Influence of solvent and soil type on the pressurised fluid extraction of PAHs

Pressurised fluid extraction (PFE) of polycyclic aromatic hydrocarbons (PAHs) from a certified reference material (CRM) 524 has been firstly optimised following a central composite design. The instrumental parameters of the PFE (pressure, temperature, extraction time and number of solvent cycles) were studied in order to obtain maximum extraction yields. Neither pressure nor extraction time or temperature seemed to have any significant effect on the extraction yield, therefore one extraction cycle was enough to exhaustively extract all the PAHs from CRM 524. Once the instrumental conditions were established, the extraction yields obtained with eight different solvents or solvent mixtures [acetone, dichloromethane, acetonitrile, acetone-dichloromethane (1 + 1 v/v), acetone-isohexane (1 + 1 v/v), isohexane, methanol and toluene] from the CRM 524 were compared and showed that the best recoveries were obtained with acetone-isohexane (1 + 1 v/v). Finally, the effect of sand, silt, clay and the organic matter content of soil was investigated with respect to recovery of PAHs by PFE with different solvents or solvent mixtures for aged soil samples. In this case, eight soils with different sand, silt, clay and organic matter contents were slurry spiked with PAHs and aged for 19 days. Three aliquots of each slurry spiked soil were extracted with the previously mentioned solvents and the results were studied by means of principal component analysis (PCA) of the whole data set (soil composition, solubility parameter of the solvent and recoveries of all PAHs) and partial least squares (PLS). Clay and organic matter content and the squared solubility parameter have the highest correlation with the recovery of PAHs from soil samples.     

Mitigating exotic impacts: restoring deer mouse populations elevated by an exotic food subsidy.

The threat posed by exotic organisms to native systems has led to extensive research on exotic invaders, yet management of invasives has progressed relatively slowly. This is partly due to poor understanding of how exotic species management influences native organisms. To address this shortfall, we experimentally evaluated the efficacy of an invasives management tool for restoring native deer mouse (Peromyscus maniculatus) populations elevated by exotic species. The exotic insects, Urophora spp., were introduced in North America for biological control of the Eurasian invader, spotted knapweed (Centaurea maculosa), but instead of controlling C. maculosa, Urophora have become an important food resource that doubles P. maniculatus populations, with substantial indirect effects on other organisms. We hypothesized that herbicide suppression of Urophora's host plant would reduce the Urophora food resource and restore P. maniculatus populations to natural levels. Prior to treatment, mouse populations did not differ between controls and treatments, but following treatment, P. maniculatus were half as abundant where treatment reduced Urophora. Peromyscus maniculatus is insensitive to direct herbicide effects, and herbicide-induced habitat changes could not explain the P. maniculatus response. Treatment-induced reductions of the Urophora food resource offered the most parsimonious explanation for the mouse response: Multistate mark-recapture models indicated that P. maniculatus survival declined where Urophora were removed, and survival rates were more correlated with variation in population size than movement rates. Other demographic and reproductive parameters (sex ratios, reproductive status, pregnancy rates, and juvenile recruitment) were unaffected by treatment. These results suggest the Urophora biocontrol elevated P. maniculatus survival, and the herbicide treatment restored mouse populations by removing the exotic food and reducing survival. This work illustrates the importance of mechanistic understandings of community and population ecology for improving invasive species management.     

Analysis of two-state multivariate phenotypic change in ecological studies

Analyses of two-state phenotypic change are common in ecological research. Some examples include phenotypic changes due to phenotypic plasticity between two environments, changes due to predator/non-predator character shifts, character displacement via competitive interactions, and patterns of sexual dimorphism. However, methods for analyzing phenotypic change for multivariate data have not been rigorously developed. Here we outline a method for testing vectors of phenotypic change in terms of two important attributes: the magnitude of change (vector length) and the direction of change described by trait covariation (angular difference between vectors). We describe a permutation procedure for testing these attributes, which allows non-targeted sources of variation to be held constant. We provide examples that illustrate the importance of considering vector attributes of phenotypic change in biological studies, and we demonstrate how greater inference can be made than by evaluating variance components with MANOVA alone. Finally, we consider how our method may be extended to more complex data.     

拉萨市垃圾焚烧飞灰重金属特性分析及风险评价

焚烧是城市垃圾处理主流技术,飞灰作为垃圾焚烧主要污染物成为垃圾焚烧污染控制关键环节。采集拉萨市垃圾焚烧发电厂飞灰样品,分析了飞灰中重金属含量及浸出毒性特征,并采用改进的潜在风险评价法及健康风险评价法评价飞灰中重金属的潜在风险。结果表明:拉萨市飞灰中重金属含量较高,且Pb的浸出浓度超过GB 5085.3-2007《危险废物鉴别标准 浸出毒性鉴别》浸出液最高允许值的16倍。污染评价结果表明,拉萨市飞灰中Pb对环境具有极强的污染风险。健康风险评价结果表明,飞灰中重金属对人体的致癌风险在可接受范围内,但其非致癌风险值高于美国国家环境保护局(EPA)推荐的非致癌风险值(HQ ≤ 1),对人体具有较高的非致癌风险。其中 Pb对成人和儿童的非致癌风险值分别为3.8975和9.7458,是非致癌风险的主要贡献者。     

成都市臭氧污染特征及气象成因研究

为研究成都市臭氧(O3)污染特征及其气象成因,对2014—2016年成都市6个国控环境监测站和同期气象台站逐小时地面观测数据进行了研究分析.结果表明:近4年来成都市O3污染日趋严重,O3年均浓度不断上升,较2013年升高51.2μg·m-3.O3浓度存在明显的季节变化特征:春、夏季较高,秋、冬季则较低,且各季节O3浓度变化具有很强的长期持续性特征.O3浓度日变化特征呈明显的单峰型分布,8:00出现最低值,15:00—16:00出现峰值,超标时段主要出现在13:00—17:00.O3浓度变化与紫外辐射、气温呈正相关关系,与相对湿度、风速呈负相关关系,且当紫外辐射大于12 MJ·m-2、气温高于15℃、相对湿度低于65%、西风或偏东北风控制时,成都市容易发生高浓度O3污染.     

Predicting richness effects on ecosystem function in natural communities: insights from high-elevation streams

. Despite the increased complexity of experimental and theoretical studies on the biodiversity-ecosystem functioning (B-EF) relationship, a major challenge is to demonstrate whether the observed importance of biodiversity in controlled experimental systems also persists in nature. Due to their structural simplicity and their low levels of human impacts, extreme species-poor ecosystems may provide new insights into B-EF relationships in natural systems. We address this issue using shredder invertebrate communities and organic matter decomposition rates in 24 high-altitude (3200-3900 m) Neotropical streams as a study model. We first assessed the effects of stream characteristics and shredder diversity and abundance on organic matter decomposition rates in coarse- and fine-mesh bags. We found the interaction term shredder richness x shredder abundance had the most significant impact on decomposition rates in the field, although water discharge may also play a role locally. We also examined the relative contribution of the three most abundant shredders on decomposition rates by manipulating shredder richness and community composition in a field experiment. Transgressive overyielding was detected among the three shredder species, indicating complementary resource use and/or facilitation. By integrating survey and experimental data in surface response analyses we found that observed B-EF patterns fit those predicted by a linear model that described litter decomposition rates as a function of increasing shredder richness and the relative abundance of the most efficient shredders. Finally, the validity of our approach was tested in a broader context by using two independent but comparable data sets from 49 French and Swedish streams showing more complex shredder community structure. Results revealed that richness and identity effects on decomposition rates were lost with increasing shredder community complexity. Our approach of combining experimental and empirical data with modeling in species-poor ecosystems may serve as an impetus for new B-EF studies. If theory can explain B-EF in low-diversity ecosystems, it may also have credibility in more complex ones.