A Novel In Situ Method for Simultaneously and Selectively Measuring AsIII, SbIII, and SeIV in Freshwater and Soils.

Anthropogenic and climatic perturbations redistribute arsenic (As), antimony (Sb), and selenium (Se) within the environment. The speciation characteristics of these elements determine their behavior and biogeochemical cycling, but these redox-sensitive species are challenging to capture, with few methods able to harmonize measurements across the whole plant-soil-ecosystem continuum. In this study, we developed a novel diffusive gradient in thin films (DGT) method based on aminopropyl and mercaptopropyl bi-functionalized mesoporous silica spheres (AMBS) to achieve in-situ, simultaneous, and selective quantification of AsIII, SbIII, and SeIV, three typical/toxic but difficult to measure inorganic species. When used for environmental monitoring within a river catchment, AMBS-DGT exhibited stable/accurate predictions of these species despite varying water chemistries (ionic strength 0.01-200 mmol L-1 NO3-, pH 5-9 for AsIII and SbIII, and pH 5-7.5 for SeIV). Furthermore, river deployments also showed that time-averaged species concentrations by AMBS-DGT were reproducible compared with high-frequency sampling and measurement by high performance liquid chromatography coupled with inductively coupled plasma mass spectroscopy. When AMBS-DGT was used for sub-mm scale chemical imaging of soil solute fluxes, the method resolved concomitant redox-constrained spatial patterns of AsIII, SbIII, and SeIV associated with root O2 penetration within anaerobic soil. Improved capabilities for measurement of compartment interfaces and microniche features are critical alongside the measurement of larger-scale hydrological processes that dictate the fine-scale effects, with the AMBS-DGT achieving this for AsIII, SbIII, and SeIV.

A typical case study from smelter-contaminated soil: new insights into the environmental availability of heavy metals using an integrated mineralogy characterization.

Mineralogy was an important driver for the environmental release of heavy metals. Therefore, the present work was conducted by coupling mineral liberation analyzer (MLA) with complementary geochemical tests to evaluate the geochemical behaviors and their potential environmental risks of heavy metals in the smelter contaminated soil. MLA analysis showed that the soil contained 34.0% of quartz, 17.15% of biotite, 1.36% of metal sulfides, 19.48% of metal oxides, and 0.04% of gypsum. Moreover, As, Pb, and Zn were primarily hosted by arsenopyrite (29.29%), galena (88.41%), and limonite (24.15%), respectively. The integrated geochemical results indicated that among the studied metals, Cd, Cu, Mn, Pb, and Zn were found to be more bioavailable, bioaccessible, and mobile. Based on the combined mineralogical and geochemical results, the environmental release of smelter-driven elements such as Cd, Cu, Mn, Pb, and Zn were mainly controlled by the acidic dissolution of minerals with neutralizing potential, the reductive dissolution of Fe/Mn oxides, and the partial oxidation of metal sulfide minerals. The present study results have confirmed the great importance of mineralogy analysis and geochemical approaches to explain the contribution of smelting activities to soil pollution risks.

Application of alkyl polyglycosides for enhanced bioremediation of petroleum hydrocarbon-contaminated soil using Sphingomonas changbaiensis and Pseudomonas stutzeri.

Bioremediation is considered a cost-effective and environmentally sound method for degradation of petroleum hydrocarbons in contaminated soils. This study investigated the effects of biosurfactant alkyl polyglycosides (APG) on enhanced biodegradation of petroleum hydrocarbon-contaminated soils using Sphingomonas changbaiensis and Pseudomonas stutzeri and explored the mechanism responsible for the enhanced petroleum hydrocarbon degradation. To accomplish this, the following treatments were evaluated: (1) bioaugmentation with Sphingomonas changbaiensis; (2) bioaugmentation with Pseudomonas stutzeri; (3) a combination of Sphingomonas changbaiensis and APG; and (4) a combination of Pseudomonas stutzeri and APG. The results showed that the degradation rates of total petroleum hydrocarbons (TPH) in contaminated soil samples bioaugmented with S. changbaiensis and P. stutzeri for 30 days were 39.2 ± 1.9% and 47.2 ± 1.2%, respectively. The addition of biosurfactant APG enhanced the bioremediation processes and improved the biodegradation rates. The biodegradation rate at 1.5 g/kg APG in soil samples bioaugmented with S. changbaiensis was 52.1 ± 2.0%, while the rate at 1.5 g/kg APG in soil samples bioaugmented with P. stutzeri was 59.0 ± 1.8%. The half-life decreased from 39.7 d to 24.5 d and from 29.6 to 20.1 d when the dosage of APG was 1.5 g/kg in contaminated soil samples bioaugmented with S. changbaiensis and P. stutzeri, respectively. Mechanism studies showed that the addition of APG can increase the TPH solubility, promote the sorption of TPH onto microbial cells and subsequent trans-membrane transport by APG-induced structural changes, stimulate microbial activities and participate in the co-metabolism. Therefore, the combination of bioaugmentation and APG is an effective method for remediation of petroleum hydrocarbon-contaminated soil.

Treatment of decabromodiphenyl ether (BDE209) contaminated soil by solubilizer-enhanced electrokinetics coupled with ZVI-PRB.

Decabromodiphenyl ether (BDE209) is a typical soil contaminant released from e-waste recycling sites (EWRSs). Electrokinetics (EK) has been considered as an excellent treatment technology with a promising potential to effectively remove organic pollutants in soil. In this study, the treatment of BDE209-polluted soil by EK was explored. All the EK experiments were conducted under a constant voltage gradient (2 V cm-1) for 14 days. Deionized water (DI water), hydroxypropyl-ß-cyclodextrin (HPCD), sodium dodecyl sulfate (SDS), and humic acid (HA) were applied as the processing fluid. The experimental results showed that all the solubilizers could effectively promote the mobility and transport of BDE209 in the soil via the electro-osmotic flow (EOF) or electromigration. The removal efficiencies achieved in S1 section were 24, 22, and 26% using HPCD, SDS, and HA as the processing fluid. However, the removal of BDE209 for the entire soil cell was not achieved until zero valence iron (ZVI) was inserted at the center of soil column as a permeable reactive barrier (PRB) or (ZVI-PRB), which enhanced the degradation of BDE209. As ZVI-PRB was installed in EK5 and EK6 experiments, the corresponding average removal efficiencies increased to 16 and 13%, respectively. Additionally, the degradation products of BDE209 analyzed by GC-MS suggested that debromination of BDE209 was the main potential degradation mechanism in the EK treatment in the presence of ZVI-PRB.

Toxicological effect of joint cadmium selenium quantum dots and copper ion exposure on zebrafish.

Quantum dots (QDs) have strong adsorption capacity; therefore, their potential toxicity to aquatic organisms from the facilitated transport of other trace toxic pollutants when they coexist has received increasing interest. However, the impact of cadmium selenium (CdSe) QDs and copper ion (Cu(2+)) joint exposure on zebrafish (Danio rerio) embryo and larvae remains almost unknown. Therefore, the present study was performed to determine the developmental toxicities to zebrafish exposed to combined pollution with CdSe QDs (500 µg/L) and Cu(2+) (0, 0.1, 1, 10, and 100 µg/L CuC1(2)) compared with single exposure. Our findings for the first time revealed that: (1) QDs facilitated the accumulation of Cu(2+) in zebrafish; (2) QDs caused higher mortality, lower hatch rate, and more malformations of the exposed zebrafish; (3) junction, bifurcation, crossing, particles, and aggregation of the exposed FLI-1 transgenic zebrafish larvae can be observed; (4) embryo cell apoptosis appeared in the head and tail region; and (5) synergistic effects played an important role during joint exposure. These observations provide a basic understanding of CdSe QDs and Cu(2+) joint toxicity to aquatic organisms and suggest the need for additional research to identify the toxicological mechanism.

[Characteristics of microbial biomass in subsurface constructed wetland treating eutrophic water].

A subsurface horizontal-flow constructed wetland planted with Phragmites australis was developed and used to treat eutrophic water for nearly two years at fixed hydraulic loading rate. Substrate samples were taken at different depths respectively in the front, middle and back sites of wetland in January, May, August and October in the second year. Microbial biomass (MB) content was measured using the chloroform fumigation incubation method. The results show that the front sites have higher levels of microbial biomass carbon (MB-C), microbial biomass nitrogen (MB-N) and microbial biomass phosphorous (MB-P) than that in middle sites and back sites. The upper layers have higher levels of MB than that in the deeper layers. The MB content of wetland in January and May is higher than that in October and August. The relationship between MB and TN, TP removal efficiency of the constructed wetland was investigated. The wetland shows no apparent correlation of MB and TN removal efficiency. However, strong negative correlation is observed between MB-C and TP removal efficiency (r = -0.98, p < 0.05) and between MB-N, MB-P and TP removal efficiency (r = -0.99, p < 0.01). In constructed wetland, MB is also an active nutrient storage involved in nutrient cycling and can be used by wetland plant. MB content varies among a range level with plant growth and temperature in a growth year. Under experiment conditions, the range of MB-C, MB-N and MB-P was respectively 85.0-160.6, 16.3-34.9 and 3.12-5.77 microg x g(-1) in the second year. Seasonal variation of MB and nutrient removal is resulted from the factors integrated with temperature, microorganisms, plant, substrate and enzyme.