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261.
为了解城市景观水体中产超广谱β-内酰胺酶(extended-spectrum β-lactamases,ESBLs)细菌的种属分布和耐药特征,从西安市4处景观水体中分离出385株异养菌,利用双纸片协同试验筛选产ESBLs菌,并通过16S rDNA测序比对鉴定其种属.使用K-B纸片琼脂扩散法测定产ESBLs菌对氨苄西林、四环素、磺胺甲恶唑、环丙沙星和头孢唑肟的耐药表型.采用聚合酶链反应测定这些菌株是否携带β-内酰胺类耐药基因blaTEM、blaCTX-M和blaSHV以及I类整合酶基因intI.结果表明:从城市景观水体中分离出19株产ESBLs菌,在异养菌中的占比为4.94%.这些产ESBLs菌株共计6属10种,主要为大肠埃希氏菌.它们对氨苄西林、四环素和磺胺甲恶唑普遍耐药,多重耐药菌占比为57.89%.这些产ESBLs菌株中I类整合子检出率高达89.47%,但3种β-内酰胺酶耐药基因的检出率很低. 相似文献
262.
Stambuk-Giljanović N 《Environmental monitoring and assessment》2005,104(1-3):235-268
The purpose of this study was to monitor and record the specific characteristics and properties of most of the important water resources in Dalmatia located in Southern Croatia for a period of 5 years (1998–2002) according to established standards for drinking water. The paper presents a detailed account of their chemical content, the classification and the concentration of salts. The bacteriological pollution levels are indicated by the total coliform bacterial levels (MPN coli/100 mL). The water characteristics are expressed by coefficients, which represent the ratios between water ingredients. The Ca/Mg eq ratio, SO4/Cl eq ratio and K1, K2 for bicarbonate hardness were calculated. The hygienic characteristics of the water samples were expressed by the total coliform bacteria estimation (MPN coli/100 mL), the permanganate consumption (KMnO4) and biological oxygen demand (BOD5). Karst waters in Dalmatia are moderately hard, the SO4/Cl ratio is 0.38–1.6, non-corrosive (K1 lower than 0.2) and not significantly mineralised (< 500 mg/L minerals). Sulphate waters are generally hard, the SO4/Cl ratio is higher than 1.6, K1 is 0.2–0.65. Marine waters are quite hard or hard, particularly at the river estuaries, the SO4/Cl ratio is lower than 0.38, and K1 is higher than 0.65. The groundwater and springs in Dalmatia are less polluted than surface waters. A majority of these have a geometric average value of MPN coli < 150/100 mL of water observed in 24 of 42 locations studied. The highest bacteriological pollution was found in nine locations where MPN coli > 1000/100 mL and moderate pollution was found in nine locations where MPN coli is between 150 and 1000/100 mL of water. The physical and chemical parameters determined for the most sources in Dalmatia are safe below the international permissible limits. 相似文献
263.
Complex mixtures of toxic substances occurring in surface waters are difficult to characterise by chemical analyses because each compound occurs at a very low concentration and requires a specific analytical method to be identified. Ecotoxicological tests on water extracts can be used as a screening tool to evaluate quickly and simply the overall quality of a water body with regard to micropollutant contamination. In this work, a pre-concentration procedure based on solid-phase extraction (SPE), suitable for both biological testing and analytical determination, is proposed. The extraction procedure is an improved version of a methodology used to evaluate the toxicity of organic micropollutants occurring in surface waters. It offers the advantage of using disposable commercial cartridges, which are easier to manage than the columns prepared with macromolecular resins. Water extracts from two representative Italian rivers, characterised by a different gradient of potential contamination and prepared according to the new concentration techniques, are used. The acute toxicity of the water extracts is tested on Daphnia magna and the bioluminescence inhibition in Vibrio fischeri. Criteria based on the concentration factor (CF) are proposed for assessing the hazard to aquatic life due to the exposure to toxic substances in surface waters. The aim of hazard ranking is to focus analytical efforts towards those samples that show the highest toxic potential. 相似文献
264.
D. L. Anderson P. C. Rosendahl 《Journal of the American Water Resources Association》1998,34(2):235-249
ABSTRACT: South Florida and the Everglades have been under intensive development since 1850 by Federal and State governments who encouraged and financed extensive drainage and hydraulic changes, primarily for agricultural settlement. Agricultural development of the sugar industry in the northern Everglades adjacent to Lake Okeechobee rapidly progressed only after the 1900s. Political and resource management conflicts have arisen because policies which once favored development are now being reversed by policies and regulation efforts to restore and conserve natural ecosystems. Currently, the environmental and ecological impacts of agricultural land use adjacent to natural wtlands of the Everglades are being assessed. The objectives of this paper are: (1) to outline the historical development of south Florida and the sugar industry, (2) to relate this history to political and management policy changes occurring as it pertains to ecosystem restoration and the multiuser competition for water/land resources, and (3) to propose how integrated resource management might be utilized for a sustainable Everglades and south Florida. This paper outlines the historical paradox of urban settlement, land development, and agricultural production, with efforts in the recent decade to acquire, manage, and preserve land and water resources for natural areas conservation. Only though the use of integrated resource management will the defined resource conflicts be mediated. 相似文献
265.
IntroductionThereisconsiderableevidencethatpartitionbetweensolidandaqueousphasehasamajoreffectontheoccurrence,transport,fatean... 相似文献
266.
1991-1992年对重庆市郊若干酸化水体的生物待正与理化参数进行综合研究的结果表明,藻类的种类数、细胞密度、生物量和叶绿素a含量以及浮游动物的种类数等均与呈正相关,但与H+和总Al浓度呈负相关。浮游动物的个体密度在酸化水体中明显下降,但是鱼的捕食作用掩盖了其与上述化学参数之间的相关性。水体中H+和总Al浓度的增加在很大程度上对浮游生物产生了不利影响,水体的透明度、总Al.TP和SO与pH的相关性十分明显,r值分别为-0.6375、-0.6868、0.7561和0.7323。 相似文献
267.
268.
Davide?VioneEmail author Fabrizio?Merlo Valter?Maurino Claudio?Minero 《Environmental Chemistry Letters》2004,2(3):129-133
We show that the degradation of phenol by Fe(III) and hydrogen peroxide is faster in the presence of humic acids. This is most likely due to faster reduction of Fe(III)-humate complexes by H2O2/HO2·/O2–· when compared with Fe(III)-H2O complexes. The fact that humic acids, a major class of naturally occurring compounds, favour the Fenton reaction has great relevance in the field of water and soil decontamination, where organic compounds usually have a negative effect. Furthermore, it adds insight into the self-depuration processes of natural aquifers. 相似文献
269.
Hursthouse AS Matthews JM Figures JE Iqbal-Zahid P Davies IM Vaughan DH 《Environmental geochemistry and health》2003,25(2):171-203
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
270.
IntroductionHakataBayisasemi enclosedbay(from 33°34′Nto 33°41′Nandfrom 1 30°1 3′Eto 1 30°2 6′E)locatedatthenorthsideofKyushuIsland ,Japan .ThelengthandwidthofHakataBayisabout2 0kmand 1 0kmrespectively .Thesurfaceareaisabout 1 33km2 andthemeanwaterdepthisabout1 0 .5m .Thebaymout… 相似文献