Potentially Toxic Metals Research Articles

Simultaneous Removal of Cu2+, Cd2+ and Pb2+ by Modified Wheat Straw Biochar from Aqueous Solution: Preparation, Characterization and Adsorption Mechanism.

As an eco-friendly and efficient adsorbent for removal of potential toxic metals from aqueous solution, biochar has received widespread attention. In the present study, wheat straw biochar (BC) and corresponding modified biochar (HNC) were used to remove Cu2+, Cd2+ and Pb2+ from an aqueous solution. The influence of the environment factors on metals adsorption and adsorption mechanism were discussed in detail. The results showed that the HNC had porous structures and owned ample functional groups (−OH, −COOH and C−N groups) compared with the BC. In the single system, the adsorption capacities of HNC for Cu2+, Cd2+ and Pb2+ at a pH of 5.5 were 18.36, 22.83 and 49.38 mg/g, which were 76.89%, 164.36% and 22.75% higher than that of the BC, respectively. In addition, the adsorption process of Cu2+ and Cd2+ on BC and HNC fitted to the Langmuir isotherm model and pseudo-second-order kinetics, but the adsorption of Pb2+ on BC and HNC fitted to the Langmuir isotherm model and pseudo-first-order kinetics. Adsorption isotherms indicated that the adsorption of Cu2+, Cd2+ and Pb2+ by BC and HNC was a spontaneous endothermic process. The competitive adsorption of mixed metal ions (Cu2+, Cd2+ and Pb2+) revealed that HNC was more preferential to adsorb Cu2+ compared with Cd2+ and Pb2+. Furthermore, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that the main adsorption mechanisms were surface complexation and precipitation, and the adsorbed Cu2+, Cd2+ and Pb2+ on HNC mainly exist as CuO, Cd(OH)2, Pb3O4 and Pb(OH)2.

Groundwater Contamination and Health Risk Evaluation of Naturally Occurring Potential Toxic Metals of Hatiya Island, Bangladesh

Groundwater Contamination and Health Risk Evaluation of Naturally Occurring Potential Toxic Metals of Hatiya Island, Bangladesh

Release of metal elements from the Essure implant: A prospective cohort study

Objective(s)The causal mechanistic relationships between Essure® and adverse effects are unclear, but corrosion in the in-vivo environment with release of metal ions may be suspected. Here we evaluated the concentrations of nickel (Ni), chromium (Cr) and tin (Sn) in the peritoneal fluid (PF) and in the fallopian tube (FT) during laparoscopic Essure® removal compared to a control group. Study designNi, Cr and Sn concentrations were determined in the PF and FT from two groups(group A: symptomatic patients with Essure®) vs group B (control group without Essure®) by Inductively Coupled Plasma Mass Spectrometry analysis. Correlation between metal elements concentrations and reported pre-operative symptoms was also investigated. ResultsThere were 131 patients in group A vs 92 control patients in group B. The concentrations of Cr and Ni in PF between both groups were significantly different (p < 0.0001) while there was no statistical difference for Sn (p = 0.58). There was also a significantly higher concentration in the FT for the 3 metal elements in group A than in group B (p < 0.0001). There were differential dynamics of the levels of metal elements based on the length of time between the placement and removal of Essure®. ConclusionsThere was a chronic exposure to metal elements in symptomatic patients with Essure® raising the question of the relationship between adverse effects and these potential toxic metals.

Bringing citizen science to life: Evaluation of a national citizen science program for public benefit

The Australian citizen science research programs, VegeSafe and DustSafe, are novel and wide-reaching. Together, they capture the largest number of community-generated domestic garden soil and indoor house dust samples and associated trace metal analysis of any similar programme globally, totalling 26,500 samples from 7,200 homes in Australia alone. All citizen science research programs need to balance often conflicting expectations and imperatives of the researchers and the participants. This paper assesses VegeSafe and DustSafe participant and researcher outcomes against common goals of citizen science programs, including participant engagement, accessibility, motivations and learning in order to evaluate the programs’ impact and usefulness. Questionnaire data from 522 questionnaires were analysed which showed that VegeSafe and DustSafe have: enhanced participants’ involvement in science (76%), understanding of science (62%); addressed specific community concerns (91%); and were considered useful (93%). The success of the VegeSafe and DustSafe programs can be measured by the number of samples received, households engaged and its geographic footprint across Australia's most populated cities. The participant questionnaire provided deeper insight into positive participant outcomes, including participant autonomy in the scientific process and changes in attitudes and behaviours towards science. Many participants adopted interventions to mitigate potential toxic trace metal exposure in their domestic spaces after receiving their results. The VegeSafe and DustSafe programs provide valuable examples of how to establish programs to meet community needs effectively, educate the community and bring about positive change to ultimately improve community health.

Beneficial Role of Selenium (Se) Biofortification in Developing Resilience Against Potentially Toxic Metal and Metalloid Stress in Crops: Recent Trends in Genetic Engineering and Omics Approaches

Beneficial Role of Selenium (Se) Biofortification in Developing Resilience Against Potentially Toxic Metal and Metalloid Stress in Crops: Recent Trends in Genetic Engineering and Omics Approaches

Chemical characteristics of groundnut and sheanut shell biochars as adsorbents and soil conditioners in the era of ecological sustainability

This study investigated the influence of pyrolysis temperatures on characteristics of groundnut and sheanut shell biochars as potential adsorbents and soil conditioners. Groundnut and sheanut shell biochars were produced at pyrolysis temperatures of 350 ± 5 °C and 700 ± 5 °C using muffle furnace. The chemical characteristics of the biochars were analysed, potential contamination and ecological risk were determined based on the metal enrichment index and potential ecological risk index (PERI). pH values of the biochars ranged from 9.42 to 10.23 and 662.33 to 3206.67 μS/cm for electrical conductivity. The total compositions of carbon and nitrogen for GB350, GB700, SB350 and SB700 ranged from 58.13% to 70.23% and 0.45% to 1.37%, respectively. The minerals composition of GB350, GB700, SB350 and SB700 ranged from 12944.92 to 20873.30 mg/kg for potassium, 192.24 to 410.72 mg/kg for sodium, 3567.98 to 13451.83 mg/kg for calcium and 1150.33 to 3414.34 mg/kg for magnesium. The pH of the biochars is found to be alkaline which upsurge with increasing pyrolysis temperature. Concentrations of nutrients such as calcium, potassium, magnesium and phosphorus diverse in groundnut shells feedstocks due to the pyrolysis conditions. The groundnut and sheanut shell biochars can increase essential nutrients such as nitrogen, phosphorus, and potassium in soil, which are conducive to growth of plant. The availability of phosphorus in the biochars make it phosphorus-rich and can be used as slow-release fertilisers. The potential toxic metals in the groundnut and sheanut shell biochars have values that suggested low contamination and less potential ecological risk making the biochars ecofriendly. Groundnut and sheanut shell biochars can be used in fields as an adsorbent and a soil amendment based on its chemical characteristics.

Copyrolysis of food waste and rice husk to biochar to create a sustainable resource for soil amendment: A pilot-scale case study in Jinhua, China

Worldwide, massive amounts of food waste have been generated at increasingly accelerated rates, posing potentially great risks to the environment. Shifting traditional waste treatment to a sustainable bioeconomy thus challenges food chain management worldwide. In this study, food waste was copyrolyzed with rice husk to produce biochar with a pilot-scale industrialized system. The efficiency of the material conversion and the properties and functions of the produced biochars as well as the potential environmental impacts of pyrolysis were evaluated using in situ measurements, physico-chemical characterization and in vitro (pot) experiments with biochar. The results showed that the emissions of potential toxic compounds and metals from the pyrolysis system were within the guideline limits under the legislation of China or the EU commission. On average, biochar yielded approximately 20% of feedstock and contained a total organic carbon content of 433 g kg−1. In the pot experiment, Chinese cabbage yield and quality were significantly improved, and the plant uptake of heavy metals was significantly reduced in soil amended with food waste biochar compared to no biochar amendment. Furthermore, the food waste biochar was blended with mineral nutrients to create a biochar based compounded N-P-K fertilizer. Application of the biochar based compound fertilizer exerted a significant positive effect on cabbage growth and nutrient use efficiency relative to a conventional mineral compound fertilizer. For per tonne of dry mass of food waste, copyrolysis costed less than 60 USD but gained a gross profit of more than 30 USD. Therefore, the copyrolysis of food waste with crop residues could be applicable to the safe recycling of food waste into value added products to raise agricultural production.

Vertical Distribution and Chemical Fractionation of Heavy Metals in Dated Sediment Cores from the Saronikos Gulf, Greece

The Saronikos Gulf is under a lot of anthropogenic pressure, such as the urban expansion of the metropolitan area of Athens, the port of Piraeus and marinas, industrial activities, and tourism. Heavy metal pollution has been a major environmental problem in the area for many decades. Sedimentary cores have proven to be an invaluable indicator of heavy metal pollution, as they can reveal not only the current metal inputs but also the evolution of pollution over time, and with the appropriate geochemical analyses, they can provide information on the potential toxicity of metals. In this study, the temporal evolution and the chemical speciation of eleven elements were examined in sediment cores from Elefsis Bay and the Inner Saronikos Gulf, with an emphasis on the emerging environmental hazards (V and Ag). The results showed extensive pollution of the sediments by Ni, Cr, Cu, Zn, As, Mo, Cd, and Pb from the 1910s and 1960s in Eastern and Western Elefsis Bay, respectively. A significant decrease of the sediment enrichment in V, Ni, Cr, Cu, Zn, As, Cd, Pb, and Ag since 2000 was observed in the part of the Inner Saronikos Gulf that is mainly influenced by the WWTP of Athens. However, a toxicity assessment using the metal contents of the surface sediments showed that most of the trace elements studied still pose a moderate to high risk of toxicity to benthic ecosystems. The present study highlighted the urgent need for focused research and the management of trace element inputs, particularly Ag in the Inner Saronikos Gulf, where severe sediment modification was evident.

Potentially Toxic Metals in the High-Biomass Non-Hyperaccumulating Plant Amaranthus viridis: Human Health Risks and Phytoremediation Potentials.

Simple SummaryThe goal of this study was to measure the concentrations of four potentially toxic metals in green amaranth (leaves, stems, and roots) collected from 11 sampling sites in Peninsular Malaysia. The danger of the metal concentrations to human health was assessed. The metal levels were highest in the root parts, followed by stems and leafy parts. The positive relationships of metals between plant parts and the habitat topsoils suggested that the green amaranth could be used as a useful biomonitoring agent of Cd, Fe, and Ni pollution. In addition, the green amaranth was also a very promising phytoextraction agent of Ni and Zn and a very promising phytostabiliser of Cd and Fe. This indicates that green amaranth can be used in the phytoremediation of the polluted soils by Cd, Fe, Ni, and Zn. The human health risk assessment for the potentially toxic metals (PTMs) in the leaves of green amaranth indicated that the four metals posed no non-carcinogenic dangers to consumers. However, it is of utmost importance to monitor PTMs in Amaranthus fields periodically.Human health risk and phytoremediation of potentially toxic metals (PTMs) in the edible vegetables have been widely discussed recently. This study aimed to determine the concentrations of four PTMs, namely Cd, Fe, Ni, and Zn) in Amaranthus viridis (leaves, stems, and roots) collected from 11 sampling sites in Peninsular Malaysia and to assess their human health risk (HHR). In general, the metal levels followed the order: roots > stems > leaves. The metal concentrations (µg/g) in the leaves of A. viridis ranged from 0.45 to 2.18 dry weight (dw) (0.05–0.26 wet weight (ww)), 74.8 to 535 dw (8.97–64.2 ww), 2.02 to 7.45 dw (0.24–0.89 ww), and 65.2 to 521 dw (7.83–62.6 ww), for Cd, Fe, Ni, and Zn, respectively. The positive relationships between the metals, the plant parts, and the geochemical factions of their habitat topsoils indicated the potential of A. viridis as a good biomonitor of Cd, Fe, and Ni pollution. With most of the values of the bioconcentration factor (BCF) > 1.0 and the transfer factor (TF) > 1.0, A. viridis was a very promising phytoextraction agent of Ni and Zn. Additionally, with most of the values of BCF > 1.0 and TF < 1.0, A. viridis was a very promising phytostabiliser of Cd and Fe. With respect to HHR, the target hazard quotients (THQ) for Cd, Fe, Pb, and Zn in the leaves of A. viridis were all below 1.00, indicating there were no non-carcinogenic risks of the four metals to consumers, including children and adults. Nevertheless, routine monitoring of PTMs in Amaranthus farms is much needed.

Sorption of cadmium, zinc and copper in dominant soils of the Zagreb aquifer system, Croatia

Contamination of soils with potentially toxic metals (PTMs) is an environmental problem. In this study, sorption of cadmium (Cd), zinc (Zn) and copper (Cu) in four soil profiles (two Fluvisols, one Gleysol, and one Cambisol), representing the dominant soils of the Zagreb aquifer system, were studied using a multi element laboratory batch test. Mathematical expressions were applied to establish the relationship between the concentration of the adsorbent in the liquid phase and the solid phaSe at equilibrium and in laboratory conditions. The study revealed that the investigated soils have a higher capacity to sorb Cu than Zn and Cd. The most significant physicochemical characteristics of soils, influencing sorption, are pH, carbonate content (minerals) and organic matter. Although all PTMs in all analyzed soils had a similar sorption capacity, the variation of sorption was higher in the siltic soils (Fluvisols) compared with the texturally finer (loamic) Gleysol and Cambisol soils, as well as in the subsoil horizons compared with the topsoils. Results indicate that sorption of PTMs is more influenced by physicochemical characteristics at different soil depths than by soil type, which is confirmed with a higher affinity for Zn and Cd bonding in the topsoil horizons. Also, it has been shown that Cd may pose more of a threat to soils and groundwater due to its toxicity and relatively high mobility in comparison with Zn and Cu.

Contamination, probabilistic health risk assessment and quantitative source apportionment of potentially toxic metals (PTMs) in street dust of a highly developed city in north of Iran

Street dust (SD) are the particulates that primarily originated from Earth's crust and secondary alteration and erosion of natural and anthropogenic materials. The multi-dimensional pollution and health risk assessment of potentially toxic metals (PTMs) in these particles remain unknown in the majority of world urban areas. The elemental concentration, mineralogy, and micro-morphology of street dust were determined by inductively coupled plasma mass spectrometry (ICP-MS), SEM-EDX, XRD, and petrographical observation. Multivariate statistical analysis combined with positive matrix factorization (PMF) and Monte-Carlo simulations were applied to source identification and health risk assessment of PTMs. A severe enrichment of Sb, Cu and Zn and moderate contamination of Sn, Pb, and Cr were observed in the samples particularly in the areas with higher loads of traffic. The results of geochemical indices showed that K, Al, Mn, and V have natural/geogenic origins. While Sb, Pb, Cr, Cu, and Zn showed an enrichment relative to the background values with dominant anthropogenic sources. The results were confirmed by source appointment techniques. The results of deterministic and probabilistic health risk assessment by Monte-Carlo simulations revealed the non-carcinogenic nature of As, Mn, and Pb for children mainly through skin and ingestion routes. It can be concluded that the chemical compound of street dust in Gorgan city is affected by both natural (loess deposits) and anthropogenic sources. Also, children are in the risk of exposure to PTMs in street dust more than adults.

Ecological-Health Risks of Potentially Toxic Metals in Mangrove Sediments near Estuaries after Years of Piggery Farming Bans in Peninsular Malaysia

The Sepang Besar River (SBR) was reported to be highly contaminated with Cu and Zn due to piggery farming wastes before 1998. Following the piggery farming ban (PFB) in 1998 in Bukit Pelanduk, the present study aimed to assess the ecological-health risks of potentially toxic metals (PTMs) (Cu, Pb, and Zn) in the mangrove surface sediments from SBR. Two adjacent rivers, namely the Sepang Kecil River and Lukut River, were also included for comparison purposes. The PTMs of present sediment samples collected in 2007 and 2010 were compared with those reported before and after PFB. The PTMs levels were lower than those of established sediment quality guidelines. Results of bioavailable fractions, individual contamination factor, risk assessment code, potentially ecological risk index (PERI), and non-carcinogenic risk (with HI &lt; 1.0 based on the pathways of Cu, Pb, and Zn and the order: ingestion &gt; dermal contact &gt; inhalation), the present findings indicated that the three rivers had caused no ecological-health risks of Cu, Pb, and Zn. In particular, SBR estuary had drastic lower levels of Zn (7.48–9.40 times lower between 1998 and 2010) and Cu (8.30–36.9 times lower between 1998 and 2010), after 12 years of PFB. Based on the exponential decay model, the PERI values showed that the estuary of SBR has been improved from a “considerable ecological risk” to a “minimal ecological risk” after 12 years of PFB. This is the first paper on the ecological-health risks of Cu, Pb, and Zn in the estuary of SBR. Future monitoring is still necessary for effective risk management of the mangrove ecosystem at SBR.

Copper and Zinc Levels in Commercial Marine Fish from Setiu, East Coast of Peninsular Malaysia.

Potentially toxic metals (PTMs) in edible marine fish have been widely reported from at least 15 different regions or countries in the literature. This evidently demonstrates the importance of monitoring the PTMs in fish fillets from a human health risk (HHR) point of view. This study aims to assess the HHR of Cu and Zn in 19 species of marine fish from popular marine fish loading sites at Setiu in Terengganu, on the east coast of Peninsular Malaysia, collected between August 2016 and February 2017. With overall ranges of concentrations (mg/kg dry weight) of Cu (1.50–7.83), and Zn (24.1–80.5), the 19 species of marine fishes from Setiu are good sources of these essential elements because they are below the maximum permissible limits set by seafood safety guidelines. The target hazard quotient values of Cu and Zn were lower than one, indicating non-carcinogenic risks of Cu and Zn in fish consumption. It was also found that the calculated values of the estimated weekly intake were below the established provisional tolerable weekly intake of Cu and Zn. It can be concluded that the consumption of fish from Setiu would not pose adverse effects from the PTMs to consumers. Nonetheless, continuous monitoring is necessary to ensure the safety of consumers who rely heavily on marine fish in Setiu coastal waters.

Heavy metal contaminations of soil in waste dumping and non-dumping sites in Khulna: Human health risk assessment

Potential toxic heavy metals are omnipresent in soil. Risk-based environmental management of soil refers to looking for the sources and exposure routes of heavy metals in human body associating with possible health risks of populace. The level of some heavy metals in waste dumping and non-dumping sites in Khulna was appraised. The soil pollution indices and health risks model were evaluated for the pollution status of soil and health risks among the local people, respectively. The prominent pollution was noticed in Koye Bazar dumping site due to the findings of higher value of geoaccumulation index (Igeo) (0.57), contamination factor (Cf) (2.22), and enrichment factor (EF) (2.52) for lead. The amount of iron in Mohammad Nagar dumpsite was estimated as 34397.00 mg kg−1, whilst the trace amount of Cr (0.39 mg kg−1) was analyzed in Koye bazar waste non-dumping site. The iron content in all dumping sites as well as lead in site-1 (S1) and site-3 (S3) exceeded the safe limit. Health risk indices model revealed that iron might exert the non-carcinogenic effects on both adults and child. But, chromium might have minimum carcinogenic risks (9.47E-07 in site-5) on adults. Besides, target cancer risks (TCR) value revealed that carcinogenic risks of cadmium for child and adults were ranged between 1.41E and 06 for adult in site-4 (S4) to 1.14E-05 for child in site-3 (S3). But, lead had no prominent carcinogenic effects on both child and adults.

AVALIAÇÃO DE METAIS POTENCIALMENTE TÓXICOS EM CHORUME PROVENIENTE DE ÁREA DE DEPOSIÇÃO DE RESÍDUOS SÓLIDOS EM BELÉM – PARÁ

EVALUATION OF POTENTIALLY TOXIC METALS IN LEACHES FROM SOLID WASTE DEPOSITION AREA IN BELÉMPARÁ. The formation of solid waste is a global challenge regarding environmental preservation. Due to the lifestyle of modern society, which aims to improve practicality, new products are constantly being released in the market and increasing the formation of waste. The decomposition of waste from various origins produces a dark liquid named leachate, which presents high rates of organic and inorganic compounds. The objective of this study was to assess the concentration of potentially toxic metals in the leachate collected from the Aurá dump. The concentrations of Cd, Cu, Cr, Mn, Ni, Pb, and Zn were evaluated in leachate samples collected in a period of a year, covering two typical seasonal periods of the Amazon region with more and less rainfall. The leachate samples collected in the Aurá dump were determined in the Toxicology Laboratory of Instituto Evandro Chagas (IEC), by means of Plasma/ Inductively Coupled Optical Emission Spectrometry (ICP-OES). The Cr, Mn, and Pb metals analyzed in the slurry samples are in a concentration above the maximum limits specified by CONAMA Resolution No. 430/2011, causing significant environmental concerns.

Assessments of the Ecological and Health Risks of Potentially Toxic Metals in the Topsoils of Different Land Uses: A Case Study in Peninsular Malaysia.

Simple SummaryThis study reported the ecological risks and human health risk assessments of five potentially toxic metals in the topsoils of six land uses in Peninsular Malaysia. It was found that industry, landfill, rubbish heap, and mining areas were categorized as “very high ecological risk”. The land uses of industry, landfill and rubbish heap were found to have higher hazard quotient values for the three pathways of the five metals for children and adults, when compared to the mining, plantation, and residential areas. The values for both the non-carcinogenic (Cd, Cu, Ni, and Zn), and carcinogenic risks for inhalation (Cd and Ni) obtained for children and adults in this study showed no harmful health effects on their health. However, of public concern, the hazard index, for Pb of children at the landfill and the rubbish heap showed non-carcinogenic risk for children. Therefore, children need to be taken care from public standpoint. They should be advised not to play in the topsoils near industry, landfill and rubbish heap areas. The present findings are important for the environmental management of potentially toxic metals especially in the land uses of industry, landfill and rubbish heap in Peninsular Malaysia.Human activities due to different land uses are being studied widely in many countries. This study aimed to determine the ecological risks and human health risk assessments (HHRA) of Cd, Pb, Ni, Cu, and Zn in the topsoils of six land uses in Peninsular Malaysia. The ranges of the potentially toxic metals (PTMs) in the soils (mg/kg, dry weight) of this study were 0.24–12.43 for Cd (mean: 1.94), 4.66–2363 for Cu (mean: 228), 2576–116,344 for Fe (mean: 32,618), 2.38–75.67 for Ni (mean: 16.04), 7.22–969 for Pb (mean: 115) and 11.03–3820 for Zn (mean: 512). For the ecological risk assessments, the potential ecological risk index (PERI) for single metals indicated that the severity of pollution of the five metals decreased in the following sequence: Cd > Cu > Pb > Zn > Ni. It was found that industry, landfill, rubbish heap, and mining areas were categorized as “very high ecological risk”. For HHRA, the land uses of industry, landfill and rubbish heap were found to have higher hazard quotient (HQ) values for the three pathways (with the order: ingestion > dermal contact > inhalation ingestion) of the five metals for children and adults, when compared to the mining, plantation, and residential areas. The values for both the non-carcinogenic (Cd, Cu, Ni, and Zn), and carcinogenic risks (CR) for inhalation (Cd and Ni) obtained for children and adults in this study showed no serious adverse health impacts on their health. However, of public concern, the hazard index (HI), for Pb of children at the landfill (L-3) and the rubbish heap (RH-3) sites exceeded 1.0, indicating non-carcinogenic risk (NCR) for children. Therefore, these PERI and HHRA results provided fundamental data for PTMs pollution mitigation and environmental management in areas of different land uses in Peninsular Malaysia.

Heavy Metal Contamination and Human Health Implications in the Chan Thnal Reservoir, Cambodia

Chan Thnal reservoir, built during the Pol Pot period, is the major water source for the people in Krang Chek commune, Kampong Speu Province, Cambodia. Metal pollution caused by agricultural activities, improper wastewater treatment, and municipal waste disposal poses serious environmental health problems. In this study, the concentrations of four potential toxic metals (i.e., Cd, Cu, Pb, and Zn) from six locations across the reservoir were investigated both in the water and sediment. The results reflected progressive deterioration and indicated moderate to heavy pollution from the metals. The metal levels in the water were in the order of Zn &gt; Cu &gt; Pb &gt; Cd. The statistical analysis revealed primary sources of heavy metals contamination in the water. Cd, Cu, Zn, and Pb in the water likely originate from anthropogenic activities including agricultural runoff (i.e., the use of fertilizers and pesticides) and urban runoff (i.e., improper wastewater discharge and waste disposal). Among the four metals, the Pb levels in the water significantly exceeded the guideline for drinking water in all locations. The health risk assessment revealed serious non-carcinogenic risks of Pb intake in the children at the age below 10 and infants. Appropriate control and protection strategies are urgently needed to cut off the main Pb exposure pathway in pregnant women, children, and infants.

Development of a toxicokinetic-toxicodynamic model simulating chronic copper toxicity to the Zebra mussel based on subcellular fractionation.

A toxicokinetic-toxicodynamic model based on subcellular metal partitioning is presented for simulating chronic toxicity of copper (Cu) from the estimated concentration in the fraction of potentially toxic metal (PTM). As such, the model allows for considering the significance of different pathways of metal sequestration in predicting metal toxicity. In the metabolically available pool (MAP), excess metals above the metabolic requirements and the detoxification and elimination capacity form the PTM fraction. The reversibly and irreversibly detoxified fractions were distinguished in the biologically detoxified compartment, while responses of organisms were related to Cu accumulation in the PTM fraction. The model was calibrated using the data on Cu concentrations in subcellular fractions and physiological responses measured by the glutathione S-transferase activity and the lipid peroxidation level during 24-day exposure of the Zebra mussel to Cu at concentrations of 25 and 50µg/L and varying Na+ concentrations up to 4.0mmol/L. The model was capable of explaining dynamics in the subcellular Cu partitioning, e.g. the trade-off between elimination and detoxification as well as the dependence of net accumulation, elimination, detoxification, and metabolism on the exposure level. Increases in the net accumulation rate in the MAP contributed to increased concentrations of Cu in this fraction. Moreover, these results are indicative of ineffective detoxification at high exposure levels and spill-over effects of detoxification.

Toxicity of coal fly ash and coal gangue leachate to Daphnia magna: Focusing on typical heavy metals

To identify potential toxicity of heavy metals (HMs) in coal fly ash (FA) and coal gangue (CG), this study measured Cd, Cr, Cu, Zn, Pb and Ni in two FAs and two CGs, and assessed their leachates' toxicity to Daphnia magna (D. magna). The results showed that the selected HMs in material and their leachates were low. However, under simplified Elendt M7 medium exposure system, the added leachates inhibited the survival and reproduction of D. magna. The HMs in D. magna increased as leachate increased, and D. magna mortality increased as the HMs in D. magna increased overall. The Cr and Ni in D. magna both showed significant linear positive correlation with the mortality. These indicated that HMs in leachate dilutions were important reason to inhibit D. magna. Moreover, the HMs in leachate also changed the biomarkers and caused oxidative stress in D. magna. Antioxidant system and cell structure of D. magna were further destroyed as leachates increased. The leachates’ inhabitation (mortality and living offspring) to D. magna depended on the properties of FA and CG, and the chemical composition of their leachates. Element level (e.g., C, S and N) and their chemical speciation (e.g., S2− and NH4+) likely impacted the leaching rate and toxicity of HMs.

Facilitation of Morus alba L. intercropped with Sedum alfredii H. and Arundo donax L. on soil contaminated with potentially toxic metals

Tree-herb intercropping is a prospective approach for the ecological remediation of soil contaminated with potentially toxic metals (PTMs). In this study, the facilitation and microbial community response of woody plant Morus alba L. intercropped with Cd/Zn hyperaccumulator Sedum alfredii H. and pioneer plant Arundo donax L. were carried out in the PTM-contaminated soil. The results indicated that the intercropping system can improve M. alba L. growth, as well as increase its PTMs uptake. The dried biomass of M. alba L. in the intercropping system was increased observably (p < 0.05) by 55.1%. Meanwhile, the contents of chlorophyll in M. alba L. leaves, PTMs contents in M. alba L. roots, and the relative abundance of Rhizobiaceae, Singulisphaera, Isosphaeraceae, and Arthrobacter in the M. alba L. rhizosphere were also notably (p < 0.05) enhanced. Meanwhile, the interactions of microorganisms in the intercropped plants rhizosphere might contribute to improving the biological quality of the contaminated soil. Soil sucrase and acid phosphatase activities in the intercropping system were significantly (p < 0.05) increased by 97.03% and 34.91% relative to the control. Furthermore, in the intercropping system, 93.61%, 61.30%, and 79.18% of Cd, Pb, and Zn were extracted by S. alfredii H., 72.16% of Cu was extracted by A. donax L., and 46.38% of Mn was extracted by M. alba L., which indicated that the extraction amounts of PTMs among the intercropped plants were relatively compensated. The results suggested that the tree-herb intercropping might increase the coexistence of plants and facilitate the adaptability for ecological remediation of PTM-contaminated soils.