集输油环境氟橡胶O形圈老化行为实验研究*

为研究氟橡胶O形圈在集输油环境中的老化行为特征，以长庆油田使用的氟橡胶O形圈(位于非金属复合管连接接头处)为研究对象，采用宏观与微观相结合的方法，通过挂片实验分析氟橡胶O形圈在不同介质（采出油，采出水）、温度（25，50 ℃）、压力条件（0.1,4,6 MPa）下老化后的形貌、质量、拉伸性能及硬度。结果表明:采出油、采出水均能引起O形圈发生溶胀，从而降低O形圈的强度、韧性、硬度；采出水引起的溶胀显著高于采出油更易导致O形圈表面产生坑洞缺陷；渗透速率随温度升高而急剧增加，压力对渗透速率的影响不明显；硬度降低较小，最大降幅为4.17%。结合现场服役813 d的密封圈SEM形貌，证实集输介质渗透会引起氟橡胶圈溶胀、导致表面产生坑洞等缺陷。     

环境空气自动监测方法检出限相关问题探讨

探讨了环境空气自动监测中实际评估方法检出限的意义,详细介绍了常规气态污染物自动监测方法检出限的评估方法。并以EC 9850型SO2分析仪为例,说明了环境空气自动监测的测定步骤和方法检出限的计算。     

Seed plant phylogenetic diversity and species richness in conservation planning within a global biodiversity hotspot in eastern Asia

One of the main goals of conservation biology is to understand the factors shaping variation in biodiversity across the planet. This understanding is critical for conservation planners to be able to develop effective conservation strategies. Although many studies have focused on species richness and the protection of rare and endemic species, less attention has been paid to the protection of the phylogenetic dimension of biodiversity. We explored how phylogenetic diversity, species richness, and phylogenetic community structure vary in seed plant communities along an elevational gradient in a relatively understudied high mountain region, the Dulong Valley, in southeastern Tibet, China. As expected, phylogenetic diversity was well correlated with species richness among the elevational bands and among communities. At the community level, evergreen broad‐leaved forests had the highest levels of species richness and phylogenetic diversity. Using null model analyses, we found evidence of nonrandom phylogenetic structure across the region. Evergreen broad‐leaved forests were phylogenetically overdispersed, whereas other vegetation types tended to be phylogenetically clustered. We suggest that communities with high species richness or overdispersed phylogenetic structure should be a focus for biodiversity conservation within the Dulong Valley because these areas may help maximize the potential of this flora to respond to future global change. In biodiversity hotspots worldwide, we suggest that the phylogenetic structure of a community may serve as a useful measure of phylogenetic diversity in the context of conservation planning.     

Levels and distribution of Dechloranes in sediments of Lake Taihu,China

The occurrence and spatial distribution of dechloranes including mirex, dechlorane plus (DP), dechlorane (Dec) 602, Dec 603, and Dec 604 in surficial sediments of Lake Taihu were investigated in this study. The concentrations of mirex and DP ranged from below detection limit (BDL) to 1.29 ng g^?1 dw and 0.051 to 2.10 ng g^?1 dw, respectively. Dec 602, Dec 603, and Dec 604 on the other hand, were BDL in any of the samples. The contamination levels of DP were higher than that of Mirex at 21 of all 22 sampling sites. Levels of mirex and DP in the lake sediments were correlated when an extremely high mirex value was removed. Both mirex and DP levels were correlated with the amount of organic matters in the sediment samples. Spatial distribution of mirex and DP suggested that these two chemicals in the lake had similar input sources except for one site. Comparison to previously reported flame retardants’ levels in the sediments shows that DP levels were similar with the levels of tetrabromobisphenol A, hexabromocyclododecane but lower than PBDEs and organophosphates levels in Lake Taihu. The higher levels in the north-east part of Lake Taihu adjacent to two major cities: Wuxi and Suzhou, indicated that city effluent might be a major source for DP contamination in the lake.