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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 0.192mg/kg (west area), 0.071mg/kg (central area), 3.961mg/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. [ABSTRACT FROM AUTHOR]

Heavy metal contamination of mine tailings is one of the most serious environmental challenges facing the mining industry worldwide. Conventional technologies used for the treatment of such tailing soils are expensive both in terms of operation and capital costs as well as being not so effective. In the present study, an indigenous calcifying urease producing bacterial strain was isolated from copper mine tailing soil and used for bioimmobilization of copper, lead and cadmium in contaminated mine tailing soils. Phylogenetic analysis of the 16S rRNA gene sequence identified it asBacillus firmus. The efficiency of metal bioimmobilization was based on microbially induced calcite precipitation (MICP). A five-stage sequential soil extraction procedure was carried out to obtain distribution patterns for the different metals. The mobility of the toxic metals was found to be significantly reduced in the exchangeable fraction with their concentrations markedly increasing in the carbonated fraction after bioremediation. Scanning electron microscopy showed the precipitation of calcite in association with the bacterial cells. Calcium carbonate minerals such as calcite, gwihabaite and aragonite were identified in the bioremediated tailings soils using X-ray diffraction (XRD). It is concluded that MICP holds considerable promise for the remediation of mine tailing soils by efficient immobilization of toxic metals such as copper, lead and cadmium. [ABSTRACT FROM AUTHOR]

Heavy metals and Al in tea products are of increasing concern. In this study, contents of Al, Cd, Co, Cr, Cu, Ni, and Pb in commercially available green tea and its infusions were measured by ICP-MS and ICPAES. Both target hazard quotient (THQ) and hazard index (HI) were employed to assess the potential health risk of studied metals in tea leaves and infusions to drinkers. Results showed that the average contents of Al, Cd, Co, Cr, Cu, Ni, and Pb in tea leaves were 487.57, 0.055, 0.29, 1.63, 17.04, 7.71, and 0.92 mg/kg, respectively. Except for Cu, metal contents were within their maximum limits (1, 5, 30, and 5 mg/kg for Cd, Cr, Cu, and Pb, respectively) of current standards for tea products. Concentrations of metals in tea infusions were all below their maximum limits (0.2, 0.005, 0.05, 1.0, 0.02, and 0.01 mg/L for Al, Cd, Cr(VI), Cu, Ni, and Pb, respectively) for drinking water, and decreased with the increase of infusion times. Pb, Cd, Cu, and Al mainly remained in tea leaves. The THQ from 2.33× 10−5 to 1.47×10−1 and HI from1.41×10−2 to 3.45×10−1 values in tea infusions were all less than 1, suggesting that consumption of tea infusions would not cause significant health risks for consumers. More attention should be paid to monitor Co content in green tea. Both THQ and HI values decreased with the increase of infusion times. Results of this study suggest that tea drinkers should discard the first tea infusion and drink the following infusions. [ABSTRACT FROM AUTHOR]

Heavy metals and As in rice are of increasing concern in China. In this study, concentrations of Pb, Cd, Cu, Cr, Sb, Ni, and As in rice collected from markets in Fuzhou, China, were investigated by ICP-MS and AFS, and their potential health risk to inhabitants were estimated by target hazard quotient (THQ), hazard index (HI), and target cancer risk (TR). The results showed that the concentrations of the seven studied elements in rice grain were all below the permissible limits of China's national standards for foodstuffs (NY/T 419–2007 and GB 2726–2012). For non-carcinogenic risk, the THQ values of individual elements were within the safe interval. However, without considering the bio-accessibility and speciation of toxic elements, the HI values suggest inhabitants in Fuzhou may experience potential health effects due to rice consumption. Cadmium is the major contributor to HI, followed by As. The TR values of As for adults and children were both higher than the acceptable range. The results of this study suggest that more attention should be paid toward monitoring toxic substances (especially Cd and As) in rice in order to assure the food safety for consumers in Fuzhou, China. [ABSTRACT FROM AUTHOR]

Pb, Zn and Cu were determined in 35 Preserved Egg (PE) samples, 25 Salted Egg (SE) samples and 40 Egg Preserved in Rice Wine (EPRW) samples collected from Jiangxi province by ICP-MS. The corresponding health risk for consumers was assessed by the target hazard quotients (THQ) and hazard index (HI). Average Pb, Zn and Cu content in all samples was 0.125 mg/kg, 10.939 mg/kg and 2.094 mg/kg, respectively. Average Pb content in PE was significantly higher than in SE and EPRW. THQ and HI values were less than 1, indicating that intake of heavy metals from PE, SE and EPRW will not pose a significant hazard risk to humans. However, more attention should be paid to control the ingestion by PE, which is the main source of Pb, Zn and Cu for consumers among these three egg products. [ABSTRACT FROM AUTHOR]

The global energy crisis and heavy metal pollution are the common problems of the world. It is noted that the microbial fuel cell (MFC) has been developed as a promising technique for sustainable energy production and simultaneously coupled with the remediation of heavy metals from water and soil. This paper reviewed the performances of MFCs for heavy metal removal from soil and water. Electrochemical and microbial biocatalytic reactions synergistically resulted in power generation and the high removal efficiencies of several heavy metals in wastewater, such as copper, hexavalent chromium, mercury, silver, thallium. The coupling system of MFCs and microbial electrolysis cells (MECs) successfully reduced cadmium and lead without external energy input. Moreover, the effects of pH and electrode materials on the MFCs in water were discussed. In addition, the remediation of heavy metal-contaminated soil by MFCs were summarized, noting that plant-MFC performed very well in the heavy metal removal. [ABSTRACT FROM AUTHOR]

Considering that pollutants can be transferred to the human body through food consumption, food safety is of great concern to the consumers. In order to evaluate the health risk of heavy metals to consumers by milk categories and consumer age groups via the ingestion of milk products, the contents of Pb, Cr, Cd, Cu, Al, Ni, Zn, and Co in fermented, sterilized, and modified milk samples collected from markets in Nanchang, China, were measured by ICP-MS, and the potential health risk was assessed by the method of target hazard quotients (THQ) and hazard index (HI). Results of this study showed that the contents of all studied elements, excluding Zn, were within the food safety limits. The mean daily exposures were estimated to be safe on comparison with the reference dose. However, total metal THQ (TTHQ) and HI values based on maximum exposure were larger than one for a baby age 0-3, which indicated that the long-term high consumption of milk products would result in high health risk for infants. The results also showed that the contribution of fermented milk to total THQ was larger than other milk products. Therefore, more attention should be paid to control the dietary intake of milk products by babies age 0-3, and we should monitor the potential risk caused by the ingestion of fermented milk. [ABSTRACT FROM AUTHOR]

Ureolytic bacteria can be a promising mediator used for the immobilization of potentially toxic elements via microbially-induced carbonate precipitation (MICP) process from biodegradable ions to carbonate form. Electronic waste (E-waste) environment is very complex compared to general metal contaminated soil, however, MICP has not been studied under such an environment. In this study, three bacterial strains were successfully isolated from an E-waste area in Guiyu, China, and indicated to have positive ureolytic behavior with significant heavy metal resistance (specific to Cu and Pb), among which, a strain of Lysinibacillus sp. was proven to show a great persistence in heavy metal immobilization. This featured strain can tolerate up to 100 ppm copper and 1000 ppm lead according to minimal inhibitory concentration (MIC) results, and its urease activity was well-adapted to metal effects. Results also revealed the positive correlation (R2 = 0.9819) between metal concentrations and surface layer protein content present in bacterial cells. The underlying mechanism on the role of S-layer protein in heavy metal immobilization during biocalcification was elucidated. The metabolic system of heavy metal resistance for these E-waste derived isolates is novel and represents a point of interest for possible environmental applications to immobilize toxic heavy metals from electronic waste sites. • Lysinibacillus sp. of E-waste area showed a great persistence in heavy metal immobilization. • Biocalcification by ureolytic Lysinibacillus lead to immobilization of 100 ppm Cu and 1000 ppm Pb. • The metal concentrations and bacterial S-layer protein content were positively correlated. • The role of S-layer protein in metal immobilization during biocalcification was elucidated. [ABSTRACT FROM AUTHOR]

An overexploitation of earth resources results in acid deposition in soil, which adversely impacts soil ecosystems and biodiversity and affects conventional heavy metal remediation using immobilization. A series of column experiments was conducted in this study to compare the cadmium (Cd) retention stability through biotic and abiotic carbonate precipitation impacted by simulated acid rain (SAR), to build a comprehensive understanding of cadmium speciation and distribution along soil depth and to elucidate the biogeochemical bacteria-soil-heavy metal interfaces. The strain of Sporosarcina pasteurii DSM 33 was used to trigger the biotic carbonate precipitation and cultivated throughout the 60-day column incubation. Results of soil pH, electrical conductivity (EC), and quantitative CdCO 3 /CaCO 3 analysis concluded that the combination of biotic and abiotic soil treatment could reinforce soil buffering capacity as a strong defense mechanism against acid rain disturbance. Up to 1.8 ± 0.04 U/mg urease enzyme activity was observed in combination soil from day 10, confirming the sustained effect of urease-mediated microbial carbonate precipitation. Cadmium speciation and distribution analyses provided new insights into the dual stimulation of carbonate-bound and Fe/Mn-bound phases of cadmium immobilization under microbially induced carbonate precipitation (MICP). As confirmed by the microbial community analysis, outsourcing urea triggered diverse microbial metabolic responses, notably carbonate precipitation and dissimilatory iron metabolism, in both oxygen-rich topsoil and oxygen-depleted subsurface layers. The overall investigation suggests the feasibility of applying MICP for soil Cd remediation under harsh environments and stratagem by selecting microbial functionality to overcome environmental challenges. [Display omitted] • A series column experiment was conducted to compare the Cd retention stability in soil. • Biotic and abiotic carbonate precipitation impacted by simulated acid rain (SAR) was studied. • The combined precipitation treatment could reinforce soil buffering capacity against acid rain. • Dual stimulation of both carbonate-bound and Fe/Mn-bound phases of cadmium immobilization was observed. [ABSTRACT FROM AUTHOR]

Heavy metals are the most common pollutant of soil and water, and are being the center of attention due to their toxicity and carcinogenic nature for environment and human health. Microbially induced carbonate precipitation (MICP) is one of well-known processes in recent years for metals immobilization; however, it could have preference for divalent metal ions as MICP directly precipitates calcium ions. Thus, the present research mainly focused on the MICP for the remediation of divalent Pb(II) and hexavalent Cr(VI) in solution using ureolytic Staphylococcus epidermidis. The urease activity led to the metal removal in MICP process, and the removal efficiency of Pb(II) and Cr(VI) was up to 86% and 76.8% (with initial metals concentration 25 mg l−1), respectively. The FTIR spectra revealed number of peaks indicative of CO 3 bonding and formation of carbonate compounds in MICP samples; however, such peaks were clearly identified in MICP-Pb than MICP-Cr(VI) due to direct precipitation or immobilization ability of similar valency (Ca2+ and Pb2+). The SEM images also showed the deposition contained metals produced by co-precipitation with calcium clearly. The results showed significant difference in terms of Cr(VI) – and Pb(II) – immobilization, and MICP depicted clear efficacy or preference in the immobilization of divalent over multivalent metal ions. • Microbially induced carbonate precipitation (MICP) is effective in metals immobilization. • Ureolytic Staphylococcus epidermidis was employed for the first time in MICP. • MICP for the immobilization of divalent Pb(II) and hexavalent Cr(VI) was carried out. • MICP depicted efficacy or preference in immobilization of divalent over multivalent metal ions. [ABSTRACT FROM AUTHOR]

While microbially induced calcite precipitation (MICP) has been extensively studied by using bacteria for the mineralization of heavy metals, this process is still not completely characterized regarding the remediation of metals from solution and soil using fungi. Thus, in the present study, a ureolytic fungal strain, Penicillium chrysogenum CS1, isolated from cement sludge was, firstly, utilized for the biomineralization of chromate and lead from an aqueous solution. Although this fungal strain immobilized a relatively lower amount of Cr(VI) than Pb in solution, at 200 mg L −1 Pb, fungal-based MICP removed 98.8% of Pb in 12 days. The biomineralization process was characterized by SEM-EDX, which confirmed the typical shape of carbonate crystals precipitated by the fungal strain in addition to the presence of the main elements in the form of metal carbonates. FTIR spectroscopy predicted the functional groups that were responsible for the formation of metal carbonates, while XRD identified biominerals in the form of calcite, vaterite, calcium chromium oxide carbonate and hydrocerussite. Further, when this fungal strain was utilized for metals remediation in soil, an increase in the carbonate-bound fraction of metals in soil was observed. The percentage of exchangeable Cr(VI) decreased from 41.60% to 1.95%, while exchangeable Pb decreased from 41.27% to 2.19% in contaminated soil. This is one of the few studies in which fungal-mediated calcite precipitation is characterized in the remediation of heavy metals. [ABSTRACT FROM AUTHOR]