乙醇胺热降解-氧化降解循环过程及SO2在其中的影响

使用半连续式不锈钢搅拌反应釜,研究了质量分数30%的乙醇胺(MEA)水溶液(CO2负载量0.4 mol·mol-1)的热降解-氧化降解循环过程,旨在探讨循环过程对MEA降解的影响,以及SO2对MEA热降解、氧化降解和循环过程产生的影响.其中,热降解的实验条件为120℃,降解时间为2周,在密闭反应器内进行;氧化降解的实验条件为55℃,约121.59 kPa,向溶液中持续通入模拟烟气,总气量为7.5 L·min-1,其中包括2%CO2、0~150 ppm SO2和空气.实验结果表明,在先进行热降解再进行氧化降解的过程中,MEA的热降解产物N-(2-羟乙基)乙二胺等会在氧化降解的过程中发生进一步反应,且原本氧化降解中生成的亚硝酸根会有部分进一步被氧化,生成硝酸根.在循环过程中,MEA的整体降解程度比单独进行热降解、氧化降解实验中有所提高.研究表明,添加亚硫酸根会加剧热降解中的氨气生成量,而在氧化降解中,SO2又表现出了明显的抑制作用.在循环过程中,这两者均有体现,SO2仍起到一定的抑制降解的作用.     

天津某住宅区降雨径流颗粒粒径分布及污染物赋存形态

为考察城市不同下垫面降雨径流中颗粒粒径分布及与污染物的关系,2020年7—8月在相同降雨条件下对天津市某居民区油毡屋面、塑钢屋面、水泥瓦屋面和沥青路面的6场降雨事件进行采样,分析降雨径流污染特征及颗粒物分布. 结果表明:①沥青路面降雨径流中悬浮颗粒物（suspended solids, SS）浓度最高,与油毡屋面、塑钢屋面和水泥瓦屋面径流SS浓度在统计上有显著差异(P<0.05);②不同下垫面降雨径流中颗粒物粒径主要分布在10~200 μm之间,4种下垫面中值粒径（D₅₀）浓度在计量上均有显著差异(P<0.05);③粒径在10~50 μm的颗粒物占比最大,在油毡屋面、塑钢屋面、水泥瓦屋面和沥青路面径流中占比分别为30.95%、25.53%、30.41%和50.47%,粒径大于300 μm的颗粒物体积分数占比最小;④降雨径流中颗粒物是污染物的主要载体,径流中化学需氧量（COD）和总磷（TP）主要以颗粒态形式存在,而总氮（TN）主要以溶解态形式存在. 通过对降雨径流中颗粒物粒径分布和污染物赋存形态的研究,以期为城市径流污染控制及雨水净化方法的选取提供数据支撑.      

Pollution levels and characteristics of phthalate esters in indoor air of offices

The pollution status and characteristics of PAEs (phthalate esters) were investigated in indoor air of offices, and PAEs of both gas-phase and particulate-phase were detected in all the samples. The concentration (sum of the gas phase and the particulate phase) was 4748.24 ng/m³, ranging between 3070.09 and 6700.14 ng/m³. Diethyl phthalate, dibutyl phthalate, and di(2-ethylhexyl) phthalate were the most abundant compounds, together accounting for 70% of the ∑ 6PAEs. Dividing the particulate-phase PAEs into four size ranges (< 2.5, 2.5–5, 5–10, > 10 μm), the result indicated that PAEs in PM_2.5 were the most abundant, with the proportion of 72.64%. In addition, the PAE concentration in PM_2.5 correlated significantly with the total particulate-phase PAEs (R² = 0.85). Thus, the amount of PAEs in PM_2.5 can be estimated from the total amount of particulate-phase PAEs using this proportion. In a comparison between the offices and a newly decorated study room, it was found that pollution characteristics were similar between these two places. Thus, it is implied that the PAE concentration decreased by 50% 2 yr after decorating.     

Effects of plant diversity on greenhouse gas emissions in microcosms simulating vertical constructed wetlands with high ammonium loading

Wastewater with relatively high nitrogen concentrations is a major source of nitrous oxide (N₂O) and methane (CH₄) emissions and exerts multiple stresses on the environment. Studies have shown that plant diversity plays an important role in ecosystem functioning. However, the effects of plant species diversity on CH₄ and N₂O emissions under high ammonium (NH₄⁺-N) loading rates remain unclear. In this study, a microcosm experiment simulating vertical constructed wetlands supplied with high NH₄⁺-N water levels was established. The treatments included four species richness levels (1, 2, 3, 4) and 15 species compositions. There was no significant relationship between species richness and N₂O emissions. However, N₂O emissions were significantly reduced by specific plant species composition. Notably, the communities with the presence of Rumex japonicus L. reduced N₂O emissions by 62% compared to communities without this species. This reduction in N₂O emissions may have been a result of decreased N concentrations and increased plant biomass. CH₄ emissions did not respond to plant species richness or species identity. Overall, plant species identity surpassed species richness in lowering N₂O emissions from constructed wetlands with high NH₄⁺-N water. The results also suggest that communities with R. japonicus could achieve higher N removal and lower greenhouse gas emissions than other wetland species.     

Dielectric barrier discharge plasma-assisted modification of g-C3N4/Ag2O/TiO2-NRs composite enhanced photoelectrocatalytic activity

Dielectric barrier discharge (DBD) plasma applied as surface treatment technology was employed for the modification of Ag₂O and graphitic carbon nitride (g-C₃N₄) powders. Subsequently, the pretreated powders were sequentially loaded onto TiO₂ nanorods (TiO₂-NRs) via electro-deposition, followed by calcination at N₂ atmosphere. The results indicated that at the optimal plasma discharge time of 5 min for modification of g-C₃N₄ and Ag₂O, photocurrent density of ternary composite was 6 times to bare TiO₂-NRs under UV-visible light irradiation. Phenol was degraded by using DBD plasma-modified g-C₃N₄/Ag₂O/TiO₂-NRs electrode to analyze the photoelectrocatalytic performance. The removal rate of phenol for g-C₃N₄-5/Ag₂O-5/TiO₂-NRs electrode was about 3.07 times to that for TiO₂-NRs electrode. During active species scavengers’ analysis, superoxide radicals and hydroxyl radicals were the main oxidation active species for pollutants degradation. A possible electron-hole separation and transfer mechanism of ternary composite with high photoelectrocatalytic performance was proposed.     

持久性有机污染物的作物吸收及迁移模型研究进展

持久性有机污染物(Persistent Organic pollutant,POPs)是指通过各种环境介质(大气、水、生物体等)能够长距离迁移并长期存在于环境中的人工合成的有机污染物。本文阐述了全球POPs的主要环境过程和各环境介质中POPs的暴露水平,探讨了作物对POPs的吸收过程、吸收机制和生态效应,并基于现有的环境多介质逸度模型和根区水质模型,分析了持久性有机污染物作物吸收过程模拟模型中存在的问题及未来的发展方向。目前,对POPs作物吸收机制及其模拟的研究较少,但随着我国对粮食安全和农业可持续发展的持续关注,这一领域的模拟研究将对科学解析POPs归趋、合理制定风险管控措施和有效确保粮食质量安全等提供重要科学支撑。     

典型平原河网区水体富营养化特征、成因分析及控制对策研究

本文以嘉兴市北部湖荡区为典型研究区域,通过现场调研、来源分析等,揭示了平原河网区水体富营养化状态,明确了水污染主要成因,并提出控制对策.研究结果显示,北部湖荡区总磷、高锰酸盐指数、五日生化需氧量、化学需氧量、总氮、氨氮等各污染物含量呈现显著的时空分布特征,西部片区水质较东部片区差,5月水质较9月差(总磷除外);富营养化...     

Extracting humic acids from digested sludge by alkaline treatment and ultrafiltration

The concentration of hardly biodegradable humic substances in sludge would relatively increase after anaerobic digestion due to the degradation of other organic substances. Thus, extracting humic substances from digested sludge as a liquid organic fertilizer was tested using alkaline treatment and ultrafiltration, and the dewaterability of the residual sludge was also tested. The results showed that the contents of humic acids and fulvic acids in digested sludge were 16.4 mg/g total solids and 88.9 mg/g total solids, respectively, and most of the humic acids had a molecular weight higher than 50 kDa. Hence, the membrane with a molecular weight cut-off of 50 kDa was used for humic acids recovery from the centrifugation supernatant after alkaline sludge disintegration with an optimum NaOH dose of 0.1 mol/L. Under these conditions, the total concentration of humic acids and fulvic acids was 4239 mg/L in the retention solution, which can be further concentrated and processed for liquid fertilizer. The total recovery rate of sludge humic acids and fulvic acids was about 25 %. The dewatering performance of the residual sludge was better than that of the untreated sludge when the residual sludge was diluted to a water content of 95–98 % and then conditioned with polyacrylamide at a dose of 10–30 mg/L.     

An extended input-output table for environmental and resources accounting

Environmentally Extended Input-Output(EEIO)tables have become a powerful element in supporting information-based environmental and economic policies.National-and provincial-level 10 tables are currently published by the National Bureau of Statistics of the People's Republic of China according to well-defined conventions.However,county-level 10tables are not provided as a rule by official statistics organizations.This paper conducts an overview of compiling EEIO tables for environmental and resources accounting at the county level and then answers several questions:First,what kind of data should be prepared for the compilation of county-level EEIO tables?Second,how can we set up comprehensive EEIO tables at the county level?Third,regarding the survey methods and the indirect modeling,which one should be chosen to build EEIO tables at the county level?Finally,what policy questions could such a table answer?EEIO tables at the county level can be used to predict the economic impacts of environmental policies and to perform trend and scenario analysis.     

Distribution,sources, and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in surface water in industrial affected areas of the Three Gorges Reservoir,China

Water samples were collected from wastewater treatment plant (WWTP), drain water (DW), major tributaries (MT), and main course of the Yangtze River (MY) in areas of three industrial parks (IPs) in Chongqing city in the Three Gorges Reservoir (TGR). Sixteen EPA priority polycyclic aromatic hydrocarbon (PAH) pollutants were quantified to identify the effects of industrial activities on water quality of the TGR. The results showed that 11 individual PAHs were quantified and 5 PAHs (naphthalene (Nap), acenaphthylene (Acy), benzo[k]fluoranthene (BkF), indeno[1,2,3-cd]pyrene (InP), and benzo[g,h,i]perylene (BgP)) were under detection limits in all of the water samples. Three-ring and four-ring PAHs were the most detected PAHs. Concentrations of individual PAHs were in the range of not detected (nd) to 24.3 ng/L. Total PAH concentrations for each site ranged from nd to 42.9 ng/L and were lower compared to those in other studies. The mean PAH concentrations for sites WWTP, DW, MT, and MY showed as follows: DW (25.9 ng/L) > MY (15.5 ng/L) > MT (14.0 ng/L) > WWTP (9.3 ng/L), and DW contains the highest PAH concentrations. Source identification ratios showed that petroleum and combustion of biomass coal and petroleum were the main sources of PAHs. The results of potential ecosystem risk assessment indicated that, although PAH concentrations in MT and MY are likely harmless to ecosystem, contaminations of PAHs in DW were listed as middle levels and some management strategies and remediation actions, like strengthen clean production processes and banning illegal sewage discharging activities, etc., should be taken to lighten the ecosystem risk caused by PAHs especially risks caused by water discharging drains.