Yanxin Wang

Analysis of veterinary antibiotic residues in swine wastewater and environmental water samples using optimized SPE-LC/MS/MS

Strategies for sample preparation, solid-phase extraction (SPE), clean-up, and detection conditions of an optimized solid-phase extraction-liquid chromatography/mass/mass spectrometry (SPE-LC/MS/MS) method for determining multi-residues of four classes of widely used antibiotics in pig farms, sulfonamides (SAs), fluoroquinolone (FQs), tetracycline (TCs) and chloramphenicol (CAP) were presented. The multi-residue analysis was used in MS analysis, selecting two precursor ions to produce ion transitions for each target compound. Samples of swine wastewater, lake water and groundwater collected from two pig farms in central China were used to test the applicability of the multi-residue analysis method. The average antibiotics concentrations in groundwater, lake water, final effluent and influent swine wastewater were, respectively, 1.6-8.6, 5.7-11.6, 7.9-1172.3 and 8.5-21692.7 ng L(-1) in summer; respectively, 2.0-7.3, 6.7-11.7, 5.8-409.5 and 32.8-11276.6 ng L(-1) in winter. The limits of quantification were 0.8-4.1, 1.4-5.5, 1.8-11.5 and 6.4-104.4 ng L(-1), respectively, in groundwater, lake water, final effluent and influent swine wastewater. Results of multi-residue analysis of antibiotics in the samples indicate that SAs, FQs and TCs were widely used veterinary medicines in the pig farms. As compared with previous studies, higher elimination rates (more than 80%) of the antibiotics (except DC) were observed in effluent in this study. More detailed work is indispensable to investigate the fate and transport of antibiotics in the environment and to find out cost-effective approaches of removing antibiotics from swine wastewater and contaminated sites.

Natural Occurrence of Arsenic in Shallow Groundwater, Shanyin, Datong Basin, China

Abstract In Shanyin, Shanxi province, China, As concentration in shallow groundwater exceeds guide concentrations, set internationally and nationally at 10–50 µg/L, and may reach 1932.0 µg/L, which has resulted in severe clinical symptoms of arsenic toxity. In this article, chemical characteristics of groundwaters containing anomalous As and mechanisms of arsenic release to shallow groundwaters were studied. Groundwaters containing anomalous As in the study area were characterized by higher pH, higher concentration of phosphate, higher concentration of naphthenic acid, and lower concentrations of sulfate and nitrate. Microbial metabolism of sedimentary organic matter, which is present as high as 1.0% organic C, results in the lower concentrations of sulfate and nitrate. The reactions decrease Eh and produce CO2, which promotes the dissolution of carbonates and increases pH. The clay minerals and colloids including organic matters scavenging arsenic would release arsenic to groundwater in higher pH and lower Eh environment. In addition, the competitive absorption between As and anions (such as phosphate and fluoride) contributes to the release of As from kaolinite, montmorillonite, illite, and Fe oxyhydroxides. Naphthenic acid also promotes mobilization and translocation of As in groundwater systems.

Microbial Diversity in High Arsenic Groundwater in Hetao Basin of Inner Mongolia, China

The microbial diversity and community structure in twenty-one groundwater samples from high arsenic shallow aquifers of Hetao Basin, Inner Mongolia, China was investigated with an integrated approach including polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene phylogenetic analyses. A total of 25 bacterial and 32 archaeal DGGE bands were exercised for sequencing. Phylogenetic analyses showed that the bacterial DGGE bands were dominated by Proteobacteria, and the archaeal bands were dominated by Thaumarchaeota and Euryarchaeota. Based on arsenic concentrations, three samples (corresponding to low, medium, and high level of arsenic, respectively) were selected for construction of 16S rRNA gene clone libraries. A total of 912 (468 and 444 for bacteria and archaea, respectively) 16S rRNA gene clone sequences were obtained and subjected to phylogenetic analyses. The results showed that bacterial communities of these samples were dominated by Acinetobacter, Pseudomonas, Massilia, Dietzia, Planococcus, Brevundimonas, Aquabacterium and Geobacter, and archaeal communities by Nitrosophaera, Thermoprotei and Methanosaeta. The relative abundance of major groups varied as a function of changes in groundwater geochemistry. Acinetobacter, Brevundimonas, Geobacter, Thermoprotei and Methanosaeta dominated in high arsenic samples with high concentrations of methane and Fe(II), and low concentrations of SO2− 4 and NO− 3, while Pseudomonas and Nitrosophaera were abundant in low arsenic groundwater. These results imply that microbes play an important role in arsenic mobilization in the shallow aquifers of Hetao Basin, Inner Mongolia.

A microcalorimetric method for studying the toxic effect of different diphenol species on the growth of Escherichia coli

A microcalorimetric technique based on bacterial heat-output was explored to evaluate the toxic effect of different diphenol species on the growth of Escherichia coli (E. coli). Power-time curves of the growth metabolism for E. coli in the presence of different diphenol species were studied using a multi-channel microcalorimetric system with an ampoule method at 37°C. The growth rate constant (k), generation time (t G), inhibitory ratio (I), half-inhibitory concentration (IC 50) and the total thermal effect (Q T) for E. coli were obtained. The results show that catechol and hydroquinone are more toxic to E. coli than resorcinol. In all cases, the growth rate constants of E. coli (in log phase) decreased as the concentrations of these diphenols increased. Among these diphenols species, catechol was found to be the most poisonous species at an IC 50 of 323.5 μ g/mL against E. coli. Hydroquinone exhibited moderate virulence with an IC 50 of 1196 μ g/mL and resorcinol had the lowest toxicity with an IC 50 of 2113 μ g/mL. The microcalorimetric bioassay can be a quantitative, inexpensive, and versatile method for acute cellular toxicity study.

Multivariate analysis of the heterogeneous geochemical processes controlling arsenic enrichment in a shallow groundwater system

The effects of various geochemical processes on arsenic enrichment in a high-arsenic aquifer at Jianghan Plain in Central China were investigated using multivariate models developed from combined adaptive neuro-fuzzy inference system (ANFIS) and multiple linear regression (MLR). The results indicated that the optimum variable group for the AFNIS model consisted of bicarbonate, ammonium, phosphorus, iron, manganese, fluorescence index, pH, and siderite saturation. These data suggest that reductive dissolution of iron/manganese oxides, phosphate-competitive adsorption, pH-dependent desorption, and siderite precipitation could integrally affect arsenic concentration. Analysis of the MLR models indicated that reductive dissolution of iron(III) was primarily responsible for arsenic mobilization in groundwaters with low arsenic concentration. By contrast, for groundwaters with high arsenic concentration (i.e., > 170 μg/L), reductive dissolution of iron oxides approached a dynamic equilibrium. The desorption effects from phosphate-competitive adsorption and the increase in pH exhibited arsenic enrichment superior to that caused by iron(III) reductive dissolution as the groundwater chemistry evolved. The inhibition effect of siderite precipitation on arsenic mobilization was expected to exist in groundwater that was highly saturated with siderite. The results suggest an evolutionary dominance of specific geochemical process over other factors controlling arsenic concentration, which presented a heterogeneous distribution in aquifers. Supplemental materials are available for this article. Go to the publishers online edition of the Journal of Environmental Science and Health, Part A, to view the supplemental file.

Comparative survey of bacterial and archaeal communities in high arsenic shallow aquifers using 454 pyrosequencing and traditional methods

A survey of bacterial and archaeal community structure was carried out in 10 shallow tube wells in a high arsenic groundwater system located in Hetao Basin, Inner Mongolia by 16S rRNA gene based two-step nested PCR-DGGE, clone libraries and 454 pyrosequencing. 12 bacterial and 18 archaeal DGGE bands and 26–136 species-level OTUs were detected for all the samples. 299 bacterial and 283 archaeal 16S rRNA gene clones for two typical samples were identified by phylogenetic analysis. Most of the results from these different methods were consistent with the dominant bacterial populations. But the proportions of the microbial populations were mostly different and the bacterial communities in most of these samples from pyrosequencing were both more abundant and more diverse than those from the traditional methods. Even after quality filtering, pyrosequencing revealed some populations including Alishewanella, Sulfuricurvum, Arthrobacter, Sporosarcina and Algoriphagus which were not detected with traditional techniques. The most dominant bacterial populations in these samples identified as some arsenic, iron, nitrogen and sulfur reducing and oxidizing related populations including Acinetobacter, Pseudomonas, Flavobacterium, Brevundimonas, Massilia, Planococcus, and Aquabacterium and archaeal communities Nitrosophaera and Methanosaeta. Acinetobacter and Pseudomonas were distinctly abundant in most of these samples. Methanogens were found as the dominant archeal population with three methods. From the results of traditional methods, the dominant archaeal populations apparently changed from phylum Thaumarchaeota to Euryarchaeota with the arsenic concentrations increasing. But this structure dynamic change was not revealed with pyrosequencing. Our results imply that an integrated approach combining the traditional methods and next generation sequencing approaches to characterize the microbial communities in high arsenic groundwater is recommended.

Headspace solid-phase microextraction (HS-SPME) and solid-phase extraction (SPE) concentration for quantification of malodorous substances in piggery wastewater.

Quantification of malodorous substances at trace concentration levels in piggery wastewater remains a great challenge for environmental studies. The objective of this study was to determine the 4-methylphenol, 4-ethylphenol, indole and skatole (3-methylindole) of piggery wastewaters in anaerobic facilities by headspace solid-phase microextraction (HS-SPME) and solid-phase extraction (SPE) pre-concentration. The validation results of both pre-concentrations revealed high selectivity and sensitivity. The detection of malodorous substances can provide clues to track the source of these contaminants. The results of real sample detection showed that all of these malodor substances appeared in both influent and effluent wastewaters.

Microcalorimetric Investigation of the Toxic Effect of Iron Species on Escherichia coli

ABSTRACT A microcalorimetric technique based on bacterial heat output was explored to evaluate the toxic effect of iron species on Escherichia coli. Power–time curves of the growth metabolism of E. coli and the effect of different iron species on it were studied using the TAM III multichannel microcalorimetric system, isothermal mode, at 37°C. The differences in shape of the power–time curves and the thermodynamic and kinetic characteristics of E. coli growth have been compared. The thermodynamic parameters, that is, growth rate constant (k), inhibitory ratio (I), half-inhibitory concentration (IC50), Pmax, and Qtotal, have been calculated. The experimental results reveal that the sequence of antibiotic activity of the different iron species (three forms) on E. coli growth is Fe3+ (ferric citrate) > Fe2+ (ferrous chloride) > Fe3+ (ferric chloride). These results are important to further studies of the physiology and pharmacology of iron species as antibacterial agents.

Adsorption Mechanism of Humic Acid on Cu/Fe Bimetallic Particles and Its Influence on the Reduction of Nitrobenzene in Groundwater

Humic acid (HA) is ubiquitous in groundwater, and poses great influence on the biogeochemical controls on, as well as treatment of, contaminants. This study deals with the adsorption of HA on a bimetallic iron system, Cu/Fe, and its influence on the reduction of nitrobenzene in synthetic groundwater. The adsorption kinetics, isotherms, and enthalpy of HA on bimetallic Cu/Fe particles are investigated. Compared with the adsorption of HA on Fe0 particles, the adsorption on Cu/Fe is faster than that on Fe0. The adsorption isotherms of HA at different pH values and temperatures show that the adsorption is always greater on Cu/Fe than on Fe0, and increases when the pH decreases and temperature increases. Moreover, the influences of pH and temperature on adsorption by Cu/Fe are less than those observed in adsorption on Fe0. The adsorption enthalpy on Cu/Fe is lower than that on Fe0, and both adsorptions are spontaneous and endothermic. Characterization of the corrosion products by SEM-EDX, XRD, and XPS reveals the appearance of maghemite (γ-Fe2O3) and magnetite (Fe3O4) on Cu/Fe with HA adsorption, which were more crystalline than those of Fe0, indicating that bimetallic Cu/Fe facilitated the formation of crystalline corrosion products. The adsorption of HA accelerates the release of iron ions but suppresses the reduction of nitrobenzene. Compared with Fe0, Cu/Fe accelerates the adsorption of HA and Cu/Fe increases the reduction of nitrobenzene. The suppression on nitrobenzene reduction increased with the increase in HA concentration.