Heavy metals in apple orchard soils and fruits and their health risks in Liaodong Peninsula, Northeast China

Determination of copper ion at trace levels in apple tea samples by simultaneous complexation and spray assisted microextraction method prior to detection by flame atomic absorption spectrophotometry

In the present study, a green and sensitive analytical method for the determination of copper ion at trace levels in apple tea samples was developed. Simultaneous complexation/extraction of the analyte were achieved by spraying-based fine droplet formation liquid-phase microextraction (SFDF-LPME). Copper ion was complexed with a Schiff base chelating agent called as N,N'-Bis(salicylidene)-1,2-phenylenediamine (BSP). Under the optimum conditions, the developed SFDF-LPME-FAAS and FAAS system were assessed with respect to limit of detection (LOD), limit of quantitation (LOQ), linearity and percent relative standard deviation (%RSD). LOD and LOQ values for SFDF-LPME-FAAS method were found to be 6.0 and 19.9 µg/kg, respectively. Enhancement in calibration sensitivity for developed method was found as 23 folds. In addition, accuracy/suitability of the developed SFDF-LPME-FAAS method were confirmed by spiking experiments. Two different apple tea samples were spiked to different concentration values and percent recovery results from 91.1 and 123.8 % proved the accuracy/suitability of the method.

Rootstock-scion interaction affects Malus transcriptome profiles in response to cadmium

Apple production is threatened by cadmium contamination in orchards. Cd accumulation and tolerance in grafted Malus plants is affected by rootstock, scion, and their interaction. This dataset is part of an experiment investigating the molecular mechanism of Cd bioaccumulation and tolerance in different apple rootstock-scion combinations. We exposed four rootstock-scion combinations to Cd treatment consisting of Hanfu and Fuji apple (Malus domestica) scions grafted onto apple rootstocks of M. baccata or M. micromalus "qingzhoulinqin". RNA sequencing was conducted in roots and leaves of grafting combinations under 0 or 50 μM CdCl2 conditions. A comprehensive transcriptional dataset of affected rootstock, scion, and their interaction among different graft combinations was obtained. This dataset provides new insights in the transcriptional control of Cd bioaccumulation and tolerance in grafting plants regulated by rootstock and scion. Herein, we discuss the molecular mechanism underlying Cd absorption and bioaccumulation.

MRTCM: A comprehensive dataset for probabilistic risk assessment of metals and metalloids in traditional Chinese medicine

Traditional Chinese medicine (TCM) is still considered a global complementary or alternative medical system, but exogenous hazardous contaminants remain in TCM even after decocting. Besides, it is time-consuming to conduct a risk assessment of trace elements in TCMs with a non-automatic approach due to the wide variety of TCMs. Here, we present MRTCM, a cloud-computing infrastructure for automating the probabilistic risk assessment of metals and metalloids in TCM. MRTCM includes a consumption database and a pollutant database involving forty million rows of consumption data and fourteen types of TCM potentially toxic elements concentrations. The algorithm of probabilistic risk assessment was also packaged in MRTCM to assess the risks of eight elements with Monte Carlo simulation. The results demonstrated that 96.64% and 99.46% had no non-carcinogenic risk (hazard indices (HI) were < 1.0) for animal and herbal medicines consumers, respectively. After twenty years of exposure, less than 1% of the total carcinogenic risk (CR_t) was > 10^-4 for TCM consumers, indicating that they are at potential risk for carcinogenicity. Sensitivity analysis revealed that annual consumption and concentration were the main variables affecting the assessment results. Ultimately, a priority management list of TCMs was also generated, indicating that more attention should be paid to the non-carcinogenic risks of As, Mn, and Hg and the carcinogenic risks of As and Cr in Pheretima and Cr in Arcae Conch. In general, MRTCM could significantly enhance the efficiency of risk assessment in TCM and provide reasonable guidance for policymakers to optimize risk management.

The concentration of potentially toxic elements (PTEs) in apple fruit: a global systematic review, meta-analysis, and health risk assessment

The presence of potentially toxic elements (PTEs) in crops can directly/indirectly affect consumers' health. The contamination of apple as one of the most consumed fruits with PTEs such as lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and nickel (Ni) leads to carcinogenic risk (CR) and non-carcinogenic risk (n-CR). In this regard, a systematic review, meta-analysis, and health risk assessment regarding the concentration of the PTEs in apples was conducted using international databases such as Scopus and PubMed. According to the results, the rank order of PTEs in apple fruits was Pb (427.45 µg/kg-wet weight) > Ni (228.74 µg/kg-wet weight) > Cr (212.43 µg/kg-wet weight) > As (123.93 µg/kg-wet weight) > Cd (15.28 µg/kg-wet weight). n-CR was higher than 1 for the USA, Serbia for adults, and Poland for children. CR for adults in Serbia, Spain, Greece, China, Bangladesh, and Pakistan and children in Serbia, Spain, Greece, China, and Bangladesh were not acceptable (CR > 1.00E - 06 value). In this regard, the pooled PTEs of apples can cause CR and n-CR issues. Therefore, constant monitoring and reduction of pesticide application are strongly recommended for controlling PTEs in apple fruits.

GABA-mediated inhibition of cadmium uptake and accumulation in apples

GABA, a four-carbon non-protein amino acid, plays an important role in animals and plants. We previously found GABA could alleviate alkali stress in apple seedlings. However, its physiological mechanism under heavy metal cadmium (Cd) stress need to be further studied. Thus, we explored its biological role in response to Cd stress. It was verified that 0.5 mM GABA could effectively alleviate Cd toxicity. Using NMT technique, we found that exogenous GABA could significantly reduce the net Cd²⁺ fluxes in apple roots, and Cd content was significantly lower than that in roots under Cd stress. Further analysis indicated exogenous GABA could significantly reduce the expression of genes related to the uptake and transport of Cd in apples under Cd stress. In addition, exogenous GABA could significantly increase the content of amino acids in apple roots under Cd stress. GAD is a key enzyme in GABA synthesis, we obtained transgenic apple roots of overexpression MdGAD1. Compared with the control, transgenic roots accumulated less Cd, maintained lower Cd uptake by roots, and lower expression of related transport genes. These results showed that GABA could effectively alleviate Cd toxicity in apple seedlings and provide a new perspective of GABA to alleviate Cd stress.

Assessment of metal enrichment and contamination in surface sediment of Mandovi estuary, Goa, West coast of India

Metal concentration in the sediments was determined to assess the metal enrichment and level of contamination in the Mandovi estuary. The metal distribution in the Mandovi estuary revealed preferential input through open-cast iron-ore mining, industrial, fishing, and agricultural activities. The heavy riverine runoff associated with high rainfall influenced the distribution of Mn, Zn, and Pb during monsoon season. In addition, sediment grain size and associated organic matter governed metal distribution in surface sediments. The role of grain size and organic matter along with Fe-Mn oxides in the distribution of metals was construed through correlation and factor analysis. Geo-accumulation index, contamination factor, and potential contamination index indicated contamination of surficial sediments of the Mandovi estuary with Cr and Pb.

Occurrence and dietary exposure of heavy metals in marketed vegetables and fruits of Shandong Province, China

The contamination of heavy metals in vegetables and fruits is a serious threat to food safety and human health. The present study was designed to investigate the occurrence and dietary exposure of lead (Pb), arsenic (As), cadmium (Cd), and mercury (Hg) in vegetables and fruits in Shandong Province, China. Results demonstrated that the mean level of total heavy metals was 30.25 µg/kg. The most frequently found heavy metal was Cd (69.2%) with a mean value of 11.54 µg/kg. The mean exposure values of Pb, As, Cd, and Hg in vegetables were 0.052, 0.045, 0.038, and 2.40 × 10-3 µg/kg bw/day, respectively. Moreover, the calculated hazard quotient (HQ) values of mean levels for these four heavy metals were all less than 1, indicating the health risk of heavy metal exposure caused by vegetable consumption was low. This study has displayed baseline information on heavy metal contamination in vegetables and fruits, which can provide useful data support for the formulation of relevant standards and government management.

Polycyclic aromatic hydrocarbons, pesticides, and metals in olive: analysis and probabilistic risk assessment

In the present study, levels of 22 pesticides, eight metals, and 16 polycyclic aromatic hydrocarbons (PAHs) in 1800 Iranian olive samples (20 cultivars from six different cultivation zones), were determined; then, health risk posed by oral consumption of the olive samples to Iranian consumers was assessed. Quantification of PAHs and pesticides was done by chromatography-mass spectrometry (GC-MS), and metal levels were determined using inductively coupled plasma-optical emission spectrometry (ICP-OES). There were no significant differences among the cultivars and zones in terms of the levels of the tested compounds. Target hazard quotients (THQ) were <1.0 for all pesticides, and total hazard indices (HI) indicated di minimis risk. At the 25th or 95th centiles, Incremental Life Time Cancer Risks (ILCRs) for carcinogenic elements, arsenic, and lead and noncarcinogenic metals did not exhibit a significant hazard (HI <1.0 for both cases). At the 25th or 95th centiles, ILCR and margins of exposure (MoE) for PAHs indicated di minimis risk. Sensitivity analysis showed that concentrations of contaminants had the most significant effect on carcinogenic and noncarcinogenic risks.

Health and ecological risk assessment and simulation of heavy metal-contaminated soil of Tehran landfill

The toxic effects of heavy metals in landfill soils have become a significant concern for human health. The present study aimed to estimate the health and ecological risk associated with soil heavy metal in Tehran landfill. A total of 48 soil samples were taken from the landfill and residential area and were analyzed using inductively coupled plasma-optical emission spectroscopy. The results showed the following order for heavy metal levels in landfill soil: Al > Fe > Mn > Zn > Cr > Cu > Pb > Ni > Co > As > Cd. The investigated ecological indices showed moderate to high heavy metal pollution. The principal component analysis revealed that the concentration of Pb, Cu, Zn, Cr, and Ni in the investigated soil was mainly affected by anthropogenic activities. Although the hazard index (HI) value in children was 6.5 times greater than that of adults, this value for both landfill workers and residents of the target area was at a safe level (HI ≤ 1). In the residential area, the Incremental Lifetime Cancer Risk (ILCR) value of adults (1.4 × 10-4) was greater than children ILCR value (1.2 × 10-4). Monte Carlo simulation and sensitivity analysis showed input variables such as exposure duration, exposure frequency, Ni concentration, soil ingestion rate, and As concentration have a positive effect on ILCR of 41.3, 24.3, 9.4, 9.0, and 2.9% in children, respectively. These results indicate that the landfill soil and the adjacent residential area are affected by heavy metal contamination and that the current solid waste management policies need to be revised.

Heavy metal ions' poisoning behavior-inspired etched UiO-66/CTS aerogel for Pb(II) and Cd(II) removal from aqueous and apple juice

Here, inspired by the poisoning process of heavy metal in human body that the accidental ingested heavy metal can anchor to the functional groups of DNA/protein/enzyme to exert their toxicities during the rapid blood circulation, we developed the adsorbent that enveloped Etched UiO-66 with abundant functional groups into chitosan (CTS) aerogel to capture Pb(II) and Cd(II) in aqueous and apple juice. SEM, XRD and FTIR spectra were used to characterize the Etched UiO-66/CTS aerogel. The results showed that Etched UiO-66/CTS aerogel has a three-dimensional porous structure, and -OH groups of CTS interact with Zr(IV) of Etched UiO-66 to form the stable UiO-66/CTS aerogel. Benefiting from the intrinsic properties of porous and abundant functional groups, Etched UiO-66/CTS aerogel exhibits satisfactory adsorption capacities of 654.9 mg g^-1 for Pb(II) and 343.9 mg g^-1 for Cd(II) at 45 °C. Moreover, the aerogel shows excellent removal efficiencies of 98.21% for Pb(II) and 98.70% for Cd(II) with initial concentration of 1.0 mg L^-1 in apple juice with little effect on the quality of apple juice. This strategy of mimetic heavy metal ions' poisoning behavior opens up a new avenue for the removal of heavy metal ions in complex matrices.

Potential ecological and health risk assessment of different kiwifruit orchards in Qianjiang district, Chongqing city, China

Heavy metal (HM) pollution in orchards is becoming serious in many countries, and some fruit HMs exceed the safety limits. In this study, contents of 8 HMs (Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn) in 5 kiwifruit orchard soils and the tissues (roots, twigs, leaves, fruits) of 4 kiwifruit varieties collected from Qianjiang district, Chongqing city, China, were determined. Seven HMs could meet priority protection class I, except for Cd with slightly poor environmental quality, including 4% and 53% of the samples belonging to the strict control class III and safe utilization class II, respectively. The potential ecological risk index (235.30) indicated that the HMs in the orchard soil were of medium potential ecological risk. The HMs' migration from rock to soil was very obvious. Kiwifruit was easy to accumulate Cu from soil and it had high Zn and Ni translocations to above-ground parts from roots. Compared with other tissues, HMs' concentrations in fruits were the lowest. From the perspective of human health, about 8.3% and 0.83% of the fruit samples for Cr and Cu exceeded the national maximum permissible levels, respectively; fortunately, the health risk index (HRI) values for all the fruit samples were within the safe limits.

Geochemical Characteristics of Heavy Metals in Soil and Blueberries of the Core Majiang Blueberry Production Area

By using field survey, sampling, and indoor analysis, we analyzed the geochemical characteristics of heavy metals in the blueberries and soil of the core blueberry production area of Majiang in Guizhou, China. Analyses were based on national standards for soil pollution risk control on agricultural land (GB15618-2018) and pollution index limits in food (GB2762-2017/2012). The results demonstrated that heavy metal content in the soil profile of this area exceeds standards, but standards were exceeded mainly in the lower layer of the profile, and blueberry growth was not substantially affected. Except for in Lanmenggu, heavy metals in the cultivation soil layer of Majiang Blueberry Farms did not considerably exceed standards. The content of heavy metals in blueberry did not exceed the standard, so it was a safe fruit. These results can provide a reference for the safe cultivation of Majiang blueberries.

Particulate Matter Accumulation on Apples and Plums: Roads Do Not Represent the Greatest Threat

Particulate matter (PM) is a mixture of solid and liquid substances of organic and inorganic character suspended in air. Plants are used as biological filters of air. However, PM can be deposited on their edible parts, with a negative effect on people’s health. The aim of this study was to document the PM accumulation on apples and plums harvested from orchards located alongside roads with differing amounts of traffic. Plums accumulated more PM than apples. The deposition of PM on apples increased during fruit development and was highest at harvest. The impact of road type, traffic intensity, and distance from the road on PM accumulation on fruit was small. The least PM was adsorbed by apples harvested from an orchard located close to a road with the highest traffic, while in the case of plums, no effect of the road on PM deposition was recorded. The amount of PM accumulated on fruits depended on the species (fruit morphology, harvest period), activities undertaken in the orchard (early pruning exposes fruits to PM, ecological preparations increase fruit viscosity), and sources of pollution other than the roads located close to the orchard. Washing fruits with water removed half of the accumulated PM.

Ecological and health risks of soil and grape heavy metals in long-term fertilized vineyards (Chaharmahal and Bakhtiari province of Iran)

Heavy metal pollution in food-producing ecosystems resulting from long-term fertilizing and other agricultural practices is causing major concern due to its health risk potential for human and other organisms. This study was designed to investigate heavy metal concentrations (Cu, Zn, Pb, Cr and Cd) and assess their ecological risk using contamination factor (Cf), pollution load index (PLI) and ecological risk index. Health risk assessment (HRA) was also estimated by investigating non-carcinogenic and carcinogenic risks of soil via oral ingestion, dermal contact, inhalation, and health risk of grape consumption. To this aim, 38 fertilized vineyards of the region were investigated during harvesting seasons of 2016 and 2017. The results showed a same ranking order of the metals in the soil and grape that was Zn > Cu > Pb > Cr > Cd. The average concentrations of Zn and Pb in the grape samples were significantly higher than the national permissible limits. According to Cf and PLI indices, Cd had the most ecological risk compared to the other studied metals. The HRA results showed that adults and children are not exposed to non-carcinogenic risk from the studied heavy metals in the vineyard soils. But, it was a tolerable level of carcinogenic health risk only by Cr in some of the vineyards. The PLI had most significant correlation (p < 0.01) with the other studied indices. So, it can be considered as a rapid and applicable index to assess ecological and health risk of heavy metals in the region. To food-chain security and community health, some comprehensive managing plans are necessary to increase farmer's awareness about the standard amount of chemical fertilizers and pesticides. Furthermore, continuous monitoring of heavy metals in soil and grape of the vineyards should be performed.

Copper accumulation, subcellular partitioning and physiological and molecular responses in relation to different copper tolerance in apple rootstocks

To unravel the physiological and molecular regulation mechanisms underlying the variation in copper (Cu)accumulation, translocation and tolerance among five apple rootstocks, seedlings were exposed to either basal or excess Cu. Excess Cu suppressed plant biomass and root architecture, which was less pronounced in Malus prunifolia Borkh., indicating its relatively higher Cu tolerance. Among the five apple rootstocks, M. prunifolia exhibited the highest Cu concentration and bio-concentration factor in roots but the lowest translocation factor, indicating its greater ability to immobilize Cu and restrict translocation to the aerial parts. Higher Cu concentration in cell wall fraction but lower Cu proportion in membrane-containing and organelle-rich fractions were found in M. prunifolia. Compared with the other four apple rootstocks under excess Cu conditions, M. prunifolia had a lower increment of hydrogen peroxide in roots and leaves and malondialdehyde in roots, but higher concentrations of carbohydrates and enhanced antioxidants. Transcript levels of genes involved in Cu uptake, transport and detoxification revealed species-specific differences that are probably related to alterations in Cu tolerance. M. prunifolia had relatively higher gene transcript levels including copper transporters 2 (COPT2), COPT6 and zinc/iron-regulated transporter-related protein 2 (ZIP2), which probably took part in Cu uptake, and C-type ATP-binding cassette transporter 2 (ABCC2), copper chaperone for Cu/Zn superoxide dismutase (CCS), Cu/Zn superoxide dismutase 1 (CSD1) and metallothionein 2 (MT2) probably implicated in Cu detoxification, and relatively lower mRNA levels of yellow stripe-like transporter 3 (YSL3) and heavy metal ATPase 5 (HMA5) involved in transport of Cu to aerial parts. These results suggest that M. prunifolia is more tolerant to excess Cu than the other four apple rootstocks under the current experimental conditions, which is probably attributed to more Cu retention in roots, subcellular partitioning, well-coordinated antioxidant defense mechanisms and transcriptional expression of genes involved in Cu uptake, translocation and detoxification.

Biostimulation of carbonate precipitation process in soil for copper immobilization

The urease-based microbially induced carbonate precipitation (MICP) is known as effective remediation strategy in soil metals remediation; however, all related studies confined to bioaugmentation. In the present study, biostimulation process was adopted for the first time in accelerating MICP in copper (Cu) immobilization in soil. The abundance, composition, and diversity of the bacterial community after biostimulation were assessed with MiSeq Illumina sequencing analysis that confirmed number and types of ureolytic and calcifying bacteria grown significantly leading to MICP process, compared to untreated soil. The results demonstrated that biostimulation induced calcite precipitation in soil that immobilized Cu mainly in carbonated fraction of soil, while soluble-exchangeable fraction decreased from 45.54 mg kg^-1 to 1.55 mg kg^-1 Cu in soil. Scanning electron microscopy (SEM) cum energy-dispersive X-ray spectroscopy (EDX) evaluated structure and elemental composition in Cu immobilization after biostimulation. Fourier Transform-Infra Red (FTIR) spectroscopy depicted functional chemical groups involved in copper immobilization, while X-Ray Diffraction (XRD) identified main crystalline phases or biominerals formed during biostimulation in order to carryout Cu remediation from soil.

Pollution and health risk assessment of heavy metals in agricultural soil, atmospheric dust and major food crops in Kermanshah province, Iran

A total of 167 samples of agricultural soil, atmospheric dust and food crops (wheat and maize) were collected, and four heavy metals, including Zn, Cu, Ni, and Cr, were analyzed for their concentrations, pollution levels and human health risks. The mean heavy metal contents in the agricultural soil and atmospheric dust were exceeds background values and lower than their IEQS (Iranian Environmental Quality Standard) with an exception of Ni. A pollution assessment by Geo-accumulation Index (I_geo) showed that the pollution levels were in the order of Ni> Cu> Cr> Zn for agricultural soils and Ni> Cu> Zn> Cr for atmospheric dust. The Ni levels can be considered "moderately to heavily contaminated" status. The human health risk assessment indicated that non-carcinogenic values were below the threshold values (1), and main exposure pathway of heavy metals to both children and adults are ingestion. The carcinogenic risks values for Ni and Cr were higher than the safe value (1 × 10^-6), suggesting that all receptors (especially wheat) in Kermanshah province might have significant and acceptable potential health risk because of exposure to Ni and Cr. The carcinogenic risk for children and adults has a descending order of Ni> Cr, except for wheat. These results provide basic information on heavy metal contamination control and human health risk assessment management in the Kermanshah province.

Residue Dynamics and Risk Assessment of Prochloraz and Its Metabolite 2,4,6-Trichlorophenol in Apple

The residue dynamics and risk assessment of prochloraz and its metabolite 2,4,6-trichlorophenol (2,4,6-TCP) in apple under different treatment concentrations were investigated using a GC-ECD method. The derivatization percent of prochloraz to 2,4,6-TCP was stable and complete. The recoveries of prochloraz and 2,4,6-TCP were 82.9–114.4%, and the coefficients of variation (CV) were 0.7–8.6% for the whole fruit, apple pulp, and apple peel samples. Under the application of 2 °C 2.0 g/L, 2 °C 1.0 g/L, 20 °C 2.0 g/L, and 20 °C 1.0 g/L treatment, the half-life for the degradation of prochloraz was 57.8–86.6 d in the whole fruit and apple peel, and the prochloraz concentration in the apple pulp increased gradually until a peak (0.72 mg·kg⁻¹) was reached. The concentration of 2,4,6-TCP was below 0.1 mg·kg⁻¹ in four treatment conditions and not detected (<LOD) in apple pulp. Finally, based on the detection of market samples in Hefei (China), we believe that the residual level of prochloraz in apples meets the requirements of the Chinese standards.

Integration of Cadmium Accumulation, Subcellular Distribution, and Physiological Responses to Understand Cadmium Tolerance in Apple Rootstocks

Cadmium (Cd) is a nonessential and highly toxic element causing agricultural problems. However, little information is available about the variation in Cd tolerance among apple rootstocks and its underlying physiological regulation mechanisms. This study investigated Cd accumulation, subcellular distribution, and chemical forms as well as physiological changes among four apple rootstocks exposed to either 0 or 300 μM CdCl2. The results showed that variations in Cd tolerance existed among these rootstocks. Cd exposure caused decline in photosynthesis, chlorophyll and biomass in four apple rootstocks, which was less pronounced in M. baccata, indicating its higher Cd tolerance. This finding was corroborated with higher Cd tolerance indexes (TIs) of the whole plant in M. baccata than those in the other three apple rootstocks. Among the four apple rootstocks, M. baccata displayed the lowest Cd concentrations in roots, wood, and leaves, the smallest total Cd amounts as well as the lowest BCF. In apple rootstocks, it was found that to immobilize Cd in cell wall and soluble fraction (most likely in vacuole) and to convert it into pectate- or protein- integrated forms and undissolved Cd phosphate forms may be the primary strategies to reduce Cd mobility and toxicity. The physiological changes including ROS, carbohydrates and antioxidants were in line with the variations of Cd tolerance among four apple rootstocks. In comparison with the other three apple rootstocks, M. baccata had lower concentrations of ROS in roots and bark, H2O2 in roots and leaves and MDA in roots, wood and bark, but higher concentrations of soluble sugars in bark and starch in roots and leaves, and enhanced antioxidants. These results indicate that M. baccata are more tolerant to Cd stress than the other three apple rootstocks under the current experiment conditions, which is probably related to Cd accumulation, subcellular partitioning and chemical forms of Cd and well-coordinated antioxidant defense mechanisms.

Source identification and spatial distribution of heavy metals in tobacco-growing soils in Shandong province of China with multivariate and geostatistical analysis

Samples of surface soil from tobacco (Nicotiana tabacum L.) fields were analysed for heavy metals and showed the following concentrations (mean of 246 samples, mg/kg): As, 5.10; Cd, 0.11; Cr, 49.49; Cu, 14.72; Hg, 0.08; Ni, 19.28; Pb. 20.20 and Zn, 30.76. The values of the index of geoaccumulation (I geo) and of the enrichment factor indicated modest enrichment with As, Cd, Cr, Hg, Ni or Pb. Principal component analysis and cluster analysis correctly allocated each investigated element to its source, whether anthropogenic or natural. The results were consistent with estimated inputs of heavy metals from fertilizers, irrigation water and atmospheric deposition. The variation in the concentrations of As, Cd, Cu, Pb and Zn in the soil was mainly due to long-term agricultural practises, and that of Cr and Ni was mainly due to the soil parent material, whereas the source of Hg was industrial activity, which ultimately led to atmospheric deposition. Atmospheric deposition was the main exogenous source of heavy metals, and fertilizers also played an important role in the accumulation of these elements in soil. Identifying the sources of heavy metals in agricultural soils can serve as a basis for appropriate action to control and reduce the addition of heavy metals to cultivated soils.

Heavy metal contents, distribution, and prediction in a regional soil-wheat system

The entry of heavy metals into the food chain is of concern for potential health risks. To investigate the spatial relationships of heavy metals in a regional soil-wheat system, 99 pairs of surface soil (0-15 cm) and wheat grain samples were collected from Changshu, China, a typical county in the Yangtze Delta region. Both soil and wheat grain samples were analyzed for total Cd, Cu, Ni, Pb, and Zn. DTPA-extractable metals and major physico-chemical properties were also determined for soil samples. Moderate accumulation of heavy metals was found in soils and wheat grains, especially Cd. However, the levels were within the target hazard quotients (THQ) safe values with respect to non-carcinogenic risks, but more attention should be paid to Cd. Spatially, Cd, Cu, Ni, and Zn in wheat grains and soils had similar geographical patterns, whereas Pb showed opposite trends. Cross-correlograms further quantitatively confirmed the spatial relationships of heavy metals in wheat grains and soils. In addition, heavy metals in wheat grains were significantly spatially correlated with most soil physio-chemical properties. Particularly, a set of regression models for Cd in wheat grains were established with a maximum predictive success of 65%. These models can be used to predict Cd in wheat grains, and thus allows farmers to decrease the threat by certain framing practices such as ameliorating soil pH or growing a less metal-accumulating cultivar.

Heavy metals in navel orange orchards of Xinfeng County and their transfer from soils to navel oranges

This study investigated heavy metal concentrations in soils and navel oranges of Xinfeng County, a well-known navel orange producing area of China. The results showed that the average concentrations of lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As) and mercury (Hg) in orchard soils all increased compared to the regional background values, especially for Cd, which increased by 422%. When compared to the Chinese Environmental Quality Standard for soil (GB15618-1995), Pb, Cr and Hg concentrations in all orchard soil samples were below the limit standards, but Cd concentrations in 24 soil samples (21%) and As concentrations in 8 soil samples (7%) exceeded the limit standards. However, concentrations of all heavy metals in navel orange pulps were within the National Food Safety Standard of China (GB 2762-2012). Dietary risk assessment also showed that the exposure to these five heavy metals by consumption of navel oranges could hardly pose adverse health effects on adults and children. Since the range and degree of soil Cd pollution was widest and the most severe of all, Cd was taken as an example to reveal the transfer characteristics of heavy metals in soil-navel orange system. Cd concentrations in different organs of navel orange trees decreased in the following order: root>leaf>peel>pulp. That navel oranges planted in the Cd contaminated soils were within the national food safety standard was mainly due to the low transfer factor for Cd from soil to pulp (TFpulp). Further studies showed that TFpulp was significantly negatively correlated with soil pH, organic carbon (OC) and cation exchange capacity (CEC). Based on these soil properties, a prediction equation for TFpulp was established, which indicated that the risk for Cd concentration of navel orange pulp exceeding the national food limit is generally low, when soil Cd concentration is below 7.30 mg/kg. If appropriate actions are taken to increase soil pH, OC and CEC, Cd concentrations in navel orange pulps could be further reduced.

Contamination and health risks from heavy metals in cultivated soil in Zhangjiakou City of Hebei Province, China

A total of 79 topsoil samples (ranging from 0 to 20 cm in depth) were collected from a grape cultivation area of Zhangjiakou City, China. The total concentrations of As, Cd, Hg, Cr, Cu, Mn, Ni, Pb, and Zn in soil samples were determined to evaluate pollution levels and associated health risks in each sample. Pollution levels were calculated using enrichment factors (EF) and geoaccumulation index (I geo). Health risks for adults and children were quantified using hazard indexes (HI) and aggregate carcinogenic risks (ACR). The mean concentrations of measured heavy metals Cd, Hg, and Cu, only in the grape cultivation soil samples, were higher than the background values of heavy metals in Hebei Province. According to principal component analysis (PCA), the anthropogenic activities related to agronomic and fossil fuel combustion practices attributed to higher accumulations of Cd, Hg, and Cu, which have slightly polluted about 10-40% of the sampled soils. However, the HI for all of the heavy metals were lower than 1 (within safe limits), and the ACR of As was in the 10(-6)-10(-4) range (a tolerable level). This suggests the absence of both non-carcinogenic and carcinogenic health risks for adults and children through oral ingestion and dermal absorption exposure pathways in the studied area. It should be also noted that the heightened vulnerability of children to health risks was accounted for higher HI and ACR values. Consequently, heavy metal concentrations (e.g., Cd, Hg, Cu) should be periodically monitored in these soils and improved soil management practices are required to minimize possible impacts on children's health.