Applications of Crown Ether Cross-Linked Chitosan for the Analysis of Lead and Cadmium in Environmental Water Samples

A new type of crown ether cross-linked chitosan was synthesized by the reaction of chitosan with 4,4′-dibromodibenzo-18-crown-6 (Br-DBC). Its token structure was analyzed with FT-IR and NMR and the adsorption behaviors for lead and cadmium in environmental water samples by FAAS were studied. In addition the best analysis conditions were discussed and the adsorption mechanism was explained. As the enrichment factor is above 100, both recoveries are 94%–106%, the detection limits of lead and cadmium are 0.5μg·L?1 and 0.04 μg·L?1 and the relatively standard deviations of lead and cadmium are 3.1% and 2.8% respectively, this new method was successfully applied to the determination of environmental water samples. This method is fast and simple and it greatly enhances the determination ability of FAAS for lead and cadmium.

National Food Contamination Monitoring Programmes-Levels of Mercury, Lead and Cadmium in Chinese Foods

Six hundred and thirty-four food samples of six kinds were collected from Beijing,Shanghai, Jiangsu, Sichuan, Jilin and Guangdong areas, China and Hg, Pb, Cd contents were determined. The results showed that their levels in the Chinese foods were low; their levels in meat, egg, milk and fish were generally below the national hygienic standard. The average daily dietary intake of Hg, Pb, Cd were 7.25 μg, 103.77μg and 30.72 μg respectively and they were all less than the ADI established by WHO

Lead and Cadmium Adsorption onto Iron Oxides and Manganese Oxides in the Natural Surface Coatings Collected on Natural Substances in the Songhua River of China

Natural surface coatings collected from natural substances （NSCsNS） were employed to study the roles of the main chemical components （iron oxides, manganese oxides, and other components） in controlling the adsorption of lead（Pb） and cadmium（Cd） in aquatic environments. The selective chemical extraction followed by the adsorption of Pb and Cd experiments and statistical analysis, were used to investigate the adsorption property of each component. Hydroxylamine hydrochloride was used to remove manganese oxides selectively, and sodium dithionite was used to extract iron oxides and manganese oxides. The result indicated that iron oxides and manganese oxides played an important role in the adsorption of Pb and Cd on NSCsNS, and the relative contribution was about two-thirds. The contribution of manganese oxides was the greatest, with a lesser role indicated for other components. The adsorption ability of manganese oxides for Pb and Cd was greater than that of iron oxides or other components for Pb and Cd. The Pb adsorption observed in each component was greater than Cd adsorption.

A study of differential potentiometric stripping analysis for lead and cadmium with Nafion coated carbon fibre electrode

The differential potentiometric stripping analysis (DPSA) with Nafion coated carbon fibre electrode has been studied, and a method to determine lead and cadmium in urine directly has been attempted. The effect of various experimental parameters on the DPSA response is discussed. The experimental conditions include 0.2M sodium perchlorate, deposition potential of-1.0 or -1.1 V and using 20 ppm mercuric ion as oxidizing agent. The response of the signal is in linear relation with the concentrations of lead and cadmium respectively up to 0.5 ppm. The electrode coated with Nafion film alleviates the interference from organics in urine samples.

Remediation mechanism of“double-resistant”bacteria—Sedum alfredii Hance on Pb-and Cd-contaminated soil

Background:Concentrations of heavy metals continue to increase in soil environments as a result of both anthro-pogenic activities and natural processes.Cadmium(Cd)and lead(Pb)is one of the most toxic heavy metals and pose health risks to both humans and the ecosystem.Therefore,effectively solving the problem of heavy metal pollution is the concern of soil workers.Among the existing remediation techniques,only the combined use of microorganisms and plants for remediation of heavy metal-contaminated soil is the greenest and most developed one.Consequently,based on this background,this study investigates the remediation mechanism of Pb and Cd heavy metals using the combined action of bacteria and Sedum alfredii Hance.Methods:In order to enrich the research theory of combined plant and microorganism remediation of heavy metal-contaminated soil,we constructed a heavy metal composite pollution remediation system by combining Pb and Cd-tolerant bacteria with the Pb and Cd hyperaccumulator plant—Sedum alfredii Hance to investigate its combined remediation effect on Pb and Cd composite contaminated soil.Results:The results showed that resistant bacteria were able to promote enrichment of Pb and Cd in Sedum alfredii Hance and J2(200 ml of bacterial solution)was significantly(P<0.05)more effective than J1(100 ml of bacterial solution).The resistant bacteria were able to alleviate the toxic effects of Pb and Cd heavy metals on Sedum alfredii Hance and promote growth while reducing rhizosphere soil pH.The resistant bacteria were able to significantly reduce the effective state of Pb and Cd in the rhizosphere soil(P<0.05),with the greatest reduction in the effective state of Pb in treatment A(Cd7Pb100 mg/kg),where J2 was reduced by 9.98%compared to J0,and the greatest reduction in the effective state of Cd in treatment C(Cd28Pb400 mg/kg),where J2 was 43.53%lower than J0.In addition,the resistant bacteria were able to increase the exchangeable state Cd content by 0.97 to 9.85%.The resistant bacteria had a weakly promoting effect and a highly inhibitory effect on the absorption of Pb by Sedum alfredii Hance.Conclusions:The resistant bacteria can change the rhizosphere environment and significantly improve the remedia-tion effect of Sedum alfredii Hance on heavy metal cadmium.The role of“double-resistant”bacteria in promoting the accumulation of Cd was greater than that of Pb.