Sulfidation of nanoscale zerovalent iron (nZVI) has attracted increasing interest for improving the reactivity and selectivity of nZVI towards various contaminants, such as aqueous Cr(VI) removal. ...However, the benefits derived from sulfide modification that govern the removal of Cr(VI) remains unclear, which was studied in this work. S-nZVI with higher S/Fe molar ratio showed higher surface area, the discrepancy between the surface-area-normalized removal capacity of Cr(VI) by S-nZVI with different S/Fe indicated that the removal of Cr(VI) was also affected by other factors, such as electron transfer ability, surface-bounded Fe(II) species, and surface charges. High specific surface area would provide more active site for Cr(VI) removal, and as an efficient electron conductor, acicular-like FeSx phase would also favor electron transfer from Fe0 core to Cr(VI). Low initial pH also enhanced the Cr(VI) removal, and the Cr(VI) removal capacity by S-nZVI and nZVI was not affected by aging process, these results confirmed that the Fe(II) species also played an important role in the Cr(VI) removal. Other influence factors were also investigated for potential application, including temperature, initial Cr(VI) concentration, ionic strength, and co-existed ions. The removal mechanism of Cr(VI) by S-nZVI involved the sulfide modification to increase the specific surface area and provide more active sites, the corrosion of Fe0 to produce surface-bounded Fe(II) species to adsorb Cr(VI) species, followed by the favored reduction of Cr(VI) to Cr(III) due to the electron transfer ability of FeSx, then the formation of Cr(III)/Fe(III) hydroxides precipitates.
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•S-nZVI showed better reactivity than pristine nZVI towards Cr(VI).•S/Fe molar ratio had significant effects on the reactivity of S-nZVI.•Cr(VI) was removed through adsorption, reduction, and co-precipitation.•FeSx on S-nZVI facilitated the electron transfer and acted as reducing agent.•S-nZVI maintained high Cr(VI) removal efficiency after aged 12 days.
Understanding the spatial distribution and apportioning the sources of water pollution are important in the study and efficient management of water resources. In this work, we considered data for 13 ...water quality variables collected during the year 2004 at 46 monitoring sites along the Qiantang River (China). Fuzzy comprehensive analysis categorized the data into three major pollution zones (low, moderate, and high) based on national quality standards for surface waters, China. Most sites classified as “low pollution zones” (LP) occurred in the main river channel, whereas those classified as “moderate and high pollution zones” (MP and HP, respectively) occurred in the tributaries. Factor analysis identified two potential pollution sources that explained 67% of the total variance in LP, two potential pollution sources that explained 73% of the total variance in MP, and three potential pollution sources that explained 80% of the total variance in HP. UNMIX was used to estimate contributions from identified pollution sources to each water quality variable and each monitoring site. Most water quality variables were influenced primarily by pollution due to industrial wastewater, agricultural activities and urban runoff. In LP, non-point source pollution such as agricultural runoff and urban runoff dominated; in MP and HP, mixed source pollution dominated. The pollution in the small tributaries was more serious than that in the main channel. These results provide information for developing better pollution control strategies for the Qiantang River.
In recent years, air pollution events have occurred frequently in China during the winter. Most studies have focused on the physical and chemical composition of polluted air. Some studies have ...examined the bacterial bioaerosols both indoors and outdoors. But few studies have focused on the relationship between air pollution and bacteria, especially pathogenic bacteria. Airborne PM samples with different diameters and different air quality index values were collected in Hangzhou, China from December 2014 to January 2015. High-throughput sequencing of 16S rRNA was used to categorize the airborne bacteria. Based on the NCBI database, the “Human Pathogen Database” was established, which is related to human health. Among all the PM samples, the diversity and concentration of total bacteria were lowest in the moderately or heavily polluted air. However, in the PM2.5 and PM10 samples, the relative abundances of pathogenic bacteria were highest in the heavily and moderately polluted air respectively. Considering the PM samples with different particle sizes, the diversities of total bacteria and the proportion of pathogenic bacteria in the PM10 samples were different from those in the PM2.5 and TSP samples. The composition of PM samples with different sizes range may be responsible for the variances. The relative humidity, carbon monoxide and ozone concentrations were the main factors, which affected the diversity of total bacteria and the proportion of pathogenic bacteria. Among the different environmental samples, the compositions of the total bacteria were very similar in all the airborne PM samples, but different from those in the water, surface soil, and ground dust samples. Which may be attributed to that the long-distance transport of the airflow may influence the composition of the airborne bacteria. This study of the pathogenic bacteria in airborne PM samples can provide a reference for environmental and public health researchers.
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•Total bacteria and pathogenic bacteria in airborne particulate matter were studied.•Air quality levels had a influence on total bacteria and pathogenic bacteria.•Particle sizes effected the distribution of total bacteria and pathogenic bacteria.•Relative humidity, carbon monoxide and ozone were the main factors.•The potential source environments of total bacteria were investigated.
Different concentrations and sizes of particulate matter, and various environmental factors were related to the variance of total bacteria and pathogenic bacteria.
Anaerobic oxidation of methane coupled to nitrite reduction (n-damo) plays an important role in global carbon and nitrogen cycles and also is a potential bioprocess in wastewater treatment. In this ...work, the effects of environmental conditions – temperature, pH and salinity – on the metabolic activity and growth rate of n-damo bacteria were investigated by short-term batch test and long-term bacterial incubation. Quantitative PCR and 16S rRNA and pmoA gene sequencing were applied to detect the microbial community in the long-term incubation. The results indicated that all the three environmental factors significantly affected the metabolic activity and growth rate of n-damo bacteria and the optimum temperature, pH and salinity were 35 °C, 7.6 and 0 g NaCl L−1, respectively. Notably, salinity adaption of n-damo bacteria was first observed under salinity stress of 20 g NaCl L−1. It's predicted that n-damo process might occur in saline environments and future work could focus on this.
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•First systematically investigated the effects of environmental factors on n-damo.•Derived or modified equations to describe the effects of environmental factors.•First discovered the salinity adaption of n-damo bacteria.•Predicted that n-damo might occur in saline environments.
Microorganisms are ubiquitous in the atmosphere, where they can disperse for a long distance. However, it remains poorly understood how these airborne microorganisms vary and which factors influence ...the microbial distribution in different anthropogenic activity regions. To explore the regional differences of bacteria and fungi in airborne particles, PM2.5 and PM10 samples were collected in the urban and rural areas of Hangzhou. The bacterial and fungal communities in the urban atmosphere was more similar to each other than those in the rural atmosphere. Analyses conducted by the concentration weighted trajectory model demonstrated that the local environment contributed more to the similarity of airborne bacteria and fungi compared with the atmospheric transport. The concentrations of local air pollutants (PM2.5, PM10, NO2, SO2 and CO) were positively correlated with the similarity of the bacterial and fungal communities. Additionally, the concentrations of these air pollutants in the urban site were about 1.5 times than those in the rural site. This implicated that anthropogenic activity, which is the essential cause of air pollutants, influenced the similarity of airborne bacteria and fungi in the urban area. This work ascertains the outdoor bacterial and fungal distribution in the urban and the rural atmosphere and provides a prospective model for studying the contributing factors of airborne bacteria and fungi.
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•Airborne microorganisms were more similar in more urbanized site.•Atmospheric transport made contribution to the source of bacteria and fungi.•Local environment made a greater contribution to the source of bacteria and fungi.•Air pollutants were positively correlated with the similarity of bacteria and fungi.
Exploring the distribution difference and influence factors of airborne bacteria and fungi in urban and rural areas shed light on the relationships between airborne microorganisms and air pollutants.
The accumulation of cadmium (Cd) in Oryza sativa L., the world’s most significant staple crop, is a health threat to millions of people. The objective of this study was to evaluate the effectiveness ...of commercially available biofertilizers (with high (BF2) and low organic matter (OM) content (BF1)) on Cd accumulation in two types of soils and to determine the bacterial community responses by high-throughput sequencing. The study was conducted in the form of pot experiment in greenhouse in 2018. Four treatments were set: BF1, BF2, organic fertilizer (OF), and control (CK) and the amendments were applied before the rice cultivation. The results showed that the addition of biofertilizers immobilized or mobilized Cd in soils, depending on the soil type and the OM content in biofertilizers. The exogenous OM in biofertilizers was the driving factor for the difference in pH and Cd accumulation in rice grains. The application of biofertilizers with high OM content was effective in reducing Cd accumulation in the rice grains (19.7% lower than CK) by significantly increasing soil pH (from 6.02 to 6.67) in acid silt loam soil (TZ). The consumption of acid fermentation products by soil chemoorganotrophs and the complexation of organic anions in the biofertilizer treatment tended to buffer the pH drop in the drainage and decrease the Cd availability. However, in the weak acid silty clay loam soil (SX), the addition of biofertilizer with high OM significantly increased Cd accumulation in rice grains (21.9% higher than CK), probably owing to the release of acid substances, resulting from the significant increase of the predominant bacteria Chloroflexi. The addition of biofertilizer with low OM content did not significantly change Cd accumulation in rice grains or affect the soil microbial structures in both soils. In conclusion, the effects of biofertilizer on rice Cd accumulation were related to the OM content and soil bacterial community. Biofertilizers with high organic matter may not be suitable for amendments in the paddy soils with high clay content to reduce Cd accumulation in rice grains.
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•Effects of biofertilizers on Cd accumulation in rice were soil specific.•OM in biofertilizers was the driving factor for the variance in soil pH.•Soil texture and farming conditions affected the predominant microbes.•Soil pH was negatively correlated with Cd accumulation in rice grains.
In this study, bamboo biochar (BBC) was proposed as a practical carbonaceous material for the in situ remediation of organic pollutants. Column leaching experiments were used to evaluate the ...leachability of pentachlorophenol (PCP) in soil amended with BBC (0, 1, 2, and 5%; w/w). After leaching, the residual bioavailability of PCP in the soil column was determined by chemical extraction methods (methanol and distilled water). The results showed that compared to the control, the addition of 5% BBC decreased the cumulative leach-loss content of PCP by 42%, and also reduced PCP concentrations by 56 and 65% in methanol and distilled water extracts, respectively. Moreover, the linear leaching curves for the 10-h leaching time indicated that the rapid release process may be dependent on the continuous diffusion and partition mechanism. Regression analyses showed a significant (p<0.001) relationship between the BBC percentage and cumulative content of leached PCP, in addition, a significant relationship between BBC percentage and the chemical extraction of PCP with correlation coefficients (R2) greater than 0.9. Therefore, adding BBC to soil could prevent PCP further contamination such as bioavailability, surface or groundwater contamination through leaching.
► Bamboo biochar (BBC) has potential ability to remediate PCP-contaminated soil. ► BBC lowers PCP leachability and its residual bioavailability in soil. ► The continuous diffusion is linear proportionality to leaching times (0–10h).
Anaerobic oxidation of methane (AOM) coupled to nitrite reduction is a novel AOM process that is mediated by denitrifying methanotrophs. To date, enrichments of these denitrifying methanotrophs have ...been confined to freshwater systems; however, the recent findings of 16S rRNA and pmoA gene sequences in marine sediments suggest a possible occurrence of AOM coupled to nitrite reduction in marine systems. In this research, a marine denitrifying methanotrophic culture was obtained after 20 months of enrichment. Activity testing and quantitative PCR (qPCR) analysis were then conducted and showed that the methane oxidation activity and the number of NC10 bacteria increased correlatively during the enrichment period. 16S rRNA gene sequencing indicated that only bacteria in group A of the NC10 phylum were enriched and responsible for the resulting methane oxidation activity, although a diverse community of NC10 bacteria was harbored in the inoculum. Fluorescence in situ hybridization showed that NC10 bacteria were dominant in the enrichment culture after 20 months. The effect of salinity on the marine denitrifying methanotrophic culture was investigated, and the apparent optimal salinity was 20.5‰, which suggested that halophilic bacterial AOM coupled to nitrite reduction was obtained. Moreover, the apparent substrate affinity coefficients of the halophilic denitrifying methanotrophs were determined to be 9.8 ± 2.2 μM for methane and 8.7 ± 1.5 μM for nitrite.
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•Foliar uptake of airborne lead (Pb) was investigated.•Bioavailable isotope ratios were associated with hydrophilic absorption.•Foliar uptake of Pb in the field was mainly from ...atmospheric deposition.•Aerosol BCF of ryegrass was higher in spring than that in winter.•Foliar uptake of Pb should consider both aerosol Pb and seasonal influence.
Foliar uptake of airborne lead (Pb) may be particularly important for Pb accumulation in plant organs. However, the aerosol bioconcentration factor (BCF) in different seasons has seldom been reported. In the present study, we collected ryegrass (Lolium perenne L.) and size-segregated aerosols (SSA) during the corresponding growing seasons, and analyzed these for both Pb concentrations and isotopic ratios. Airborne Pb showed a seasonally varying concentration that was approximately 20% higher in winter than in spring. The bioavailability index, however, was higher in spring. Coupling the stable isotope technique with the bioavailable Pb of aerosol was more reliable in identifying airborne Pb accumulation in leaves than the total determination, suggesting that the hydrophilic absorption pathway was probably dominant for the foliar uptake of Pb in ryegrass. Contributions of airborne Pb accumulation were 88%–92% for washed ryegrass growing outdoors, indicating that the foliar uptake of Pb in the field was mainly from atmospheric deposition. The aerosol BCF of Pb for ryegrass was 6.4–11.4 m3/g in winter and 22.9–31.5 m3/g in spring. The increased aerosol BCF in spring was due to the suitable temperature, abundant rainfall, and increased Pb solubility of the aerosol. Therefore, our results indicate that, for the foliar uptake of Pb, both the aerosol Pb concentration, composition, and seasonal influence should be considered.
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