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351.
Helena Moreno Traba Noelia Domínguez-Morueco Eva Barreno 《Journal of environmental science and health. Part. B》2017,52(4):223-228
The identification of new organisms for environmental toxicology bioassays is currently a priority, since these tools are strongly limited by the ecological relevance of taxa used to study global change. Lichens are sensitive bioindicators of air quality and their microalgae are an untapped source for new low-cost miniaturized bioassays with ecological importance. In order to increase the availability of a wider range of taxa for bioassays, the sensitivity of two symbiotic lichen microalgae, Asterochloris erici and Trebouxia sp. TR9, to atrazine was evaluated. To achieve this goal, axenic cultures of these phycobionts in suspension were exposed to a range of environmental concentrations of the herbicide atrazine, a common water pollutant. Optical density and chlorophyll autofluorescence were used as endpoints of ecotoxicity and ecophysiology on cell suspensions. Results show that lichen microalgae show high sensitivity to very low doses of atrazine, being higher in Asterochloris erici than in Trebouxia sp. TR9. We conclude that environmental concentrations of atrazine could modify population dynamics probably through a shift in reproduction strategies of these organisms. This seminal work is a breakthrough in the use of lichen microalgae in the assessment of micropollution effects on biodiversity. 相似文献
352.
Kenneth T. Bogen Ankur Singhal 《Journal of environmental science and health. Part. B》2017,52(2):138-146
Estimates of dermal permeability (Kp), obtained by fitting an updated human PBPK model for malathion to previously reported data on excreted urinary metabolites after 29 volunteers were dermally exposed to measured values of [14C]malathion dermal load (L), were used to examine the empirical relationship between Kp and L. The PBPK model was adapted from previously reported human biokinetic and PBPK models for malathion, fit to previously reported urinary excretion data after oral [14C]malathion intake by volunteers, and then augmented to incorporate a standard Kp approach to modeling dermal-uptake kinetics. Good to excellent PBPK-model fits were obtained to all of 29 sets of cumulative urinary metabolite-excretion data (ave. [±1 SD] R2 = 0.953 [±0.064]). Contrary to the assumption that Kp and L are independent typically applied for dermally administered liquids or solutions, the 29 PBPK-based estimates of Kp obtained for malathion exhibit a strong positive association with the 2/3rds power of L (log-log Pearson correlation = 0.925, p = ~0). Possible explanations of this observation involving physico-chemical characteristics and/or in vivo cutaneous effects of malathion are discussed. The PBPK model presented, and our observation that Kp estimates obtained by fitting this model to human experimental urinary-excretion data correlate well with L2/3, allow more realistic assessments of absorbed and metabolized dose during or after a variety of scenarios involving actual or potential dermal or multi-route malathion exposures, including for pesticide workers or farmers who apply malathion to crops. 相似文献
353.
Uranium traces were measured by laser fluorimeter in groundwater samples collected from four districts of Rajasthan state in India. The average values of uranium concentration in groundwater in Sri Ganganagar, Hanumangarh, Churu, and Sikar districts were determined to be: 57, 50, 40, and 21 µg L?1, respectively. These recorded values were compared with the maximum contamination levels recommended for drinking water by various health and environmental protection agencies. The associated age-dependent radiation dose is estimated by taking the prescribed water intake values of different age groups. The average cancer mortality and morbidity risks are calculated to be 5.6 × 10?5 and 8.8 × 10?5 respectively, indicate that the probability of carcinogenic risks is negligible. About half (49%) of the analyzed samples showed hazard quotient > 1.0, indicating significant risk due to chemical toxicity of uranium. 相似文献
354.
355.
对5种大气自然降尘主要化学成分进行分析,并对其与表皮葡萄球菌相互作用后各培养液中pH值、葡萄糖(GLU)、电解质以及Mn2 、Zn2 、Fe3 、Ni3 等浓度的变化进行测定,以比较粉尘的化学成分及物理性状对试验目标菌生长的影响.同时通过SEM分析对粉尘与细菌作用过程中细菌形态和界面作用的情况进行了研究.结果表明,各种大气尘粒所含化学成分不同,与细菌作用后离子溶出量也不完全相同;Ca2 或Mg2 含量高的大气尘粒能使表皮葡萄球菌数量增大并增加其对GLU的利用;粉尘颗粒越小,越易与菌体结合;另外,粉尘颗粒形状的不规则性也大大增加了其与菌体间的膜界结合程度. 相似文献
356.
采用微电极测定溶解氧有效扩散系数的研究 总被引:2,自引:0,他引:2
生物载体内部溶解氧的传质是影响载体同步硝化反硝化性能的重要因素.介绍了一种以溶解氧微电极为测试工具,获得球形生物载体内部溶解氧扩散系数的方法.采用自制的溶解氧微电极检测沿载体半径方向上的溶解氧分布,结合扩散-反应方程拟合获得载体内部的溶解氧有效扩散系数.结果表明,在载体填充率为25%的情况下,连续流球形载体反应器可实现同步硝化反硝化,对有机物的去除负荷达到5.6 kg/(m3·d).沿载体半径方向里层1/2区域范围内溶解氧消耗为零,载体内能够形成明显的缺氧/厌氧区.溶解氧分布曲线的拟合结果表明,载体内部溶解氧有效扩散系数为0.017?2 m2/d,传质过程以紊动传质为主. 相似文献
357.
Mehdi Razzaghi 《Environmental and Ecological Statistics》2009,16(1):25-36
To establish allowable daily intakes for humans from animal bioassay experiments, benchmark doses corresponding to low levels
of risk have been proposed to replace the no-observed-adverse-effect level for non-cancer endpoints. When the experimental
outcomes are quantal, each animal can be classified with or without the disease. The proportion of affected animals is observed
as a function of dose and calculation of the benchmark dose is relatively simple. For quantitative responses, on the other
hand, one method is to convert the continuous data to quantal data and proceed with benchmark dose estimation. Another method
which has found more popularity (Crump, Risk Anal 15:79–89; 1995) is to fit an appropriate dose–response model to the continuous
data, and directly estimate the risk and benchmark doses. The normal distribution has often been used in the past as a dose–response
model. However, for non-symmetric data, the normal distribution can lead to erroneous results. Here, we propose the use of
the class of beta-normal distribution and demonstrate its application in risk assessment for quantitative responses. The most
important feature of this class of distributions is its generality, encompassing a wide range of distributional shapes including
the normal distribution as a special case. The properties of the model are briefly discussed and risk estimates are derived
based on the asymptotic properties of the maximum likelihood estimates. An example is used for illustration.
相似文献
Mehdi RazzaghiEmail: |
358.
359.
Decomposition studies were carried out at sites throughout Sweden, including the four Integrated Monitoring sites. Scots pine
needle litterbag weight loss measurements over 3 or 5 years were determined at 26 sites and repeated up to 27 times, depending
on the site. Humus layer respiration rates were determined for 20 sites in 1987–1989 and repeated in 2007–2008. Partial Least
Squares (PLS) regression was used to elucidate the relative importance of climatic and soil factors. Annual needle weight
losses decreased only slowly (20–10%) over 3–5 years for all northern (>60°N) sites but decreased sharply from 30 to 10% in
the third year in southern (<60°N) sites. Respiration rates of southern sites were less (40% on average) than those of northern
sites. Humus layer N was positively correlated to needle weight loss during the first and the second years, but negatively
correlated in the third year and to respiration rates. The results indicated that litter formed in southern Sweden became
more recalcitrant in later stages of decomposition compared to litter produced in northern Sweden. 相似文献
360.
Radon and gamma dose rate measurements were performed in 512 schools in 8 of the 13 regions of Greece. The distribution of radon concentration was well described by a lognormal distribution. Most (86%) of the radon concentrations were between 60 and 250 Bq m−3 with a most probable value of 135 Bq m−3. The arithmetic and geometric means of the radon concentration are 149 Bq m−3 and 126 Bq m−3 respectively. The maximum measured radon gas concentration was 958 Bq m−3. As expected, no correlation between radon gas concentration and indoor gamma dose rate was observed. However, if only mean values for each region are considered, a linear correlation between radon gas concentration and gamma dose rate is apparent. Despite the fact that the results of radon concentration in schools cannot be applied directly for the estimation of radon concentration in homes, the results of the present survey indicate that it is desirable to perform an extended survey of indoor radon in homes for at least one region in Northern Greece. 相似文献