Geochemical fractionation and ecological risks assessment of benthic sediment-bound heavy metals from coastal ecosystems off the Equatorial Atlantic Ocean

This study determines the pollution, fractionation, and ecological risks of sediment-bound heavy metals from coastal ecosystems off the Equatorial Atlantic Ocean. Contamination Factor(CF), pollution load index(PLI), and geoaccumulation index(Igeo) were used to assess the extent of the heavy metal pollution, while the potential ecological risk was evaluated using the risks assessment code(RAC) and Hkanson potential ecological risk. The analysis revealed concentrations(mg/g, dw) of the cadmium(Cd),chromium(Cr), copper(Cu), nickel(Ni), and lead(Pb) in sediments for wet and dry seasons vary from 4.40-5.08, 14.80-21.09. 35.03-44.8, 2.14-2.28, and 172.24-196.39, respectively. The results also showed that the metal fractionation percentages in the residual, oxidizable, and reducible fractions are the most significant, while the exchangeable and carbonate bound trace metals are relatively low. The RAC values indicate no risk for Cd and Ni and low risk for other metals at all the studied sites during both seasons.Potential ecological risk analysis of the heavy metal concentrations indicates that Cd had high individual potential ecological risk, while the other metals have low risk at all investigated sites. The multi-elemental potential ecological risk indices(R_1) indicate high ecological risk in all the ecosystems.     

三峡库区汉丰湖鱼类群落结构的季节变化

为了解汉丰湖鱼类群落结构的季节变化特征,以便为汉丰湖鱼类资源的合理利用及保护提供理论依据,于2014年12月、2015年4、7和10月按季度共4次对汉丰湖鱼类群落结构进行调查与分析.结果表明:共采集到鱼类8538尾,38种,隶属于5目9科32属;其中,鲤形目鱼类有28种,占总物种数的73.68%.鱼类组成以湖泊定居性种类为主,瓦氏黄颡鱼(Pelteobagrus vachelli)、蛇鮈(Saurogobio dabryi)、银鮈(Squalidus argentatus)、鲫(Carassius auratus)、光泽黄颡鱼(Pelteobagrus nitidus)、鲤(Cyprinus carpio)和贝氏(Hemiculter bleekeri)为汉丰湖的重要优势种,占总尾数的67.45%.汉丰湖鱼类群落Shannon-Wiener多样性指数、Pielous均匀度指数和Margalef丰富度指数在冬季最高,而Pielous均匀度指数在不同季节相对稳定.Jaccard群落相似性指数较高,季节间种类相似度较高.鱼类群落稳定性分析表明,冬季稳定性最高,其次为春季,夏季稳定性最低.湖泊生境尤其是水位的变化对汉丰湖鱼类群落结构影响明显.     

Distribution,potential sources and ecological risks of two persistent organic pollutants in the intertidal sediment at the Shuangtaizi Estuary,Bohai Sea of China

Spatial distribution, source apportionment, and potential ecological risks of sixteen polycyclic aromatic hydrocarbons (PAHs) and seven endocrine disrupting compounds (EDCs) in the intertidal sediment at the Shuangtaizi Estuary, Bohai Sea of China were analyzed. Results showed that the total PAH concentrations ranged from 28.79 ng g^? 1 dw to 281.97 ng g^? 1 dw (mean: 115.92 ng g^? 1 dw) and the total EDC concentrations from 0.52 ng g^? 1 dw to 126.73 ng g^? 1 dw (mean: 37.49 ng g^? 1 dw). The distribution pattern for the PAHs was generally different from that of the EDCs possibly due to their distinct sources and n-octanol-/water partition coefficients (K_OW). Qualitative and quantitative analytical results showed that PAH sources were mainly from a mixture of pyrogenic and petrogenic contributions. The higher levels at the southeast of Geligang indicated that the EDC pollutants may have mainly originated from the plastic industry and other chemical plants located along the Liao River. Ecological risk assessment revealed that PAHs exhibited low ecotoxicological effects, whereas EDCs, especially 4-tert-octylphenol and bisphenol A, had high ecological hazard to the estuarine biota.     

高烈度区大跨刚构-连续梁桥地震响应分析

为研究大跨刚构-连续梁桥在高烈度地区的地震响应,选取羊记沟左线大桥为工程背景,利用Midas软件建立多个有限元模型,考虑纵、横桥向的水平地震波输入,比较反应谱与时程分析结果,获得结构动力响应特点,为大跨刚构-连续梁桥的抗震设计提供参考依据。结果表明:刚构-连续体系仅单墩刚构时不宜采用反应谱分析,高烈度地区桥梁进行地震响应时程分析时,选用与场地适应的地震波的同时,应考虑采用本地地震参数转化人工波作为地震激励源。桥墩不等高时,可通过改变墩截面形状及其与主梁连接方式调节内力分布,避免矮墩刚度大导致的内力集中。     

邢台地区地壳各向异性特征初步研究

邢台地区处于华北平原地震带中南段, 是华北地区活跃的地震活动区。 本研究根据该地区的构造环境, 采用SAM方法研究地壳各向异性特征, 通过对邢台地区台站的数字波形进行分析, 初步得到邢台地区的剪切波分裂参数, 该地区的快剪切波平均偏振方向为73.9°±40.2°, 慢剪切波平均时间延迟为(2.74±1.54) ms/km。 结果表明, 快剪切波平均偏振方向与华北区域最大主压应力场方向基本一致, 但是受到局部断裂的制约, 部分台站下方的快剪切波的偏振方向显示为NWW方向。     

夏季亚洲季风区对流层-平流层不可逆质量交换特征分析

基于2005年NCEP/GFS分析资料和拉格朗日粒子扩散模式的“Domain Filling”技术,以气块穿越对流层顶后的滞留时间为标准,诊断分析了夏季亚洲季风区对流层-平流层质量交换,重点讨论了对平流层大气成分收支具有实际意义的不可逆双向质量交换过程,并利用前向（后向）轨迹追踪方法,分析了其4天的“源（汇）”特征.研究结果表明：(1)对流层-平流层质量交换(Troposphere-Stratosphere mass Exchange,STE)的计算对滞留时间阈值的选择具有较强敏感性,大多数的气块在1～2天内可频繁地往返对流层顶.这些瞬时交换事件的考虑与否对穿越对流层顶的质量交换计算的准确性具有重要影响,尤其在中纬度的风暴轴区域.(2)从亚洲季风区对流层-平流层质量净交换纬向平均上看,45°N以南的区域为对流层向平流层的质量输送(Troposphere to Stratosphere mass Transport,TST),副热带地区为最强的上升支,而在45°N~55°N的中纬度地区是平流层向对流层质量输送（Stratosphere to Troposphere mass Transport,STT）.地理分布上,STT主要分布在青藏高原以北的东亚地区,与亚洲季风区夏季大尺度的槽区相对应.夏季整个亚洲季风区都是TST发生的区域,最大值位于青藏高原东南侧及其附近区域,该区域占亚洲季风区不可逆TST夏季平均总量的46%.(3)对流层-平流层质量交换的“源汇”特征分析表明,STT主要源于100°E以西、50°N以北的高纬地区,向下可以输送到中国东北部及朝鲜半岛北部等中纬度区域.而TST主要来源于中纬度和副热带地区的大气输送,向上穿越对流层顶高度以后,可分别向高纬的极地和热带地区输送,这意味着亚洲季风区夏季的TST水汽输送可能进入“热带管”中,进而可能对全球平流层水汽平衡产生重要影响.     

基于时-空ETAS模型给出的川滇地区背景地震活动和强震潜在危险区

利用基于时-空传染型余震序列（Epidemic Type Aftershock Sequence, 简称ETAS）模型的随机除丛法,重新审视了2008年5月12日汶川M_S8.0地震前可能存在的长期地震活动异常,研究了川滇地区背景地震活动特征,并评估了当前的强震危险状态.对川滇地区1970年以来的M_L3.0以上的背景地震和丛集地震活动的研究结果表明,该地区地震丛集特征明显、时空分布很不均匀、地震序列常有前震事件.直接将概率值作为地震计数的权重,对地震丛集率空间分布图像分析表明,汶川M_S8.0地震前,龙门山断裂带中南段存在着长期、大范围的地震丛集率低值区,震前该段处于应力闭锁状态.对川滇地区地震丛集率低值区内背景地震与全部地震的累积次数、b值和新定义的Δb等统计参量的分析表明,龙日坝与龙门山断裂带具有地震活动的关联性,川滇地区当前的强震潜在危险区可能是巧家地区和汶川M_S8.0地震破裂尚未穿越的龙门山断裂带南段.此外,还发现b值倾向于反映局部应力场变化,而Δb能较为敏感地给出更大范围应力场的相对变化.     

2008年汶川8.0级地震前川滇地区6级以上地震平静异常

2008年5月12日四川汶川8.0级地震前,川滇地区出现了显著的地震平静异常:M≥6.0、M≥6.5和M≥7.0地震平静时间分别达3.63年、8.29年和12.27年。通过对1900年以来川滇地区M≥6.0、M≥6.5和M≥7.0地震时间分布特征的统计分析,发现这些平静异常现象在川滇地区近100年来的地震活动性中是非常显著的。在M≥7.0地震平静时间大于5年的条件下,M≥6.0(1.0σ以上)和M≥6.5地震(1.5σ以上)平静异常在统计上具有显著性和重现性,可能是这类7级地震前一个重要或典型的异常现象。     

Study on Ground Motion Attenuation Relation in Shanghai and Its Adjacent Region

Based on intensity data in Shanghai and its adjacent region, the intensity attenuation relation is determined. Selecting the western United States as a reference area where there are rich strong ground motion records and intensity data, and by determining ground motion attenuation relation in an area lacking in strong ground motion data, we obtain the ground motion attenuation relation in Shanghai and its adjacent region.