污水生物除磷若干影响因素分析

在系统阐述污水生物除磷机理的基础上,深入分析了微生物群体平衡、城市污水水质、环境因子以及工艺运行参数和运行方式等方面对生物除磷效果的影响.分析结果表明:生物除磷系统的溶解氧浓度不宜太高,一般好氧区DO＜2 mg/L,厌氧区DO＜0.2 mg/L;厌氧段存在硝酸盐对生物释磷有负面影响,缺氧段存在一定浓度的硝酸盐有利于生物聚磷;碳源必须充分、易降解;TKN/COD＜0.1的城市污水有利于生物除磷;pH偏碱性可提高生物除磷效率;低温对生物除磷效果影响不明显.     

Comparison of carbonyl compounds emissions from diesel engine fueled with biodiesel and diesel

The characteristics of carbonyl compounds emissions were investigated on a direct injection, turbocharged diesel engine fueled with pure biodiesel derived from soybean oil. The gas-phase carbonyls were collected by 2,4-dinitrophenylhydrazine (DNPH)-coated silica cartridges from diluted exhaust and analyzed by HPLC with UV detector. A commercial standard mixture including 14 carbonyl compounds was used for quantitative analysis. The experimental results indicate that biodiesel-fueled engine almost has triple carbonyls emissions of diesel-fueled engine. The weighted carbonyls emission of 8-mode test cycle of biodiesel is 90.8 mg (kW h)^?1 and that of diesel is 30.7 mg (kW h)^?1. The formaldehyde is the most abundant compound of carbonyls for both biodiesel and diesel, taking part for 46.2% and 62.7% respectively. The next most significant compounds are acetaldehyde, acrolein and acetone for both fuels. The engine fueled with biodiesel emits a comparatively high content of propionaldehyde and methacrolein. Biodiesel, as an alternative fuel, has lower specific reactivity (SR) caused by carbonyls compared with diesel. When fueled with biodiesel, carbonyl compounds make more contribution to total hydrocarbon emission.     

Adsorption and redox reactions of heavy metals on synthesized Mn oxide minerals

Several Mn oxide minerals commonly occurring in soils were synthesized by modified or optimized methods. The morphologies, structures, compositions and surface properties of the synthesized Mn oxide minerals were characterized. Adsorption and redox reactions of heavy metals on these minerals in relation to the mineral structures and surface properties were also investigated. The synthesized birnessite, todorokite, cryptomelane, and hausmannite were single-phased minerals and had the typical morphologies from analyses of XRD and TEM/ED. The PZCs of the synthesized birnessite, todorokite and cryptomelane were 1.75, 3.50 and 2.10, respectively. The magnitude order of their surface variable negative charge was: birnessite> or =cryptomelane>todorokite. The hausmannite had a much higher PZC than others with the least surface variable negative charge. Birnessite exhibited the largest adsorption capacity on heavy metals Pb(2+), Cu(2+), Co(2+), Cd(2+) and Zn(2+), while hausmannite the smallest one. Birnessite, cryptomelane and todorokite showed the greatest adsorption capacity on Pb(2+) among the tested heavy metals. Hydration tendency (pK(1)) of the heavy metals and the surface variable charge of the Mn minerals had significant impacts on the adsorption. The ability in Cr(III) oxidation and concomitant release of Mn(2+) varied greatly depending on the structure, composition, surface properties and crystallinity of the minerals. The maximum amounts of Cr(III) oxidized by the Mn oxide minerals in order were (mmol/kg): birnessite (1330.0)>cryptomelane (422.6)>todorokite (59.7)>hausmannite (36.6).     

Differences in distributions,assembly mechanisms,and putative interactions of AOB and NOB at a large spatial scale

● Nitrifiers in WWTP were investigated at large spatial scale. ● AOB populations varied greatly but NOB populations were similar among cities. ● Drift dominated both AOB and NOB assembling processes. ● DO did not show a significant effect on NOB. ● NOB tended to cooperate with AOB and non-nitrifying microorganisms. Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) play crucial roles in removing nitrogen from sewage in wastewater treatment plants (WWTPs) to protect water resources. However, the differences in ecological properties and putative interactions of AOB and NOB in WWTPs at a large spatial scale remain unclear. Hence, 132 activated sludge (AS) samples collected from 11 cities across China were studied by utilizing 16S rRNA gene sequencing technology. Results indicated that Nitrosomonas and Nitrosospira accounted for similar ratios of the AOB community and might play nearly equal roles in ammonia oxidation in AS. However, Nitrospira greatly outnumbered other NOB genera, with proportions varying from 94.7% to 99.9% of the NOB community in all WWTPs. Similar compositions and, hence, a low distance–decay turnover rate of NOB (0.035) across China were observed. This scenario might have partly resulted from the high proportions of homogenizing dispersal (~13%). Additionally, drift presented dominant roles in AOB and NOB assembling mechanisms (85.2% and 81.6% for AOB and NOB, respectively). The partial Mantel test illustrated that sludge retention time and temperature were the primary environmental factors affecting AOB and NOB communities. Network results showed that NOB played a leading role in maintaining module structures and node connections in AS. Moreover, most links between NOB and other microorganisms were positive, indicating that NOB were involved in complex symbioses with bacteria in AS.     

杭州城市大气消光系数和能见度的影响因子研究

为了解杭州市能见度下降与大气污染之间的关系，在2001年5月至2002年5月对不同粒径的颗粒物（PM10、PM2.5）的质量浓度进行了观测，结合晴天天气条件下的大气能见度，推算污染物和水汽分子对大气的消光散射，发现细微颗粒物的散射消光特性对杭州市能见度下降起主要作用，并得到能见度与细微颗粒物浓度比值（PM2．5／PM10）的关系；分析了大气能见度和消光系数与PM2．5／PM10和相对湿度的相关系数。     

Risk assessment and validation of farmland abandonment based on time series change detection

Environmental Science and Pollution Research - Farmland abandonment, a widespread phenomenon during land-use transition, leads to a cycling or vanishing evolution of farmland resources. As...     

The health consequences of greenhouse gas emissions: a potential pathway

Environmental Geochemistry and Health - Excessive greenhouse gas emissions might be the major culprit for environmental degradation, which have direct and indirect adverse impacts in various ways....     

内分泌干扰物对核受体二聚化影响的研究进展

环境内分泌干扰物(endocrine disrupting chemicals,EDCs)可模仿或拮抗天然激素与核受体结合,干扰核受体的同源或异源二聚,进而通过共调节因子的招募调控转录活性,最终引起内分泌干扰效应.目前研究主要针对EDCs与核受体的结合过程,忽视了其对核受体二聚化过程的影响,而该过程的阻断可直接导致转录失活.EDCs对于不同核受体二聚化的影响不同,只有激动剂EDCs能够促进雄激素受体(androgen receptor,AR)的同源二聚化,而雌激素受体(estrogen receptor,ER)在与具有激动或拮抗活性的EDCs结合后都可诱导ER二聚体的形成,但二聚化类型不同.通过检索ToxCast和Tox21数据库发现多达227种EDCs可以诱导ER二聚化,相比于ERα-ERα同源二聚体(6.09％ ～7.38％的活性率),EDCs更易诱导ERα-ERβ异源二聚体(11.25％ ～12.22％的活性率)和ERβ-ERβ同源二聚体(10.02％ ～11.69％的活性率).EDCs也能够差异性诱导其他核受体如维生素D受体(vitamin D receptor,VDR)与维甲酸X受体(retinoid X receptor,RXR)形成的异源二聚体,不同类型的二聚体对于研究EDCs转录活性的生理学相关性具有重要意义.基于经济合作与发展组织(Organization for Economic Co-operation and Development,OECD)报告的参考化学品研究发现,相比于配受体结合活性,二聚活性与转录活性之间有着更好的相关关系.本文从EDCs介导的核受体二聚化转录机制、二聚化与转录活性间的关系以及二聚化研究方法三方面,总结EDCs对核受体二聚化的影响,以期为深入理解EDCs的分子作用机制,推进化合物的内分泌干扰风险评估提供参考.     

Laboratory investigation on high- and low-temperature performances of asphalt mastics modified by waste oil shale ash

Journal of Material Cycles and Waste Management - The objective of this study was to use two kinds of waste oil shale ash (OSA) as partial replacements of conventional mineral filler for evaluating...     

Preparation and uranium (VI) biosorption for tri-amidoxime modified marine fungus material

Environmental Science and Pollution Research - The preparation, characterization, and uranium (VI) adsorption properties of tri-amidoxime modified marine fungus material (ZZF51-GPTS-EDA-AM/ZGEA)...