Soil threshold values for cadmium based on paired soil-vegetable content analyses of greenhouse vegetable production systems in China: Implications for safe food production

Thallium content in vegetables and derivation of threshold for safe food production in soil: A meta-analysis

Soil thallium (Tl) pollution is a serious environmental problem, and vegetables are the primary pathway for human exposure to Tl. Therefore, it is important to investigate the characteristics of soil Tl uptake by vegetables. In this study, the meta-analysis approach was first applied to explore the relationship between Tl content in vegetables and soil environment, as well as key factors influencing soil physical-chemical properties, and to derive soil thresholds for Tl. The results indicated that various types of vegetables have different capabilities for Tl accumulation. Vegetables from contaminated areas showed high Tl accumulation, and the geomean Tl content in different types of vegetables was in the following order: leafy > root-stalk > solanaceous vegetables. Taro and kale had significantly higher capability to accumulate soil Tl among the 35 species studied, with Tl bioconcentration factor values of 0.060 and 0.133, respectively. Pearson correlation analysis and meta-analysis revealed that the Tl content in vegetables was significantly correlated with soil pH and Tl content in soil. The linear predictive model for Tl accumulation in vegetables based on soil Tl content described the data well, and the fitting coefficient R2 increased with soil pH value. According to potential dietary toxicity, the derived soil Tl thresholds for all, leafy and root-stalk vegetables increased with an increase in soil pH, and were in the range of 1.46-6.72, 1.74-5.26 and 0.92-6.06 mg/kg, respectively. The soil Tl thresholds for kale, lettuce and carrot were in the range of 0.24-4.89, 2.94-3.32 and 3.77-14.43 mg/kg, respectively. Ingestion of kale, beet, sweet potato, potato, taro, pepper, turnip, Chinese cabbage, eggplant and carrot poses potential health risks. The study provides scientific guidance for vegetable production in Tl-contaminated areas and can help with the selection of vegetable species suitable for avoiding the absorption of Tl from contaminated soil.

Impact of Vanadium-Containing Stone Coal Smelting on Trace Metals in an Agricultural Soil-Vegetable System: Accumulation, Transfer, and Health Risks

Dietary exposure to trace metals (TMs) through vegetable consumption has been identified as a potential risk to human health. Fifty-one paired agricultural soil and leaf vegetable samples were collected around V-containing stone coal smelting sites in Hunan Province, China, to study the contamination and transfer characteristics of TMs (Cd, Cr, Cu, Pb, V, and Zn) in the soil-vegetable system. The health risk to local residents through vegetable ingestion was evaluated using Monte Carlo simulations. The results showed that 96.2%, 23.1%, 53.8%, 30.8%, 96.2%, and 69.2% of the soil samples had Cd, Cr, Cu, Pb, V, and Zn contents exceeding their related maximum allowable values, respectively. Cadmium and V were the primary pollutants based on the I_geo values. Moreover, 46.9% and 48.4% of vegetable samples exceeded the maximum permissible levels for Cd and Pb, respectively. There was a negative correlation between the bioaccumulation factors for Cd and V of the vegetable and soil physicochemical properties, including pH, organic matter, and free Fe₂O₃ content. Ingestion of garland chrysanthemum and pak choi posed high health risks, and Cd, V, and Pb were the primary contributors. These findings will help design strategies to minimize contamination and human exposure to soil-vegetable systems caused by V-containing stone coal smelting.

Adsorption Characteristics of Iron on Different Layered Loess Soils

In view of the problem of Fe³⁺ pollution in an iron sulfur mine, different layers of loess soil in the Bijie area were used for adsorption to alleviate the mine wastewater pollution by natural treatment. The effects of the initial concentration of Fe³⁺, adsorption time and pH value on the adsorption performance of top, core and subsoil layers of loess soils were studied by the oscillatory equilibrium method, and the adsorption mechanism of these three soils was analyzed through a kinetic adsorption experiment and infrared spectroscopy. The results showed that the adsorption capacity of Fe³⁺ was improved by increasing the initial concentration and reaction time, but the adsorption rate of the adsorption capacity of Fe³⁺ was reduced. The adsorption rate of Fe³⁺ in the subsoil layer was faster than that in the other two layers. The higher the pH, the higher the adsorption capacity. After the pH was higher than 3.06, it had little effect on the adsorption capacity, but the adsorption rate increased. The first-order kinetic equation, second-order kinetic equation and Elovich equation were suitable for iron adsorption kinetics of three soils. The fitting correlation coefficient of the second-order kinetic equation was close to one, indicating the main role of chemical adsorption. The adsorption rate constant of the subsoil layer was about two times and three times that of the core soil layer and the topsoil layer. The Langmuir model can better fit the isothermal adsorption process. The results of infrared spectroscopy of soil showed that the content of soil organic matter played an important role in the adsorption capacity of Fe³⁺. The subsoil layer had a higher concentration of organic matter and more abundant functional groups, so the adsorption capacity of Fe³⁺ was the highest. The results could provide a theoretical basis for the removal of iron in acid mine wastewater.

Selection of rice and maize varieties with low cadmium accumulation and derivation of soil environmental thresholds in karst

Cadmium (Cd) is considered the primary dietary toxic element. Previous studies have demonstrated significant differences in heavy metal accumulation among crop species. However, this information in karst areas with low heavy metal activity is missing. In this study, the uptake and accumulation characteristics of cadmium in soil-crop samples of group 504 in the core karst region of East Asia were analyzed. Cadmium low-accumulating maize and rice were screened using cluster and Pareto analytic methods. In addition, a new method, the species-sensitive distribution model (SSD), was proposed, which could be used to estimate the environmental threshold for cadmium in regional cropland. The results showed that both maize and rice soils in the research area were contaminated with varying degrees of cadmium. The total concentrations of cadmium ω(T-Cd) in maize and rice fields are 0.18-1.32 and 0.20-4.42 mg kg^-1, respectively. The ω(T-Cd) of heavy metals in maize kernels and rice grains is 0.002-0.429 and 0.003-0.393 mg kg^-1, respectively. The bioaccumulation factor (BCF) of cadmium in maize ranged from 0.0079 to 0.9701, with a coefficient of variation of 1.71; the BCF of cadmium in rice ranged from 0.0074 to 0.1345, with a coefficient of variation of 0.99. According to cluster and Pareto analyses, the maize crop varieties with low cadmium accumulation suitable for local cultivation were screened as JHY809, JDY808, AD778, SN3H and SY13, and the rice varieties were DMY6188, GY725, NY6368, SY451 and DX4103. In addition, the environmental cadmium threshold ranges of 0.30-10.05 mg kg^-1 and 0.89-24.39 mg kg^-1 for maize and rice soils, respectively, were deduced in this study. This threshold will ensure that 5-95% of maize and rice will not be contaminated with cadmium in the soil.

Anthropogenic activities affecting metal transfer and health risk in plastic-shed soil-vegetable-human system via changing soil pH and metal contents

Accumulation and concomitant risk of metals in plastic-shed soil (PSS)-vegetable system around industrial areas have attracted growing public concern recently, while limited studies have focused on human bioaccessible metals in various plastic-shed vegetables and health risk calculated using bioaccessible metals. Previous studies showed that intensive farming and industrial activities could prominently affect metal migration from PSS to vegetables via altering PSS pH, total and bioavailable metal contents. In contrast, whether changes in PSS pH and metal contents control bioaccessible metals in vegetables and health risk is still unknown. For PSS management and sustainable plastic-shed vegetable production in the areas with rapid industrialization, 41 PSS and 32 plastic-shed vegetable samples were sampled from the industrial areas of Yangtze River Delta, China to systematically clarify the specific connections among anthropogenic activities, soil pH and metal contents, and metal transfer and health risk in PSS-vegetable-human system. The results indicated that Cr and Cd contents in 15.6% and 9.38% of vegetable samples exceeded the allowable limits in China. Tolerable cancer risk existed and was mainly induced by bioaccessible Cr in vegetables. Decreased PSS pH mainly caused by heavy use of nitrogen fertilizers increased bioavailable Ni, Cd, Zn, Pb, and Cu in PSS and subsequently enhanced their total and bioaccessible contents in vegetables. Prominent Cr accumulation in PSS induced by industrial wastewater irrigation exacerbated Cr uptake by vegetables, which increased bioaccessible Cr in vegetables and contributed greatly to cancer risk. To reduce transfer and health risk especially of Cd and Cr in the food chain, some appropriate measures related to source control and remediation should be proposed for preventing and mitigating PSS acidification and Cr accumulation.

Biofilm-overproducing Bacillus subtilis B12ΔYwcc decreases Cd uptake in Chinese cabbage through increasing Cd-immobilizing related gene abundance and root surface colonization

Biofilm-producing bacteria can decrease Cd uptake in vegetables, but mechanisms underlying this effect are poorly characterized. In this study, two mutant strains B12ΔYwcc and B12ΔSlrR were constructed from a biofilm-producing Bacillus subtilis strain B12. Then, the impacts of strain B12 and its high biofilm-producing mutant strain B12ΔYwcc and low biofilm-producing mutant strain B12ΔSlrR on Cd availability and uptake in Chinese cabbage and the related mechanisms were investigated in the Cd-polluted soil. Strain B12 and its mutants B12ΔYwcc and B12ΔSlrR increased the dry biomasses of edible tissues by 54%-130% compared with the controls. Strain B12 and its mutant B12ΔYwcc reduced the soil available Cd content by 36%-50% and root and edible tissue Cd contents by 23%-50% compared with the controls. Furthermore, the mutant strain B12ΔYwcc reduced the edible tissue Cd content by 40% and increased the polysaccharide content by 23%, invertase activity by 139%, and gene copies of the cumA by 4.5-fold, epsA by 7.1-fold, and cadA by 4.3-fold, which were involved in Cd adsorption in the rhizosphere soils, respectively, compared with strain B12. The polysaccharide content and cumA, epsA, and cadA gene copy numbers showed significantly reverse correlations with the available Cd content. Notably, the mutant strain B12ΔYwcc showed better ability to colonize the vegetable root surface than strain B12. These findings demonstrated that the biofilm-overproducing mutant strain B12ΔYwcc increased the polysaccharide production and Cd-immobilizing related cumA, epsA, and cadA gene copies, resulting in lower Cd availability and accumulation in Chinese cabbage in the Cd-polluted soil.

Influence of soil properties on cadmium accumulation in vegetables: Thresholds, prediction and pathway models based on big data

Soil properties, such as soil pH, soil organic matter (SOM), cation exchange capacity (CEC), are the most important factors affecting cadmium (Cd) accumulation in vegetables. In this study, we conducted big data mining of 31,342 soil and vegetable samples to examine the influence of soil properties (soil pH, SOM, CEC, Zn and Mn content) on the accumulation of Cd in root, solanaceous, and leafy vegetables in Hunan Province, China. Specifically, the Cd accumulation capability was in the following order: leafy vegetables > root vegetables > solanaceous vegetables. The soil property thresholds for safety production in vegetables were determined by establishing nonlinear models between Cd bioaccumulation factor (BCF) and the individual soil property, and were 6.5 (pH), 30.0 g/kg (SOM), 13.0 cmol/kg (CEC), 100-140 mg/kg (Zn), and 300-400 mg/kg (Mn). When soil property values were higher than the thresholds, Cd accumulation in vegetables tended to be stable. Prediction models showed that pH and soil Zn were the leading factors influencing Cd accumulation in root vegetables, explaining 87% of the variance; pH, SOM, soil Zn and Mn explained 68% of the variance in solanaceous vegetables; pH and SOM were the main contributors in leafy vegetables, explaining 65% of the variance. Further, variance partitioning analysis (VPA) revealed that the interaction effect of the corresponding key soil properties contributed mostly to BCF. Meanwhile, partial least squares (PLS) path modeling was employed to analyze the path and the interactive effects of soil properties on Cd BCF. pH and SOM were found to be the biggest two players affecting BCF in PLS-models, and the most substantial interactive influence paths of soil properties on BCF were different among the three types of vegetables.

Health Risk Assessment and Multivariate Statistical Analysis of Heavy Metals in Vegetables of Khyber Pakhtunkhwa Region, Pakistan

The level of heavy metals in vegetables grown in soil irrigated with various sources of water and the health risks associated with the consumption of these vegetables were assessed in this study. Samples of water, soil, and vegetables were collected from farmer fields. After digestion in acidic solution, analytical measurements were made using an atomic absorption spectrophotometer. The mean concentration of Pb, Cr, Cd, Cu, Zn, Ni, Fe, and Mn in the soil of two sampling area were in the range from 60.00 to 84.00 mg kg^-1, 68.00 to 98.00 mg kg^-1, 1.60 to 2.60 mg kg^-1, 26.10 to 33.20 mg kg^-1, 22.60 to 30.80 mg kg^-1, 50.10 to 78.30 mg kg^-1, 420.00 to 471.00 mg kg^-1, and 270.20 to 340.50 mg kg^-1, respectively. Heavy metals in soil varied significantly at (P ≤ 0.001) among sampling area. The nine heavy metals were divided into two clusters for wastewater and soil, according to cluster analysis. The number of variables was reduced using principal component analysis, which yielded three latent factors, one for wastewater and one for soil. Pb, Cr, Cd, Cu, Zn, Ni, Fe, and Mn concentrations were significantly higher at P ≤ 0.001 in nine vegetables grown on soil irrigated with untreated wastewater than in vegetables grown on fresh-tube well-water-irrigated soil. The health risks associated with metal intake were assessed using the estimated daily intake of metals (EDIM), hazard quotients (HQs), and hazard index (HI). The rates of metal transfer to vegetables have been determined. Except for Pb and Cd, all of the elements' EDMI values were found to be lower than their RfD values. The corresponding HRI values of metals in the various vegetables were found to be below 1, implying that vegetable consumption in the studied region poses no carcinogenic risk. Constant determination of heavy metals in all fruits and vegetables is essential for the assessment of health risks associated with dietary metal exposure. The study has provided valuable information to the general public about the use of wastewater for irrigation of vegetables.

Assessment of Contents and Health Impacts of Four Metals in Chongming Asparagus-Geographical and Seasonal Aspects

In this paper, the contents of four typical metals (Pb, Cd, Hg, and As) in asparagus, water, and soil from Chongming Island were quantitatively determined by inductively coupled plasma mass spectrometry (ICP-MS). The contents of these metals in asparagus showed a common rule of Pb > As > Cd > Hg in different harvest seasons and regions. Significant seasonal differences were found in the contents by difference analysis, but no obvious regional differences were observed. Furthermore, the asparagus did not accumulate these four metals from the soil in Chongming Island by the assessment of bio-concentration factor. The asparagus was proved safe by the analysis of single-factor pollution index and Nemerow pollution index. Through combining the analysis of the above indexes and the geological accumulation index, we found that 51.62% of soil samples were mildly polluted by cadmium. The results of health risk analysis showed that the risk value of children was higher than that of adults under oral exposure, but the four metals in asparagus possessed no obvious risk to health. The above assessments illustrate that the daily consumption of asparagus in Chongming Island will not cause potential health impacts. It is of benefit to ensure the quality and economic interests of asparagus planting in Chongming Island through the investigation of this study.

RNA-Seq Identification of Cd Responsive Transporters Provides Insights into the Association of Oxidation Resistance and Cd Accumulation in Cucumis sativus L

Greenhouse vegetable production (GVP) has grown rapidly and has become a major force for cucumber production in China. In highly intensive GVP systems, excessive fertilization results in soil acidification, increasing Cd accumulation and oxidative stress damage in vegetables as well as increasing health risk of vegetable consumers. Therefore, enhancing antioxidant capacity and activating the expression level of Cd transporter genes seem to be feasible solutions to promote plant resistance to Cd stress and to reduce accumulated Cd concentration. Here, we used transcriptomics to identify five cucumber transporter genes (CsNRAMP1, CsNRAMP4, CsHMA1, CsZIP1, and CsZIP8) in response to cadmium stress, which were involved in Cd transport activity in yeast. Ionomics, gene expression, and REDOX reaction level association analyses have shown that the transcript of CsNRAMP4 was positively correlated with Cd accumulation and antioxidant capacity of cucumber roots. The expression level of CsHMA1 was negatively correlated with Cd-induced antioxidant capacity. The overexpression of CsHMA1 significantly relieved Cd stress-induced antioxidant activities. In addition, shoots with high CsHMA2 expression remarkably presented Cd bioaccumulation. Grafting experiments confirmed that CsHMA1 contributed to the high antioxidant capacity of cucumber, while CsHMA2 was responsible for the transport of Cd from the roots to the shoots. Our study elucidated a novel regulatory mechanism for Cd transport and oxidative damage removal in horticultural melons and provided a perspective to regulate Cd transport artificially by modulating Cd accumulation and resistance in plants.

A risk-based approach for the safety analysis of eight trace elements in Chinese flowering cabbage (Brassica parachinensis L.) in China

BACKGROUND

Most countries set regulatory values for the total trace element (TE) concentrations in soil, although there is growing interest in using a risk-based approach to evaluate the bioavailable TE using dilute salt extractants or other soil parameters, including pH and organic carbon_. The present study compares the current regulatory system (based on total TEs and pH) and a risk-based approach using 0.01 mol L^-1 CaCl₂ to estimate the bioavailable fraction.

RESULTS

In total, 150 paired samples of Chinese flowering cabbages (Brassica parachinensis) and their growth soils were collected, and the total and extractable concentrations of chromium (Cr), cadmium (Cd), lead (Pb), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As) and mercury (Hg), as well as soil pH and organic matter content, were measured. No more than 3.33% of the edible parts exceeded Chinese food safety standards, even when growing in soils exceeding the current regulatory thresholds by over 50%. The total soil Cd (1.5 mg kg^-1 ), as well as the extractable concentrations of Cd (0.1 mg kg^-1 ), Ni (0.03 mg kg^-1 ) and Zn (0.1 mg kg^-1 ), are the key factors affecting the TE concentrations in B. parachinensis.

CONCLUSION

Our findings suggest that the current soil regulatory guidelines for safe production of B. parachinensis are overly strict and conservative. A risk-based approach based on the extractable TE concentrations would provide a better indication for plant uptake of soil TEs and avoid the waste of farmlands that can still produce safe vegetables. Future research should focus on providing crop-specific available TE concentration guidelines to promote effective utilization of farmlands. © 2021 Society of Chemical Industry.

Environmental Impact of Potentially Toxic Elements on Tropical Soils Used for Large-Scale Crop Commodities in the Eastern Amazon, Brazil

The Amazon soils demand high rates of fertilizer application to express high agricultural potential, making it necessary to carry out frequent monitoring of ecological functions and biogeochemical processes in this important biome. The concentrations of As, Ba, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn and contamination indexes were studied in Oxisol and Ultisols cultivated with citrus (Citrus sinensis (L.) Osbeck), oil palm (Elaeis guineensis Jacq.) and black pepper (Piper nigrum L.), at 26, 10 and 5 years of implantation, respectively. The potential risk of contamination was estimated by the enrichment (EF) and bioaccumulation (BAF) factors. Moderate enrichment of Ba, Pb and Zn (2 < EF < 5) and significant enrichment of As and Cu (5 < EF < 20) were observed. In addition, the following orders of bioaccumulation were found: oil palm—Cu > Zn > Hg > Ni > Ba > Co > As > Cr > Cd ≈ Pb; black pepper—Zn > Hg > Cu > Ba > Ni > Co > Pb >> As > Cr > Cd; and citrus—Hg > Ni > Ba > Zn > Co > Cu > As > Pb >> Cr > Cd. However, all elements are in concentrations below the prevention and investigation values established by Brazilian legislation, that is, the management practices in the crops studied are not contributing with damage to soil and human health risks.

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.

Transfer of heavy metals in fruits and vegetables grown in greenhouse cultivation systems and their health risks in Northwest China

Due to the high cropping index and substantial agricultural inputs in greenhouse cultivation systems (GCS) compared to traditional farming methods, the environmental problems caused by heavy metals in GCS are becoming increasingly serious. The concentration of the heavy metals As, Cd, Cr, Cu, Pb and Zn in soil and food crops were analyzed and assessed in two study areas. There were greater accumulation of heavy metals in soils from Central Shaanxi (CS) than that from Northern Shaanxi (NS). However, heavy metal concentrations in leafy vegetables were higher in NS compared to CS, particularly Cr accumulation in leafy vegetables. Overall, leafy vegetables contained higher concentrations of heavy metals than fresh fruits and fruit vegetables from both areas. The heavy metal transfer factors (TF) for fresh fruits and fruit vegetables were as follows: Cu > Zn > Cd > Cr > As > Pb. However, in leafy vegetables, Cd had a higher TF value than the other metals tested. The target hazard quotient (THQ) values were less than 1 for fruits and vegetables, except for As in leafy vegetables from NS. The THQ values indicated that As contamination was the most serious concern, followed by Cu > Zn > Cd > Pb > Cr in both areas. The soil threshold value (STV) based on THQ showed that the level of As in leafy vegetables grown in alkaline soil was 10.85, which was inferior to the current standards. This study demonstrates the health risks associated with the heavy metal content of fruits and vegetables grown in GCS and suggests that necessary measures should be taken to reduce the accumulation of heavy metals in GCS crops in northwest China.

Cadmium uptake from soil and transport by leafy vegetables: A meta-analysis

Cadmium (Cd) pollution in soil is a serious problem affecting environmental safety and human health, and the majority of Cd in human body comes from edible vegetables, especially leafy vegetables. Therefore, it is necessary to understand the absorption and transport of Cd soil by leafy vegetables. In this study, the meta-analysis method was firstly employed to study the relationship of Cd in leafy vegetables and soil systems. The results showed that different kinds of leafy vegetables have different abilities of Cd accumulation (measured by bioconcentration factor (BCF)) and transportation (measured by translocation factor (TF)): Brassica juncea (BCF = 5.10) and Brassica pekinensis (BCF = 1.90) had significantly higher ability to absorb cadmium in soil among the 19 studied species, Brassica pekinensis (TF = 2.52), Coriandrum sativum (TF = 2.18) had significantly higher cadmium transport capacity than other 11 species. To further clarify the influence of the three main factors of soil pH, Cd content and leafy vegetable species on the Cd enrichment ability of leafy vegetables, the regression equation was obtained by meta-regression analysis. BCF is affected by species, soil pH, soil cadmium content in the order from high to low. It was found that the estimated range of SOM for safe production of leafy vegetables is 20-30 g/kg. It could also be observed that soil cation exchange capacity (CEC) had a negative correlation with BCF, while soil salinity had a strong positive correlation with BCF. This study can provide a reliable reference for leafy vegetable security production in the Cd polluted field and aids in selecting species suitable for avoiding the absorption of heavy metals from polluted soil.

Long-term effects of intensive application of manure on heavy metal pollution risk in protected-field vegetable production

Heavy metal contamination in protected-field vegetable production has aroused widespread concern and manure is considered to be one of the contamination sources. Little is known about its long-term effects on heavy metal pollution in uncontaminated soils. A 15-year protected-field vegetable production experiment was carried out with three manure treatments (chicken manure: cattle manure = 3:1) with high (HMAR), medium (MMAR) and low (LMAR) application rates to evaluate the long-term risks of heavy metal pollution. It was found that continuous and high manure application rates significantly increased the total concentrations of soil Cd, Zn, Cr, and Cu rather than Pb, Ni or As. The high application rate of manure also increased soil available heavy metals although the soil organic matter was increased as well. Though total soil Cd under the HMAR exceeded the threshold of national soil standard, Cd content in tomato and fennel still complied with the food safety requirements of vegetables. Generally, the accumulation rates of soil Zn, Cu, and Cr with 1 t⋅ha^-1 of manure application in three treatments were ranked by HMAR < MMAR < LMAR. Based on the results of the ratio of heavy metal accumulation risk (RAR), Zn, Cu, and Cr under HMAR and Cd and Zn under MMAR would exceed their soil threshold values within 100 years and RAR could be a useful indicator for monitoring the long-term risk of soil heavy metal pollution. Recommended manure application rates to guarantee a 100-year period of clean production were 44, 74, and 63 t⋅ha^-1⋅yr^-1 for Zn, Cu, and Cr, respectively. Measurements should be taken to minimize the risk of heavy metals (Cd, Zn, Cr, and Cu) pollution sourced from manure to ensure food safety and 'cleaner' protected-field vegetable production.

Legal measures to prevent and manage soil contamination and to increase food safety for consumer health: The case of Spain

This article contains a brief overview of the European and Spanish environmental law framework for the prevention of soil contamination, for the management of contaminated soils and for consumers health protection in relation to agricultural crops. Some important aspects of the legislative framework for the prevention and management of soil contamination include recognising the possible risk to both human health and ecosystems that certain agricultural and industrial activities pose given the use of organic and inorganic chemical substances of a hazardous nature and pathogenic microorganisms. It is worth highlighting the milestone that many national constitutions include about the right to the environment. This right entails the obligation to protect it and to, therefore, protect soil from any degradation, including contamination. Legislation that protects soil from contamination and, consequently human health and ecosystems, is related mainly to agricultural activities (use of sewage sludge on farmlands, use of wastewater for irrigation, use of organic fertilisers and pesticides), and to industrial and commercial soil-contaminating activities. Consumer protection may be achieved through a legal system of environmental liability, specific measures to prevent contaminants entering soil, managing contaminated soils and a food traceability system. It is crucial to make the penalties for soil contamination offenses, and for violators of protective prohibitions, effective, proportionate and dissuasive. Global standards and guidelines on soil contamination could provide national legislative systems with substantive and procedural legal mechanisms to help prevent and manage soil contamination.

Concentration, uptake and human dietary intake of novel brominated flame retardants in greenhouse and conventional vegetables

The possible adverse effects of organic pollutants entering vegetables have attracted increasing attention in recent years. However, research on the behavior of novel brominated flame retardants (NBFRs) in soil-vegetable systems is still limited. This work was initiated to investigate the uptake of seven representative NBFRs by vegetables from bulk soil and suspended soil particles under greenhouse and conventional conditions. The mean concentrations of the sum of seven NBFRs (Σ₇ NBFRs) were 2.8 and 3.8 ng g^-1 dw in greenhouse tomatoes and cucumbers, respectively, and 1.1 and 1.7 ng g^-1 dw in conventional tomatoes and cucumbers, respectively. Greenhouse vegetables had higher concentrations of Σ₇ NBFRs than conventional vegetables. The root bioaccumulation factors (RBCFs) of tomatoes and cucumbers in response to NBFRs ranged from 0.6 to 6.3. The range of fruit bioaccumulation factors (FBCFs) was 0.3-7.0. The bioaccumulation factors (BCFs) in greenhouse vegetables were significantly higher than those in conventional vegetables, indicating that greenhouses increased the uptake of NBFRs by vegetables. To address human dietary exposure to NBFRs, the estimated dietary intake (EDI) and the amounts available for human absorption (EDI_ba) were calculated using vegetable consumption and gastrointestinal absorption, respectively. The mean EDI values of NBFRs from greenhouse and conventional tomato consumption were 344 ng d^-1 and 109 ng d^-1, respectively. The mean EDI values of NBFRs from greenhouse and conventional cucumber consumption were 445 ng d^-1 and 217 ng d^-1, respectively. The higher EDI values of NBFRs implied that consuming greenhouse vegetables was associated with higher health risks than consuming conventional vegetables. The mean EDI_ba values of the DBDPEs were 68 ng d^-1 and 46 ng d^-1 for tomatoes and cucumbers, respectively, and were significantly different from the EDI values due to lower bioaccessibility. Gastrointestinal absorption should not be neglected during risk assessments of human exposure to pollutants.