Acute toxicity of ammonia to a freshwater teleost,Labeo bata larvae

Ammonia toxicity tests were performed with Labeo bata (bata) larvae of three different size groups. One hundred percent survival of larvae (500.0?±?4.0?mg) was recorded when exposed to ammonia concentrations of 1.0–13.56?mg?L^?1 at 96?h of exposure. Bata larvae exposed to ammonia concentrations of 15.8–25?mg?L^?1 showed 10–74% mortalities. The 96?h LC₅₀ value for 200 (±5), 250 (±2) and 500 (±4) mg bata larvae were 11.5, 16.8 and 22.5?mg?L^?1 un-ionised ammonia concentrations, respectively. When fish were exposed to different doses of ammonia, behavioural changes immediately occurred even at the lowest dose. At first, the fish became hyperexcitable, the skin darkened and they showed an increased ventilation frequency, fish behaviour became normal, 24?h after exposure. A 96?h LC₅₀ value of un-ionised ammonia showed direct relationship with the increasing size of bata larvae.     

Statistical analysis of bioassays,based on hazard modelling

A stochastic model is proposed to describe time-dependent lethal effects of toxic compounds. It is based on simple mechanistic assumptions and provides a measure for the toxicity of a chemical compound, the so-called killing rate. The killing rate seems a promising alternative for the LC50. The model also provides the no-effect level and the LC50, both as a function of exposure time. The model is applied to real data and to simulated data.     

Environmental quality criteria: Some considerations

The physicochemical characteristics of the recipient environment into which chemical contaminants are deposited may influence their chemical speciation, mobility, bioavailability, and toxicity. In formulating Water Quality Criteria, the Environmental Protection Agency of the United States (EPA) considered the modifying effect of abiotic environmental factors on pollutant toxicity in an innovative regulatory approach. Scientific knowledge of the interactions and correlations between pollutant toxicity and abiotic factors remains limited. Recognition of the influence of the physicochemical characteristics of the recipient environment on pollutant toxicity has implications for the eventual formulation of regional, rather than uniform and national, criteria. In addition, in developing Water Quality Criteria that incorporate the effects of pollutants on aquatic life, EPA primarily focused on toxicity to aquatic animals and plants (including unicellular algae). The effects of pollutants on microbe-mediated ecological processes that are necessary for maintaining the state and quality of the ecosphere (such as biogeochemical cyclings, litter decomposition, and mineralization) were not included in the formulation of the Water Quality Criteria. To facilitate the recognition and quantification of adverse effects of pollutants on these ecological processes, the development of a computation, termed the ecological dosage 50% (EcD₅₀) is recommended. Such a formulation could also be applied to setting environmental quality criteria for terrestrial ecosystems.     

Photo-Fenton法降解水中新型污染物双氯芬酸及降解产物的毒性评价

研究了photo-Fenton反应对非甾体抗炎药双氯芬酸的降解和矿化.同时,探讨了H2O2、Fe2+初始浓度、pH值等因素对photo-Fenton反应的影响,确定了最佳操作条件,并进行了各种氧化法的比较.结果表明,对于UV/H2O2/Fe2+反应系统下双氯芬酸的降解,其降解速率受到反应条件的强烈影响.双氯芬酸初始浓度为20mg·L-1时,适宜操作条件是pH值为5,初始FeSO4浓度为5mg·L-1,初始H2O2浓度为200mg·L-1.在最佳条件下,各种氧化法的降解能力趋势为UV/Fenton>UV/H2O2>Fenton>UV.由于反应中有中间产物的生成,双氯芬酸的矿化过程要长于降解过程,其生物毒性也是随着反应的进行先增大而后减小.     

高效液相色谱串联质谱法测定有机磷农药残留

采用一种简便、快速的样品前处理方法提取烟草中22种有机磷农药残留,以甲醇/水为流动相,经高效液相色谱分离,在串联质谱多反应监测(MRM)模式下进行定量分析.22种农药在0.002 μg/mL~0.2 μg/mL内的线性关系良好(r>0.998),最小检出限为0.67 μg/kg~9.15 μg/kg,回收率为70%~102%,相对标准偏差不大于8.96%.     

高效液相色谱串联质谱法测定烟草中有机氮农药残留

用乙腈、水混合液(体积比1:1)提取,提取液经无水硫酸镁和PSA吸附剂处理,经0.45μm滤膜过滤后,以乙腈/水(含5 mmol/L乙酸铵)溶液作流动相,流速200μl/min,采用高效液相色谱-串联质谱法同时测定了烟草中6种有机氮的农药残留量。检测限为0.01～0.10μg/kg,回收率为70%～107%,相对标准偏差不大于8.92%。     

Elevated atmospheric CO2 and drought effects on leaf gas exchange properties of barley

Atmospheric CO₂ concentration (C_a) is rising, predicted to cause global warming, and alter precipitation patterns. During 1994, spring barley (Hordeum vulgare L. cv. Alexis) was grown in a strip-split-plot experimental design to determine the effects that the main plot C_a treatments [A: Ambient at 370 μmol (CO₂) mol⁻¹; E: Enriched with free-air CO₂ enrichment (FACE) at ∼550 μmol (CO₂) mol⁻¹] had on several gas exchange properties of fully expanded sunlit primary leaves. The interacting strip-split-plot irrigation treatments were Dry or Wet [50% (D) or 100% (W) replacement of potential evapotranspiration] at ample nitrogen (261 kg N ha⁻¹) and phosphorous (29 kg P ha⁻¹) fertility. Elevated C_a facilitated drought avoidance by reducing stomatal conductance (g_s) by 34% that conserved water and enabled stomata to remain open for a longer period into a drought. This resulted in a 28% reduction in drought-induced midafternoon depression in net assimilation rate (A). Elevated C_a increased A by 37% under Dry and 23% under Wet. Any reduction in A under Wet conditions occurred because of nonstomatal limitations, whereas under Dry it occurred because of stomatal limitations. Elevated C_a increased the diurnal integral of A (A′) that resulted in an increase in the seasonal-long integral of A′ (A″) for barley leaves by 12% (P = 0.14) under both Dry and Wet - 650, 730, 905 and 1020 ± 65 g (C) m⁻² y⁻¹ for AD, ED, AW and EW treatments, respectively. Elevated C_a increased season-long average dry weight (DW_S; crown, shoots) by 14% (P = 0.02), whereas deficit irrigation reduced DW_S by 7% (P = 0.06), although these values may have been affected by a short but severe pea aphid [Acyrthosiphon pisum (Harris)] infestation. Hence, an elevated-C_a-based improvement in gas exchange properties enhanced growth of a barley crop.     

7种金属离子对中国林蛙和中华大蟾蜍蝌蚪的急性毒性比较研究

为评估Cu2+,Hg2+,Cr6+,Cd2+,Li+,Al3+和Co2+7种金属离子对中国林蛙(Rana Chensinensis)和中华大蟾蜍(Bufo gargarizans)蝌蚪的急性毒性效应,采用生物毒性试验方法对中国林蛙和中华大蟾蜍36期蝌蚪,进行上述7种金属离子的急性毒性试验,分别测定了这7种金属离子对中国林蛙蝌蚪和中华大蟾蜍蝌蚪的半数致死浓度(LC50)。此外,分析了中国林蛙和中华大蟾蜍36期蝌蚪的肥满度、肝指数等形态指标。结果显示,Cu2+、Hg2+、Cr6+、Cd2+、Li1+、Al3+、Co2+对中国林蛙蝌蚪的96h-LC50分别为0.270 mg·L-1、0.803 mg·L-1、2.375 mg·L-1、7.351 mg·L-1、11.273 mg·L-1、17.265 mg·L-1和20.973 mg·L-1。对中华大蟾蜍蝌蚪的96 h-LC50分别0.593 mg·L-1、0.593 mg·L-1、2.827 mg·L-1、2.592 mg·L-1、12.656 mg·L-1、14.020 mg·L-1和57.435 mg·L-1。中国林蛙蝌蚪对Cu2+、Cr6+、Li+、Co6+4种金属离子的敏感性相对较高,而中华大蟾蜍蝌蚪对Hg2+、Cd2+、Al3+3种金属离子的敏感性相对较高。形态指标的差异是中国林蛙与中华大蟾蜍蝌蚪对同一金属离子敏感性差异的原因之一。     

Acute toxic effects of phenanthrene on Chinese mitten crab Eriocheir sinensis北大核心CSCD

Phenanthrene is a persistent organic pollutant frequently found in aquatic environments. This paper aimed to assess the acute effects (96 h) of phenanthrene on Chinese mitten crab (Eriocheir sinensis), a key economic aquatic animal in China. An acute semi-static toxic test was carried out to expose E. sinensis to water-borne phenanthrene with different concentrations (1.00, 1.63, 2.65, 4.31 and 7.00 mg L-1) for 96 hours. Mortality and toxic reactions were used as effect criteria. Furthermore, the oxidative stress relative biomarkers (activities of CAT, SOD, GST and content of MDA in hepatopancreas and gills) were measured for E. sinensis exposed to four lower concentrations of phenanthrene (1.00, 1.63, 2.65 and 4.31 mg L-1). The median lethal concentration (LC50) for 24,48 and 96 hour phenanthrene exposure was 16.7, 2.96 and 2.14 mg L-1, respectively; and the safe concentration (SC) of phenanthrene on E. sinensis was 0.214 mg L-1. Phenanthrene significantly increased the activity of CAT in hepatopancreas and gills, and showed a significant dose-effect relationship in hepatopancreas. Bell-shape response patterns were found in the activities of GST and SOD in the hepatopancreas and gills, with significant increases of hepatopancreas GST at 1.00 and 1.63 mg L-1 (P < 0.05), and a significant decrease at 4.31mg L-1 (P < 0.05). Phenanthrene significantly increased the contents of gills MDA at 2.65mg L-1 and hepatopancreas MDA at all four concentrations of phenanthrene. Phenanthrene, especially of high concentration, is highly toxic on E. sinensis, causing lipid peroxidative damage and even acute mortality. Meanwhile, E. sinensis can adapt to lower concentrations of phenanthrene by increasing the activities of SOD, CAT and GST. Because the CAT and GST activities of the gill and hepatopancreas are very sensitive to the presence of high-concentration phenanthrene, they can be used as highly sensitive biomarkers for phenanthrene polluted water.     

PBS基共聚物及其模拟降解产物对赤子爱胜蚓急性生态毒性的研究

采用滤纸接触法和自然土壤法,通过急性毒性实验分别研究了20℃时不同分子量PBS（聚丁二酸丁二醇酯poly（butylene succinate））基聚合物及其模拟降解产物二元酸、二元醇对赤子爱胜蚓（Eisenia foetida）的存活和生长的影响。研究结果表明：48 h内二元酸、二元醇质量浓度在低于3 400 mg.L-1时对蚯蚓的存活没有影响,滤纸接触法测得丁二酸、己二酸、1,4-丁二醇、1,6-己二醇对蚯蚓的LC50分别为：3 523、3 402、74 907、18 160 mg.L-1;在自然土壤实验中,相比空白实验,蚯蚓在含有不同分子量、不同质量分数的PBS及PBS-co-HS、PBS-co-BA土壤中经过14 d的培养,体质量明显增加,且所有的蚯蚓没有任何病状或伤口出现。以上结果表明PBS基聚合物对该物种是安全的。