion, three alkaline amendments (A, B and D) with similar effective remediation effect were employed in four other Cd-contaminated soils. Results indicated that both negative effect (D treatment) and promoting effect (A and B treatment) existed in the next 3 years.

Comprehensive assessment of heavy metal risk in soil-crop systems along the Yangtze River in Nanjing, Southeast China.

Conventional assessment of soil environmental quality commonly focuses on soil heavy metals (HMs), neglecting the HMs in agricultural products. To response this shortcoming, a comprehensive assessment combining both soil environmental quality and agricultural product security for evaluating soil HM impact is urgently required. This comprehensive assessment incorporates not only the HM contents in soil and agricultural product but also soil environmental quality standards, soil elemental background values, and safety standards for HMs in agricultural products. In this study, it was applied to evaluate the potential risk of HMs in soil-crop systems (i.e., soil-vegetable, soil-maize, soil-rice, and soil-wheat systems) along the Yangtze River in Nanjing, Jiangsu Province, Southeast China. Furthermore, 114Cd/110Cd isotope ratio analysis was used to identify the specific contamination sources. The mean concentrations of Cd, As, Hg, Pb, Cu, Zn, and Cr in the surface soils (0-20 cm) were 0.26, 11.07, 0.09, 32.63, 38.57, and 107.92 mg kg-1, respectively, exceeding the corresponding soil background values. Fertilizer and atmospheric deposition were the major anthropogenic sources of HM contamination in crop-growing soils. In addition to the crop type, soil pH and organic matter also influenced the transfer of HMs from soils to the edible parts of crops. Results of comprehensive assessment revealed that approximately 11.1% of paired soil-crop sites were multi-contaminated by HMs, among which paddy soils had the highest potential risk of HMs followed by maize soils, vegetable soils, and wheat soils. To evaluate the potential risk of HMs in arable land, this study provides a novel, scientific and reliable approach via integrating soil environmental quality and agricultural product security.

[Draft of soil environmental function regionalization of China]. / 中国土壤环境功能区划方案.

Soil environmental function regionalization is of significance for soil environmental classification management in China. In this paper, we discussed the broad and narrow concept of soil environmental function and its corresponding attributes. Based on the constraint analysis on the soil environmental quality to function, relationship between soil environmental function and quality was illustrated. Compared with different methods and indices of soil environmental function regionalization, we established the index system of soil environmental function regionalization according to the soil environmental suitability and function. The proposed draft of soil environmental function regionalization included four first-class function types, 10 second-class function types, and 75 soil environmental functional areas. According to the differences among those functional areas, we proposed corresponding management countermeasures. The results provided scientific basis for the control and prevention of soil pollution and the control of regional risk in China.

Soil and soil environmental quality monitoring in China: a review.

Over the past few decades, numerous concerns have been raised in China over the issue of environmental sustainability. Various soil survey and monitoring programs have been carried out in China to study soil quality, and to provide a scientific basis for environment policy making. This paper provides an overview of past and current soil quality surveys and monitoring activities in China. This paper includes a summary of concerns over background concentrations of elements in soil, and soil environmental standards and guidelines in China. Levels of pollution in urban soil, agricultural soil, and soil in mining and smelting areas were compared using the concentrations and pollution indexes. In addition to soil surveys, soil monitoring is essential to study the data and to examine the effects of contaminants in soils. However, the current soil quality monitoring system was insufficient to accurately determine the soil quality status of soils across China. For accurate soil monitoring in China, it will be necessary to set up routine monitoring systems at various scales (national, provincial, and local scales), taking into consideration monitoring indicators and quality assurance. This is currently an important priority for the environmental protection administration of China.