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191.
以采用MINDO/3、MNDO和AMI算法计算的17种多环芳烃(PAHs)的前线分子轨道能为分子结构参数,进行了这些PAHs光解速率常数的定量结构-性质相关(QSPR)的研究,并与基于PM3算法得到的QSPR模型进行了比较,研究结果表明,应用PM3算法得到的前线分子轨道能进行这些PAHs光解速率常数QSPR拟合的结果最好,其次是AMI算法,而MINDO/3和MNDO算法得到的结果较差。  相似文献   
192.
废水中氨氮的去除与利用   总被引:21,自引:0,他引:21  
化学沉淀剂可去除废水中的氨氮,并得到有用复合肥MgNH4PO4。探讨了诸反应对氨氮去除率的影响。  相似文献   
193.
高浓度甲基橙溶液的低压湿式催化氧化处理   总被引:4,自引:0,他引:4  
谢磊  杨润昌 《环境工程》1999,17(6):69-71
以高浓度甲基橙溶液模拟偶氮染料废水,采用低压湿式催化氧化法(LPWCO)进行处理,考察了H2O2投量、温度、FeSO4投量、硫酸浓度、甲基橙浓度等因素对甲基橙脱色率的影响。结果表明,LPWCO法能有效地使高浓度(大于400mg/L)甲基橙溶液脱色,脱色率大于95%,而H2O2投量不到Fenton法的5%。  相似文献   
194.
三界谷来地区主要出露中、新生代火山岩。进行 1/5万区域地质调查时,采用火山活动旋回-火山构造-火山地层-岩相、岩性-体化思路,按照同旋回火山机构或火山喷发区为单元,确定岩石地层单位和填图单元。火山岩划分为九种岩相类型,建立了两个岩相模式和一个三相一体成因模式。根据火山岩浆作用的旋回性及其产物与火山构造形迹时、空、成因一致性原理,将中、新生代火山岩浆作用分为四个火山活动旋回,圈定了相应的火山机构或火山喷发中心,建立了竹田头复活破火山演化模式。新生代玄武岩中发现二辉斜长麻粒岩等深源包体,为研究区域深部地质作用过程提供了证据。侵入岩按岩石谱系单元划分了七个岩石单元一个超单元,将侵入岩-潜火山岩-火山岩作为岩浆作用整体研究,为正确阐明岩浆作用及其演化规律奠定了基础。区域线型构造发育,与环形火山构造组合,形成火山岩区特有的线一环构造格局。中上元古界陈蔡群变质岩划分为上、下两个岩组,探讨了变质岩的原岩性质及其形成的大地构造环境。  相似文献   
195.
196.
Estuarine ecosystems are largely influenced by watersheds directly connected to them. In the Mobile Bay, Alabama watersheds we examined the effect of land cover and land use (LCLU) changes on discharge rate, water properties, and submerged aquatic vegetation, including freshwater macrophytes and seagrasses, throughout the estuary. LCLU scenarios from 1948, 1992, 2001, and 2030 were used to influence watershed and hydrodynamic models and evaluate the impact of LCLU change on shallow aquatic ecosystems. Overall, our modeling results found that LCLU changes increased freshwater flows into Mobile Bay altering temperature, salinity, and total suspended sediments (TSS). Increased urban land uses coupled with decreased agricultural/pasture lands reduced TSS in the water column. However, increased urbanization or agricultural/pasture land coupled with decreased forest land resulted in higher TSS concentrations. Higher sediment loads were usually strongly correlated with higher TSS levels, except in areas where a large extent of wetlands retained sediment discharged during rainfall events. The modeling results indicated improved water clarity in the shallow aquatic regions of Mississippi Sound and degraded water clarity in the Wolf Bay estuary. This integrated modeling approach will provide new knowledge and tools for coastal resource managers to manage shallow aquatic habitats that provide critical ecosystem services.  相似文献   
197.
The objective of this study is to investigate the occurrence of haloacetic acids (HAAs), a group of disinfection byproducts, in swimming pool and spa water. The samples were collected from six indoor pools, six outdoor pools and three spas in Pennsylvania, the United States, and from five outdoor pools and nine indoor pools in Beijing, China. Five HAAs (HAA5), including monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid were analyzed. Total chlorine, pH and total organic carbon concentration were analyzed as well. Results indicated that the levels of HAA5 in swimming pools and spas in the United States ranged from 70 to 3980μg·L^-1, with an arithmetic average at 1440μg·L^-1 and a median level at 1150μg·L^-1. These levels are much higher than the levels reported in chlorinated drinking water and are likely due to organic matters released from swimmers' bodies. The levels of HAA5 in swimming pools in China ranged from 13 to 332μg·L^-1, with an arithmetic average at 117μg·L^-1 and a median level at 114μg·L^-1. The lower HAA levels in swimming pools in China were due to the lower chlorine residuals. Results from this study can help water professionals to better understand the formation and stability of HAAs in chlorinated water and assess risks associated with exposures to HAAs in swimming pools and spas.  相似文献   
198.
我国云南省曲靖的宣威和富源等地是全世界肺癌高发区,为了研究环境介质中铜(Cu)等重金属的暴露与体内分布特征,探讨Cu与肺癌的相关性,在当地开展肺癌环境流行病学调查,采集宣威和富源高发区人群饮食、饮水以及人体血浆和肺组织样品,微波消解ICP-MS法测定样品中Cu等元素.结果显示,当地居民使用燃料类型是影响肺癌高发的重要因素.高发区人群Cu的日摄入总量低于我国推荐的每日膳食中营养素供给量(RDA).肺癌组血液中Cu含量显著高于对照组,肺癌组织中Cu含量显著高于癌旁组织和正常组织,且肺癌患者的血浆和肺组织中Cu/Zn比值均升高.Pearson相关性分析结果表明,Cu和Ni、Cu和Pb呈显著正相关,提示在致癌作用上具有协同效应;Cu和Fe、Cu和Zn呈显著负相关,提示具有抑制或拮抗作用.多因素Logistic回归结果表明,Cu是肺癌发生的重要影响因素,人体中Cu含量和Cu/Zn比值可为肺癌的早期预防和诊断提供科学依据.  相似文献   
199.
Variable ocean conditions can greatly impact prey assemblages and predator foraging in marine ecosystems. Our goal was to better understand how a change in ocean conditions influenced dietary niche overlap among a suite of midtrophic-level predators. We examined the diets of three fishes and one seabird off central Oregon during two boreal summer upwelling periods with contrasting El Niño (2010) and La Niña (2011) conditions. We found greater niche specialization during El Niño and increased niche overlap during La Niña in both the nekton and micronekton diet components, especially in the larger, more offshore predators. However, only the two smaller, more nearshore predators exhibited interannual variation in diet composition. Concurrent trawl surveys confirmed that changes in components of predator diets reflected changes in the prey community. Using multiple predators across diverse taxa and life histories provided a comprehensive understanding of food-web dynamics during changing ocean conditions.  相似文献   
200.
Fishing and habitat degradation have increased the extinction risk of sharks, and conservation strategies recognize that survival of juveniles is critical for the effective management of shark populations. Despite the rapid expansion of marine protected areas (MPAs) globally, the paucity of shark‐monitoring data on large scales (100s–1000s km) means that the effectiveness of MPAs in halting shark declines remains unclear. Using data collected by baited remote underwater video systems (BRUVS) in northwestern Australia, we developed generalized linear models to elucidate the ecological drivers of habitat suitability for juvenile sharks. We assessed occurrence patterns at the order and species levels. We included all juvenile sharks sampled and the 3 most abundant species sampled separately (grey reef [Carcharhinus amblyrhynchos], sandbar [Carcharhinus plumbeus], and whitetip reef sharks [Triaenodon obesus]). We predicted the occurrence of juvenile sharks across 490,515 km2 of coastal waters and quantified the representation of highly suitable habitats within MPAs. Our species‐level models had higher accuracy (? ≥ 0.69) and deviance explained (≥48%) than our order‐level model (? = 0.36 and deviance explained of 10%). Maps of predicted occurrence revealed different species‐specific patterns of highly suitable habitat. These differences likely reflect different physiological or resource requirements between individual species and validate concerns over the utility of conservation targets based on aggregate species groups as opposed to a species‐focused approach. Highly suitable habitats were poorly represented in MPAs with the most restrictions on extractive activities. This spatial mismatch possibly indicates a lack of explicit conservation targets and information on species distribution during the planning process. Non‐extractive BRUVS provided a useful platform for building the suitability models across large scales to assist conservation planning across multiple maritime jurisdictions, and our approach provides a simple for method for testing the effectiveness of MPAs.  相似文献   
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