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941.
氢氧化镁是一种正在研究的用于脱除烟气中低浓度CO2的化学吸收剂。为了掌握工业用氢氧化镁粉末的溶解速率,利用缓冲溶液,在不改变溶液体积的情况下对不同悬浊液浓度、溶液温度、溶液pH值和搅拌速率情况下的氢氧化镁粉末溶解速率进行了研究。提高悬浊液浓度、提高溶液温度、降低溶液pH值和提高搅拌速率均能增大氢氧化镁的溶解速率。悬浊液浓度从0.1 mol/L增加到1 mol/L时,溶解速率增大了2.2倍;温度从23℃增加到52℃时,溶解速率增大了4.3~9.5倍;pH值从9.8降低到6.6时,溶解速率增大了78~225倍;搅拌速率从350 r/min增加到700 r/min时,溶解速率增大了1~2倍。 相似文献
942.
Consumption inhibition in natural populations, namely due to contaminants, may have direct and immediate effects on ecosystems, by hampering ecosystem key functions (e.g., organic matter decomposition, grazing), long before effects at the individual level (e.g., reproduction, growth, emergence) have time-delayed consequences at successively higher levels of biological organization. The present study aimed at developing a cost-effective (short and easy) toxicity test based on the postexposure feeding of a freshwater amphipod present in the Iberian Peninsula and at evaluating the immediate impact of contamination on the population-level consumption rate. First, methodologies to quantify postexposure feeding were developed and optimized, the most important criterion being a feeding period as short as possible to minimize physiological recovery from the contaminant exposure. Second, the sensitivities of 48-h postexposure feeding and 48-h lethality tests were compared, using a reference chemical - copper. Third, the latter responses were integrated in a single parameter, the median population consumption inhibitory concentration. When Echinogammarus meridionalis males were fed on 100 defrosted Artemia franciscananauplii during 30 min in darkness at 19-21 °C, the eaten proportion was approximately 80%, without truncated data distributions. The 48-h median effective copper concentration for postexposure feeding was approximately two times lower than the 48-h LC50 - 91 versus 198 μg L−1, respectively. Two techniques were used to quantify the median population consumption inhibitory copper concentration, both leading to similar values (75 and 68 μg L−1). In conclusion, when contaminant concentrations elicit both lethality and feeding depression, the integration of both responses can provide an ecologically relevant evaluation on the potency of a contaminant to immediately disrupt ecosystem functioning. 相似文献
943.
Anjos RM Juri Ayub J Cid AS Cardoso R Lacerda T 《Journal of environmental radioactivity》2011,102(11):1055-1061
Health hazard from natural radioactivity in Brazilian granites, covering the walls and floor in a typical dwelling room, was assessed by indirect methods to predict external gamma-ray dose rates and radon concentrations. The gamma-ray dose rate was estimated by a Monte Carlo simulation method and validated by in-situ measurements with a NaI spectrometer. Activity concentrations of 232Th, 226Ra, and 40K in an extensive selection of Brazilian commercial granite samples measured by using gamma-ray spectrometry were found to be 4.5-450 Bq kg−1, 4.9-160 Bq kg−1 and 190-2029 Bq kg−1, respectively. The maximum external gamma-ray dose rate from floor and walls covered with the Brazilian granites in the typical dwelling room (5.0 m × 4.0 m area, 2.8 m height) was found to be 120 nGy h−1, which is comparable with the average worldwide exposure to external terrestrial radiation of 80 nGy h−1 due to natural sources, proposed by United Nations Scientific Committee on the Effects of Atomic Radiation. Radon concentrations in the room were also estimated by a simple mass balance equation and exhalation rates calculated from the measured values of 226Ra concentrations and the material properties. The results showed that the radon concentration in the room ventilated adequately (0.5 h−1) will be lower than 100 Bq m−3, value recommended as a reference level by the World Health Organization. 相似文献
944.
Hettiarachchi VC Hettiaratchi PJ Mehrotra AK Kumar S 《Environmental pollution (Barking, Essex : 1987)》2011,159(6):1715-1720
Methane biofiltration (MBF) is a novel low-cost technique for reducing low volume point source emissions of methane (CH4). MBF uses a granular medium, such as soil or compost, to support the growth of methanotrophic bacteria responsible for converting CH4 to carbon dioxide (CO2) and water (H2O). A field research program was undertaken to evaluate the potential to treat low volume point source engineered CH4 emissions using an MBF at a natural gas monitoring station. A new comprehensive three-dimensional numerical model was developed incorporating advection-diffusive flow of gas, biological reactions and heat and moisture flow. The one-dimensional version of this model was used as a guiding tool for designing and operating the MBF. The long-term monitoring results of the field MBF are also presented. The field MBF operated with no control of precipitation, evaporation, and temperature, provided more than 80% of CH4 oxidation throughout spring, summer, and fall seasons. The numerical model was able to predict the CH4 oxidation behavior of the field MBF with high accuracy. The numerical model simulations are presented for estimating CH4 oxidation efficiencies under various operating conditions, including different filter bed depths and CH4 flux rates. The field observations as well as numerical model simulations indicated that the long-term performance of MBFs is strongly dependent on environmental factors, such as ambient temperature and precipitation. 相似文献
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循环冷却系统浓缩排污水是电厂最大的排污水,是节水减排和废水零排放的关键问题之一。以河源电厂为例,分析了电厂进水水质条件;选用了5种水稳剂,采取极限碳酸盐硬度计算浓缩倍率的方法,通过静动态阻垢、防腐与杀菌试验,探明了各种药剂的极限浓缩倍率,论证了河源电厂循环冷却系统10倍以上的浓缩倍率运行方式的可行性。按试验所确定的原则,河源电厂循环冷却水系统按10倍的浓缩倍率运行,一年来未出现腐蚀与结垢现象。分析了实际运行期间的运行数据,对我国循环冷却水处理、节约用水、减少排污具有一定的示范意义。 相似文献
950.
The success of enhanced biological phosphorus removal (EBPR) depends on the constant availability of volatile fatty acids (VFAs). To reduce costs, waste streams would be a preferred source. Since VFAs were shown to vary in the incoming sewage and fermentate from primary sludge the next available source is waste activated sludge (WAS). The opportunity is particularly good in plants where WAS is stored before shipment. Little information is however available on the rate of VFA release from such sludge, especially at the lower temperatures and under the storage conditions typically found in colder climates. Bench-scale batch tests were performed to investigate the effect of temperature and requirement for mixing on VFA generation from WAS generated in full scale non-EBPR wastewater treatment plant. WAS fermentation was found highly temperature-dependent. Hydrolysis rate constant (kh) values of 0.17, 0.08 and 0.04 d−1 at 24.6, 14 and 4 °C were obtained, respectively. Arrhenius temperature coefficient was calculated to be 1.07. It took 5 d to complete hydrolysis at 24.6 °C, 7 d at 14 °C, and 9 d at 4 °C. The fermentation lasted for 20 d. At 24.6 °C the mixed reactor reached 84% of the overall VFA production only in 5 d. When temperature dropped to 14 and 4 °C, the ratio of VFA production at day 10 to overall VFA production in the mixed reactor were 62% and 48%, respectively. The overall VFA-COD concentration in the non-mixed reactors was much lower than the mixed reactors. The information is important for the designer as there was uncertainty with the effect of temperature and mixing on sludge fermentation. 相似文献