Coupled Aerobic Methane Oxidation and Arsenate Reduction Contributes to Soil-Arsenic Mobilization in Agricultural Fields.

Microbial oxidation of organic compounds can promote arsenic release by reducing soil-associated arsenate to the more mobile form arsenite. While anaerobic oxidation of methane has been demonstrated to reduce arsenate, it remains elusive whether and to what extent aerobic methane oxidation (aeMO) can contribute to reductive arsenic mobilization. To fill this knowledge gap, we performed incubations of both microbial laboratory cultures and soil samples from arsenic-contaminated agricultural fields in China. Incubations with laboratory cultures showed that aeMO could couple to arsenate reduction, wherein the former bioprocess was carried out by aerobic methanotrophs and the latter by a non-methanotrophic bacterium belonging to a novel and uncultivated representative of Burkholderiaceae. Metagenomic analyses combined with metabolite measurements suggested that formate served as the interspecies electron carrier linking aeMO to arsenate reduction. Such coupled bioprocesses also take place in the real world, supported by a similar stoichiometry and gene activity in the incubations with natural paddy soils, and contribute up to 76.2% of soil-arsenic mobilization into pore waters in the top layer of the soils where oxygen was present. Overall, this study reveals a previously overlooked yet significant contribution of aeMO to reductive arsenic mobilization.

A mixed blessing of viruses in wastewater treatment plants.

Activated sludge of wastewater treatment plants harbors a very high diversity of both microorganisms and viruses, wherein the latter control microbial dynamics and metabolisms by infection and lysis of cells. However, it remains poorly understood how viruses impact the biochemical processes of activated sludge, for example in terms of treatment efficiency and pollutant removal. Using metagenomic and metatranscriptomic deep sequencing, the present study recovered thousands of viral sequences from activated sludge samples of three conventional wastewater treatment plants. Gene-sharing network indicated that most of viruses could not be assigned to known viral genera, implying activated sludge as an underexplored reservoir for new viruses and viral diversity. In silico predictions of virus-host linkages demonstrated that infected microbial hosts, mostly belonging to bacteria, were transcriptionally active and able to hydrolyze polymers including starches, celluloses, and proteins. Some viruses encode auxiliary metabolic genes (AMGs) involved in carbon, nitrogen, and sulfur cycling, and antibiotic resistance genes (ARGs) for resistance to multiple drugs. The virus-encoded AMGs may enhance the biodegradation of contaminants like starches and celluloses, suggesting a positive role for viruses in strengthening the performance of activated sludge. However, ARGs would be disseminated to different microorganisms using viruses as gene shuttles, demonstrating the possibility for viruses to facilitate the spread of antibiotic resistance in the environment. Collectively, this study highlights the mixed blessing of viruses in wastewater treatment plants, and deciphers how they manipulate the biochemical processes in the activated sludge, with implications for both environmental protection and ecosystem security.

Bacterial diversity in the sediment from polymetallic nodule fields of the Clarion-Clipperton Fracture Zone.

The Clarion-Clipperton Fracture Zone (CCFZ) is located in the northeastern equatorial Pacific and contains abundant polymetallic nodules. To investigate its bacterial diversity, four libraries of 16S rRNA genes were constructed from sediments of four stations in different areas of the CCFZ. In total, 313 clones sequenced from the 4 libraries were assigned into 14 phylogenetic groups and 1 group of 28 unclassified bacteria. High bacterial diversity was predicted by the rarefaction analysis. The most dominant group overall was Proteobacteria, but there was variation in each library: Gammaproteobacteria was the most dominant group in two libraries, E2005-01 and ES0502, while Alphaproteobacteria and Deltaproteobacteria were the most dominant groups in libraries EP2005-03 and WS0505, respectively. Seven groups, including Alphaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Betaproteobacteria, Acidobacteria, Actinobacteria, and Bacteroidetes, were common to all four libraries. The remaining minor groups were distributed in libraries with different patterns. Most clones sequenced in this study were clustered with uncultured bacteria obtained from the environment, such as the ocean crust and marine sediment, but only distantly related to isolates. Bacteria involved in the cycling of metals, sulfur and nitrogen were detected, and their relationship with their habitat was discussed. This study sheds light on the bacterial communities associated with polymetallic nodules in the CCFZ and provides primary data on the bacterial diversity of this area.

[Sorption of 1-naphthol to plant cuticular waxes with different states].

Wax components are ubiquitous in natural environments (such as plant and soil) and play a significant role in sorption of organic contaminants. To elucidate their sorption characteristics, cuticular waxes were isolated from the fruits of apple by organic solvent extraction method, and then the isolated-wax was reconstructed on montmorillonite with different loadings. Sorption behaviors of one polar organic pollutant, 1-naphthol, to isolated-wax, reconstructed-wax, and cuticle-associated-wax samples were compared by batch sorption method. Sorption properties of wax-montmorillonite complexes dependent on different wax-loadings were also investigated. Isotherms of 1-naphthol to wax samples were nonlinear, and fitted well with Freundlich equation. Although sorption of wax in the plant cuticle was weakened by other components of cuticle, its contribution to whole sorption of the cuticle increased with solute aqueous equilibrium concentration. Sorption coefficients at three equilibrium concentrations (1, 10, 100 microg/mL) were calculated, depending on solute concentrations and wax-loadings. Sorption coefficients normalized organic carbon contents (Koc) decreased with the increase of solute aqueous concentration. At low solute aqueous concentration, Koc values increased with the wax-loading increasing, reached maximum, and then decreased. At high solute aqueous concentration, Koc values were almost independent on wax-loadings. These observations indicated that partition was the dominant mechanism at high solute concentration, while specific interactions were involved as additional mechanisms at low solute concentration. Koc values of wax components in different states were in the order of reconstructed-wax (321.2) > isolated-wax (190.4) > cuticular-attached-wax (128.4), suggested that the sorption capability of wax was promoted once they were input into soil environment and then coated on mineral surface.

[Concentration and distribution of PAHs in vegetables grown near an iron and steel industrial area].

Concentrations of 15 kinds of polycyclic aromatic hydrocarbon (PAHs) were determined in 8 vegetable species and their growing environment (soil and atmosphere) near an iron and steel industrial area. The total concentrations of 15 kinds of PAHs (sigma PAHs) were 227.1 - 1 533.2 ng/g, 759.1 ng/g in average. The concentrations of 8 carcinogenic PAHs (sigma carePAHs) were 7.1 - 231.2 ng/g, 70.6 ng/g in average. Of the various vegetable species determined, the highest polyaromatic burden was observed in the leafy vegetables, followed by melon and fruit species, while the rhizome species accumulated the lowest amount. In melon and fruit species, most PAHs were accumulated on the peel, only about 30% transfer into the core. The ability of the plant accumulating PAHs was mainly influenced by the lipid content of the plant. Leaf with pubescence or rough surface was found to have higher sigma PAHs than the other, and the fibre higher than the taproot, when the lipid contents were close.

[Sorption characteristics of surfactant onto bentonite using microwave irradiation].

The sorption curve of cetylpyridinium chloride (CPC) onto bentonite by microwave irradiation was studied. The effects of microwave reaction time and CPC concentration on interlayer spacing and organic carbon content of organobentonite were tested, respectively. Thermodynamics and kinetics of sorption of CPC onto bentonite by microwave irradiation were studied. The saturated adsorption amount of CPC to bentonite with microwave irradiation time from 90 s to 120 s was equal to that of conventional sorption, up to 0.001 63 mol x g(-1). On the condition of microwave irradiation time with 2 min and concentration of CPC with 1.20 mmol x L(-1), the interlayer spacing was attained to 2.44 nm at the best, and organic carbon content was 23.45%. The atomic force microscopy (AFM) showed that the typical layer morphological structure of bentonite was not devastated by microwave. Contrast to conventional sorption, sorption of CPC onto bentonite was greatly influenced by microwave, velocity constant of sorption reaction was increased 107.6 times, and free energy of sorption reaction system was decreased.

[Prediction of PAHs uptake by ryegrass with a partition-limited model].

The performance of a partition-limited model on prediction of four PAHs (acenaphthene, fluorene, phenanthrene and pyrene) uptake by ryegrass simultaneously was evaluated using a hydroponic system. Results suggest that the model has a good performance on prediction of PAHs uptake. However, the model focused on root translocation only, while excluded foliar uptake, which resulted in a poor performance on prediction of PAHs in shoots. The differences of simulated and experimented concentrations of PAHs were less than 57.4% for roots and less than 98.5% for shoots respectively. If the influence of foliar uptake on the performance of the model was taken into account, the differences for all the four PAHs would be reduced significantly. Since the influence of foliar uptake increased with the increase of the hydrophobic property of the PAHs, the differences decreased with an order of pyrene> phenanthrene> fluorene> acenaphthene, among which the maximum difference for pyrene decreased from 98.5% down to 69.4%.

[Simultaneous sorption of aqueous phenanthrene and phosphate onto bentonites modified with AlCl3 and CTMAB].

Inorganic-organic bentonites (Al-CTMAB-Bent) were synthesized by modifying bentonites with AlCl3 and cetyltrimethyl ammonium bromide (CTMAB). Simultaneous sorption of aqueous phenanthrene and phosphate onto Al-CTMAB-Bent were examined. Removal rates of phenanthrene and phosphate from water are 96.3% and 90.2%, respectively, at their respective initial concentrations of 1 mg/L and 5 mg/L when the added amount of Al-CTMAB-Bent was 1.25 g/L. The residual turbidity of Al-CTMAB-Bent suspension decreased 81.4% comparing to that of organobentonite suspension after 1 hour settlement. Thus inorganic-organic bentonite can be used to treat wastewater containing both organic pollutants and phosphate.

[Mechanism and impact for microwave-enhanced integrative sorption of dye to mixture of surfactant and bentonite from water].

Microwave-enhanced integrative sorption (MEIS) of dye to mixture of surfactant and bentonite was put forward. The order of factor for integrative method was obtained by the orthogonal experiment. The optimal conditions, properties, kinetics and mechanisms for microwave-enhanced integrative sorption of Neutral Red S-BR to bentonite from water were investigated. Comparative study on decolorization rates of Neutral Red S-BR by other sorption method and MEIS from water were conducted. It is concluded that the order of factor for integrative method is amount of surfactant, bentonite and microwave time. The optimal condition for MEIS is that the ratio of amount of bentonite and water is equal to 1/1 000, the concentration of cetylpyridinium chloride (CPC) is 120 mg/L (equivalent to 28% cation exchange capacity of bentonite) and microwave time is 60s. Comparative with organobentonite, the decolorization rates of Neutral Red S-BR to bentonite are greatly increased by MEIS at higher concentration of dye, amount of surfactant is greatly decreased, and the saturated sorption capacity and the reactive rate of sorption of dye to bentonite are greatly increased by microwave.

Thermodynamics of phenanthrene partition into solid organic matter from water.

The thermodynamic behavior of organic contaminants in soils is essential to develop remediation technologies and assess risk from alternative technologies. Thermodynamics of phenanthrene partition into four solids(three soils and a bentonite) from water were investigated. The thermodynamics parameters (deltaH, deltaG degrees, deltaS degrees) were calculated according to experimental data. The total sorption heats of phenanthrene to solids from water ranged from -7.93 to -17.1 kJ/mol, which were less exothermic than the condensation heat of phenanthrene-solid (i.e., -18.6 kJ/mol). The partition heats of phenanthrene dissolved into solid organic matter ranged from 23.1 to 32.2 kJ/mol, which were less endothermic than the aqueous dissolved heat of phenanthrene (i.e., 40.2 kJ/mol), and were more endothermic than the fusion heat of phenanthrene-solid (i.e., 18.6 kJ/mol). The standard free energy changes, deltaG degrees, are all negative which suggested that phenanthrene sorption into solid was a spontaneous process. The positive values of standard entropy changes, deltaS degrees, show a gain in entropy for the transfer of phenanthrene at the stated standard state. Due to solubility-enhancement of phenanthrene, the partition coefficients normalized by organic carbon contents decrease with increasing system temperature (i.e., ln Koc = -0.284 ln S + 9.82 (n = 4, r2 = 0.992)). The solubility of phenanthrene in solid organic matter increased with increasing temperatures. Transports of phenanthrene in different latitude locations and seasons would be predicted according to its sorption thermodynamics behavior.

PAHs in aquatic sediment in Hangzhou, China: analytical methods, pollution pattern, risk assessment and sources.

Eleven surface sediment samples, from Hangzhou section of Qiantang River and Jinghang Canal, west Lake the inland river were collected to investigate 17 polycyclic aromatic hydrocarbons (PAHs) pollution in aquatic sediments of Hangzhou. Accelerated solvent extraction(ASE) was used to extract PAHs from sediments with satisfactory recoveries. It was found that the total PAHs in the sediments ranged from 308.4 to 3037 ng/g dw, and PAHs pollution in sediments from Jinghang Canal were the heaviest. Lowest effect level (LEL) and severe effect level (SEL) sediment quality guidelines were introduced to perform risk assessment for PAHs pollution in aquatic sediments. Only one sample in Jinghang Canal had adverse impact on benthic organism. 2-3 ring PAHs had a noticeable contribution to total PAHs, especially NA, PHEN. A quantity method was used to determine the major source, the results showed petroleum origin was the chief source to PAHs pollution in all sediments with the exception of sediments from Jinghang Canal where combustion sources had a larger contribution.

PAHs pollution from traffic sources in air of Hangzhou, China: trend and influencing factors.

PAHs pollution in air of arterial roads was investigated from October 1998 to October 2001 in Hangzhou, China. The results showed that sigma10 PAHs was 13-36 microg/m3, among which, BaP, a strong carcinogenic kind ranged from 0.034 microg/m3 to 0.12 microg/m3. PAHs pollutions in four seasons were winter > autumn > spring-summer. The annual averages of sigmaPAHs concentration were 25 microg/m3 for 1999, 28 microg/m3 for 2000, and 29 microg/m3 for 2001, respectively. Leaded gasoline was banned in December 1998 in Hangzhou, thus comparative measurements with PAHs in leaded and lead-free gasoline powered motor exhausts made it certain that the use of lead-free gasoline leaded to a heavier PAHs pollution in roadside air from December, 1998, in China, and sigmaPAHs in air samples after the lead-banning were more than twice of that in samples before the action. For the large contribution of vehicle discharge to air pollution in roadside, further research was performed to suggest the factors influencing PAHs distribution in vehicle exhaust in order to control air pollution effectively. Compared to gasoline engines, emissions from diesel engines were less toxic, although they might produce more PAHs. Of the same vehicular and oil type, automobiles of longer mileages produced more toxic PAHs. PAHs distributions in the vehicular exhausts were related to the oil type. Large difference was found in the abundance of 3-, 5- and 6-ring PAHs between exhausts from gasoline and diesel oil engines. Diesel oil engines produced relative lighter PAHs such as NAPH, ACEN, FLUOR, while gasoline engines emitted heavier kinds such as BkF, IN and BP. The automobile produced more PAHs with the increase of mileage especially FLUR, PY, BaP, BP. Some significant ratios for traffic source in Hangzhou such as PHEN/AN, FLUR/PY, IN/BP were 0.50-4.3, 0.58-7.4, 0.51-1.5, respectively. A source fingerprint for vehicle exhausts of a mixture of vehicle and oil types in the city district for light-duty vehicle was the abundance of BaA, followed by NAPH, BP, IN. 4-ring PAHs such as FLUR, PY, BaA and CHRY were the most predominant kinds followed by 6-ring PAHs(BP, IN).

[Pollution survey of carbonyl compounds in train air].

The methods for sampling and analyzing 10 carbonyl compounds such as formaldehyde, acetaldehyde, acrolein, acetone, propionaldehyde, crotonaldehyde, butyraldehyde, benzaldehyde, cyclohexanone, valeraldehyde in indoor air were proposed with the sampling efficiency, recovery and detection limit being 92% - 100%, 91% - 104%, 0.26ng/m3 - 0.82ng/m3, respectively. Pollution survey of 10 carbonyl compounds in air of 6 trains was conducted. It was indicated that the total concentrations of carbonyl compounds were 0. 1591 mg/m3 - 0.2828 mg/m3 with the average concentration of 0.2330 mg/m3, the average concentrations of formaldehyde, acetaldehyde and acetone were 0.0922 mg/m3, 0.0499 mg/m3 and 0.0580 mg/m3, accounted for 42.6%, 21.4%, 24.9% of the total carbonyl compounds' concentrations, respectively. The carbonyl compounds probably came from woodwork and tobacco. The intake of carbonyl compounds for the passengers was approximately 0.043 mg/h - 0.076 mg/h.

Phytoremediation for phenanthrene and pyrene contaminated soils.

Phytoremediation of soil contaminated with phenanthrene and pyrene was investigated using twelve plant species. Plant uptake and accumulation of these chemicals were evaluated. At the end of the experiment(45 d), the remaining respective concentrations of soil phenanthrene and pyrene in spiked vegetated soils, with initial phenanthrene of 133.3 mg/kg and pyrene of 171.5 mg/kg, were 8.71-16.4 and 44.9--65.0 mg/kg, generally 4.7%--49.4% and 7.1%--35.9% lower than their concentrations in the non-vegetated soils. The loss of phenanthrene and pyrene in vegetated spiked soils were 88.2%--93.0% and 62.3%--73.8% of the added amounts of these contaminants, respectively. Although plant uptake and accumulation of these compounds were evident, and root concentrations and RCFs (root concentration factors; defined as the ratio of PAH concentrations in roots and in the soils on a dry weight basis) of these compounds significantly positively correlated to root lipid contents, plant uptake and accumulation only accounted for less than 0.01% and 0.23% of the enhanced loss of these chemicals in vegetated versus non-vegetated soils. In contrast, plant-promoted microbial biodegradation was the dominant mechanism of the phytoremediation for soil phenanthrene and pyrene contamination. Results from this study suggested a feasibility of the establishment of phytoremediation for soil PAH contamination.

Incorporating sorption/desorption of organic pollutants into river water quality model.

Preliminary research was conducted about how to incorporate sorption/desorption of organic pollutants with suspended solids and sediments into single-chemical and one-dimensional water quality model of Jinghang Canal. Sedimentation-resuspension coefficient k3 was deduced; characteristics of organic pollutants, concentrations and components of suspended solids/sediments and hydrological and hydraulic conditions were integrated into k3 and further into river water quality model; impact of sorption/desorption of organic pollutants with suspended solids and sediments on prediction function of the model was discussed. Results demonstrated that this impact is pronounced for organic pollutants with relatively large Koc and Kow, especially when they are also conservative and f.o of river suspended solids/sediments is high, and that incorporation of sorption/desorption of organic pollutants into river water quality model can improve its prediction accuracy.

[Survey sources of polycyclic aromatic hydrocarbons in surface water of Hangzhou by K(OC)* values].

Ten polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in 9 surface water samples of Qiantang River and Hangzhou Canal in Hangzhou, China, in December of 2002. It was observed that the sum of PAHs concentrations ranged from 1.104 to 9.663 microg x L(-1) in surface water, from 132.7 to 7343 microg x kg(-1) dry sediments, and from 59.71 to 219.5 microg x kg(-1) dry soils. The accumulative coefficients of PAHs in sediments and soils (K) and apparent partition coefficients normalized by solid organic carbon contents (K(OC)*) were calculated. In Hangzhou Canal, K and K(OC)* values in sediments increased with downstream, and ratio of K(OC)* on sediment to K(OC)* on soil were much larger than 1. Those indicated that Hangzhou Canal was heavily polluted by PAHs released from factory wastewater and PAHs in sediment were mainly sources of PAHs in surface water. In Qiantang River, K and K(OC)* values in sediments decreased with the downstream, and the ratio of K(OC)* on sediment to K(OC)* on soil near 1, and ratio fOC of sediment to fOC of soil approximate to 1, which showed that PAHs in Qiantang River were attributed to soil runoff.

[Adsorption of cation-nonionic mixed surfactants onto sediment and their effects on adsorption of nitrobenzene from water].

Adsorption behaviors of nitrobenzene, a nonionic surfactant (Triton X-100), a cation surfactant (CPC) and their mixture onto a sediment were investigated. The adsorption of Triton X-100 onto the sediment is enhanced with increasing of co-existed CPC at relatively low concentrations but decreased at relatively high concentrations. The adsorption of CPC onto the sediment decreased a little with increasing of co-existed Triton X-100. In natural waters, cation surfactants and nonionic surfactants will be largely adsorbed by soils or sediments. The adsorption of nitrobenzene onto sediment is linear and enhanced by the co-existed Triton X-100 or CPC, and will be significantly enhanced by the mixture of CPC-Triton X-100. Therefore, cation-nonionic mixed surfactants are potentially used to enhance adsorption of organic contaminants onto soils or sediments and to prepare organobentonite for improving their performance in wastewater treatment.

[Adsorption behavior and mechanisms in dual-solutes of Pb2+ and p-nitrophenol by organobentonites].

The sorption behavior for organobentonites to sorb organic pollutants from metal-organic pollutant systems were investigated. The results suggested that in organobentonite/Pb2+/p-nitrophenol solute systems, Pb2+ can slow the sorption velocity of organobentonite to adsorb p-nitrophenol from water. Pb2+ and p-nitriphenol exhibit a competitive effect. The competitive effects were relevant to ration of p-nitrophenol and Pb2+ and adsorption mechanisms of organobentonites. Bentonite modified with TMAB adsorbing contaminants primarily by an adsorption process, and the process exhibits a stonger competitive effect in multi-solute systems.

Sorption of BTEX mixtures to organobenonites.

Organobentonites synthesized by replacing the metal ions in bentonite with cetyltrimethylammonium (CTMA) or tetramethylammonium cation (TMA) were investigated for their behaviors to sorb benzene, toluene, p-xylene from water. The results served to distinguish the sorption mechanisms (adsorption or partition) of the two types of organobentonites. Bentonites modified with short-chain alkyl functional groups (e.g., TMA) sorb organic contaminants primarily by an adsorption process, in which the sorbed amount decreases with increasing steric hindrance of the organic compound and the process exhibits a competitive effect because of steric hindrance in multisolute systems. In contrast, the sorption of contaminants to organobentonites modified with long-chain alkyl groups (e.g., CTMA) occurs by partition process without exhibiting a competitive effect, and the additional organic compounds may induce a cosorptive effect. In the latter case, the measured distribution coefficients of organic compounds between organobentonites and water (log Kd) are positively correlated with the octanol-water partition coefficients of the compounds (logKow) and the sorption process exhibits no competitive effect in multi-solute systems.

An analysis on spatial variation of urban human thermal comfort in Hangzhou, China.

Urban human thermal comfort (UHTC) is affected for interacting of weather condition and underlying surface framework of urban area. Urban underlying surface temperature value and Normalized Difference Vegetation Index (NDVI) were calculated using image interpreting and supervised classification technique by ERDAS IMAGE software using 1991 and 1999 Landsat TM images data. Reference to the relational standard of assessing human thermal comfort and other meteorology data of Hangzhou City in summer, air temperature and relative humidity variation of different land types of underlying surface were inversed. By choosing discomfort index as an indictor, the spatial distribution characteristic and the spatial variation degree of UHTC were estimated and mapped on a middle scale, that is, in six districts of Hangzhou. The main characteristics of UHTC spatial variation from 1991 to 1999 were revealed using a GIS-based calculation model. The variation mechanism were analyzed and discussed from the viewpoint of city planning, construction and environmental protection.