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Bolan, Shiv,Kunhikrishnan, Anitha,Seshadri, Balaji,Choppala, Girish,Naidu, Ravi,Bolan, Nanthi S.,Ok, Yong Sik,Zhang, Ming,Li, Chun-Guang,Li, Feng,Noller, Barry,Kirkham, Mary Beth Elsevier 2017 Environment international Vol.108 No.-
<P><B>Abstract</B></P> <P>The last few decades have seen the rise of alternative medical approaches including the use of herbal supplements, natural products, and traditional medicines, which are collectively known as ‘Complementary medicines’. However, there are increasing concerns on the safety and health benefits of these medicines. One of the main hazards with the use of complementary medicines is the presence of heavy metal(loid)s such as arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg). This review deals with the characteristics of complementary medicines in terms of heavy metal(loid)s sources, distribution, bioavailability, toxicity, and human risk assessment. The heavy metal(loid)s in these medicines are derived from uptake by medicinal plants, cross-contamination during processing, and therapeutic input of metal(loid)s. This paper discusses the distribution of heavy metal(loid)s in these medicines, in terms of their nature, concentration, and speciation. The importance of determining bioavailability towards human health risk assessment was emphasized by the need to estimate daily intake of heavy metal(loid)s in complementary medicines. The review ends with selected case studies of heavy metal(loid) toxicity from complementary medicines with specific reference to As, Cd, Pb, and Hg. The future research opportunities mentioned in the conclusion of review will help researchers to explore new avenues, methodologies, and approaches to the issue of heavy metal(loid)s in complementary medicines, thereby generating new regulations and proposing fresh approach towards safe use of these medicines.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A first-time comprehensive overview on the health risk assessment of heavy metal(loid)s in complementary medicines </LI> <LI> Ayurvedic medicines contain toxic levels of heavy metal(loid)s including As, Cd, Hg and Pb </LI> <LI> The bioavailability of metal(loid)s in complementary medicines depends on speciation of these metals </LI> <LI> Regular intake of some complementary medicines has caused metal(loid) toxicity in humans </LI> <LI> Health risk assessment can be achieved based on the daily intake of complementary medicines and total metal(loid) content </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Interactions between heavy metal(loid)s and complementary medicines.</P> <P>[DISPLAY OMISSION]</P>
Interactions of food waste compost with metals and metal-chelant complexes during soil remediation
Beiyuan, Jingzi,Tsang, Daniel C.W.,Bolan, Nanthi S.,Baek, Kitae,Ok, Yong Sik,Li, Xiang-Dong Elsevier 2018 JOURNAL OF CLEANER PRODUCTION Vol.192 No.-
<P><B>Abstract</B></P> <P>For removing potentially toxic elements (PTEs) from field-contaminated soils, cost-effective soil remediation has been a worldwide concern. As one of the widely employed techniques, chelant-enhanced phytoremediation can remove PTEs with marginal impact on the soil properties, yet the newly formed metal-chelant complexes cannot be completely captured and extracted by the plants. This arouses concerns about downstream migration and secondary contamination of the metal-chelant complexes and free chelant. Organic amendments, such as food waste compost (FWC), may stabilize metals and/or metal-chelant complexes, improve soil properties and plant growth, and reduce waste volume. Therefore, FWC may provide a solution for the migration of metal-chelant complexes and free chelant. Two chelants were selected in this study: EDTA (ethylene-diaminetetraacetic-acid) and its biodegradable isomer EDDS ([<I>S,S</I>]-ethylenediaminedisuccinic acid). The interactions between FWC and metals, metal-EDTA/metal-EDDS complexes in a field-contaminated soil (mainly by Cu, Zn, and Pb) were investigated. Batch adsorption isotherms indicated a strong adsorption capacity of FWC for uncomplexed Cu, Zn, and Pb ions. Significant adsorption of Pb-EDDS (∼100%), Zn-EDDS (>77%), and Cu-EDTA (36–76%) complexes on the FWC was found at apparent equilibrium. The adsorption capacity of Cu-EDDS (32–38%), Pb-EDTA (∼20%), and Zn-EDTA (∼0%) complexes was limited. However, the co-existence of FWC and EDDS increased the mobilization of Cu and Zn, while the co-existence of FWC and EDTA reduced the available amounts of Cu and Pb in solution. Metal speciation calculation showed that nearly all extracted Cu, Zn, and Pb were complexed with chelants in the solution, while notable amount of dissolved Fe (but not Al and Ca) was associated with dissolved organic matter. In this study, FWC can be useful for minimizing the unintended leaching of Cu- and Pb-EDTA complexes in EDTA-enhanced phytoremediation, yet it might be less suitable for the case of EDDS. A novel integration of recycled waste can enhance the effectiveness of sustainable remediation of contaminated soils.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Large amounts of dissolved organic matter released from food waste compost (FWC). </LI> <LI> Cu, Zn, and Pb ions significantly adsorbed to FWC. </LI> <LI> Yet metal-EDDS/EDTA complexes showed diverse adsorption behaviours on FWC. </LI> <LI> Cu-EDDS complexes can be adsorbed to FWC yet the Cu mobility increased with FWC. </LI> <LI> FMC-derived DOM mitigated the EDTA-induced solubilization of Cu and Pb in soil. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Beiyuan, Jingzi,Tsang, Daniel C.W.,Valix, Marjorie,Baek, Kitae,Ok, Yong Sik,Zhang, Weihua,Bolan, Nanthi S.,Rinklebe, Jö,rg,Li, Xiang-Dong Elsevier 2018 CHEMOSPHERE - Vol.205 No.-
<P><B>Abstract</B></P> <P>Chelant-enhanced soil washing, such as EDTA (ethylenediaminetetraacetic acid) and biodegradable EDDS ([<I>S,S</I>]-ethylene-diamine-disuccinic acid), has been widely studied, however, EDTA is persistent under natural conditions while EDDS has a low efficiency for Pb extraction. Therefore, we investigated the efficacy of mixed chelants (EDDS and EDTA mixture at 1:1 M ratio) for the removal of Cu, Zn, and Pb from a field-contaminated soil using various washing schemes (multi-pulse, step-gradient chelant, and continuous washing schemes). Speciation modelling of the target metals, mineral elements, and EDDS/EDTA was performed, while the leachability and bioaccessibility of residual metals in the treated soils were also assessed. Our results suggested that the combined use of EDDS and EDTA reached equivalent extraction efficiency of the target metals as EDTA, i.e., 50% reduction in the dosage of EDTA was made possible. This was accomplished by selective extraction of Cu by EDDS and Pb by EDTA, which was supported by the results of speciation calculation. Multi-pulse washing scheme with intermittent water rinsing steps removed entrapped metal-chelant complexes and free chelants, therefore reducing the leachability and bioaccessibility of residual metals in the treated soils. Step-gradient chelant washing with the maximum dosage of chelants in the first washing step only achieved marginal improvement but undesirably promoted Pb bioaccessibility. Continuous washing for 24 h enhanced metal extraction but promoted mineral dissolution, together with a large amount of uncomplexed chelants and increase in Cu leachability. Thus the combined use of EDDS and EDTA in multi-pulse washing is recommended for further studies.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mixture of EDDS and EDTA extracted comparable amount of PTEs as EDTA washing. </LI> <LI> Mixed chelants allowed complementary metal complexation and higher efficiency. </LI> <LI> Multi-pulse washing better utilized chelants and reduced leachability/bioaccessibility. </LI> <LI> Step-gradient chelant dosage hardly improved extraction but increased bioaccessible Pb. </LI> <LI> Continuous washing increased amounts of uncomplexed chelants and dissolved minerals. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Yoo, Jong-Chan,Beiyuan, Jingzi,Wang, Lei,Tsang, Daniel C.W.,Baek, Kitae,Bolan, Nanthi S.,Ok, Yong Sik,Li, Xiang-Dong Elsevier 2018 Science of the Total Environment Vol.616 No.-
<P><B>Abstract</B></P> <P>In this study, soil washing and stabilization as a two-step soil remediation strategy was performed to remediate Pb- and Cu-contaminated soils from shooting range and railway sites. Ferric nitrate (Fe(NO<SUB>3</SUB>)<SUB>3</SUB>) and [<I>S,S</I>]-ethylenediamine disuccinate (EDDS) were used as washing agents, whereas three types of sludge-derived biochars and phosphogypsum were employed as soil stabilizers. While Fe(NO<SUB>3</SUB>)<SUB>3</SUB> extracted larger amounts of metals compared to EDDS (84% Pb and 64% Cu from shooting range soil; 30% Pb and 40% Cu from railway site soil), it caused severe soil acidification. Both Fe(NO<SUB>3</SUB>)<SUB>3</SUB> and EDDS washing enhanced the mobility of residual metals in the two soils, which in most cases could be mitigated by subsequent 2-month stabilization by sludge-derived biochars or phosphogypsum. By contrast, the metal bioaccessibility could only be reduced by soil washing. Nutrient-rich sludge-derived biochar replenished available P and K in both soils, whereas Fe(NO<SUB>3</SUB>)<SUB>3</SUB> washing provided available nitrogen (N). Soil amendment enhanced acid phosphatase activity but marginally improved soil dehydrogenase and urease activity in the treated soils, possibly due to the influence of residual metals. This study supported the integration of soil washing (by Fe(NO<SUB>3</SUB>)<SUB>3</SUB> or EDDS) with soil stabilization (by sludge-derived biochars or phosphogypsum) for accomplishing the reduction of metal mobility and bioaccessibility, while restoring the environmental quality of the treated soils.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fe(NO<SUB>3</SUB>)<SUB>3</SUB> washing significantly removed Pb from shooting range and railway soils. </LI> <LI> Biochars neutralized acidic soil pH resulting from Fe(NO<SUB>3</SUB>)<SUB>3</SUB> washing. </LI> <LI> Phosphogypsum immobilized residual Pb by forming insoluble PbSO<SUB>4</SUB> precipitates. </LI> <LI> Sludge-derived biochars reduced metal mobility and enhanced soil quality. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>