高效液相色谱与电感耦合等离子体质谱联用测定矿泉水中的三价铬与六价铬

由于铬在各种工业生产中应用广泛,加之来源于自然界中铬的腐蚀,使得铬在环境中普遍存在.因此,对环境、食品以及水资源中的铬进行监测,并以此评价由于铬暴露所造成的潜在危害是至关重要的.Cr(Ⅲ)和Cr(Ⅵ)在价态上的差异导致其在毒性、反应活性以及生物可利用性方面存在显著不同,因此,对于铬的价态区分显得十分重要.Cr(Ⅲ)是人体的必需元素,它在葡萄糖、蛋白质以及脂肪代谢等生命活动中扮演着很重要的角色,对于成人而言,Cr(Ⅲ)的每日推荐摄取量为50到200μg;急性动物实验表明,Cr(Ⅲ)若经口摄入,会产生中等毒性,而对于Cr(Ⅵ),由于其强的氧化性,误食或者吸入后将对人体产生非常大的毒害,有证据表明,一定量的Cr(Ⅵ)暴露能刺激皮肤、鼻、眼睛以及咽喉;严重时会造成肺和肾脏循环系统以及神经组织的损害,甚至引起呼吸系统方面的癌症,鉴于此,世界卫生组织(WHO)推荐饮用水中Cr(Ⅵ)的最大允许浓度为0.05 mg·l-1,美国环境保护署(EPA)和欧盟(EU)各自颁布法令规定饮用水中总铬含量最大容许浓度分别为0.1和0.05 mg·l-1.     

Ocean acidification: assessing the vulnerability of socioeconomic systems in Small Island Developing States

Regional Environmental Change - Ocean acidification poses an increasing threat to marine ecosystems and also interacts with other anthropogenic environmental drivers. A planned response strategy...     

Watershed vulnerability predictions for the Ozarks using landscape models

Forty-six broad-scale landscape metrics derived from commonly used landscape metrics were used to develop potential indicators of total phosphorus (TP) concentration, total ammonia (TA) concentration, and Escherichia coli bacteria count among 244 sub-watersheds of the Upper White River (Ozark Mountains, USA). Indicator models were developed by correlating field-based water quality measurements and contemporaneous remote-sensing-based ecological metrics using partial least squares (PLS) analyses. The TP PLS model resulted in one significant factor explaining 91% of the variability in surface water TP concentrations. Among the 18 contributing landscape model variables for the TP PLS model, the proportions of a sub-watershed that are barren and in human use were key indicators of water chemistry in the associated sub-watersheds. The increased presence and reduced fragmentation of forested areas are negatively correlated with TP concentrations in associated sub-watersheds, particularly within close proximity to rivers and streams. The TA PLS model resulted in one significant factor explaining 93% of the variability in surface water TA concentrations. The eight contributing landscape model variables for the TA PLS model were among the same forest and urban metrics for the TP model, with a similar spatial gradient trend in relationship to distance from streams and rivers within a sub-watershed. The E. coli PLS model resulted in two significant factors explaining 99.7% of the variability in E. coli cell count. The 17 contributing landscape model variables for the E. coli PLS model were similar to the TP and TA models. The integration of model results demonstrates that forest, riparian, and urban attributes of sub-watersheds affect all three models. The results provide watershed managers in the Ozark Mountains with a broad-scale vulnerability prediction tool, focusing on TP, TA, and E. coli, and are being used to prioritize and evaluate monitoring and restoration efforts in the vicinity of the White River, a major tributary to the Mississippi River and Gulf of Mexico.     

Assessing Landscape Condition Relative to Water Resources in the Western United States: A Strategic Approach

The Environmental Monitoring and Assessment Program (EMAP) is proposing an ambitious agenda to assess the status of streams and estuaries in a 12-State area of the western United States by the end of 2003. Additionally, EMAP is proposing to access landscape conditions as they relate to stream and estuary conditions across the west. The goal of this landscape project is to develop a landscape model that can be used to identify the relative risks of streams and estuaries to potential declines due to watershed-scale, landscape conditions across the west. To do so, requires an understanding of quantitative relationships between landscape composition and pattern metrics and parameters of stream and estuary conditions. This paper describes a strategic approach for evaluating the degree to which landscape composition and pattern influence stream and estuary condition, and the development and implementation of a spatially-distributed, landscape analysis approach.     

Landscape Correlates of Breeding Bird Richness Across the United States Mid-Atlantic Region

Using a new set of landscape indicator data generated by the U.S.EPA, and a comprehensive breeding bird database from the National Breeding Bird Survey, we evaluated associations between breeding bird richness and landscape characteristics across the entire mid-Atlantic region of the United States. We evaluated how these relationships varied among different groupings (guilds) of birds based on functional, structural, and compositional aspects of individual species demographics. Forest edge was by far the most important landscape attribute affecting the richness of the lumped specialist and generalist guilds; specialist species richness was negatively associated with forest edge and generalist richness was positively associated with forest edge. Landscape variables (indicators) explained a greater proportion of specialist species richness than the generalist guild (46% and 31%, respectively). The lower value in generalists may reflect finer-scale distributions of open habitat that go undetected by the Landsat satellite, open habitats created by roads (the areas from which breeding bird data are obtained), and the lumping of a wide variety of species into the generalist category. A further breakdown of species into 16 guilds showed considerable variation in the response of breeding birds to landscape conditions; forest obligate species had the strongest association with landscape indicators measured in this study (55% of the total variation explained) and forest generalists and open ground nesters the lowest (17% of the total variation explained). The variable response of guild species richness to landscape pattern suggests that one must consider species' demographics when assessing the consequences of landscape change on breeding birds.     

Inhibition of glycosidases by Lepidoptera; roles in the insects and leads to novel compounds?

Summary Glycosidase inhibitors are widespread in plants and can be sequestered by Lepidoptera, for which they can presumably serve as defences by making the insects indigestible to a range of potential predators. As a result of this study of eight British species of moth and butterfly it was found that glycosidase inhibitors in the insects could then be detected in the larval food plants which were not previously known to contain them; however, some were only detectable in the plants after concentration. In some cases the inhibition of specific glycosidases by Lepidoptera was detected even though the insects had not apparently acquired them from their food plants. Inhibition of-N-acetylglucosaminidase was observed in most of the adult Lepidoptera analysed but further work is required to identify the inhibitors, though they are likely to be nitrogen-containing compounds. Weak anti-HIV activity was also observed in the glycosidase-inhibiting fractions ofAcherontia atropos and the plantUrtica dioica.     

Methodologies for determination of antimony in terrestrial environmental samples

Methodologies for the environmental analysis of total antimony and aqueous chemical speciation are critically reviewed, including preparation techniques for aqueous and solid matrices and the determination of solid state partitioning and recommendations are given for future research directions. Concentrations of total antimony commonly present in aqueous and solid environmental samples are readily determined using present day analytical techniques. This has resulted primarily from technological advances in microwave digestion for solid matrices and the development of plasma based analyte detection systems. ICP-AES and ICP-MS techniques are both utilised for the environmental analysis of total antimony concentrations. However, ICP-MS is increasingly favoured as a result of reduced spectral interferences and the potential for analyte detection in the pg mL(-1) range. Determination of aqueous antimony speciation presents a number of complex analytical challenges and highly selective separation and identification techniques are required prior to detection. The majority of published techniques including common applications of hydride generation are insufficiently selective for the determination of intrinsic chemical speciation and often only oxidation state data are obtained. The recent in-line applications of HPLC-ICP-MS offer the potential for highly selective separations of aqueous antimony species and determination of detailed chemical speciation data. However, considerable development work is required to optimise chromatographic separations and identify uncharacterised species resident in environmental systems. Analytical techniques to aid the determination of antimony's associations with solid environmental matrices include the application of chemical extraction procedures and leaching experiments. To date, this area of analytical research has received little attention and further studies are required to elucidate this aspect of antimony's environmental chemistry.     

Life in extreme environments: survival strategy of the endolithic desert lichen Verrucaria rubrocincta

Verrucaria rubrocincta Breuss is an endolithic lichen that inhabits caliche plates exposed on the surface of the Sonoran Desert. Caliche surface temperatures are regularly in excess of 60 degrees C during the summer and approach 0 degrees C in the winter. Incident light intensities are high, with photosynthetically active radiation levels typically to 2,600 micromol/m(2) s(-1) during the summer. A cross-section of rock inhabited by V. rubrocincta shows an anatomical zonation comprising an upper micrite layer, a photobiont layer containing clusters of algal cells, and a pseudomedulla embedded in the caliche. Hyphae of the pseudomedulla become less numerous with depth below the rock surface. Stable carbon and oxygen isotopic data for the caliche and micrite fall into two sloping, well-separated arrays on a delta(13)C-delta(18)O plot. The delta(13)C(PDB) of the micrite ranges from 2.1 to 8.1 and delta(18)O(SMOW) from 25.4 to 28.9, whereas delta(13)C(PDB) of the caliche ranges from -4.7 to 0.7 and delta(18)O(SMOW) from 23.7 to 29.2. The isotopic data of the micrite can be explained by preferential fixing of (12)C into the alga, leaving local (13)C enrichment and evaporative enrichment of (18)O in the water. The (14)C dates of the micrite range from recent to 884 years b.p., indicating that "dead" carbon from the caliche is not a significant source for the lichen-precipitated micrite. The endolithic growth is an adaptation to the environmental extremes of exposed rock surfaces in the hot desert. The micrite layer is highly reflective and reduces light intensity to the algae below and acts as an efficient sunscreen that blocks harmful UV radiation. The micrite also acts as a cap to the lichen and helps trap moisture. The lichen survives by the combined effects of biodeterioration and biomineralization. Biodeterioration of the caliche concomitant with biomineralization of a protective surface coating of micrite results in the distinctive anatomy of V. rubrocincta.     

Phosphorus and nitrogen in soil, plants, and overland flow from sheep-grazed pastures fertilized with different rates of superphosphate

Eutrophication of waterways through delivery of phosphorus (P) and nitrogen (N) from farmland is a problem in many countries. Loss of nutrients from grazed grassland via overland flow is well demonstrated, but the sources of these nutrients and the processes controlling their mobilization into water are not well understood. Much of the nutrient loss in overland flow from grazed pastures may be due to generally increased fertility of the soil–plant system (i.e. background or ‘systematic’ nutrient loss) rather than to immediate loss after fertilizer application [Nash, D., Clemow, L., Hannah, M., Barlow, K., Gangaiya, P., 2005. Modelling phosphorus exports from rain-fed and irrigated pastures in southern Australia. Aust. J. Soil Res. 43, 745–755]. The main aim of this study was to measure the effects of long-term (25 years) superphosphate (Ca(H₂PO₄)₂ + 2CaSO₄) fertilizer application (0–23 kg/(ha year)) on P and N in soil, plants, and potential background P and N movement in overland flow (generated using a rainfall simulator) from sheep-grazed pastures in southern Australia. Measurements were taken in autumn, under dry soil conditions, and in winter, under wet soil conditions, 12 and 15 months after the last fertilizer applications, respectively. Superphosphate application caused a strong increase in plant P, soil total P, Olsen P, and Colwell P; and a weaker increase in plant N, soil total N, and inorganic N (ammonium and nitrate). Soil P and N were concentrated in the surface 25 mm of soil. Soil water-extractable P, calcium chloride-extractable P, and calcium chloride organic P were in general only poorly associated with fertilizer application. The concentration of P and, to a lesser extent, the concentration of N in overland flow increased with increasing fertilizer application and showed strong seasonal differences (0.06–0.77 mg P/L and 0.6–5.5 mg N/L in autumn; 0.04–0.20 mg P/L and 0.4–1.7 mg N/L in winter). The P in overland flow was predominantly dissolved reactive P in autumn and particulate P in winter. The N in overland flow contained significant proportions of dissolved organic N, dissolved inorganic N (ammonium and nitrate), and particulate N. The concentrations of P and N in overland flow usually exceeded State water quality targets (<0.04 mg P/L and <0.90 mg N/L), suggesting that background losses of nutrients from these pasture systems could contribute to the eutrophication of waterways.