Equilibrium partitioning theory to predict the sediment toxicity of the anionic surfactant C(12)-2-LAS to Corophium volutator

The study of the effect of the sorption of linear alkylbenzene sulfonates (LAS) on the bioavailability to marine benthic organisms is essential to refine the environmental risk assessment of these compounds. According to the equilibrium partitioning theory (EqP), the effect concentration in water-only exposure will be similar to the effect concentration in the sediment pore water. In this work, sorption and desorption experiments with two marine sediments were carried out using the compound C₁₂-2-LAS. The effect of the sediment sorption on the toxicity of benthic organisms was studied in water-only and in sediment bioassays with the marine mud shrimp Corophium volutator. In addition, three common spiking methods were tested for its application in the toxicity tests, as well as the stability of the surfactant during the water-only and sediment-water test duration. LC50 values obtained from water-only exposure showed a good correspondence with the pore water concentrations calculated from the sorption and desorption isotherms in the spiked sediments.     

DGT和CaCl2提取下冶炼场地及周边土壤Cd固液分配特征

通过梯度扩散薄膜(DGT)和CaCl₂等提取方法,研究了典型冶炼场地及周边多种类型土壤中Cd有效态含量和固液分配特征,并构建回归预测模型.结果表明:场地渣土混合土壤、林地表层和深层土壤中Cd有效态含量较高,DGT提取结果分别为23.2,1.90和2.53μg/kg,农田深层土壤、杂填土和素填土较低,分别为0.03, 0.05和0.03μg/kg.土壤Cd固液分配系数(Kd)在杂填土、素填土、渣土混合土壤中最高,黏土、农田土壤次之,全风化土和林地土壤最低.总体上DGT测定的Kd值高于Ca Cl₂测定结果,CaCl₂土液比、提取液pH值显著影响Kd值结果(P<0.05). CaCl₂提取结果能够通过线性回归有效预测DGT测定的K_d (R²=0.89～0.93).     

Interpreting beta‐diversity components over time to conserve metacommunities in highly dynamic ecosystems

The concept of metacommunity (i.e., a set of local communities linked by dispersal) has gained great popularity among community ecologists. However, metacommunity research mostly addresses questions on spatial patterns of biodiversity at the regional scale, whereas conservation planning requires quantifying temporal variation in those metacommunities and the contributions that individual (local) sites make to regional dynamics. We propose that recent advances in diversity‐partitioning methods may allow for a better understanding of metacommunity dynamics and the identification of keystone sites. We used time series of the 2 components of beta diversity (richness and replacement) and the contributions of local sites to these components to examine which sites controlled source‐sink dynamics in a highly dynamic model system (an intermittent river). The relative importance of the richness and replacement components of beta diversity fluctuated over time, and sample aggregation led to underestimation of beta diversity by up to 35%. Our literature review revealed that research on intermittent rivers would benefit greatly from examination of beta‐diversity components over time. Adequately appraising spatiotemporal variability in community composition and identifying sites that are pivotal for maintaining biodiversity at the landscape scale are key needs for conservation prioritization and planning. Thus, our framework may be used to guide conservation actions in highly dynamic ecosystems when time‐series data describing biodiversity across sites connected by dispersal are available.     

河流沉积物重金属污染质量控制基准的研究 Ⅱ.相平衡分配方法(EqP)

以重金属污染严重的江西乐安江表层沉积物为对象，利用热力学相平衡分配法（ＥｑＰ）和相关基础数据库，研究探讨了该流域沉积物中重金属污染的数值型质量控制基准（ＳＱＣ）。结果表明，铜矿采矿活动导致某些江段沉积物中铜实际污染程度远高于相应的ＳＱＣ水平。另外，由于沿江中、小工矿企业废水的随意排放，同样造成附近沉积物中铅、锌、铬等重金属含量不同程度地超出各自的基准数值。此ＳＱＣ的建立为制订该流域沉积物质量管理标     

关于成矿流体地球化学研究的几个问题

成矿流体地球化学是当前正蓬勃发展的流体地质学研究的一个重要分支。本文对八十年代以来国际上关于成矿流体地球化学研究的几个问题做了阐述，涉及到元素在熔体－溶液平衡体系中的分配、热水溶液系统中成矿元素的配合物形式及其主要影响因素，金属从成矿流体中沉淀机理研究等。提出了在成矿流体地球化学研究方面应重视的问题。     

Environmental control and spatial structure in ecological communities: an example using oribatid mites (Acari,Oribatei)

We have recently proposed to use partial canonical ordinations to partition the variation of species abundance data into four additive components: environmental at a local scale, the spatial component of the environmental influence, pure spatial, and an undetermined fraction. By means of an example, we show how to use the information contained in these fractions to provide better insight into the data. In particular, the interpretation is assisted by separately mapping the various canonical axes and relating them to possible generating processes. We derive a general framework for the causal interpretation of the various fractions of this partition, which includes the environmental and the biotic control models, as well as historical dynamics.Daniel Borcard is research associate in animal ecology at Universite de Neuchâtel, Switzerland. He is interested in soil ecology, and presently working on fundamental and applied projects dealing with peat bog ecology and protection, community succession dynamics, as well as effects of agriculture on mite and insect communities. In order to develop the statistical tools necessary for these projects, he also works in collaboration with Pierre Legendre on modeling the spatial structure of ecological communities. $Pierre Legendre is professor of quantitative biology at Universite de Montreal. He is a former Killam Research Fellow (1989–91), and a member of the Royal Society of Canada since 1992. He is the author of some 100 refereed articles, over 250 papers presented at scientific meetings and research seminars, dealing with numerical ecology, community ecology, environmental assessment and spatial analysis, and textbooks (in French and English) on numerical ecology. During the past 5 years, he served as the Secretary-Treasurer of the International Federation of Classification Societies. *We thank Dr V.M. Behan-Pelletier, of Agriculture Canada, for her help in the identification of the Oribatid mites, and Mrs Lucie Fortin and Dr P. Neumann, Universite de Montreal, for their identifications of the Sphagnum species. This research was carried out during tenure of a Postdoctoral Fellowship of the Swiss National Foundation for Scientific Research by D. Borcard, and of a Killam Research Fellowship of the Canada Council by P. Legendre. It was also supported by NSERC grant No. A7738 to P. Legendre. This is contribution No. 392 of the Groupe d'Écologie des Eaux douccs, Universite de Montreal. The authors wish to dedicate this paper with gratitude to Mr Alain Vaudor, computer analyst in Pierre Legendre's laboratory, who has largely contributed to the planning of this research. Mr Vaudor passed away on October 31, 1991, at age 46. The package for multivariate and spatial data analysis that he has produced during his computer scientist career is available to researchers from P. Legendre.     

Effects of male removal on female foraging behavior in the Eurasian treecreeper

In old, spruce-dominated forests of central Finland, Eurasian treecreepers Certhia familiaris divide their territories spatially during the breeding season. Females forage primarily on the upper parts of the tree trunks, while males use the lower parts of the tree trunks. In this study we removed males from eight territories in the early nestling period to see if the mate's absence would change the foraging patterns of the resident female. Widowed females foraged at lower heights, thus behaving more like paired males. These females also spent less time on each tree and on each foraging bout than did paired females. We conclude that male removal facilitated the change in a female's foraging niche and foraging time at the trees. Females may re-optimize their foraging site selection owing to the absence of dominant males and a consequent need to increase their parental care. Behavioral plasticity may be the mechanism of niche partitioning between the sexes in this species. Received: 28 June 1996 / Accepted after revision: 27 March 1997     

Reverse quantitative structure-activity relationship for modelling the sorption of esfenvalerate to dissolved organic matter. A multivariate approach

The sorption of the pyrethroid, esfenvalerate, to the dissolved and/or dispersed fraction of eight different natural humic compounds has been investigated. The dissolved organic matters (DOMs) included in this study originate from ground water, soil pore water, and surface waters. Sorption was modelled at DOM concentration levels where equilibrium partitioning of esfenvalerate between DOM and the aqueous bulk phase prevails. The inherent characteristics of the eight different humic materials, quantified in the preceding paper by Thomsen et al. (2002, this issue (PII: S0045-6535(02)00335-1)), have been used as explanatory variables for modelling this equilibrium partitioning. Using a reverse QSAR approach based on by projection-into-latent-structure regression (PLS-R) inherent sorbent properties determining for the sorption affinity of esfenvalerate to DOM were analysed. For all humic substances a decrease in the DOM-normalised equilibrium-partitioning coefficient, K_DOM, with increasing concentration of DOM was observed. Significant variations in K_DOM values, as function of the inherent characteristics of the individual humic substances, were found at DOM concentrations of 75 and 100 ppm, respectively. The latter is a strong indication of variations in sorption mechanisms of esfenvalerate to DOM of varying inherent properties. Groupings in the principal property space quantifying DOMs may indicate that separate models are needed for quantifying the equilibrium partitioning to different classes of DOM.     

A tool for estimating the contribution of water-soluble organic compounds to the particle mass and condensational growth in the atmosphere

In this theoretical investigation, we elucidated several factors governing the ability of organic, water-soluble vapours to participate into either the secondary organic aerosol formation or particle condensational growth in the atmosphere. The corresponding requirements for physico-chemical properties of the vapour were estimated. These estimates were also compared with the properties of several difunctional carboxylic acids identified in the atmosphere. Our analysis indicates that while many of the considered compounds are expected to contribute to the total particle mass in the atmosphere, their role in particle condensational growth process remains uncertain. This uncertainty emerges from the fact that the saturation ratio of an organic vapour does not alone determine its ability to act as a “nonvolatile” compound. Instead, the hygroscopic and chemical properties of the vapour, as well as the particle pH and size, have also to be taken into account.     

Unique products from the reaction of naphthalene with the hydroxyl radical

Many of the products of the reaction of naphthalene (Naph) with the OH radical in a reaction chamber were identified. Previously unidentified products included 1,2-naphthoquinone (NQ), oxygenated indenes and benzopyrones. Possible pathways for the formation of 1,2-NQ and 1,4-NQ are proposed. In the chamber reactions, more 1,2-NQ than 1,4-NQ partitioned to the particle phase. From this result we infer that, in the atmosphere, the percentage of 1,2-NQ in the particle phase should be greater than that for the 1,4-NQ. Because both of these compounds are considered to be toxic, and since they appear in both the gas and particle phases in the reaction chamber, and by implication in the atmosphere, it is considered important that both the gas and particle phases of these two compounds should be measured to assess their impact on human health.