Dissipation and residues of imidacloprid in amaranth under greenhouse and open field cultivations.

Despite the extensive exposure to imidacloprid residues in food plants, there has been little research on imidacloprid residues in amaranth. The dissipation trend and residue behavior of imidacloprid were evaluated to provide guidelines for imidacloprid application on amaranth under open field and greenhouse. The dissipation rate of imidacloprid in amaranth conformed to the first-order kinetic equation, and the half-lives of imidacloprid in amaranth ranged from 0.29 days in open field to 1.29 days in the greenhouse. After 7 and 14 days from the application of imidacloprid (pesticide dosage, 45 or 67.5 g a.i./ha), the amaranth under the open field and greenhouse growth could be consumed safely with average residues of 0.19 and 0.38 mg/kg, respectively. This result demonstrated that the cultivation has the dominant influence on imidacloprid residue, and the residue of imidacloprid in amaranth planting on open field was much lower than that in the greenhouse, indicating a significant difference in the pesticide residues between the two cultivations with a p-value less than 0.05.

Microbial community composition in urban riverbank sediments: response to municipal effluents over spatial gradient.

Municipal effluents have adverse impacts on the aquatic ecosystem and especially the microbial community. This study described the compositions of sediment bacterial communities in the urban riverbank over the spatial gradient. Sediments were collected from seven sampling sites of the Macha River. The physicochemical parameters of sediment samples were determined. The bacterial communities in sediments were analyzed by 16S rRNA gene sequencing. The results showed that these sites were affected by different types of effluents, leading to regional variations in the bacterial community. The higher microbial richness and biodiversity at SM2 and SD1 sites were correlated with the levels of NH4+-N, organic matter, effective sulphur, electrical conductivity, and total dissolved solids (p < 0.01). Organic matter, total nitrogen, NH4+-N, NO3-N, pH, and effective sulphur were identified to be important drivers for bacterial community distribution. At the phylum level, Proteobacteria (32.8-71.7%) was predominant in sediments, and at the genus level, Serratia appeared at all sampling sites and accounted for the dominant genus. Sulphate-reducing bacteria, nitrifiers, and denitrifiers were detected and closely related to contaminants. This study expanded our understanding of municipal effluents on microbial communities in riverbank sediments, and also provided valuable information for further exploration of microbial community functions.

Phosphorus sorption capacity of biochars from different waste woods and bamboo.

Four biochars were made via pyrolysis at 500 °C using different waste plant materials, including tree branches from Cinnamonum campora (L.) Pres (CCP), Eriobotrya japonica (Thunb.) Lindl (EJL), Rohdea roth (RR) and bamboo shoots (Phyllostachys sulphurea) (PS). Phosphorus sorption capacities of the biochars were studied by isothermal experiments on their sorption kinetics. Results show that P sorption to the three wood biochars (CCP, EJL, and RR) fitted well with Lagergren pseudo second order model. However, P release was found in the PS biochar and sand amended with the PS biochar treatments during the isothermal sorption experiment. Phosphorus sorption capacity of the CCP biochar, EJL biochar and RR biochar was 4,762.0, 2, 439.0 and 1, 639.3 mg/kg, respectively. The CCP biochar showed the highest P sorption capacity due to its higher pH, lower dissolved P content, larger surface area (23.067 m2/g) and pore volume (0.058 cm3/g). The PS biochar showed the lowest P sorption due to its higher dissolved P content, more carboxyl groups, and smaller surface area (2.982 m2/g) and pore volume (0.017 cm3/g). Results suggest that the CCP biochar could be a potential alternative adsorbent for P sorption, such as removing P in wastewater treatment by constructed wetlands.

Tuning density of Si nanoparticles on graphene sheets in graphene-Si aerogels for stable lithium ion batteries.

Silicon is one of the most promising candidates for anodes of lithium ion batteries attributed to the highest theoretical specific capacity (4200 mAh/g). However, the conductivity and structural integrity during the lithiation-delithiation process are very poor, which seriously affect the actual electrochemical performance. To address these issues, we introduce graphene framework as both structural skeletons and conductive networks for silicon in this work. Through a facile freeze-drying approach, Si nanoparticles are successfully anchored on graphene sheets uniformly, and graphene form strong and conductive framework, which serves as mechanical support, electrical network, and buffer layer for Si, highly improving the structural integrity and conductivity. The electrochemical examinations indicate that the synthesized graphene-Si aerogels can deliver 104% specific capacity retention after cycled for 195 times at 0.8 A/g. Multi-walled carbon nanotubes are utilized to improve the rate property, and the resulting anode exhibits average specific capacities of 1415, 1209, 1057, 888, 781, and 646 mAh/g at charge/discharge rates of 0.05 C, 0.18 C, 0.2 C, 0.5 C, 1 C, and 2 C, respectively. Benefit from the facile synthesis and excellent cycling stability, it is expected that graphene-Si aerogels may play an important role in lithium ion battery.

Effects of long-lasting nitrogen and organic shock loadings on an engineered biofilter treating matured landfill leachate.

The decentralized bioreactor is a promising process for landfill leachate (LL) treatment, however, it is often confronted with various forms of shock loadings. To explore the robustness of bioreactors to the long-lasting substrate shocks, a long-term study of over 90 days was carried out to investigate the effects of nitrogen (mainly ammonium nitrogen, NH4-N) and organic (in terms of chemical oxygen demand, COD) shock loading on an engineered zeolite-based biofilter with alternative soil-mixed block (SMB) (EZS-biofilter) for treating matured LL. The low-, mid-, and high-strength intensity of matured LL was theoretical defined mainly according to the content of total nitrogen (TN) and COD. The experiment proved that the EZS-biofilter could effectively absorb the substrate shocks in a range of 104, 408, and 1357 mg/L as TN and 178, 590, and 1050 mg/L as COD, corresponding to the low-, medium-, and high-strength LL, respectively. A modified sensitivity index reflected that the nitrogen shock loadings exerted much more predominant influence than COD shock due to the great variation of nitrification/denitrification. The provided information in this study are beneficial for the practical engineered operation of biofilters for treating matured LL.

[Fabrication of a Biomass-Based Hydrous Zirconium Oxide Nanocomposite for Advanced Phosphate Removal].

Wheat straws were modified by 3-chloro-2-hydroxypropyl trimethylammonium chloride (CTA) to obtain aminated wheat straw St-N'. The optimum synthetic conditions were determined to be NaOH with 30% mass fraction, CTA of 100 mL, reaction temperature of 80℃, and reaction time of 3 h, which was verified by orthogonal experiments. Nano-sized hydrous zirconium oxides (HZO) were immobilized into St-N' by an in situ precipitation method to obtain the nanocomposite St-N'-Zr. The SEM, TEM, XRD, and BET results indicated that the nano-sized HZO with 50-100 nm sizes were uniformly loaded onto the inner surface of the biomass-based carrier St-N' that was amorphous in nature. A Langmuir adsorption isotherm fitted the adsorption process well, and the maximum adsorption amount was calculated to be 33.90 mg·g-1. The optimal pH range was 1.8-6.0, displaying good removal capacity of phosphate in acidic waters. In the presence of high levels of competing anions, the phosphate adsorption still retained more than 70% of the original amount, showing the higher preference of St-N'-Zr towards phosphate than towards the commercial anion exchanger D-201. After 10 cycles of adsorption-desorption, the removal efficiency remained stable, confirming the good regeneration ability and potential application of St-N'-Zr.

Simultaneous removal of Cr(VI) and 4-chlorophenol through photocatalysis by a novel anatase/titanate nanosheet composite: Synergetic promotion effect and autosynchronous doping.

Clean-up of wastewaters with coexisting heavy metals and organic contaminants is a huge issue worldwide. In this study, a novel anatase/titanate nanosheet composite material (labeled as TNS) synthesized through a one-step hydrothermal reaction was demonstrated to achieve the goal of simultaneous removal of Cr(VI) and 4-cholophenol (4-CP) from water. TEM and XRD analyses indicated the TNS was a nano-composite of anatase and titanate, with anatase acting as the primary photocatalysis center and titanate as the main adsorption site. Enhanced photocatalytic removal of co-existent Cr(VI) and 4-CP was observed in binary systems, with apparent rate constants (k1) for photocatalytic reactions of Cr(VI) and 4-CP about 3.1 and 2.6 times of that for single systems. In addition, over 99% of Cr(VI) and 4-CP was removed within 120min through photocatalysis by TNS at pH 7 in the binary system. Mechanisms for enhanced photocatalytic efficiency in the binary system are identified as: (1) a synergetic effect on the photo-reduction of Cr(VI) and photo-oxidation of 4-CP due to efficient separation of electron-hole pairs, and (2) autosynchronous doping because of reduced Cr(III) adsorption onto TNS. Furthermore, TNS could be efficiently reused after a simple acid-base treatment.

Purifying capability, enzyme activity, and nitrification potentials in December in integrated vertical flow constructed wetland with earthworms and different substrates.

The response of purifying capability, enzyme activity, nitrification potentials, and total number of bacteria in the rhizosphere in December to wetland plants, substrates, and earthworms was investigated in integrated vertical flow constructed wetlands (IVFCW). The removal efficiency of total nitrogen (TN), NH4-N, chemical oxygen demand (COD), and total phosphorus (TP) was increased when earthworms were added into IVFCW. A significantly average removal efficiency of N in IVFCW that employed river sand as substrate and in IVFCW that employed a mixture of river sand and Qing sand as substrate was not found. However, the average removal efficiency of P was higher in IVFCW with a mixture of river sand and Qing sand as substrate than in IVFCW with river sand as substrate. Invertase activity in December was higher in IVFCW that used a mixture of river sand and Qing sand as substrate than in IVFCW which used only river sand as substrate. However, urease activity, nitrification potential, and total number of bacteria in December was higher in IVFCW that employed river sand as substrate than in IVFCW with a mixture of river sand and Qing sand as substrate. The addition of earthworms into the integrated vertical flow constructed wetland increased the above-ground biomass, enzyme activity (catalase, urease, and invertase), nitrification potentials, and total number of bacteria in December. The above-ground biomass of wetland plants was significantly positively correlated with urease and nitrification potentials (p < 0.01). The addition of earthworms into IVFCW increased enzyme activity and nitrification potentials in December, which resulted in improving purifying capability.

The forms and bioavailability of phosphorus in integrated vertical flow constructed wetland with earthworms and different substrates.

A sequential extraction method was utilized to analyze seven forms of P in an integrated vertical-flow constructed wetland (IVFCW) containing earthworms and different substrates. The aluminum-bound P (Al-P) content was found to be lower, and the occluded P (Oc-P) content was higher in the IVFCW. The addition of earthworms into the influent chamber of IVFCW increased the exchange P (Ex-P), iron-bound P (Fe-P), calcium bound P (Ca-P), Oc-P, detritus-bound (De-P) and organic P (Org-P) content in the influent chamber, and also enhanced P content uptake by wetland plants. A significantly positive correlation between P content of above-ground wetland plants and the Ex-P, Fe-P, Oc-P and Org-P content in the rhizosphere was found (P<0.05), which indicated that the Ex-P, Fe-P, Oc-P and Org-P could be bio-available P. The Ex-P, Fe-P, De-P, Oc-P and Ca-P content of the influent chamber was higher where the substrate contained a mixture of Qing sand and river sand rather than only river sand. Also the IVFCW with earthworms and both Qing sand and river sand had a higher removal efficiency of P, which was related to higher P content uptake by wetland plants and P retained in IVFCW. These findings suggest that addition of earthworms in IVFCW increases the bioavailable P content, resulting in enhanced P content uptake by wetland plants.

Rural domestic waste management in Zhejiang Province, China: Characteristics, current practices, and an improved strategy.

UNLABELLED: Lack of access to adequate sanitation facilities has serious health implications for rural dwellers and can degrade the ecosystems. This study offers a systemantic and quantitative overview of historical data on rural domestic waste (RDW) production and past and current management practices in a prototype region in China, where rural areas are undergoing rapid urbanization and are confronted with great environmental challenges associated with poor RDW management practices. The results indicate that RDW is characterized with a large fraction of kitchen waste (42.9%) and high water content (53.4%). The RDW generation (RDWG) per capita between 2012 and 2020 is estimated to increase from 0.68 to 1.01 kg/d-cap. The Hill 1 model is able to adequately simulate/project the population growth in a rural area from 1993 to 2020. The annual RDWG in the region is estimated to double from 6,033,000 tons/year in 2008 to 12,030,000 tons/year by 2020. By comparing three RDW management scenarios based on the life-cycle inventory approach and cost-benefit analysis, it is strongly recommended that the present Scenario 2 (sanitary landfill treatment) be upgraded to Scenario 3 (source separation followed by composting and landfill of RDW) to significantly reduce the ecological footprint and to improve the cost-effectiveness and long-term sustainability. IMPLICATIONS: Rural domestic waste (RDW) is affecting 720 million people in China and more than 3221 million people worldwide. Consequently, handling and disposal of RDW have serious health implications to rural dwellers and the ecosystems. This study offers a systemantic and quantitative overview and analysis of historical data on RDW production and management practices in a prototype region in China, which is confronted with great environmental challenges associated with RDW. Then we predict future production of RDW and propose a sustainable RDW management strategy, which holds the promise of greatly mitigating the mounting environmental pressure associated with RDW and provides science-based guidance for decision makers and practitioners for assuring rapid yet "green" economic development.

Simulating the dynamics of polycyclic aromatic hydrocarbon (PAH) in contaminated soil through composting by COP-Compost model.

Organic pollutants (OPs) are potentially present in composts, and the assessment of their content and bioaccessibility in these composts is of paramount importance to minimize the risk of soil contamination and improve soil fertility. In this work, integration of the dynamics of organic carbon (OC) and OPs in an overall experimental framework is first proposed and adopted to validate the applicability of the COP-Compost model and to calibrate the model parameters on the basis of what has been achieved with the COP-Compost model. The COP-Compost model was evaluated via composting experiments containing 16 US Environmental Protection Agency (USEPA) polycyclic aromatic hydrocarbons (PAHs) and the sorption coefficient (Kd) values of two types of OP: fluorenthene (FLT) and pyrene (PHE). In our study, these compounds are used to characterize the sequential extraction and are quantified as soluble, sorbed, and non-extractable fractions. The model was calibrated, and coupling the OC and OP modules improved the simulation of the OP behavior and bioaccessibility during composting. The results show good agreement between the simulated and experimental results describing the evolution of different organic pollutants using the OP module, as well as the coupling module. However, no clear relationship is found between the Kd and the property of organic fractions. Further estimation of parameters is still necessary to modify the insufficiency of this present research.

Influence of UV radiation on chlorophyll, and antioxidant enzymes of wetland plants in different types of constructed wetland.

A surface- and vertical subsurface-flow-constructed wetland were designed to study the response of chlorophyll and antioxidant enzymes to elevated UV radiation in three types of wetland plants (Canna indica, Phragmites austrail, and Typha augustifolia). Results showed that (1) chlorophyll content of C. indica, P. austrail, and T. augustifolia in the constructed wetland was significantly lower where UV radiation was increased by 10 and 20 % above ambient solar level than in treatment with ambient solar UV radiation (p < 0.05). (2) The malondialdehyde (MDA) content, guaiacol peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activities of wetland plants increased with elevated UV radiation intensity. (3) The increased rate of MDA, SOD, POD, and CAT activities of C. indica, P. australis, and T. angustifolia by elevated UV radiation of 10 % was higher in vertical subsurface-flow-constructed wetland than in surface-flow-constructed wetland. The sensitivity of MDA, SOD, POD, and CAT activities of C. indica, P. austrail, and T. augustifolia to the elevated UV radiation was lower in surface-flow-constructed wetland than in the vertical subsurface-flow-constructed wetland, which was related to a reduction in UV radiation intensity through the dissolved organic carbon and suspended matter in the water. C. indica had the highest SOD and POD activities, which implied it is more sensitive to enhanced UV radiation. Therefore, different wetland plants had different antioxidant enzymes by elevated UV radiation, which were more sensitive in vertical subsurface-flow-constructed wetland than in surface-flow-constructed wetland.

Influence of earthworm Eisenia fetida on Iris pseudacorus's photosynthetic characteristics, evapotranspiration losses and purifying capacity in constructed wetland systems.

Four constructed wetland systems were studied to investigate the effects of adding Eisenia fetida on the purifying capacity of constructed wetlands. Addition of E. fetida increased the photosynthetic rate (Pn), transpiration rate (Tr) and chlorophyll meter value of leaves of Iris pseudacorus L. in the constructed wetlands by 16, 35 and 7%, respectively. Compared with the substrate only system, evapotranspiration losses were increased by 8, 48 and 56% for the wetland systems with substrate and E. fetida, with substrate and I. pseudacorus, and with substrate, I. pseudacorus and E. fetida, respectively. Addition of E. fetida to the substrate only and substrate and plant wetland systems decreased the substrate bulk density by 3 and 6%, respectively. The addition of E. fetida to the system with substrate and plants increased the removal efficiency of chemical oxygen demand (CODMn), total nitrogen (TN) and total phosphorus by 5, 7 and 22%, respectively. Evapotranspiration losses were significantly positively correlated with the removal efficiency of CODMn (P < 0.01). The significantly negative correlation between the removal efficiency TN and bulk density was found (P < 0.05). Therefore, E. fetida could stimulate I. pseudacorus growth and improve the substrate bulk density in the constructed wetland, resulting in enhanced purifying capacity.

Effect of earthworm Eisenia fetida and wetland plants on nitrification and denitrification potentials in vertical flow constructed wetland.

The response of nitrification potentials, denitrification potentials, and N removal efficiency to the introduction of earthworms and wetland plants in a vertical flow constructed wetland system was investigated. Addition of earthworms increased nitrification and denitrification potentials of substrate in non-vegetated constructed wetland by 236% and 8%, respectively; it increased nitrification and denitrification potentials in rhizosphere in vegetated constructed wetland (Phragmites austrail, Typha augustifolia and Canna indica), 105% and 5%, 187% and 12%, and 268% and 15% respectively. Denitrification potentials in rhizosphere of three wetland plants were not significantly different, but nitrification potentials in rhizosphere followed the order of C. indica>T. augustifolia>P. australis when addition of earthworms into constructed wetland. Addition of earthworms to the vegetated constructed significantly increased the total number of bacteria and fungi of substrates (P<0.05). The total number of bacteria was significantly correlated with nitrification potentials (r=913, P<0.01) and denitrification potentials (r=840, P<0.01), respectively. The N concentration of stems and leaves of C. indica were significantly higher in the constructed wetland with earthworms (P<0.05). Earthworms had greater impact on nitrification potentials than denitrification potentials. The removal efficiency of N was improved via stimulated nitrification potentials by earthworms and higher N uptake by wetland plants.