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AbstractAdsorption and desorption of Cu(II), Zn(II), Pb(II) and Cd(II) on a Red soil (RS, Udic Ferrosols) and a Wushan soil (WS, Anthrosol) amended with nanoscale hydroxyapatite (nano‐HAP) were studied by batch experiments. The adsorption isotherms show that different kinds of heavy metals had different affinity to the soils in the order of Cu(II) > Pb(II) > Cd(II) > Zn(II). The amount of each heavy metal adsorbed on the RS was lower than that on the WS, because the former had lower CEC and pH than the latter. The amendment of nano‐HAP in the soils significantly enhanced the adsorption of heavy metals, in comparison with the treatment receiving no nano‐HAP. The Kf, simulated from the adsorption isotherms, increased from 78 to 2180 for Cu(II), 16.6 to 59.5 for Zn(II), and 17.9 to174 for Cd(II) on the RS, and from 995 to 6410 for Cu(II), 52.5 to 92.4 for Zn(II), and 59.2 to 199 for Cd(II) on the WS, when 0.20 g nano‐HAP was added into 1.00 g soil. The nano‐HAP remarkably inhibited desorption of heavy metals from the soils, suggesting that the addition of nano‐HAP can significantly reduce the mobilization of heavy metals and increase their geochemical stability in metal contaminated soils. © 2009 American Institute of Chemical Engineers Environ Prog, 2010

Purification is a separated post-treatment step after the synthesis of nanocrystals (NCs) in order to exclude excess ligands and monomers in NC solution. The common purification process involves many manipulations, such as concentrating, addition of anti-solvents and centrifugation, which are troublesome and time consuming. In this work, we originally integrate NC synthesis and NC purification in one-pot via selecting water-ethanol co-environment for NC synthesis and NC purification. Our research shows that NCs can grow in water-ethanol mixture. When growing into critical size, NCs will automatically precipitate from the solution. Element analysis demonstrates that precipitates fraction fits well with stoichiometric of ligand-capped NCs. Excess monomers are left in supernatant, and thus achieving automatically purification of NCs in the water-ethanol co-environment. By adjusting the volume ratios of water and ethanol in bi-solvent system, different-sized purified NCs can be controlled. Besides, this water-ethanol co-environment can be used in both thermal-promoted and hydrazine-promoted growth.

A continuous flow microbial fuel cell constructed wetland (MFC-CW) coupled with a biofilm electrode reactor (BER) system was constructed to remove sulfamethoxazole (SMX). The BER unit powered by the stacked MFC-CWs was used as a pretreatment unit, and effluent flowed into the MFC-CW for further degradation. The experimental results indicated that the removal rate of 2 or 4 mg/L SMX in a BER unit was nearly 90%, and the total removal rate in the coupled system was over 99%. As the hydraulic retention time (HRT) was reduced from 16 h to 4 h, the SMX removal rate in the BER decreased from 75% to 48%. However, the total removal rate in the coupled system was still over 97%. The maximum SMX removal rate in the MFC-CW, which accounted for 42%-55% of the total removal, was obtained in the anode layer. In addition, the relative abundances of sul genes detected in the systems were in the order of sulI > sulII > sulIII, and significant positive correlations of sul gene copy numbers versus SMX concentration and 16S rRNA gene copy numbers were observed. Furthermore, significant negative correlations were identified between sul genes, 16S rRNA gene copy numbers, and HRT. The abundances of the sul genes in the effluent of the MFC-CW were lower than the abundances observed in the BER effluent. High-throughput sequencing revealed that the microbial community diversity of the BER was affected by running time, power supply forms and HRT. Bio-electricity from the MFC-CW may reduce microbial community diversity and contribute to reduction of the antibiotic resistance gene (ARG) abundance in the BER. Taken together, the BER-MFC-CW coupled system is a potential tool to treat wastewater containing SMX and attenuate corresponding ARG abundance.

To remove membrane fouling, a bio-electrochemical system that can generate a micro-electric field and micro-current was constructed. After 11 days of operation, the trans-membrane pressure difference of membrane modules in the open- and closed-circuit groups increased by 35.8 kPa and 6.2 kPa, respectively. The concentrations of total polysaccharide and protein in the open-circuit group were 1.8 and 1.1 times higher than those in the closed-circuit group, respectively. In addition, X-ray photoelectron spectroscopy and thermogravimetric analysis showed that inorganic crystals such as calcium carbonate were present on the membrane surface, and the concentration of calcium ion in the control group was 14.7 times that of the experimental group. High-throughput sequencing demonstrated that the enrichment of some electroactive bacteria and other microorganisms has a positive effect on the control of membrane fouling. Therefore, this system can effectively alleviate membrane fouling of a bioreactor, by targeting the membrane foulants.

Soil enzyme activity is a sensitive indicator of soil quality changes. The response of soil enzyme activity to different land uses is important in addressing the issues of agricultural sustainability. The objectives of this study were to investigate the effects of short-term land use conversions on soil specific enzyme activity (per unit microbial biomass carbon) of sodic soils and compare the responses of soil absolute (per unit soil mass) and specific enzyme activities in northeastern China. Four specific enzyme activities, including catalase, invertase, urease and alkaline phosphatase were assayed at 0 to 20 cm depth under five land uses, including cropland (CL), alfalfa perennial forage (AF), monoculture grassland (AG), monoculture grassland for hay once a year (AG + M) and successional regrowth grassland (RG). The specific activities of catalase, urease and alkaline phosphatase at 10 to 20 cm depth were 117.3%, 40.0% and 35.6% higher than that in 0 to 10 cm depth, irrespective to the land uses. Conversion of cropland to re-vegetation land increased the specific activities of catalase (2.8%), invertase (99.0%), urease (14.3%) and alkaline phosphatase (14.0%). Under land uses of AF, AG + M, AG and RG, the geometric mean (0.2%, 32.8%, 65.7% and 24.3%, respectively) and sum (2.6%, 38.0%, 82.8% and 29.6%, respectively) of specific enzyme activities at 0 to 20 cm depth were higher than that under CL treatment. The soil specific enzyme activities showed the better discrimination to different land uses than the soil absolute enzyme activities. In conclusion, re-vegetation has a positive effect on the improvement of soil enzyme activity in northeastern China, and the responses of soil specific enzyme activities to short-term land-use conversions are more obvious than the absolute enzyme activities, which could be used as s suitable and sensitive indicator of land use change in semiarid agroecosystems.

Eco-ditches are being explored to maximize their capability of capturing pollutants and mitigate any harmful side effects in rivers. In this study, mesocosm plastic drum sediment and field experiments were set up to screen 18 plant species found in ditches and identify those with potential for high biomass production and nutrients removal. Terrestrial plants grown in the mesocosm system were shown to be able to acclimate to aquatic conditions and to survive in primary domestic sewage. About 73-95% increase in plant biomass was recorded. Removal efficiencies for total nitrogen, total phosphorus, and ammonium-nitrogen from the sewage of 72-99%, 64-99%, and 75-100%, respectively, were recorded. Furthermore, complete removal of the applied nitrate-nitrogen load was achieved in mesocosm systems. Findings also show that all species, but especially Acorus calamus, Canna indica, Canna lily, Cyperus alternifolius, Colocasia gigantea, Eichhornia crassipes, Iris sibirica, and Typha latifolia had the highest efficiencies for nitrogen and phosphorous removal. The N and P mass balance analysis demonstrated that plant uptake and sediment N and P accumulation accounted for 41-86% and 18-49% of the total influent TN and TP loads, respectively. In addition, the amounts of nitrogen and phosphorous uptake by these plant species were influenced significantly by biomass. The field-culture experiment further identified Canna indica followed by Cyperus alternifolius as the most promising for high biomass production and nutrients uptake. Therefore, these plants may be recommended for extensive use in treating highly eutrophicated rivers. Outcomes of this work can be useful for model design specifications in eco-ditch mitigation of sewage pollution.

Although the world is gradually moving towards renewable energy resources, the coal industry will continue to be a major energy supply sector in the foreseeable future. However, by-products such as coal fly ash (CFA), coal bottom ash (CBA), and boiler slag are generated during coal combustion, and have become a significant environmental concern. There is an urgent need for transdisciplinary efforts in research, policy, and practice to reduce these by-products substantially. Many studies have focused on the environmental management and comprehensive utilization of CFA. As a comparison, less attention has been paid to CBA. Therefore, this critical review provides a holistic picture of CBA, from the generation, fundamental characteristics, environmental concerns to potential applications, and benefits analysis. Based on the fundamental characteristics, CBA can be considered as a sustainable and renewable resource with great potential to produce value-added materials. High-value applications and current research related to CBA, including construction and ceramic industry, wastewater remediation, soil amelioration, energy catalysis, valuable metals recovery, and material synthesis, are systemically presented and compared. It emphasizes the environmental and economic benefits of the sustainable applications of CBA as well. Particularly, it indicates that CBA is a promising candidate in normal, lightweight, self-compacting, and ultra-high-performance concrete, which shows a reduction in both energy consumption and greenhouse gas emissions during concrete production. This work provides new insights into the greener and sustainable applications of CBA, and it will offer a practical guide for the sustainable development of the coal industry.

Effects of iron oxide amendment into freshwater sediments on performance of sediment microbial fuel cell (SMFC) were investigated. It was found that amending amorphous bulk ferric oxyhydroxide, and crystalline goethite and magnetite did not affect SMFC operation. However, amendment of the mixed solution including soluble ferric citrate and colloidal iron oxyhydroxide, stably improved SMFC performance with voltage outputs up to threefolds higher than those without amendment. The enhanced voltage production corresponded to lower anode potential, but was not related to organic matter removal in sediments. Further experiments demonstrated that colloidal iron oxyhydroxide instead of soluble ferric iron played an important role in voltage production through maintaining high-concentration ferrous iron in pore water of sediments as electron shuttle and for chemical oxidation on the anode. Thus, colloidal iron oxyhydroxide amendment was a promising strategy to improve power production from SMFC employed in sediments especially with low content of organic matters.

The environmental footprints of China’s high-speed railway (HSR) have attracted much attention nationally and internationally. Although there is some research focusing on CO2 emissions, a comprehensive environmental impacts assessment of HSR construction is still lacking. In this study, the emissions of the Beijing–Tianjin intercity HSR line was calculated using a hybrid input–output life cycle assessment method to quantify the environmental impacts of HSR throughout its construction. The environmental footprints during the construction stage were analyzed in terms of different subsystems and sectors. The results showed that bridges contribute the largest environmental footprints at approximately 60%, followed by rail and electric multiple unit (EMU) systems. The top three sectors that contribute to pollutant emissions are the metal smelting and rolling industry, transport equipment manufacturing, and non-metallic mineral production. CO2 and NOx are the major pollutants directly emitted by site equipment operation. More chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN), and petroleum are emitted in EMU production than in rail construction, while NH3-N is emitted more in rails instead. Cd, Pb, As, and Hg are the significant pollutants in the metal smelting and rolling industry, whereas Cr, Cu, and Zn are the main heavy metal emissions in the transport equipment manufacturing sector. Heavy metals are the main types of environmental footprints in bridges, stations, and electric systems. Water pollutants are the main environmental impacts for rail and EMU systems, and the emissions of air pollutants are significant in subgrades. The production efficiency of upstream materials, desulfurization and denitration in fossil combustion, and the length of the bridge construction should be considered for an HSR under construction, in order to become environmentally friendly and sustainable.