Removal, transformation and ecological risk assessment of pesticide in rural wastewater by field-scale horizontal flow constructed wetlands of treated effluent.

Constructed wetlands (CWs) are widely used in sewage treatment in rural areas, but there are only a few studies on field-scale CWs in treating wastewater-borne pesticides. In this study, the treatment and metabolic transformation of 29 pesticides in rural domestic sewage by 10 field-scale horizontal flow CWs (HF-CWs), each with a treatment scale of 36‒5000 m3/d and operated for 2‒10 years, in Guangzhou, Southern China was investigated. The risk of pesticides in treated effluent and main factors influencing such risk were evaluated. Results demonstrated that HF-CWs could remove pesticides in sewage and reduce their ecological risk in effluent, but the degree varied among types of pesticides. Herbicides had the highest mean removal rate (67.35 %) followed by insecticides (60.13 %), and the least was fungicides (53.22 %). In terms of single pesticide compounds, the mean removal rate of butachlor was the highest (73.32 %), then acetochlor (69.41 %), atrazine (68.28 %), metolachlor (58.40 %), and oxadixyl (53.28 %). The overall removal rates of targeted pesticides in each HF-CWs ranged from 11 %‒57 %, excluding two HF-CWs showing increases in pesticides in treated effluent. Residues of malathion, phorate, and endosulfan in effluent had high-risks (RQ > 5). The pesticide concentration in effluent was mainly affected by that in influent (P = 0.042), and source control was the key to reducing risk. The main metabolic pathways of pesticide in HF-CWs were oxidation, with hydroxyl group to carbonyl group or to form sulfones, the second pathways by hydrolysis, aerobic condition was conducive to the transformation of pesticides. Sulfones were generally more toxic than the metabolites produced by hydrolytic pathways. The present study provides a reference on pesticides for the purification performance improvement, long-term maintenance, and practical sustainable application of field-scale HF-CWs.

Curbing per- and polyfluoroalkyl substances (PFASs): First investigation in a constructed wetland-microbial fuel cell system.

The presence of per- and polyfluoroalkyl substances (PFASs) in water environments has been linked to a slew of negative health effects in both animals and humans, but the green and eco-sustainable removal technologies remain largely unknown. Constructed wetland coupled microbial fuel cell (CW-MFC) is termed a "green process" to control pollutants and recover energy. However, so far, no study has investigated the removal of PFASs and their effects on the performance of the CW-MFC systems. Here, we investigated the removal performance of PFOA and PFOS in the CW-MFC systems both in the absence and presence of electricity circuit, and explored the distribution and fate of PFASs and their interactions with other elements in the systems. Our findings demonstrated excellent removal efficiency of >96% PFOA and PFOS in CW-MFC systems. PFOA and PFOS were distributed throughout the system via wastewater flow, while electrode material and plants are the main enrichment sites in which MFC enhanced up to 10% PFASs removal. However, a loss of 7.2-13.5% of nitrogen removal and a decrease of 7.3% in bioelectricity output were observed when PFASs were introduced in the system. The driven force led to the loss of nitrogen removal and bioelectricity generation lies in the accumulation of PFASs in system composition, which affected microbial activity and community composition, damaging the health of the plant, and in turn reducing CW-MFC's functioning. No doubt, CW-MFC systems provide an alternative technique for PFASs removal, alleviating some limitations to the physical and chemical techniques, but further investigation is highly needed.

Initial ecological restoration assessment of an urban river in the subtropical region in China.

Rivers in urbanised cities are often polluted, black, and odorous, with poor water quality and deteriorated ecology. Despite many river restoration studies, assessments of ecological responses to river restoration practices remain scant. Benthic animals are useful biological indicators showing the change and succession of river ecosystems; however, previous studies have mainly focussed on a few target species without considering overall ecosystem integrity. Here, we used a multi-index biological assessment method, benthic index of biological integrity (B-IBI) to assess ecological responses to river restoration of the Shahe River in subtropical region of China. Spatiotemporal changes in the macrobenthos community structure after restoration were monitored to explore species succession. We found that the number of macrobenthos species increased from 16 to 42, with the emergence of some pollution-sensitive species during the restoration period. Molluscs showed widespread recovery, and their relative proportions almost doubled from 12.5% to 24.4%. Oligochaetes and chironomids were the pioneer species in the recovering communities, while gastropod molluscs and pollution-sensitive aquatic insects were transitional species that first settled during the initial recovery period. Based on our survey data, 25 candidate metrics were selected, and five core metrics (total taxa, Simpson diversity index, percentage of crustaceans and molluscs, percentage of predators, and percentage of collector-gatherers) were identified after screening to establish the B-IBI. Our analysis revealed a distinct improvement in the overall health of the river, with the proportions of "excellent" and "good" sites increasing from zero to 28.6% and from 14.3% to 42.9%, respectively. A correlation analysis indicated that water flow, molluscs, and total phosphorus content were the three drivers of ecological recovery in the Shahe River. Overall, our study demonstrates the importance of governance and restoration of rivers in tropical and subtropical cities, and provides valuable evidence that can guide the design and evaluation of river restoration works.

Interrelation between macrophytes roots and cathode in constructed wetland-microbial fuel cells: Further evidence.

As an essential component in constructed wetland-microbial fuel cells (CW-MFC) system, the macrophytes play multiple roles in bioelectricity generation and decontaminants performance. However, the interrelation between macrophytes roots and cathode has not been fully investigated despite the fact that plant cultivation strategy is a critical issue in practice. For the first time, this study was designed to explore the interaction between macrophytes and cathode in CW-MFC by planting Cyperus altrnlifolius at relatively different positions from the cathode. The results showed that plants exhibited higher bioelectricity generation and dramatically improved pollution removal, as well as the improved richness and diversity of cathode microbes. More significantly, the relative locations between the plant roots and the cathode could lead to different cathode working patterns, while the optimal cathode pattern "plant root-assisted bio- & air-cathode" was formed when the plant roots are directly placed on the air-cathode layer in CW-MFC. The insight into the plant root and cathode relationship lies in whether the "multi-function cathode" can be established. This study contributes to increase the knowledge regarding the presence and behavior of plant roots and cathode throughout a CW-MFC system.

The in vivo and vitro degradation of sulfonamides in wetland plants reducing phytotoxicity and environmental pollution.

Aquatic plants can be used for in situ remediation of water-borne pharmaceutical compounds; however, such information and that of the potential risks of metabolites released into the environment are limited. This study determined the capacity of Canna indica and Acorus calamus used in the remediation of water-borne sulfonamides (SA). The tolerance, removal, accumulation, and biotransformation of various water-borne SAs were investigated in vivo by exposing plants to SA solutions (50 µg/L and 500 µg/L). After 28 days, C. indica removed more SAs (89.3-97.8%) than A. calamus (12.8-84.6%) and non-planted systems (8.0-69.3%). The SA removal results, except from the A. calamus system with 500 µg/L SA, fit the first-order kinetics model. The estimated half-lives of all SAs were 3-40 h and 2-60 h in the C. indica and A. calamus systems, respectively. In vivo biotransformation and rhizosphere degradation were the major phyto-removal mechanisms, constituting 24.9-81.1% and 0.0-37.1% of all SAs in the C. indica and A. calamus systems, respectively. SA acetyl metabolites were detected only in plant tissues supporting evidence for plant metabolic processes without risk into the environment. SA metabolism including oxidation, methylation, and conjugation via acetylation was potentially beneficial to accumulation and tolerate stress of antibiotic. Canna indica was more suitable for cleaning SA. Our findings better clarify the potential and low risks of phytoremediation in antibiotic-contaminated waters.

The combination sequence effect on nitrogen removal pathway in hybrid constructed wetlands treating raw sewage from multiple perspectives.

The combination sequence of traditional hybrid constructed wetlands (HCWs) affects the removal of nitrogen in raw sewage, but the effect of the combination sequence on nitrogen removal pathway have seldom been reported, especially the specific conditions allowing anammox to occur. Three-stage HCWs, namely vertical flow (VF), horizontal flow (HF) and surface flow (SF) constructed wetlands, were arranged in six different sequences to investigate nitrogen removal efficiencies and microbial removal pathways using metagenomic and stable isotope analyses. Results showed that the combination sequence significantly affected nitrogen removal pathways in HCWs. We found the best removal of total nitrogen (~50%) and ammonium (NH4+-N, ~99%) in HCWs with a VFCW in the 1st stage. Metagenomic results and stable isotope analyses further indicated that simultaneous nitrification and heterotrophic denitrification were the main pathways in unsaturated VFCW, which depended on the energy substance and electron donor supplied by chemical oxygen demand (CODCr) in raw sewage. Nitrifier, anammox bacteria and autotrophic denitrifies prevailed in the subsequent saturated CWs, which tend to nitrogen loss by partial nitrification and anammox in HFCW when fed with NH4+-N wastewater with low CODCr. Providing NH4+-N and oxygen in low CODCr wastewater was the essential step to facilitate anammox process in HFCW. It implied that the problem of poor nitrogen removal due to carbon limitation could be overcome by optimizing conditions in anammox's favor.

Plants inhibit the relative abundance of sulfonamide resistance genes and class 1 integron by influencing bacterial community in rhizosphere of constructed wetlands.

Antibiotic resistance genes (ARGs) commonly detected in wastewater can potentially lead to a health crisis. Constructed wetlands (CWs) remove ARGs and sulfonamides (SAs) from wastewater, but the importance of plants in the process is seldom reported. We compared the effect of three wetland plant species (Cyperus alternifolius, Juncus effuses, and Cyperus papyrus), sample distance from the root, and SA presence on the environmental abundance of class 1 integron (intI1) and SA resistance genes (sul) using specially designed CW rhizoboxes. Quantitative polymerase chain reaction revealed that the relative abundance of the target genes in planted CWs, especially in C. alternifolius planted CWs, was significantly lower than that in unplanted CWs (P < 0.05). The substrate in the rhizosphere or near-/moderate-rhizosphere (closest to the root) showed the lowest average relative abundance of the target genes, while the bulk substrate (without the root) showed the highest abundance of these genes, irrespective of the planted species. Further, the influence of plants was more evident after 8 weeks of wastewater treatment. The trend was the same in SA-treated and untreated groups, although the relative abundance of the target genes was significantly higher in the former (P < 0.05). The weaker correlation between the intI1 and sul genes in the rhizosphere and near-/moderate-rhizosphere in comparison to the bulk substrate in the SA group suggested that the risk of horizontal gene transfer was probably higher in the bulk substrate and unplanted CW. A partial least-squares path model revealed that dissolved organic carbon and oxygen content significantly influenced SA concentration, microbial community, and intI1 genes, and then shaping the sul genes together. Finally, redundancy analysis suggested that abundance of sul genes was influenced by bacteria enriched in the bulk substrate and unplanted CWs. The findings provide new insights into the importance for controlling risk of ARGs by wetland plants.

Bibliometric analysis of microbial sulfonamide degradation: Development, hotspots and trend directions.

Microbial sulfonamide degradation (MSD) is an efficient and safe treatment in both natural and engineered ecosystems. In order to systematically understand the research status and frontier trends of MSD, this study employed CiteSpace to conduct a bibliometric analysis of data from the Web of Science (WoS) and the China National Knowledge Infrastructure (CNKI) published from 2000 to 2021. During this time, China, Germany, Spain, the United States and Australia played leading roles by producing numerous high impact publications, while the Chinese Academy of Sciences was the leading research institution in this interdisciplinary research category. The Chemosphere was the top journal in terms of the number of citations. MSD research has gradually progressed from basic laboratory-based experiments to more complex environmental microbial communities and finally to deeper research on molecular mechanisms and engineering applications. Although multi-omics and synthetic community are the key techniques in the frontier research, they are also the current challenges in this field. A summary of published articles shows that Proteobacteria, Gammaproteobacteria, Burkholderiales and Alcaligenaceae are the most frequently observed MSD phylum, class, order and family, respectively, while Bacillus, Pseudomonas and Achromobacter are the top three MSD genera. To our knowledge, this study is the first to investigate the development and current challenges of MSD research, put forward future perspective, and form a relatively complete list of sulfonamide-degrading microorganisms for reference.

Insight into the performance discrepancy of GAC and CAC as air-cathode materials in constructed wetland-microbial fuel cell system.

Constructed wetland-microbial fuel cell (CW-MFC) has exhibited the performance discrepancy between using granular activated carbon (GAC) and columnar activated carbon (CAC) as air-cathode materials. No doubt, this is linked with electrochemical performance and decontaminants characteristics in the CW-MFC system. To provide insight into this performance discrepancy, three CW-MFCs were designed with different carbon-material to construct varied shapes of air-cathodes. The results showed that the ring-shaped cathode filled with GAC yielded a highest voltage of 458 mV with maximum power density of 13.71 mW m-2 and >90% COD removal in the CW-MFC system. The electrochemical characteristics and the electron transport system activity (ETSA) are the driven force to bring the GAC a better electron transportation and oxygen reduction reaction (ORR). This will help elucidating underlying mechanisms of different activated carbon for air-cathode and thus promote its large application.

The effect of rhizosphere and the plant species on the degradation of sulfonamides in model constructed wetlands treating synthetic domestic wastewater.

The effects of and main contributors in rhizosphere and plant species on the degradation of sulfonamides (SAs) in constructed wetland (CW) models for the treatment of domestic wastewater are currently unclear. To investigate the degradation and key rhizosphere factors of mixed SAs with sulfadiazine (SDZ), sulfapyridine (SPD), sulfamerazine (SMZ1), sulfamethazine (SMZ2), and sulfamethoxazole (SMX) at millimeter distances from the root surface, a multi-interlayer rhizobox experiment planted with Cyperus alternifolius, Juncus effusus, Cyperus papyrus, and an unvegetated control was conducted. There was a higher O2 saturation and dissolved organic carbon (DOC) content and a lower SA content in the rhizosphere and near/moderate-rhizosphere (0-3 and 3-8 mm from rhizosphere) than the far/non-rhizosphere (8-40 and 40-90 mm from rhizosphere). Bacterial abundance and community composition was indicative of the microbial degradation of SAs. Both the O2 and DOC contents promoted total bacterial abundance in different zones from CW rhizoboxes. The relative abundance of the most dominant bacteria was significantly correlated with O2, DOC, and SAs, except SMX, which also indicates other dissipation processes for SMX in the rhizosphere. Furthermore, more metabolites and aerobic SA-degrading bacteria were observed in the rhizosphere and near/moderate-rhizosphere than in the far/non-rhizosphere zones, suggesting that the effect of O2 in the rhizosphere is important in the degradation of SAs in CWs.

Keystone Species and Niche Differentiation Promote Microbial N, P, and COD Removal in Pilot Scale Constructed Wetlands Treating Domestic Sewage.

The microbial characteristics related to nitrogen (N), phosphorus (P), and chemical oxygen demand (COD) removal were investigated in three pilot scale constructed wetlands (CWs). Compared to horizontal subsurface flow (HSSF) and surface flow (SF) CWs, the aerobic vertical flow (VF) CW enriched more functional bacteria carrying genes for nitrification (nxrA, amoA), denitrification (nosZ), dephosphorization (phoD), and methane oxidation (mmoX), while the removal of COD, total P, and total N increased by 33.28%, 255.28%, and 299.06%, respectively. The co-occurrence network of functional bacteria in the HSSF CW was complex, with equivalent bacterial cooperation and competition. Both the VF and SF CWs exhibited a simple functional topological structure. The VF CW reduced functional redundancy by forming niche differentiation, which filtered out keystone species that were closely related to each other, thus achieving effective sewage purification. Alternatively, bacterial niche overlap protected a single function in the SF CW. Compared with the construction type, temperature, and plants had less effect on nutrient removal in the CWs from this subtropical region. Partial least-squares path modeling (PLS-PM) suggests that high dissolved oxygen and oxidation-reduction potential promoted a diverse bacterial community and that the nonkeystone bacteria reduced external stress for functional bacteria, thereby indirectly promoting nutrient removal.

Efficiency and plant indication of nitrogen and phosphorus removal in constructed wetlands: A field-scale study in a frost-free area.

Frost-free areas have suitable climate for wetland plant growth and constructed wetlands (CW) technology. Information on the quantification of plant biomass and uptake efficiency in field-scale CWs is limited in these climates. The removal efficiency of total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), and total suspended solids (TSS) in wastewater from sewage plants, domestic sewage, and an industrial park in 15 rural and urban CWs in Guangdong Province, China, with an average temperature of 30 °C was evaluated. The effects of influent concentration, hydraulic load, the wastewater's physicochemical properties, operating conditions, and plant uptake were analysed. The mean removal rates were 40.0%, 45.2%, 41.1%, and 71.7% for TN, TP, COD, and TSS, respectively, which were higher than the removal load of the field-scale CWs in temperate regions. Removal loads of TN, TP, COD, and TSS were highest in CWs that have been operating for 5-6 years, treating wastewater volumes of over 1 m3/m2·d. The removal efficiency was mainly related to the inflow concentration and less affected by the type of CWs. Nutrient accumulation trends were primarily linked to influent concentrations (TN: r2 = 0.89, P = 0.007; TP: r2 = 0.96, P = 0.001) and plant biomass (TN: r2 = 0.96, P = 0.001; TP: r2 = 0.92, P = 0.004). Plant biomass contributed 2%-29% and 2%-70%, respectively, to removing N and P in CWs. The average uptake concentration of N and P in aboveground plant organs (15.66 ± 4.44 mg N/g, 2.15 ± 1.18 mg P/g) was generally higher than that of other temperate plants. A strong relationship between TN and TP in the biomass was also observed; however, the relationship is only restricted by the influent TP concentration. Arundo donax is well-adapted for nutrient accumulation and adaptation and is an ideal wetland plant to purify wastewater in frost-free climates.

Where do we stand to oversee the coronaviruses in aqueous and aerosol environment? Characteristics of transmission and possible curb strategies.

By 17 October 2020, the severe acute respiratory syndrome coronavirus (SARS-CoV-2) has caused confirmed infection of more than 39,000,000 people in 217 countries and territories globally and still continues to grow. As environmental professionals, understanding how SARS-CoV-2 can be transmitted via water and air environment is a concern. We have to be ready for focusing our attention to the prompt diagnosis and potential infection control procedures of the virus in integrated water and air system. This paper reviews the state-of-the-art information from available sources of published papers, newsletters and large number of scientific websites aimed to provide a comprehensive profile on the transmission characteristics of the coronaviruses in water, sludge, and air environment, especially the water and wastewater treatment systems. The review also focused on proposing the possible curb strategies to monitor and eventually cut off the coronaviruses under the authors' knowledge and understanding.

Evaluation of factors influencing annual occurrence, bioaccumulation, and biomagnification of antibiotics in planktonic food webs of a large subtropical river in South China.

Biological pump is important to control the fate and distribution of organic contaminants, particularly in temperate and cold oligotrophic waters. However, it remains largely unknown how factors affect the long-term occurrence and fate of ionogenic organic compounds in subtropical eutrophic waters. The present study aimed to assess biogeochemical and physical factors affecting the annual occurrence, bioaccumulation, and trophic transfer of 14 antibiotics through planktonic food webs in the Pearl River, a large subtropical eutrophic river in China. This was done by carrying out 1-year simultaneous field observations of antibiotic concentrations in five water column compartments and assessing the variability of bioconcentration (BCF), bioaccumulation (BAF), and biomagnification (BMF) factors, which were influenced by plankton biomass, pH and temperature of water columns. The annual mean antibiotic concentration per site ranged from 1014.66 ±â€¯535.66 ng L-1 to 1464.63 ±â€¯1075.91 ng L-1, and was positively correlated with phytoplankton biomass, but independent of the proximity of the sites to urban areas. Antibiotic occurrences in both phytoplankton and zooplankton were greatly influenced by a biodilution effect. The annual occurrence of antibiotics in the water column was modulated by biological pumps as well as their equilibrium partitioning, and indirectly influenced of eutrophication with pH increased with phytoplankton biomass and phytoplankton life cycling. BAF of antibiotics by plankton had biphasic correlations with temperature (n = 150, R2 = 0.17-0.60, p < 0.001) and decreased with plankton biomass (n = 105-147, R2 = 0.10-0.22, p < 0.001). The trophic transfer of antibiotics from phytoplankton to zooplankton (BMFs) were positively correlated with both phytoplankton biomass (n = 30, R2 = 0.58, p < 0.001) and temperature (n = 132-150, R2 = 0.12-0.43, p < 0.001). Mean BMFs of ciprofloxacin, lomefloxacin, ofloxacin, oxytetracycline, and tetracycline ranged between 0.18 and 2.25, implying these chemicals can undergo biomagnification along planktonic food webs. The present research demonstrates the important role of biogeochemical and physical factors in the environmental fate of antibiotics at large spatiotemporal scales.

Specific metabolism related to sulfonamide tolerance and uptake in wetland plants.

Wetland plants are proven to perform well in water treatment. However, the phytoremediation capability of wetland plants for antibiotics, especially the uptake and metabolism involved in vivo, is poorly understood. In this study, we investigated the removal, uptake, and specific metabolism by Canna indica and Iris pseudacorus of five sulfonamides (SAs) using hydroponic experiments for seven days. The removal of SAs ranged from 15.2% to 98.4% in the planted groups, whereas that in the unplanted control group was much lower (12.6%-39.9%). The accumulation of SAs in plants was in a concentration-dependent manner via an active process and is not a major removal mechanism (constituted 0.31%-3.62% of the total removal load in plant system). The results also showed differences in the removal and accumulation by plant species of SAs. The acetyl conjugates (N-acetyl SA) were formed, which significantly enhanced the uptake of SAs (P < 0.001) except sulfapyridine. The concentrations of N-acetyl SA accounted for only 0.4%-23.8% of the total SAs distribution in plants, suggesting the involvement of other metabolism pathways. Methylation and oxidation metabolites were identified in plant tissues and no SA-induced growth stress occurred, revealing that antibiotic metabolism in vivo should be associated with the ability of wetland plants to accumulate antibiotic and tolerate antibiotic stress.

Enhanced removal of Microcystis bloom and microcystin-LR using microcosm constructed wetlands with bioaugmentation of degrading bacteria.

The prevalence of cyanobacterial bloom (Cyano-bloom) and hepatotoxic microcystin (MC) pollution caused by eutrophication poses serious problems to aquatic ecosystems and public health. However, conventional water treatment technologies are inefficient for removing cyanotoxins. In this study, the performance of microcosm constructed wetlands (CWs) in the removal of Cyano-bloom, microcystin-LR (MC-LR), and nutrients was investigated following repeated loading of pollutants. The effects of plant and bioaugmentation of selected MC-LR degrading bacteria on removal efficiency, degrading gene mlrA abundance, and bacterial community structure were examined. More than 90% of the MC-LR and chlorophyll-a was eliminated by CWs after 3 d of hydraulic retention time (HRT) without a lag phase. No significant differences between planted and unplanted CWs were found in the MC-LR and Cyano-bloom removal and mlrA gene abundance. Nevertheless, the plants improved nutrient removal to reduce eutrophication. Bioaugmentation markedly enhanced the degradation of MC-LR from 16.7 µg L-1 to below the threshold value within 12 h, which could help shorten the HRT of CWs by increasing functional MC-LR degrading bacteria. In the soil of CWs, the following six bacterial genera with MC-LR-degrading potential were found: Sphingopyxis, Methylotenera, Pseudomonas, Methylosinus, Novosphingobium, and Sphingomonas. Among them, the first three also significantly proliferated in CWs with bioaugmentation during MC-LR degradation, indicating their high adaptability and MC-LR removal contribution. These results suggested that CWs could provide suitable conditions for MC-LR degrading microorganism proliferation, and CWs with bioaugmentation could be effective and practical measures for the remediation of eutrophication and MC pollution.

Phytoextraction of 55-year-old wastewater-irrigated soil in a Zn-Pb mine district: effect of plant species and chelators.

Untreated water from mining sites spreads heavy metal contamination. The present study assessed the phytoextraction performance of heavy metal-accumulating plants and the effects of chemical chelators on cadmium (Cd), lead (Pb), zinc (Zn), and copper (Cu) removal from paddy fields that have been continuously irrigated with mining wastewater from mines for 55 years. Outdoor pot experiments showed that the total Pb, Zn, and Cd content was lower in the rhizosphere soil of Amaranthus hypochondriacus than in that of Sedum alfredii, Solanum nigrum, and Sorghum bicolor. The aboveground biomass (dry weight) and relative growth rate of A. hypochondriacus were significantly higher than that of the other three species (P < .05). However, the total metal accumulation was significantly higher in the A. hypochondriacus system than in the other plants' system (P < .05). The increase in shoot biomass of A. hypochondriacus depended mostly on the chelator type [ethylenediaminetetraacetic acid (EDTA), malate, oxalate, and citrate] and their application frequency. Single application of EDTA significantly increased the shoot biomass of A. hypochondriacus and total metal removal loading from soil (P < .05). In conclusion, A. hypochondriacus may be effective for in situ phytoremediation of heavy metal-contaminated farmland soil and EDTA can accelerate the phytoextraction effect.

Biogenic manganese oxides generated by green algae Desmodesmus sp. WR1 to improve bisphenol A removal.

Biogenic manganese oxides (BioMnOx) have attracted considerable attention as active oxidants, adsorbents, and catalysts. This study investigated the characteristics of algae-generated BioMnOx and determined its oxidative activity towards bisphenol A (BPA), an endocrine disrupter. Amorphous nanoparticles with a primary Mn valency of +3 were found in BioMnOx produced by Desmodesmus sp. WR1. The mechanism might be that algal growth created conditions favorable to Mn oxidation through increasing DO and pH. Initial Mn2+ concentrations of 6, 30, and 50mgL-1 produced a maximum of 5, 13, and 11mgL-1 of BioMnOx, respectively. Mn2+-enriched cultures exhibited the highest BPA removal efficiency (∼78%), while controls only reached about 27%. BioMnOx may significantly promote BPA oxidation in algae culture, enhancing the accumulation of substrates for glycosylation. Moreover, continuous BioMnOx increase and Mn2+ decrease during BPA oxidation confirmed Mn oxide regeneration. In conclusion, Mn oxide formation by microalgae has the potential to be used for environmental remediation.

Factors Affecting Behavior of Phenolic Endocrine Disruptors, Estrone and Estradiol, in Constructed Wetlands for Domestic Sewage Treatment.

This study investigated the efficiency of 12 pilot-scale constructed wetlands (CWs) with different configurations on the removal of estrone and estradiol from raw domestic sewage. An orthogonal design was employed to evaluate the impact of four principal design parameters of CWs, including four wetland types, three substrates, three plant conditions, and three hydraulic loading rates, in summer and winter. A bench-scale anoxic simulation test was performed in the laboratory to clarify the photolysis, sorption, and degradation of estrogens. Estrogens were more effectively removed by the 12 CWs during summer. The experiment showed that target estrogens were efficiently removed by wetland substrate under anoxic conditions through exothermic sorption and degradation even in winter. This suggests that the inefficient removal in CWs in winter likely resulted from subsequent cleavage of a considerable amount of estrogen conjugates in influent due to insufficient decomposition at low temperatures. The transformation from estradiol to estrone could be driven by residual microbial activities not inhibited by azide, and the reversible process was then driven by active microorganisms but not solely abiotic redox reactions. Among the four design parameters, wetland-type was the most important and downward-vertical flow CWs performed best.

Natural attenuation of toxic metal phytoavailability in 35-year-old sewage sludge-amended soil.

Toxic heavy metals persist in agricultural soils and ecosystem for many decades after their application as contaminants in sewage sludge and fertilizer products This study assessed the potential long-term risk of cadmium (Cd), lead (Pb), zinc (Zn), and copper (Cu) in land-applied sewage sludge to food crop contamination. A sewage sludge-amended soil (SAS) aged in the field more than 35 years was used in a greenhouse pot experiment with leafy vegetables (lettuce and amaranth) having strong Cd and Zn accumulation tendencies. Soil media with variable levels of available Cd, Zn, and Cu (measured using 0.01 M CaCl2 extraction) were prepared by diluting SAS with several levels of uncontaminated control soil. Despite long-term aging in the field, the sludge site soil still retains large reserves of heavy metals, residual organic matter, phosphorus, and other nutrients, but its characteristics appear to have stabilized over time. Nevertheless, lettuce and amaranth harvested from the sludge-treated soil had undesirable contents of Cd and Zn. The high plant uptake efficiency for Cd and Zn raises a concern regarding the quality and safety of leafy vegetables in particular, when these crops are grown on soils that have been amended heavily with sewage sludge products at any time in their past.