基于TMDL计划的流域氨氮管理方法分析

美国TMDL计划是关于流域管理的一套完整管理技术体系。以美国岩石小溪的氨和氮氧化物日最大负荷量为例,解析了TMDL计划实施的完整过程,展示了污染物日最大负荷量的分配方法。该管理方式可为我国流域管理领域提供思考与借鉴,并可促进我国河流治理尤其是辽河流域氨氮管理水平的提升。     

关于气溶胶颗粒物沉积率系数平均方法模型的改进研究

气溶胶颗粒物在壁面的沉积率系数模型的研究已经成为现代气溶胶动力学研究的重要课题.本文通过实验腔测量和理论分析相结合,对Koivisto等(2012)提出的平均方法模型(AM)中的关键参数(即时间间隔)的选取和对测量数据量的要求两个问题进行研究.选取目前广泛使用的最小二乘法模型(LSM)和Lai和Nazaroff(2000)提出的理论分析模型进行对比.研究发现,AM模型中的时间间隔这一关键参数,应由目前的50矫正为20;AM模型和LSM模型均要求实验测量数据个数等于或者大于10,但是AM模型在小数据量情况下的预测结果更精确.     

甲烷氧化菌在填埋场覆盖层中的工程应用(Ⅱ):基质选择性及长效性

针对已筛选获得的甲烷氧化混合菌,选取填埋场覆盖土(LCS)、矿化垃圾(AR)和塘渣(TZ)3种填埋场周边易得的材料为供试生存基质,从基质选择性及长效性角度进行了甲烷减排应用条件的探究及使用效能评估.结果表明,在TZ、LCS、AR、TZ-AR和LCS-AR这5种生存基质中,TZ-AR最适合甲烷氧化混合菌的生长,且TZ与AR的复配比例以5∶5为最佳.甲烷氧化混合菌在TZ-AR的粒径≤4 mm和含水率为20%时具有最高甲烷氧化能力.一次性接种甲烷氧化混合菌在静态体系中的最佳使用有效期为31 d.其在接种量为0.08、0.16、0.20 m L·g-1和0.25m L·g-1时甲烷氧化速率无明显差异,从工程应用角度而言,8%的接种量为最佳.     

玉米芯吸附水中Cr(Ⅵ)的特性及SEM-EDS表征分析

Cr是人和动物所必需的微量元素,但工业废水中的高浓度的Cr会对人类健康和生态环境都会造成严重的危害。为探讨玉米芯对废水中Cr(Ⅵ)的吸附特性,以期为应用玉米芯处理含Cr废水提供理论依据,在本研究中设置了3项试验:不同p H条件下的吸附试验、等温吸附试验和热力学试验,并对吸附前后的玉米芯进行扫描与能谱分析,探究玉米芯作为吸附剂对水中Cr(Ⅵ)的吸附机理。结果表明:低p H有利于玉米芯对Cr(Ⅵ)的吸附,在p H为1.0左右时,玉米芯对Cr(Ⅵ)有最佳吸附效果,最高去除率可达94.35%,最大吸附量可达23.944 0 mg·g-1;玉米芯对Cr(Ⅵ)的吸附过程符合Langmuir、Freundlich和Dubinin-Radushkevich等温吸附模型,但以Freundlich模型的拟合效果为最优,1/n为0.887 5,表明玉米芯对Cr(Ⅵ)的吸附强度适中;D-R模型中E=3.152 8 k J·mol-1,表明该吸附主要为物理吸附过程;热力学参数ΔH为-0.272 8 k J·mol-1,ΔS为0.014 3 k J·mol-1·K-1,表示玉米芯对Cr(Ⅵ)的吸附是一个自发的放热过程,且升高温度有利于吸附过程的进行;通过扫描电镜可以看出玉米芯表面产生了较多空洞结构,可能是酸性吸附质溶液可以使纤维素水解,增大了玉米芯的比表面积,形成了更有利于吸附的条件;另外玉米芯质子化的静电作用以及含氧官能团对阳离子的亲和性分别对阴离子形式的Cr(Ⅵ)和被还原成阳离子的Cr(III)有吸附作用。这些原因促进了玉米芯对Cr的吸附。     

沿海城市多灾种耦合危险性评估的初步研究——以福建泉州为例

如何处理区域内多灾种之间的相互作用关系是当前多灾种综合风险评估研究的热点和难点之一。在梳理沿海城市多灾种之间相互作用关系的基础上,提出一种基于触发关系的多灾种耦合危险性评估方法。首先选取多指标建立单灾种分级方案,计算单灾种初始危险性指数;然后构建基于触发关系的多灾种耦合规则,结合GIS技术进行空间耦合,计算耦合后的危险性指数;最后对耦合后的多灾种危险性的综合进行了探讨。以福建省泉州市为例进行了案例研究,结果表明:该方法在多灾种耦合危险性评估中具有可行性,为后续多脆弱性和多灾种综合风险的研究提供支持,为决策者进行科学风险管理提供依据。     

1961-2011年黄淮海地区极端降水时空变化特征

基于Arc GIS平台,分析了黄淮海地区1961-2011年最大1 d、3 d和5 d降雨的时空变化特征,同时利用Pearson-III分布对其进行拟合,对比1985年前后10年一遇和50年一遇最大1 d、3 d和5 d降雨的变化情况。研究结果表明:1961-2011年黄淮海地区最大1 d、3 d及5 d降水整体有下降趋势,1995年后下降趋势更为明显;海河流域极端降水量下降幅度较大,洪涝灾害风险近年来有降低趋势;淮河流域整体上存在上升趋势,但2005年后出现下降趋势,整体上洪涝风险有加剧趋势。     

雄黄矿区不同砷污染土壤中微生物群落结构及碳源利用特征

土壤砷污染是我国乃至世界范围内比较严重的环境问题.有关砷污染的生态毒理效应有很多研究,但对砷污染土壤中微生物群落的关注相对较少.本文以我国湖南省石门县雄黄矿地区长期砷污染土壤为例,采用PLFA及BIOLOG微平板技术考察了7个砷(As)污染程度不同的样点以及一个对照样点土壤微生物群落结构及碳源利用特征.结果发现,雄黄矿区存在多种重金属复合污染,除As含量较高以外,镉(Cd)和镍(Ni)的含量也超过了国家土壤环境质量三级标准.雄黄矿区土壤微生物的群落结构受到土壤有机碳(SOC)、有效磷(AP)、p H以及镁(Mg)、Cd、铁(Fe)、铜(Cu)含量的显著影响.各样点土壤微生物群落均以细菌为主,占微生物总量的71.54%~80.66%,真菌次之,放线菌最少.雄黄矿区土壤中的有效砷对微生物造成了较严重的胁迫.严重砷污染降低了微生物对于碳源利用的多样性以及均匀度.各样点微生物对于碳源的利用也表现出明显的差异.31种碳源中微生物利用较多的只有7类,分别属于糖类、胺类、羧酸类与多聚物,并且以糖类为主.     

Molecular diversity of arbuscular mycorrhizal fungi at a large-scale antimony mining area in southern China

Arbuscular mycorrhizal fungi (AMF) have great potential for assisting heavy metal hyperaccumulators in the remediation of contaminated soils. However, little information is available about the community composition of AMF under natural conditions in soils contaminated by antimony (Sb). The objective of this study was to investigate the characteristics of AMF molecular diversity, and to explore the effects of Sb content and soil properties on the AMF community structure in an Sb mining area. Four Sb mine spoils and one adjacent reference area were selected from around the Xikuangshan mine in southern China. The association of AMF molecular diversity and community composition with the rhizosphere soils of the dominant plant species was studied by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE). Results from all five studied sites showed that the diversity of AMF decreased with increasing Sb concentration. Principal component analysis (PCA) indicated that the AMF community structure was markedly different among these groups. Further redundancy analysis (RDA) showed that Sb contaminationwas the dominating factor influencing the AMF community structure in the Sb mine area. However, the multivariate analysis showed that, apart from the soil Sb content, extractable nitrogen content and organic matter content also attributed to AMF sequence distribution type. Some AMF sequences were only found in the highly contaminated area and these might be ideal candidates for improving phytoremediation efficiency in Sb mining regions. Gene sequencing analysis revealed that most species were affiliated with Glomus, suggesting that Glomus was the dominant AMF genus in the studied Sb mining area.     

Microcystis aeruginosa/Pseudomonas pseudoalcaligenes interaction effects on off-flavors in algae/bacteria co-culture system under different temperatures

We conducted an experiment to study the interaction effects of Microcystis aeruginosa and Pseudomonas pseudoalcaligenes on off-flavors in an algae/bacteria co-culture system at three temperatures (24, 28 and 32°C). Gas chromatography–mass spectrometry was applied to measure off-flavor compounds dimethyl sulfide (DMS), dimethyl trisulfide (DMTS), 2-methylisoborneol, geosmin (GEO) and β-cyclocitral. During the lag phase of co-cultured M. aeruginosa (first 15 days), P. pseudoalcaligenes significantly increased the production of DMS, DMTS and β-cyclocitral at all three temperatures. In the exponential phase of co-cultured M. aeruginosa (after 15 days), M. aeruginosa became the main factor on off-flavors in the co-culture system, and β-cyclocitral turned to the highest off-flavor compound. These results also indicated that DMS, DMTS and β-cyclocitral were the main off-flavor compounds in our M. aeruginosa/P. pseudoalcaligenes co-culture system. Univariate analysis was applied to investigate the effects of M. aeruginosa and P. pseudoalcaligenes on the production of off-flavors. The results demonstrated that both M. aeruginosa and P. pseudoalcaligenes could increase the production of DMS and DMTS, while β-cyclocitral was mainly determined by M. aeruginosa. Our results also provide some insights into understanding the relationship between cyanobacteria and heterotrophic bacteria.     

Methane and nitrous oxide emissions from a subtropical coastal embayment (Moreton Bay, Australia)

Surface water methane (CH₄) and nitrous oxide (N₂O) concentrations and fluxes were investigated in two subtropical coastal embayments (Bramble Bay and Deception Bay, which are part of the greater Moreton Bay, Australia). Measurements were done at 23 stations in seven campaigns covering different seasons during 2010-2012. Water-air fluxes were estimated using the Thin Boundary Layer approach with a combination of wind and currents-based models for the estimation of the gas transfer velocities. The two bays were strong sources of both CH₄ and N₂O with no significant differences in the degree of saturation of both gases between them during all measurement campaigns. Both CH₄ and N₂O concentrations had strong temporal but minimal spatial variability in both bays. During the seven seasons, CH₄ varied between 500% and 4000% saturation while N₂O varied between 128 and 255% in the two bays. Average seasonal CH₄ fluxes for the two bays varied between 0.5 ± 0.2 and 6.0 ± 1.5 mg CH₄/(m²·day) while N₂O varied between 0.4 ± 0.1 and 1.6 ± 0.6 mg N₂O/(m²·day). Weighted emissions (t CO₂-e) were 63%-90% N₂O dominated implying that a reduction in N₂O inputs and/or nitrogen availability in the bays may significantly reduce the bays' greenhouse gas (GHG) budget. Emissions data for tropical and subtropical systems is still scarce. This work found subtropical bays to be significant aquatic sources of both CH₄ and N₂O and puts the estimated fluxes into the global context with measurements done from other climatic regions.