Sulfur cycle as an electron mediator between carbon and nitrate in a constructed wetland microcosm

• Fe(III) accepted the most electrons from organics, followed by NO₃^‒, SO₄^2‒, and O₂. • The electrons accepted by SO₄^2‒ could be stored in the solid AVS, FeS₂-S, and S⁰. • The autotrophic denitrification driven by solid S had two-phase characteristics. • A conceptual model involving electron acceptance, storage, and donation was built. • S cycle transferred electrons between organics and NO₃^‒ with an efficiency of 15%. A constructed wetland microcosm was employed to investigate the sulfur cycle-mediated electron transfer between carbon and nitrate. Sulfate accepted electrons from organics at the average rate of 0.84 mol/(m³·d) through sulfate reduction, which accounted for 20.0% of the electron input rate. The remainder of the electrons derived from organics were accepted by dissolved oxygen (2.6%), nitrate (26.8%), and iron(III) (39.9%). The sulfide produced from sulfate reduction was transformed into acid-volatile sulfide, pyrite, and elemental sulfur, which were deposited in the substratum, storing electrons in the microcosm at the average rate of 0.52 mol/(m³·d). In the presence of nitrate, the acid-volatile and elemental sulfur were oxidized to sulfate, donating electrons at the average rate of 0.14 mol/(m³·d) and driving autotrophic denitrification at the average rate of 0.30 g N/(m³·d). The overall electron transfer efficiency of the sulfur cycle for autotrophic denitrification was 15.3%. A mass balance assessment indicated that approximately 50% of the input sulfur was discharged from the microcosm, and the remainder was removed through deposition (49%) and plant uptake (1%). Dominant sulfate-reducing (i.e., Desulfovirga, Desulforhopalus, Desulfatitalea, and Desulfatirhabdium) and sulfur-oxidizing bacteria (i.e., Thiohalobacter, Thiobacillus, Sulfuritalea, and Sulfurisoma), which jointly fulfilled a sustainable sulfur cycle, were identified. These results improved understanding of electron transfers among carbon, nitrogen, and sulfur cycles in constructed wetlands, and are of engineering significance.     

Evidence for a mutual effect of biofilms, suspended particles and sediments on DDT sorption

This report shows that biofilms and suspended particles double DDT sorption capacity on surface sediments. Sorption of pollutants by solid materials, such as biofilms, suspended particles and sediments, is a major process controlling the fate of hydrophobic pollutants in natural waters. Most previous studies focused on the sorption of hydrophobic pollutants by single-solid material, whereas few studies considered the mutual effect of different solids on the sorption. Various solid materials often interact with each other when they coexist in the same system. Therefore, pollutants sorption could be different from that in the single-solid sorption system. Here we studied the mutual effect of biofilms, suspended particles and surface sediments on the sorption of dichlorodiphenyltrichloroethane (DDT). Results showed that biofilms and suspended particles double DDT sorption capacity on surface sediments. The different effects were mainly determined by distinct components and structures of the three solid materials, particularly by organic components. Here we show the mutual effect of biofilms, suspended particles and sediments on DDT sorption.     

Urea formation from carbon dioxide and ammonia at atmospheric pressure

Urea synthesis, currently the largest use of carbon dioxide in organic synthesis, is conventionally operated at high pressure and high temperature. Here, we report for the first time that urea forms at atmosphere and ambient temperatures by negative corona discharge in gas phase. The conversion of CO₂ and yields of a solid mixture of urea and ammonium carbamate, which was identified by the ¹³C NMR spectrum, rise with reducing temperatures and increasing molar ratios of NH₃/CO₂ and discharge frequencies. The conversion of carbon dioxide was found to be 82.16?% at 20?°C and 1?atm with a molar flow ratio of n(NH₃)/n(CO₂) of 2.5. High pressure and high temperature as energy inputs are not necessary.     

An approach to calculating allowable watershed pollutant loads

To improve the management of discharge pollutants loads in the reservoirs’ watershed, an approach of the allowable pollutants loads calculation and its allocation, based on the water environment model, was proposed. Establishment of the approach framework was described at first. Under the guidance of this framework, two major steps were as follows: modeling and scenario analysis were involved and should be applied to support the decision of discharge loads management; Environmental Fluid Dynamic Code (EFDC) model was selected as the kernel model in this framework. In modeling step, spatial discretization for establishing cell map in model, data preprocessing, parameter calibration and uncertainty analysis (which is considered as the significantly relevant factor of the margin of safety (MOS)), were conducted. As a result of the research, the model-based approach presented as a combination of estimation and precise calculation, which contributed to scenario analysis step. Some integrated modules, such as scenario simulation, result analysis and plan optimization were implemented as cycles in the scenario analysis. Finally, allowable pollutant loads under various conditions were calculated. The Chaihe Reservoir in Liaoning Province, China was used as a case study for an application of the approach described above. Results of the Chaihe reservoir water quality simulation, show good agreement with field data and demonstrated that the approach used in the present study provide an efficient and appropriate methodology for pollutant load allocation.     

Systematical strategies for wastewater treatment and the generated wastes and greenhouse gases in China

China now faces double challenges of water resources shortage and severe water pollution. To resolve Chinese water pollution problems and reduce its impacts on human health, economic growth and social development, the situation of wastewater treatment was investigated. Excess sludge and greenhouse gases (GHGs) emitted during wastewater treatment were also surveyed. It is concluded that Chinese water pollution problems should be systematically resolved with inclusion of wastewater and the solid waste and GHGs generated during wastewater treatment. Strategies proposed for the wastewater treatment in China herein were also adequate for other countries, especially for the developing countries with similar economic conditions to China.     

三唑酮对大型溞21天慢性毒性效应

三唑类杀菌剂是一种在农业上广泛应用的广谱性杀菌剂。三唑类杀菌剂在农田施用后能够向土壤深处迁移和扩散,从而污染土壤和地下水体,因此三唑类杀菌剂对土壤生态环境能够造成一定的破坏。选择三唑酮为研究对象,参照经济合作与发展组织(Organization for Economic Co-operation and Developement,OECD)标准方法研究三唑酮对大型溞的慢性毒性效应。21d慢性毒性研究结果表明,大型溞繁殖指标-内禀增长率是对三唑酮最为敏感的毒性参数。其慢性毒性下限值(LCL)和慢性毒性上限值(UCL)分别为40和80μg·L-1。三唑酮对于第2代大型溞,染毒的影响比对第1代的影响更大。对第2代恢复的大型溞除了第1次产卵数没有显著性差异,其他指标都有所变化,这说明毒物被转移到子代中。     

塔里木油田库尔勒生活基地生活垃圾处理现状与对策探讨

对塔里木油田库尔勒生活基地生活垃圾的处理现状和主要构成进行调查后,结合所在城市生活垃圾的处理方式,提出库尔勒生活基地生活垃圾"分类收集与回收利用"的途径,分析了实施中可能存在的问题,探讨了具体的对策,强调要从加强环保宣传、明确管理部门责任、完善回收设施、采用半市场化处理的对策思路。     

由三个地震模式讨论1995年日本阪神大震的预报问题

本文由我们已往提出的三个地震模式讨论了１９９５年日本阪神大震（Ｍ７．２）的预报问题。这些模式是立交模式、组合模式和调制模式。此外还用柯里奥利力（Ｃｏｒｒｉｏｌｉ）的效应讨论了主震３年后最强余震的预报。     

武汉地区防汛抗洪中存在的几个主要问题与对策

简述了１９９８年武汉市防汛抗洪中存在的几个主要问题,并提出了相应的对策与建议．     

民用建筑结构燃爆事故及防灾措施

收集了一些典型民用燃气爆炸事故的实例, 在此基础上对结构的破坏形式进行了分类,并分析了引起各种结构破坏的主要原因, 通过分析提出了防止结构破坏的具体措施