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701.
Chengdu is a megacity in the southwest of China with high ozone (O3) mixing ratio. Observation of volatile organic compounds (VOCs), NO2 and O3 with high temporal resolution was conducted in Chengdu to investigate the chemical processes and causes of high O3 levels. The hourly mixing ratios of VOCs, NO2, and O3 were monitored by an online system from 28 August to 7 October, 2016. According to meteorological conditions, Chengdu, with relative warm weather and low wind speed, is favorable to O3 formation. Part of the O3 in Chengdu may be transported from the downtown area. In O3 episodes, the average mixing ratios of NO2 and O3 were 20.20?ppbv and 47.95?ppbv, respectively. In non-O3 episodes, the average mixing ratios of NO2 and O3 were 16.38?ppbv and 35.15?ppbv, respectively. The average mixing ratio of total VOCs (TVOCs) was 40.29?ppbv in non-O3 episodes, which was lower than that in O3 episodes (53.19?ppbv). Alkenes comprised 51.7% of the total O3 formation potential (OFP) in Chengdu, followed by aromatics which accounted for 24.2%. Ethylene, trans-pentene, propene, and BTEX (benzene, ethylbenzene, toluene, m/p-xylene, o-xylene) were also major contributors to the OFP in Chengdu. In O3 episodes, intensive secondary formations were observed during the campaign. Oxygenated VOCs (OVOCs), such as acetone, Methylethylketone (MEK), and Methylvinylketone (MVK) were abundant. Isoprene rapidly converted to MVK and Methacrolein (MACR) during O3 episodes. Acetone was mainly the oxidant of C3-C5 hydrocarbons. 相似文献
702.
Tianlong Zheng Peng Li Xiaoyu M Xiaohong Sun Chuanfu Wu Qunhui Wang Ming Gao 《环境科学学报(英文版)》2019,31(3):336-345
A pilot-scale multilevel contact oxidation reactors system, coupled with saran lock carriers,was applied for the treatment of poultry farm wastewater. The removal efficiencies of CODcr, ammonia, and the total nitrogen as well as the elimination performance of CODcr and total nitrogen along the three-level contact oxidation tanks under six designed operational models were investigated. Based on the performance of the nitrogen removal of the saran lock carriers and the distribution of anoxic–aerobic interspace under the suitable operation model, the mechanism of nitrogen removal of the system was also explored. The results revealed that the intermittent aeration under parallel model is the most suitable operation model, while the removal efficiencies of CODcr, ammonia, and the total nitrogen were 86.86%, 84.04%, and 80.96%, respectively. The effluent concentration of CODcr,ammonia, and the total nitrogen were 55.6 mg/L, 8.3 mg/L, and 12.0 mg/L, which satisfy both the discharge standard of pollutants for livestock and poultry breeding industry(GB18596–2001) and the first grade of the integrated wastewater discharge standard(GB 8978–1996). Moreover, the mechanism for the nitrogen removal should be attributed to the plenty of anoxic–aerobic interspaces of the biofilm and the three-dimensional spiral structure of the saran lock carriers, where the oxygen-deficient distribution was suitable for the happening of the simultaneous nitrification and denitrification process. Therefore, the multilevel contact oxidation tanks system is an effective pathway for the treatment of the poultry farm wastewater on the strength of a suitable operation model and novel carriers. 相似文献
703.
High nitrate(NO_3~-)loading in water bodies is a crucial factor inducing the eutrophication of lakes.We tried to enhance NO_3~-reduction in overlying water by coupling sediment microbial fuel cells(SMFCs)with submerged aquatic plant Ceratophyllum demersum.A comparative study was conducted by setting four treatments:open-circuit SMFC(Control),closed-circuit SMFC(SMFC-c),open-circuit SMFC with C.demersum(Plant),and closed-circuit SMFC with C.demersum(P-SMFC-c).The electrochemical parameters were documented to illustrate the bio-electrochemical characteristics of SMFC-c and P-SMFC-c.Removal pathways of NO_3~- in different treatments were studied by adding quantitative~(15)NO_3~- to water column.The results showed that the cathodic reaction in SMFC-c was mainly catalyzed by aerobic organisms attached on the cathode,including algae,Pseudomonas,Bacillus,and Albidiferax.The oxygen secreted by plants significantly improved the power generation of SMFC-c.Both electrogenesis and plants enhanced the complete removal of NO_3~- from the sediment–water system.The complete removal rates of added~(15)N increased by 17.6% and 10.2% for SMFC-c and plant,respectively,when compared with control at the end of experiment.The electrochemical/heterotrophic and aerobic denitrification on cathodes mainly drove the higher reduction of NO_3~- in SMFC-c and plant,respectively.The coexistence of electrogenesis and plants further increased the complete removal of NO_3~- with a rate of 23.1%.The heterotrophic and aerobic denitrifications were simultaneously promoted with a highest abundance of Flavobacterium,Bacillus,Geobacter,Pseudomonas,Rhodobacter,and Arenimonas on the cathode. 相似文献
704.
Hao Wang Xiangbin Ran Jingxi Li Jun Liu Wentao Wu Menglu Li Jiaye Zang 《环境科学学报(英文版)》2019,31(9):161-173
Based on the measurement of major and trace elements in suspended sediments in the low reaches of the Changjiang River during throughout a whole hydrologic year, the origins, seasonal variations, and fluxes of multielements and the human impacts on multielements transport processes have been analyzed along with the influence of weathering in the Changjiang River basin. The results show that most element contents were high in both autumn and winter and low in summer, which was largely caused by the dilution of discharge. Weathering detritus in the Changjiang River basin is the main source of most elements in suspended sediments. However, riverine pollution could bring more loadings of Cd, Pb, As and Zn into river water than it did a few decades ago. The annual average fluxes of Cd, Pb and Zn, which are major contamination elements, to the sea were 179 ± 21 tons/year, 7810 ± 675 tons/year, and 12,000 ± 1320 tons/year,respectively, in which approximately 8.7%, 11.9% and 2.7% of their loadings, respectively,were contributed by pollution inputs. Element exports mainly occurred in the summer(44.4%–57.4%) in the lower part of the Changjiang River. A general relationship between sediment retention and element content suggests a positive feedback mechanism for the decreased number of particles, in which element riverine loadings are reduced due to the enhanced trapping effect by the Three Gorges Dam(TGD). Compared to those in 1980,current element shares of the Changjiang River compared to the global budget have declined due to the construction of the TGD. 相似文献
705.
Qing Wu Li He Zhong Wei Jiang Yang Li Ting Ting Zhao Yu Han Li Cheng Zhi Huang Yuan Fang Li 《环境科学学报(英文版)》2019,31(12):203-212
Efficient removal of non-biodegradable and hazardous dyes from wastewater remains a hot research topic. Herein, a rationally designed a Cu(Ⅱ)-based metal–organic gel(Cu-MOG) with a nanoporous 3 D network structure prepared via a simple one-step mixing method was successfully employed for the removal of cationic dyes. The Cu-MOG exhibited high efficiency, with an adsorption capacity of up to 650.32 mg/g, and rapid adsorption efficiency, with the ability to adsorb 80% of Neutral Red within 1 min. The high adsorption efficiency was attributed to its large specific surface area, which enabled it to massively bind cationic dyes through electrostatic interaction, and a nanoporous structure that promoted intra-pore diffusion. Remarkably, the Cu-MOG displayed size-selective adsorption, based on adsorption studies concerning dyes of different sizes as calculated by density functional theory. Additionally, the adsorption performance of the Cu-MOG still maintained removal efficiency of 100% after three regeneration cycles. These results suggested that the Cu-MOG could be expected to be a promising and competitive candidate to conveniently process wastewater. 相似文献
706.
Jianming Yu Meng Wu Yuwei Tang Jiaqi Shi Jun Hu Zhiliang Yu Jianmeng Chen 《环境科学学报(英文版)》2019,31(12):187-194
Enzymatic electrolysis cell(EEC) has advantages over microbial electrolysis cell(MEC) due to the needless of microbe inoculation and high-efficiency of enzymatic reaction. In this study, an EEC was first applied to achieve the effective degradation of halogenated organic pollutants and dichloromethane(CH_2Cl_2) was utilized as a model pollutant. The results indicate that the degradation efficiency of CH_2Cl_2 after 2 hr reaction in the EEC was almost100%, which was significantly higher than that with enzyme(51.1%) or current(19.0%). The current induced the continuous regeneration of reduced glutathione(GSH), thus CH_2Cl_2 was degraded under the catalysis of GSH-dependent dehalogenase through stepwise dechlorination, and successively formed monochloromethane(CH_3Cl) and methane(CH_4). The kinetic result shows that with a current of 15 mA, the maximum specific degradation rate of CH_2Cl_2(3.77 × 10~(-3) hr~(-1)) was increased by 5.7 times. The optimum condition for CH_2Cl_2 dechlorination was also obtained with pH, current and temperature of 7.0, 15 mA and 35°C,respectively. Importantly, this study helps to understand the behavior of enzymes and the fate of halogenated organic pollutants with EEC, providing a possible treatment technology for halogenated organic pollutants. 相似文献
707.
长江中游历来是长江流域水灾最严重的地区,研究历史时期这一地区水灾发生的变化波动并找出其与厄尔尼诺事件的遥相关,将有助于对长江中游水灾发生的预测。对这二个时间序列自1525年以来的数据进行了统计学分析。结果表明,水灾发生的主要周期比厄尔尼诺事件发生的周期要长:后者主要表现为2年和3~4年的振动,而前者的主要周期为2年、8年和40年,其显著性也没有后者明显(但都超过了0.03的置信度)。通过进一步分析历史时期长江中游水灾与厄尔尼诺事件的耦合振动,发现它们之间存在显著的遥相关。结果表明,长江中游水灾对厄尔尼诺现象的响应不仅存在着如许多中国学者相信的短期滞后(如:1年),而且还存在着比较长时间的滞后(最长可达8年)。研究结果同时表明,如果厄尔尼诺事件发生的相距时间愈短,这一时期长江中游水灾响应的滞后时间也愈短,反之亦然。 相似文献
708.
709.
710.
利用计算机和地理信息系统软件.研究了广东省的土壤质地、土壤有机质、地势三个侵蚀因子对土壤侵蚀方面的影响,指出了广东土地抗蚀性极弱地区主要是湛江市、新丰县的小部分地区,而抗蚀性弱的区域则很大,约占全省土地面积的49.8%,遍布全省中部和南部.针对这样的现状,提出要减少抗蚀性弱和极弱地区的土壤侵蚀,必须做到:对土地的利用开垦进行统一规划;严禁乱伐森林;采取生物措施和工程措施相结合的方式防治土壤侵蚀的进一步变化. 相似文献