Accumulation Of Heavy Metals In Vegetables Research Articles

Exceptional anti-toxic growth of water spinach in arsenic and cadmium co-contaminated soil remediated using biochar loaded with Bacillus aryabhattai

Functionalized biochars are crucial for simultaneous soil remediation and safe agricultural production. However, a comprehensive understanding of the remediation mechanism and crop safety is imperative. In this work, the all-in-one biochars loaded with a Bacillus aryabhattai (B10) were developed via physisorption (BBC) and sodium alginate embedding (EBC) for simultaneous toxic As and Cd stabilization in soil. The bacteria-loaded biochar composites significantly decreased exchangeable As and Cd fractions in co-contaminated soil, with enhanced residual fractions. Heavy metal bioavailability analysis showed a maximum CaCl2-As concentration decline of 63.51% and a CaCl2-Cd decline of 50.96%. At a 3% dosage of composite, rhizosphere soil showed improved organic matter, cation exchange capacity, and enzyme activity. The aboveground portion of water spinach grown in pots was edible, with final As and Cd contents (0.347 and 0.075 mg·kg⁻¹, respectively) meeting food safety standards. Microbial analysis revealed the composite's influence on the rhizosphere microbial community, favoring beneficial bacteria and reducing plant pathogenic fungi. Additionally, it increased functional microorganisms with heavy metal-resistant genes, limiting metal migration in plants and favoring its growth. Our research highlights an effective strategy for simultaneous As and Cd immobilization in soil and inhibition of heavy metal accumulation in vegetables.

Evaluation of the Effects of Wastewater Irrigation on Heavy Metal Accumulation in Vegetables and Human Health in the Cauliflower Example : Heavy Metal Accumulation in Cauliflower.

The goals of the present research were to determine the heavy metal contents in the water-soil-cauliflower samples in industrial wastewater irrigated areas and to assess the health risks of these metals to the people. Metal analyses were carried out using the atomic absorption spectrophotometer equipped with a graphite furnace. The metal readings in the cauliflower specimens ranged from 1.153 to 1.389, 0.037 to 0.095, 0.61 to 0.892, 0.625 to 0.921, 1.165 to 2.399, 0.561 to 0.652, 0.565 to 0.585, 0.159 to 0.218 and 1.268 to 1.816mg/kg for Cd, Co, Cr, Cu, Fe, Ni, Pb, Zn and Mn, respectively. Statistics revealed that, with the exception of Pb and Co (p > 0.05), there was no statistically significant variation in the metal concentrations in the cauliflower samples according to the irrigation type. Pb, Ni, and Cr had HRI values below 1.0 and did not seem to be a hazard to human health, in contrast to Cd, Co, Cr, Cu, Fe, Ni, Pb, Zn and Mn, which glanced to constitute a health risk. Regular monitoring of vegetables irrigated with wastewater is strongly advised to reduce health hazards to people.

Heavy Metals Accumulation in Vegetables and Its Consequences on Human Health in the Areas Influenced by Industrial Activities.

The degradation of the environment due to numerous industrial practices has emerged as a major issue globally, particularly in a country like Bangladesh. The present study dispenses information about heavy metal (Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) contamination in some frequently consumed vegetables, namely, ash pumpkin, potato, bitter gourd, buffalo spinach, snake gourd, and pointed gourd grown in an industrially prone location and their repercussion on consumers' health. Proton-induced X-ray emission (PIXE) technique was used as the major analytical tool to detect heavy metal concentrations. Mean concentration and the range of Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in vegetables were detected (4.81 ± 2.79, 2.43-10.94), (497.57 ± 258.08, 181.24-886.67), (644.49 ± 298.40, 179.56-998.78), (38.88 ± 14.31, 18.88-60.12), (58.11 ± 12.58, 42.55-84.79), (137.24 ± 48.37, 71.99-208.98), (123.31 ± 63.62, 49.97-256.09), (8.09 ± 2.69, 4.29-14.94), and (4.16 ± 2.95, 1.22-9.98) mg/kg (dry weight basis), respectively. An extreme level of heavy metal contamination in vegetable samples was notified regarding the estimated metal pollution index (MPI) and Nemerow pollution index (P) value, which underpinned the health risk values. The estimated hazard index (HI) value stipulated high risk in all varieties of vegetables regardless of age group and cadmium (Cd) was found as the major contributor. Concerning the carcinogenic risk index (CR) for single elements, the value of Co, Ni, and Cr was approximated far above the USEPA threshold risk limit (CR>1E-04). Moreover, total carcinogenic risk (TCR) for all varieties of vegetables exceeded the safety threshold value for both the age group and children, in particular, were found most vulnerable. The outshot of the present study divulged associated health risks for the population group by the heavy metals via dietary intake of vegetables.

Enrichment Characteristics of Heavy Metals and Health Risk in Different Vegetables

The health risk caused by heavy metal accumulation in vegetables is of great concern. In this study, a database of heavy metal content in a vegetable-soil system in China was constructed through literature review and field sample collection. A systematic analysis of seven heavy metal contents in edible parts of vegetables and their bioaccumulation capacity among different vegetables was also performed. Additionally, the non-carcinogenic health risks of four types vegetables were assessed by using Monte Carlo simulation (MCS). The mean values of Cd, As, Pb, Cr, Hg, Cu, and Zn in the edible parts of the vegetables were 0.093, 0.024, 0.137, 0.118, 0.007, 0.622, and 3.272 mg·kg-1, and the exceedance rates of the five toxic elements were:Pb (18.5%)>Cd (12.9%)>Hg (11.5%)>Cr (4.03%)>As (0.21%). Leafy vegetables showed high Cd enrichment, and root vegetables showed high Pb enrichment, with mean bioconcentration factors of 0.264 and 0.262, respectively. Generally, legumes vegetables and solanaceous vegetables showed lower bioaccumulation for heavy metals. The health risk results indicated that the non-carcinogenic risk for single elements of vegetable intake was within the acceptable range, with the health risk for children being higher than that for adults. The mean non-carcinogenic risk for single elements were:Pb>Hg>Cd>As>Cr. The multi-element combined non-carcinogenic risks of four types vegetables were:leafy vegetables>root vegetables>legume vegetables>solanaceous vegetables. Planting lower-heavy metal bioaccumulation vegetables in heavy metal-contaminated farmland is an effective method to minimize the health risk.

Determination of trace metals in vegetables using ICP-MS

Determination of trace metals in vegetables using ICP-MS

Biochar-based microbial agent reduces U and Cd accumulation in vegetables and improves rhizosphere microecology

Microbial remediation of heavy metals in soil has been widely studied. However, bioremediation efficiency is limited in practical applications because of nutritional deficiency, low efficiency, and competition with indigenous microorganisms. Herein, we prepared a biochar-based microbial agent (BMA) by immobilizing the microbial agent (MA, containing Bacillus subtilis, Bacillus cereus, and Citrobacter sp.) on biochar for the remediation of U and Cd in soil. The results showed that BMA increased soil organic matter, cation exchange capacity, and fluorescein diacetate hydrolysis activity and dehydrogenase activity by 58.7%, 38.2%, 42.9%, and 51.1%. The availability of U and Cd were significantly decreased by 67.4% and 54.2% in BMA amended soil, thereby reducing their accumulation in vegetables. BMA greatly promoted vegetable growth. Additionally, BMA significantly altered the structure and function of rhizosphere soil microbial communities. Coincidently, more abundant ecologically beneficial bacteria like Nitrospira, Nitrosomonas, Lysobacter, and Bacillus were observed, whereas plant pathogenic fungi like Fusarium and Alternaria reduced in BMA amended soil. The network analysis revealed that BMA amendment increased the tightness and complexity of microbial communities. Importantly, the compatibility of niches and microbial species within co-occurrence network was enhanced after BMA addition. These findings provide a promising strategy for suppressing heavy metal accumulation in vegetables and promoting their growth.

Investigation of Heavy Metal Accumulation in Vegetables and Health Risk to Humans From Their Consumption

Heavy metals contamination of soil and edible parts of vegetables is presently a challenging environmental issue worldwide. The present study determined the accumulated amount of cadmium (Cd), lead (Pb), nickel (Ni), cobalt (Co), zinc (Zn), copper (Cu), and manganese (Mn) in soil, coriander, onion, and tomato collected from agricultural fields of Jhansi city, India. The bio-concentration factor and non-carcinogenic health risks were also assessed to know the vegetables’ accumulation potential of heavy metals from soil and possibility to have non-carcinogenic health risks via an intake of these vegetables. The samples were digested using di-acid solution prior to heavy metals analysis by atomic absorption spectrometric method. The average content of Cd, Pb, Ni, Co, Zn, Cu, and Mn were 2.02, 19.09, 21.56, 9.31, 35.34, 14.96, and 15.21 mg/kg dry weight (dw) in soil, 0.23, 2.12, 0.77, 0.47, 36.65, 5.92, and 21.65 mg/kg dw in coriander, 0.13, 0.66, 0.54, 0.32, 23.94, 6.25, and 20.15 mg/kg dw in onion, 0.14, 0.46, 0.89, 0.22, 16.77, 4.77, and 14.46 mg/kg dw in tomato, respectively. The bio-concentration factor revealed significant accumulation of Zn (1.04) and Mn in coriander (1.42), and in onion (1.32). The target hazard quotient and health risk index signaled that the population consuming these vegetables is risk-free. However, it is recommended that the concentration of heavy metals in the soil and crops of the study area and its related health risks be regularly monitored to avoid significant health risks in the future.

Occurrence and health risks of heavy metals in plastic-shed soils and vegetables across China

Heavy metal (HM) contamination of plastic-shed vegetable production (PSVP) areas is a great concern in China because of severe soil quality deterioration and the risk of HM accumulation in vegetables. However, the national pollution status and corresponding health risks of HM pollution in Chinese PSVP soils and vegetables are unknown. In this study, a comprehensive investigation of eight HMs (As, Cd, Cr, Cu, Hg, Ni, Pb and, Zn) pollutants and the associated risks in Chinese PSVP systems were conducted based on a database compiled from previous research. The results indicated that the mean concentrations of all eight HMs in plastic-shed soils (PS) were greater than those in adjacent open-field agricultural soils (OS), especially Cd, which exceeded its maximum limited value and had the highest average geo-accumulation index of 1.21. Longer period of PSVP cultivation can lead to soil acidification and higher accumulation of HM in PS. Obvious accumulation of HM has also occurred in vegetables grown in PSVP areas, especially in leafy vegetables. Health risk assessment revealed that enough attention should be paid to the cancer risk posed by ingesting the leafy vegetables grown in PS. Furthermore, Cd was identified as the top priority metal for risk management, followed by Cr, Pb, and Ni. Impact factors analysis indicated that high inputs of fertilizers and fungicides, lagged regulations and standards, inefficacious monitoring and management, and weak environmental awareness are the dominant factors leading to HM accumulation in PSVP systems. In the future PSVP processes, an integrated monitoring, evaluation, and management system should be established to promote a healthy and sustainable development.

Heavy metals concentration in vegetables irrigated with municipal wastewater and their human daily intake in Erbil city

Assessment of heavy metals accumulation in vegetables and their levels in human is vital in countries where wastewater is used for irrigation. In this study, The aim of this research was to investigate the concentrations of highly toxic metals such as Nickel (Ni), chrome (Cr), lead (Pb), zinc (Zn), cadmium (Cd), and copper (Cu) in wastewater, farmlands soils and vegetables (chard, celery, cress and leek), and also their possible human health risk in the area of Erbil city. The heavy metals concentration in the vegetable, soil and water samples were analyzed by using an atomic absorption spectrophotometer. Bio-concentration factor (BCF), daily intake (DI) and health risk index (HRI) were calculated in order to estimate the human health risk. Overall, results indicated that the water, soil and vegetable samples were contaminated with Ni, Cd, Cr, Cu, Pb, and Zn. The trends of these metals concentrations were as follows: 0.613 > 0.316 > 0.162 > 0.065 > 0.041 > 0.028 mL/L for Ni, Cd, Pb, Cr, Cu, and Zn, respectively in the wastewater and 189.09 > 125 > 104.92 > 41.85 > 28.58 > 21.72 for Zn, Cr, Ni, Pb, Cu and Cd mgkg−1 in the soil. The mean concentrations (mg kg−1) in the vegetable samples ranged from 22.74 to 30.30, 5.18–9.19, 29.50–33.87, 39.42–64.78, 7.87–11.83 and 77.68–117.98 for Ni, Cd, Pb, Cr, Cu and Zn, respectively. In addition, the calculated BCFs value ranged from 0.21 to 71.295, with Pb having the highest BCF. The calculated DI for Ni, Cd and Pb exceeded WHO/FAW safe limits for adult and children. Furthermore, the HRI values of Cd and Pb exceeded the safe limit (1) for both adults and children, but the values for Ni (> 1) exceeded the safe limit only for children. These findings clearly indicate that the practice of irrigating the vegetables with untreated wastewater by local farmers have caused high accumulation of heavy metals in the soils and vegetables which are posing health risk to the population in the vicinity. Therefore, regular monitoring of these metals in the wastewater-irrigated vegetables is necessary.

Effect of Wastewater Irrigation on Trace Metal Accumulation in Spinach (Spinacia oleracea L.) and Human Health Risk

The present research determines the effect of wastewater for irrigation on heavy metal accumulation in vegetables in the example of spinach (Spinacia oleracea L.) and to evaluate human health risk from consumption. Trace metal values of Cd, Cu, Cr, Fe, Zn, Ni and Mn, were determined in the water, soil and plant samples by Atomic Absorption Spectrophotometer. Trace metal concentrations in spinach samples ranged from 0.29 to 0.37, 0.14 to 1.25, 0.07 to 0.67, 1.12 to 2.48, 0.33 to 0.38, 1.92 to 2.90 and 0.51 to 0.63 mg/kg for Cd, Cr, Cu, Fe, Ni, Zn and Mn, respectively. These values of trace metals were lower than the permissible limits except for Cd. All health risk index (HRI) values except for Cd were less than 1. However, the HRI values related to spinach samples irrigated with canal water and sugar mill water were generally higher than the values of the samples irrigated with groundwater. The HRI value of Cd was higher than 1 and consumers of such vegetables in which HRI of metal was greater than 1 will be at risk.

Isolation of urease-producing bacteria and their effects on reducing Cd and Pb accumulation in lettuce (Lactuca sativa L.).

Excess Cd and Pb in agricultural soils enter the food chain and adversely affect all organisms. Therefore, it is important to find an eco-friendly way to reduce heavy metal accumulation in vegetables. We used urea agar plates to isolate urease-producing bacteria from the rhizosphere soil of lettuce in Cd- and Pb-contaminated farmland and investigated their ability to produce urease and immobilize heavy metals. The effects of these strains on the biomass, quality, and Cd and Pb accumulation of lettuce were also studied. The results showed that two urease-producing bacteria, Enterobacter bugandensis TJ6 and Bacillus megaterium HD8, were screened from the rhizosphere soil of lettuce. They had a high ability to produce urease (44.5mScm-1min-1 OD600-1 and 54.2mScm-1min-1 OD600-1, respectively) and IAA (303mgL-1 and 387mgL-1, respectively). Compared with the control, inoculation with strains TJ6 and HD8 reduced the Cd (75.3-85.8%) and Pb (74.8-87.2%) concentrations and increased the pH (from 6.92 to 8.13-8.53) in solution. A hydroponic experiment showed that the two strains increased the biomass (31.3-55.2%), improved the quality (28.6-52.6% for the soluble protein content and 34.8-88.4% for the vitamin C (Vc) content), and reduced the Cd (25.6-68.9%) and Pb (48.7-78.8%) contents of lettuce shoots (edible tissue). In addition, strain HD8 had a greater ability than strain TJ6 to reduce lettuce Cd and Pb uptake and water-soluble Cd and Pb levels in solution. These data show that the urease-producing bacteria protect lettuce against Cd and Pb toxicity by extracellular adsorption, Cd and Pb immobilization, and increased pH. The effects of heavy metal immobilization by the two strains can guarantee vegetable safety in situ for the bioremediation of heavy metal-polluted farmland.

Effects of Bacillus thuringiensis HC-2 Combined with Biochar on the Growth and Cd and Pb Accumulation of Radish in a Heavy Metal-Contaminated Farmland under Field Conditions.

The objective of this study was to explore the effect of heavy metal-resistant bacteria and biochar (BC) on reducing heavy metal accumulation in vegetables and the underlying mechanism. We tested Bacillus thuringiensis HC-2, BC, and BC+HC-2 for their ability to immobilize Cd and Pb in culture solution. We also studied the effects of these treatments on the dry weight and Cd and Pb uptake of radish in metal-contaminated soils under field conditions and the underlying mechanism. Treatment with HC-2, BC, and BC+HC-2 significantly reduced the water-soluble Cd (34–56%) and Pb (31–54%) concentrations and increased the pH and NH4+ concentration in solution compared with their vales in a control. These treatments significantly increased the dry weight of radish roots (18.4–22.8%) and leaves (37.8–39.9%) and decreased Cd (28–94%) and Pb (22–63%) content in the radish roots compared with the control. Treatment with HC-2, BC, and BC+HC-2 also significantly increased the pH, organic matter content, NH4+ content, and NH4+/NO3− ratio of rhizosphere soils, and decreased the DTPA-extractable Cd (37–58%) and Pb (26–42%) contents in rhizosphere soils of radish. Furthermore, BC+HC-2 had higher ability than the other two treatments to protect radish against Cd and Pb toxicity and increased radish biomass. Therefore, Bacillus thuringiensis HC-2 combined with biochar can ensure vegetable safety in situ for the bioremediation of heavy metal-polluted farmland.

Concentrations of heavy metals in vegetables between 2004 and 2018, and its impacts on human health in China

Heavy metals in vegetables are of great concern worldwide due to their potential bioaccumulation in human. This review-based study researched the concentrations of heavy metals in vegetables from all provinces of China between 2004 and 2018, and assessed the health risk for the residents. The results displayed the highest Pb, Cd, Cu, and Zn concentrations in vegetables were 0.192 mg/kg (west area), 0.071 mg/kg (central area), 3.961 mg/kg (central area), and 10.545 mg/kg (central area), which were lower than the maximum allowable concentration. In the national scale, the weighted average level of heavy metals in vegetables was found to be in the order of Zn > Cu > Pb > Cd. The hazard index (HI) of each province showed that beside Anhui and Hunan province, residents in other provinces of China faced a low high risk of Pb, Cd, Cu, and Zn. However, people consuming vegetables faced a high risk of Pb, Cd, Cu, and Zn in Anhui and Hunan provinces. This research may provide insight into heavy metal accumulation in vegetables and forecast to residents to cope with these problems for improved human health.

Heavy Metal Levels in Some Popular Vegetables from Some Selected Markets in Saudi Arabia

HEAVY metals accumulation in vegetables consider a world problem that may affect food safety and human health. In the present study fifteen vegetable species consisting of five leafy; Arugula (Eruca sativa), Cabbage (Brassica oleracea), Corchorus (Corchorus capsularis), Dill (Anethum graveolens) and Parsley (Petroselinum sativum); five fruits (Cucumber (Cucumis sativus), Eggplant (Solanum melongena), Green pepper (Capsicum annuum), Tomato (Solanum lycopersicum) and Zucchini (Cucurbita pepo); in addition to five tubers; Garlic (Allium sativum), Onion (Allium cepa), Radish (Raphanus sativus), Potato (Solanum tuberosum) and Yam (Ipomoea batatas) purchased from a local markets in Rafha Governorate at the Northern Border region in Kingdom of Saudi Arabia were tested for levels of cadmium (Cd), lead (Pb), arsenic (As), iron (Fe), copper (Cu) and zinc (Zn) metals using atomic absorption spectrometry. The results obtained showed that levels of Cd, Pb, As, Fe, Cu and Zn ranged from 0.13±0.073 to 1.63±0.96; 0.33±0.18 to 5.38±2.67; 0.020±0.001 to 0.052±0.033; 0.41±0.09 to 10.81±7.29; 0.49±0.13 to 4.37±0.89 and 2.05±0.80 to 94.20±73.28μg/g, respectively, for all vegetable samples. The highest average concentrations of Cd, Pb, As, Fe, Cu and Zn were recorded in leafy species as 0.46±0.19 to 1.63 ± 0.96; 0.00 to 5.38 ± 2.67; 0.00 to 0.049±0.031; 2.95±1.47 to 10.81±1.29; 1.42±0.73 to 4.37±0.89; 4.63±1.37 to 21.99±18.60μg/g, respectively. The highest mean levels 94.20±73.28 and 10.81±7.29μg/g were recorded for Zn and Fe in potato and corchorus, respectively; while the lowest mean levels 0.13±0.073 and 0.33±0.18μg/g were for Cd and Pb in garlic and radish respectively. The element concentrations of these vegetables were within safety baseline levels for human consumption.

Heavy Metal Accumulation in Vegetables and Assessment of their Potential Health Risk

Vegetables constitute essential diet components by contributing carbohydrates, proteins, vitamins, iron, calcium and other nutrients that are in short supply. The present study was conducted to evaluate vegetables such as leafy (spinach), melon (gourd, long gourd and pumpkin) and solonaceous (brinjal) for their potential to accumulate different heavy metals like Cadmium (Cd), Manganese (Mn), Chromium (Cr), Copper (Cu), Iron (Fe), Nickel (Ni), Lead (Pb) and Zinc (Zn). The content of these metals was measured by using Atomic Absorption Spectrophotometer. Mean values were recorded against each vegetable for accumulating heavy metals. It was observed that maximum concentration of Mn (137.3 mg/kg), Cr (6.62 mg/kg) and Fe (968.25 mg/kg) was found in spinach, exceeding the allowed threshold 2.2 mg/kg, 2.3 mg/kg and 425 mg/kg respectively, as set by WHO/FAO. While melon showed great potential to absorb Ni (5.05 mg/kg) which elevated safe limit 0.1 mg/kg and Cu (65 mg/kg) was within the safe range. Brinjal displayed maximum absorption of Zn (41 mg/kg), which did not cross the WHO reference limit 73 mg/kg. In case of Cd both gourd and brinjal showed equal concentration of 0.39 mg/kg but was not at the safe limit 0.241 mg/kg. However levels of Pb were below the FAO/WHO recommended limits in all the vegetables. Low concentrations of Pb indicate that these plants contribute less toxic effects of metals. Overall this order of absorption was recorded as leafyA‹ÂƒmelonA‹Âƒsolonaceous. Human DIM has also been computed and was observed below recommended values by the FAO/WHO. However, to prevent any chronic health risk and extent of heavy metal contamination, steps must be taken to reduce human activities at the sites. Regular monitoring of heavy metals in the vegetables grown in wastewater irrigated areas is also necessary.

Effects of strong reductive process on transformation of heavy metals in protected vegetable soil

The application of sewage and manure in protected vegetable cultivation can induce the occurrence of heavy metals contamination. The present research studied the transformation of heavy metals (Cd, Cu, Pb and Zn) by incubating contaminated protected soil with maize straw and then leaching. The results showed that soil pH was significantly decreased, being more evident in maize straw treatment; soil Eh dropped quickly below -280 mV. Maize straw treatment promoted the activation of Cd, Cu, Pb and Zn from soil, and the total percent of oxidizable fraction and residual fraction of Cd, Cu, Pb and Zn declined at 9th day; the amount of Cd, Cu, Pb and Zn in soil reduced 18.1%, 19.0%, 16.1% and 15.7% at 15th day, respectively. Compared to control, maize straw treatment could increase the concentrations of dissolved Cd and Zn, but Cu decreased. The concentration of colloidal-bound Cd and Pb increased, Cu decreased and no significant change occurred in Zn in maize straw treatment. Strong reductive approach could activate heavy metals in protected vegetable soil, increase the risk of heavy metals accumulation in vegetables, and possibly cause water pollution accompanied with soil water mobilization.

Heavy Metals Accumulation in Vegetables Irrigated with Industrial Influents and Possible Impact of such Vegetables on Human Health

Heavy Metals Accumulation in Vegetables Irrigated with Industrial Influents and Possible Impact of such Vegetables on Human Health

Heavy metal accumulation in vegetables grown in urban gardens

Urban agriculture is increasingly popular for social and economical benefits. However, edible crops grown in cities can be contaminated by airborne pollutants, thus leading to serious health risks. Therefore, we need a better understanding of contamination risks of urban cultivation to define safe practices. Here we study heavy metal risk in horticultural crops grown in urban gardens of Bologna, Italy. We investigated the effect of proximity to different pollution sources such as roads and railways, and the effect of the growing system used, that is soil versus soilless cultivation. We compared heavy metal concentration in urban and rural crops. We focused on surface deposition and tissue accumulation of pollutants during 3 years. Results show that in the city, crops near the road were polluted by heavy metals, with up to 160 mg per kilogram of dry weight for lettuce and 210 mg/kg for basil. The highest Cd accumulation of up to 1.2 mg/kg was found in rural tomato. Soilless planting systems enabled a reduction of heavy metal accumulation in plant tissue, of up to −71 % for rosemary leaves.

Heavy metal accumulation in balsam pear and cowpea related to the geochemical factors of variable-charge soils in the Pearl River Delta, South China.

Variable-charge (v-c) soils in subtropical areas contain considerable amounts of iron/aluminum (Fe/Al) oxides that can strongly influence the fate of heavy metals in agricultural ecosystems. However, the relationship between heavy metal accumulation in vegetables and the geochemical factors associated with v-c soils in subtropical regions remains unknown. The present study investigated heavy metal accumulation under field conditions in the Pearl River Delta (PRD) by measuring the content of 8 heavy metals (zinc (Zn), arsenic (As), copper (Cu), mercury (Hg), lead (Pb), chromium (Cr), nickel (Ni) and cadmium (Cd)) in 43 pairs of v-c soil and vegetable (balsam pear and cowpea) samples. Soil physicochemical properties including pH, texture, organic matter and oxide minerals (Fe2O3, SiO2, Al2O3, CaO, MgO, K2O and Na2O) were also analyzed. Heavy metal accumulation from soil to vegetables was assessed based on bioconcentration factors (BCFs). The results showed that soil extractable Fe, oxide minerals and chemical weathering indices of v-c soils strongly affected heavy metal accumulation, whereas the content of Zn, Cu, Cr and Ni in vegetables was strongly affected by the soil clay content. Significant correlations were found between the BCFs of heavy metals and oxide minerals. However, no significant relationship was found between pH and heavy metal accumulation (except for Cu) in balsam pear and cowpea. Correlation analyses showed that a lower oxalate/DCB- extractable Fe content might indicate greater heavy metal (Zn, Cu, Hg, Cr and Ni) accumulation in vegetables. Therefore, it can be deduced that oxalate/DCB- extractable Fe content is a critical geochemical factor that determines the bioavailability of heavy metals and that iron biogeochemical cycles play vital roles in the fate of heavy metals in vegetable fields in this area. These findings provide new insights into the behaviors and fate of heavy metals in subtropical v-c soils and can be used to develop possible guidelines for vegetable safety management.

Accumulation and health risk of heavy metals in vegetables from harmless and organic vegetable production systems of China

Heavy metal accumulation in vegetables is a growing concern for public health. Limited studies have elucidated the heavy metal accumulation characteristics and health risk of different vegetables produced in different facilities such as greenhouses and open-air fields and under different management modes such as harmless and organic. Given the concern over the aforementioned factors related to heavy metal accumulation, this study selected four typical greenhouse vegetable production bases, short-term harmless greenhouse vegetable base (SHGVB), middle-term harmless greenhouse vegetable base (MHGVB), long-term harmless greenhouse vegetable base (LHGVB), and organic greenhouse vegetable base (OGVB), in Nanjing City, China to study heavy metal accumulation in different vegetables and their associated health risks. Results showed that soils and vegetables from SHGVB and OGVB apparently accumulated fewer certain heavy metals than those from other bases, probably due to fewer planting years and special management, respectively. Greenhouse conditions significantly increased certain soil heavy metal concentrations relative to open-air conditions. However, greenhouse conditions did not significantly increase concentrations of As, Cd, Cu, Hg, and Zn in leaf vegetables. In fact, under greenhouse conditions, Pb accumulation was effectively reduced. The main source of soil heavy metals was the application of large amounts of low-grade fertilizer. There was larger health risk for producers′ children to consume vegetables from the three harmless vegetable bases than those of residents′ children. The hazard index (HI) over a large area exceeded 1 for these two kinds of children in the MHGVB and LHGVB. There was also a slight risk in the SHGVB for producers′ children solely. However, the HI of the whole area of the OGVB for two kinds of children was below 1, suggesting low risk of heavy metal exposure through the food chain. Notably, the contribution rate of Cu and Zn to the HI were high in the four bases, yet current Chinese standards provide no limit for the concentrations of Cu and Zn; thus a potential health risk concerning these metals exists.