The purpose of this study was to evaluate photodegradabilities of the following new low-nitrogen chelating agents: N-bis[(carboxymethoxy)ethyl]glycine (compound 1), N-bis[(1,2-dicarboxyethoxy)ethyl]glycine (compound 2) and N-bis[(1,2-dicarboxyethoxy)ethyl]aspartic acid (compound 3). At first photodegradation of these chelating agents as uncomplexed Na-compound 1–3 and Cu(II) complexes were tested, both in lake and distilled water, by exposing them to near-UV region radiation at the range of 315–400 nm. Uncomplexed Na-compounds 2 and 3 were selected to sunlight exposure experiments carried out in lake and distilled water. Compound 3 was also tested in sunlight as Cu and Ca complexes in both solutions. Photodegradation of Na6-compound 3 in distilled water was studied by exposing it to radiation at the wavelength of 253.7 nm. Photodegradation products were analysed by means of GC-MS (gas chromatography with mass selective detector).
The results demonstrated that compound 1 was quite photostable even as Cu complex while compounds 2 and 3 were found to be photodegradable. Over 90% reduction of compound 3 was achieved during one week and 80% reduction of compound 2 in two weeks' time when they were added as Na salt to lake water and exposed to sunlight. Compound 3 as Cu complex degraded totally in the sunlight in less than one week. In the case of compound 3, the degradation rate decreased depending on the counter cation in the order Cu > Na Ca. The study demonstrated that photodegradation of Na6-compound 3 does not result in total mineralization of the compound. A photodegradation pathway for Na6-compound 3 is proposed. 相似文献
Detailed surveys of intertidal sediments have been performed along the north and south shores of the Inner Clyde estuary, UK. Surface sediment data reveal significant spatial variation in Cr content and an association with major sediment characteristics and location within the estuary. Depth variation for Cr and other heavy metals cannot be explained by variation in major geochemical controls such as grain size and organic matter and highlights the impact of historical contamination on sediment quality. These elevated levels at depth may still have environmental impact through redox-reactivity, in association with iron and manganese. Sequential extraction of sediments and pore water analysis of Cr(VI) and Cr(III) provide detailed information on release potential from the sediments. The implication of Cr mobility for biota in the estuary has been assessed by the analysis of a common marine bivalve, Mytilus edulis (Blue Mussel) and a burrowing polychaete, Nereis diversicolor (rag worm) from a number of survey sites. Bioconcentration factors for Mytilus indicate that the weakly held portion of sediment Cr is available for uptake and in the case of Nereis, bioaccumulation appears to be inhibited by sediment organic matter. 相似文献
Summary. Domestic apple (Malus pumila)- and hawthorn (Crataegus sp.)-infesting races of Rhagoletis pomonella, Walsh (Diptera: Tephritidae) provide an excellent model to examine the role that host plant specificity plays during sympatric
speciation (i.e., divergence in the absence of geographic isolation). Previous work has shown that these races differ in their propensities
to accept apple and hawthorn fruits in behavioral choice assays, and that this discrimination translates into "host fidelity"
in the field (i.e., apple flies tend to mate on and oviposit into apples and hawthorn flies on hawthorns). ?We present the results of a study
examining possible physiological factors contributing to host choice differences in R. pomonella. We tested whether apple and hawthorn flies differ in their electroantennogram (EAG) responses to biologically relevant volatile
compounds emitted from apples and hawthorns. Significant differences were found in the relative EAG responses of apple and
hawthorn flies to host fruit compounds at five of six paired study sites across the eastern United States. The geographic
pattern of EAG variation was complex, however, with local populations of apple and hawthorn flies tending to be more similar
to one another than to flies of the same race at distant sites. This pattern was largely due to EAG responses for several
compounds showing longitudinal or latitudinal clines, the latitudinal clines being similar to those observed for allozyme
loci in the host races. We also found evidence for sex-related differences, as males tended to have higher mean EAG responses
to compounds than females. Host-associated differences were therefore nested within geographic and sex-related differentiation
in R. pomonella.?Further behavioral studies are needed to distinguish whether the EAG differences are responsible for, as opposed to being
a consequence of, host-plant fidelity and adaptation. Crosses are also required to establish a genetic basis for the EAG responses,
although we did find significant correlations between EAG scores for several compounds and the allozymes NADH-Diaphorase-2
and Hydroxyacid dehydrogenase at one of the study sites. Questions therefore remain concerning the evolutionary significance
of the EAG response differences between apple and hawthorn fly races. Nevertheless, these differences raise the possibility
that antennal responses to fruit-related volatile compounds contribute to host plant discrimination in R. pomonella. Regardless, the EAG responses represent another set of traits, in addition to diapause/eclosion time phenotypes and allozyme
frequencies, differing between apple and hawthorn host races of R. pomonella.
Received 17 March 1998; accepted 21 September 1989. 相似文献
采用顺序提取的方法对南京市典型河流和湖泊水域的沉积物进行重金属化学形态研究,分析了Cu、Zn、Pb、Cd、Ni、Cr 6种重金属元素在不同水体沉积物中各个形态赋存的含量分布特征。结果表明,6种元素生物有效性排序为:Cd PbZn Cu Ni Cr,其中Cd和Pb以弱酸提取态和可还原态为主要存在形态,其不仅会对上覆水体产生二次污染,对水生动植物也具有较强的危害性。另外,通过结果间接反映出受人类生产生活影响大的水体,受污染的程度更高,各种金属元素赋存的形态也更易迁移转化,在环境治理方面更应受到重视。 相似文献