Search

How the plastisphere mediated by the residual microplastic film in farmlands affects microhabitat systems is unclear. Here, microbial structure, assembly, and biogeochemical cycling in the plastisphere and soil in 33 typical farmland sites were analyzed by amplicon sequencing of 16S rRNA genes and ITS and metagenome analysis. The results indicated that residual microplastic film was colonized by microbes, forming a unique niche called the plastisphere. Notable differences in the microbial community structure and function were observed between soil and plastisphere. Residual microplastic film altered the microbial symbiosis and assembly processes. Stochastic processes significantly dominated the assembly of the bacterial community in the plastisphere and soil but only in the plastisphere for the fungal community. Deterministic processes significantly dominated the assembly of fungal communities only in soil. Moreover, the plastisphere mediated by the residual microplastic film acted as a preferred vector for pathogens and microorganisms associated with plastic degradation and the nitrogen and sulfur cycle. The abundance of genes associated with denitrification and sulfate reduction activity in the plastisphere was pronouncedly higher than that of soil, which increase the potential risk of nitrogen and sulfur loss. The results will offer a scientific understanding of the harm caused by the residual microplastic film in farmlands.

Successive sediment suspensions often happen in estuary, yet little research has probed into the difference in the release behaviors of organic compounds among different suspensions. This study took polycyclic aromatic hydrocarbons (PAHs) as typical organic contaminants and investigated the release behaviors between two successive suspensions with a particle entrainment simulator (PES). Results showed that successive sediment suspensions lowered the concentration of dissolved PAHs in the overlying water via facilitating the re-adsorption of dissolved PAHs onto the suspended particles. Fast-release and slow-release periods of PAHs were successively observed in the both suspensions. The concentration changes of dissolved PAHs in the second suspension were generally similar with but hysteretic to those in the first suspension. More vigorous desorption and re-absorption of PAHs were induced in the second suspension. Successive sediment suspensions obviously decreased the concentrations of mineral composition and organic matters in the overlying water, which significantly affects multiphase distribution of PAHs.

Metal speciation can provide sufficient information for environmental and geochemical researches. In this study, based on the speciation determination of Cu and Zn in the Yangtze Estuary sediments, roles of eight geochemical controls (i.e., total organic carbon (TOC), clay, Fe/Mn in five chemical fractions and salinity) are fully investigated and sequenced with correlation analysis (CA) and principal components analysis (PCA). Results show that TOC, clay and Fe/Mn oxides are key geochemical factors affecting the chemical speciation distributions of Cu and Zn in sediments, while the role of salinity appears to be more indirect effect. The influencing sequence generally follows the order: TOC> clay>Mn oxides>Fe oxides>salinity. Among the different fractions of Fe/Mn oxides, residual and total Fe content, and exchangeable and carbonate Mn exert the greatest influences, while exchangeable Fe and residual Mn show the poorest influences.

Measurement data are used to calibrate and validate the effect of models. In this study, four types of uncertainty categories covering flow measurement, sample collection, sample preservation/storage and laboratory analysis were quantified for flow, sediment and water quality measurement data under best-, typical- and worst-case scenarios. The root mean square error propagation method was used to calculate the overall uncertainty. A case study was conducted in the Daning River with the Soil and Water Assessment Tool. Based on the results, the probable error range values of flow were lower than those of sediment and nutrients, indicating greater uncertainty in the sediment and total phosphorus results. It is also indicated that the uncertainty was smaller when the model outputs had a normal distribution. This research provides scientific data of measurement uncertainty in China, which can assist modelers in evaluating model performance by quantifying the “quality” of the response data.

ABSTRACTMeasurement data are used to calibrate and validate the effect of models. In this study, four types of uncertainty categories covering flow measurement, sample collection, sample preservation/storage and laboratory analysis were quantified for flow, sediment and water quality measurement data under best-, typical- and worst-case scenarios. The root mean square error propagation method was used to calculate the overall uncertainty. A case study was conducted in the Daning River with the Soil and Water Assessment Tool. Based on the results, the probable error range values of flow were lower than those of sediment and nutrients, indicating greater uncertainty in the sediment and total phosphorus results. It is also indicated that the uncertainty was smaller when the model outputs had a normal distribution. This research provides scientific data of measurement uncertainty in China, which can assist modelers in evaluating model performance by quantifying the “quality” of the response data.

Abstract: Stormwater runoff from three types of urban surfaces, a parking lot, a street, and a building roof, was monitored during four rainfall events that occurred in the one-year period from June 2009 to June 2010. The event mean concentrations (EMC) of dissolved copper (Cu), lead (Pb), zinc (Zn), manganese (Mn), and iron (Fe) exceeded China’s National Water Quality Standards for Surface Water. The degree of heavy metal contamination was related to the type of underlying surfaces. Additionally, the concentration of dissolved heavy metals peaked shortly after the runoff began and then declined sharply as a result of adequate flushing. First flush effects of varying degrees were also observed during all of the monitored rainfall events based on the first flush ratio (FF 25). Redundancy analysis revealed that four environmental variables (rainfall depth, intensity, antecedent dry weather period and type of underlying surface) had significant effects on the strengths of the first flush effects, accounting for 72.9% of the variation in the FF 25. Dissolved metals presented varying first flush effects on different underlying surfaces that occurred in the following relative order: parking lot>roof>road for low intensity and high runoff volume rainfall events; parking lot>road>roof for high intensity and low runoff volume events. The relative strength of the first flush for dissolved heavy metals was Fe, Mn>Cu, Zn>Pb.

Abstract: Density functional theory (DFT) plays a significant role in the development of visible light responsive photocatalysts. Based on the first-principles plane-wave ultrasoft pseudopotential (USPP) method, the crystal structures of α, β, γ, and δ-Bi2O3 were optimally calculated for the total density of states (TDOS) and the partial density of states (PDOS) of Bi, O atoms. The calculation for Ti(IV) doped Bi2O3 supercell was carried out. The effects of Ti(IV)-doping on the electron structures and light absorption properties of various Bi2O3 were analyzed. The results showed that Ti 3d orbital appeared in the forbidden band of Bi2O3 and hybridized with O 2p, Bi 6p orbitals. The narrowed band gap (E g) and red-shift of light absorption edge are responsible for the enhanced photocatalytic activity of Bi2O3. The β-Bi2O3 and Ti-doped β-Bi2O3 were prepared by a hydrothermal synthesis method. The improvement of the photocatalytic activity of Bi2O3 has also been verified by the characteristics of the UV-vis diffuse reflection spectrum and the experimental evaluation of the photocatalytic degradation of crystal violet in aqueous solution.

Nine surface sediments and a dated sediment core collected from urban lakes in Wuhan, Central China, were analyzed to investigate the concentrations, occurrence, composition, and depositional fluxes of polychlorinated biphenyls (PCBs). The concentrations of ΣPCB (the sum of 39 congeners) in surface sediments ranged from 0.90 to 46.14 ng g−1dry weight. Only in Longyang Lake and Nantaizi Lake did concentrations of ΣPCB exceed the effects range low value. The concentrations of ΣPCB in the sediment core varied from 1.3 to 43.1 ng g−1The profile of ΣPCB concentrations closely reflected the changes in production and usage of PCBs in this region, and the profiles of ΣPCB fluxes were similar to those of ΣPCB concentrations, except for a distinct decrease in ΣPCB fluxes after about 1998. This was possibly due to more large‐scale cases of land use and increasingly rapidly urban development occurring in China since 2000, resulting in increased lake sediment fluxes but reduced ΣPCB fluxes. The results suggest that urban run‐off and wet deposition leaching PCBs off the land and into the lake may be the most important source of PCBs in Donghu Lake. Sedimentary profiles for PCB congeners showed a decrease in concentrations in the following order: penta∼hexa‐ > tetra‐ > tri‐ > hepta‐PCBs. The relative abundances of tri‐ and tetra‐PCBs in the core accounted for more than 80% of the total PCBs detected in sediments deposited before their first commercial use, suggesting the post‐depositional mobilization of less chlorinated PCB congeners in the sediment core. This is the first study to estimate the spatial and historical trends of PCBs in subtropical urban lakes.

Sustainable stormwater management (SSM) has gained global interests to solve both on‐site and off‐site downstream water problems. However, current structural SSM practices are often limited to small scales and their impacts on river water quality have not been fully understood. In this study, we have quantified watershed responses to SSM via multiyear monitoring and integrated modeling in an urbanizing watershed in China, while five scenarios (baseline, current SSM, improved SSM, future traditional urban development, and future improved SSM scenarios) were comparatively analyzed. The results showed that water quality of ammonia nitrogen (NH3‐N), total phosphorus (TP), chemical oxygen demand (COD), and suspended solid (SS) would deteriorate by both traditional urban development and current SSM design. Compared to other pollutants, NH3‐N and TP showed greatest deterioration by current SSM due to disproportionate management of on‐site runoff quantity‐related and quality‐related problems. Comparatively, the improved SSM design, which incorporated watershed responses into consideration, would reduce current concentrations of NH3‐N, TP, COD, and SS by 0–53.85%, 8.16–38.84%, 23.07–61.03%, and 68.82–77.82%, respectively; and improve water quality by 60–80% in future SMM scenario. Priority management and stricter objectives should be given to those urbanizing regions at the watershed scale. The results of this study should be used as references for future SSM design as well as water resource protection. Sustainable stormwater management (SSM) is vital for urban water resources and water quality protection. However, watersheds serve as the end of the SSM system, the related water quality benefits from SSM have not been fully quantified. To address this problem, five scenarios were evaluated via multiyear monitoring and integrated modeling in an urbanizing watershed. Water bodies in the urbanizing areas are more vulnerable, which would multiply several times in pollutant concentrations by traditional urbanization. However, unexpected deterioration of river quality occurred by current SSM, although local runoff and pollutant loads were controlled. The improved SSM was then given by incorporating watershed response into SSM design to handle water problems at different scales. The findings and approach could undoubtedly facilitate the SSM development and watershed management, and could be applied in other cities and countries because urban expansion has become a global issue. Unexpected river quality deterioration was found in current sustainable stormwater management (SSM) due to the neglect of relative reduction proportions in runoff and pollutant loadsVulnerable water bodies were found in urbanizing period, during which NH3‐N and TP were more sensitive to urbanization and SSMImproved SSM design was put forward by considering watershed responses through an integrated model Unexpected river quality deterioration was found in current sustainable stormwater management (SSM) due to the neglect of relative reduction proportions in runoff and pollutant loads Vulnerable water bodies were found in urbanizing period, during which NH3‐N and TP were more sensitive to urbanization and SSM Improved SSM design was put forward by considering watershed responses through an integrated model