Iron-doped hydroxyapatite for the simultaneous remediation of lead-, cadmium- and arsenic-co-contaminated soil.

Since lead, cadmium and arsenic have completely opposite chemical behaviors, it is very difficult to stabilize all these three heavy metals simultaneously. Herein, a novel iron-doped hydroxyapatite composite (Fe-HAP) was developed via an ultrasonic-assisted microwave hydrothermal method for the simultaneous remediation of lead-, cadmium-, and arsenic-co-contaminated soil in Hunan Province, South China. Using DTPA/sodium bicarbonate extractant to extract bioavailable Pb, Cd and As in soil after Fe-HAP remediation for 60 days, the immobilization efficiencies were 79.77%, 51.3% and 37.5% for Pb, Cd and As, respectively. The soil extractable and exchangeable fractions of Pb, Cd and As decreased significantly. In batch experiments, the adsorption kinetics of Pb, Cd and As on Fe-HAP were well described by pseudo-second-order models, indicating that the adsorption is controlled by chemisorption. In the Langmuir adsorption isotherm, the maximum adsorption capacities of Cd2+ and As(V) were 476.2 mg g-1 and 195.69 mg g-1, respectively, while Pb2+ fit the Freundlich model better. The XRD, SEM and XPS analyses indicated that Fe-HAP formed stable minerals of Pb5(PO4)3OH, Cd3(PO4)2·4H2O, Cd(OH)2 and Fe3(AsO4)2·6H2O with Pb, Cd and As. Overall, its facile and efficient immobilization performance indicate that Fe-HAP has potential for practical applications in integrative remediation of Pb-, Cd-, and As- co-contaminated soil.

Study on antibiotics, antibiotic resistance genes, bacterial community characteristics and their correlation in the landfill leachates.

AIM: This study aimed to investigate the contamination levels of antibiotics and antibiotic resistance genes (ARGs) in the landfill leachates and their correlations with the bacteria. METHODS AND RESULTS: Using HPLC-MS, quantitative PCR and high-throughput sequencing, we measured the pollution levels of 14 antibiotics and 10 ARGs in the leachates of the landfill in Taiyuan, China, and analysed changes in the bacterial community and the correlations of bacteria with antibiotics and ARGs. The main results showed high levels of antibiotics (like enrofloxacin, pefloxacin and oxytetracycline) and ARGs (like sulfonamides, tetracycline, macrolides, quinolones and ß-lactam-resistance genes) in the landfill leachates, along with higher diversity and richness of the bacteria. Some types of antibiotics had positive correlations with their corresponding ARGs. The dominant bacteria in the landfill leachates were Pseudomonas, Defluviitoga and Sulfurimonas, which correlated with the antibiotics and ARGs and might have potential effects on degrading them. CONCLUSIONS: Antibiotics and ARG pollution existed in the landfill leachates, while bacteria were closely associated with them. SIGNIFICANCE AND IMPACT OF THE STUDY: It will provide helpful information for the potential application of the bacteria in antibiotics and ARGs pollution control and landfill leachate management.

Effects of tetrabromobisphenol A on maize (Zea mays L.) physiological indexes, soil enzyme activity, and soil microbial biomass.

TetrabromobisphenolA (TBBPA) is the most widely used brominated flame retardant, and it has the characteristics of persistent organic pollutants (POPs), attracting considerable attention. Many studies mainly focus on TBBPA toxicological effects in aquatic animals and rodents, but the ecotoxicology data of TBBPA on plant-soil system are limited so far. In this study, we assessed the impacts of TBBPA on maize (Zea mays L.) physiological indexes, soil enzyme activity, and soil microbial biomass at different concentrations of TBBPA (0, 0.75, 3.75, 7.5, 15, 37.5 and 75 mg·kg-1) and explored their relationships. Results showed that the maize physiological indexes and chlorophyll contents were significantly decreased by TBBPA, the activities of anti-oxidative enzymes including catalase (CAT), peroxidase (POD) and polyphenol oxidase (PPO) and the contents of malondialdehyde (MDA) were remarkably enhanced. Meanwhile, TBBPA activated the CAT, POD and PPO activities in soil. The low concentrations TBBPA promoted the activities of soil urease (S-UE), neutral phosphatase (S-PE) and increased the soil microbial biomass carbon (SMBC) and nitrogen (SMBN) while the high concentrations TBBPA suppressed them. Notably, the data indicated microbial biomass had respectively a significant correlation with CAT, PPO and S-UE in soil in the presence of TBBPA, and maize chlorophyll contents were associated with SMBN, CAT, and PPO. Taken together, TBBPA caused soil pollution, affected soil enzyme activities and microbial biomass, and hindered maize growth under the current experimental condition, suggesting the interactions among maize growth, soil enzyme, soil microorganism in maize rhizosphere of TBBPA-polluted soils are very important aspects to comprehensively evaluate the ecotoxicological effects of TBBPA.