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571.
This present study assessed the chlorine tolerance of some Citrobacter species recovered from secondary effluents from the clarifiers of two wastewater treatment plants in the Eastern Cape, South Africa. The bacterial survival, chlorine lethal dose and inactivation kinetics at lethal doses were examined. Inactivation of the test bacteria (n = 20) at the recommended dose of 0.5 mg/l for 30 min exposure showed a progressive reduction in bacterial population from 4 to 5 log reduction and residuals ranged between 0.12 and 0.46 mg/l. The bactericidal activity of chlorine increased at higher dosages with a substantial reduction in viability of the bacteria and complete inactivation of the bacterial population at a lethal dose of 0.75 and 1.0 mg/l in 30 min. For the inactivation kinetics, bactericidal activity of chlorine increased with time showing a 3.67–5.4 log reduction in 10 min, 4.0–5.6 log reduction in 20 min and above 6.3 log reductions to complete sterilization of bacterial population over 30 min for all the entire test Citrobacter isolates used in this study. Furthermore, there was a strong correlation (R 2 > 0.84) between bacteria inactivation and increase in contact time. This study appears to have provided support for laboratory evidence of bacterial tolerance to chlorine disinfection at current recommended dose (0.5 mg/l for 30 min), and chlorine concentration between 0.75 and 1.0 mg/l was found to have a better disinfecting capacity to check tolerance of Citrobacter species. 相似文献
572.
为研究典型超低排放除尘技术组合下的尘排放特性,梳理了目前超低排放除尘技术改造的主流技术路线,归纳出典型的7种改造技术路线。依据典型的改造技术路线,选择了27台在2015—2017年完成改造的燃煤发电机组,并对其烟尘排放进行长期的连续监测,根据机组长期运行的排放表现对典型超低排放除尘技术路线的实际减排效果进行量化对比分析。结果表明,7种除尘改造技术路线均可达到控制烟尘排放浓度在10 mg·m~(-3)以下的超低排放标准,其中路线6改造后尘浓度控制在2 mg·m~(-3)以下。对减排效率的研究表明,各技术路线改造后的减排效率均可达到99.97%以上,计算得到机组的平均排放因子为0.025 7 kg·t~(-1)(95%置信区间0.025 4~0.026 1 kg·t~(-1)),其中路线6的排放因子最低,为0.008 6 kg·t~(-1)(95%置信区间0.008 4~0.008 8 kg·t~(-1))。 相似文献
573.
Seung Shik Park Anthony D.A. Hansen Sung Y. Cho 《Atmospheric environment (Oxford, England : 1994)》2010,44(11):1449-1455
Measurements of real-time continuous PM2.5 black carbon (BC) concentrations were made using a single-wavelength Aethalometer (@880 nm) in three different environments, i.e., an indoor office, a residential indoor living room and an urban site, to evaluate the difference in temporal behaviors of BC particles and investigate the optical shadowing effect in the Aethalometer BC data. An empirical method was used for correcting the optical saturation effect on the original BC data obtained from the measurements at the three sites. Also, the elemental carbon (EC) concentrations from 24-h filter-based measurements of PM2.5 particles were determined using a thermal optical transmittance (TOT) method at the same urban site for comparison with the Aethalometer BC results. Transient events of BC were often observed for period of a few hours at all sites, reaching a maximum level of 27.3 μg m?3 at the urban site. The diurnal cycles of the BC concentrations observed at the two indoor environments were found to be considerably affected by the air exchange rate, occupants' behavior patterns and nearby traffic emissions. The time-series plots of the Aethalometer data showed obvious discontinuities at the filter spot change, and a rise in the apparent BC concentrations after filter tape advances. Also, the relationship between the attenuation and BC concentration was found to be non-linear at all sites. The empirical approach presented here demonstrated a definite improvement in the continuity of the BC data across the time gaps of each tape advance. The compensated BC concentration was 1.10–1.23 times greater than the raw BC data, depending on the observation sites, with the highest difference observed between the raw and compensated BC data at an indoor office near a small traffic road. The 24-h integrated EC concentration was approximately 12% higher than the original 24-h average BC concentration and 6% lower than the loading compensated BC concentration, showing that the loading compensation process accounted for the saturation effect of the filter tape. 相似文献
574.
Keith Worrall Anthony Newton Ramesh Rao David Wood 《环境化学》2006,25(4):524-527
用高分离能力的气相色谱-高分辨质谱(HRGC-HRMS)核实二噁英/呋喃是一项昂贵又费时的分析工作,需要高素质的仪器操作人员,而在认证分析前采用筛选法检查样品是检测不出还是浓度超出HRGC-HRMS方法定量范围,可以大大地减少HRGC-HRMS实验室的工作负荷.最新提供的信息表明约10%筛选过的样品需用HRGC-HRMS认证/核实.有些GC/MS/MS方法需要多次进样以获得有毒和无毒的PCDD/Fs,或用功能变换法[1-4]可以确保检测出所有的有毒的2,3,7,8-氯代PCDD/Fs,但损失某些无毒的PCDD/Fs(2,3,7,8氯代PCDD/Fs除外). 相似文献
575.
Agrawal A Cronin J Tonazzi J Mark McCleskey T Ehler DS Minogue EM Whitney G Brink C Burrell AK Warner B Goldcamp MJ Schlecht PC Sonthalia P Ashley K 《Journal of environmental monitoring : JEM》2006,8(6):619-624
Beryllium is widely used in industry for its unique properties; however, occupational exposure to beryllium particles can cause potentially fatal disease. Consequently, exposure limits for beryllium particles in air and action levels on surfaces have been established to reduce exposure risks for workers. Field-portable monitoring methods for beryllium are desired in order to facilitate on-site measurement of beryllium in the workplace, so that immediate action can be taken to protect human health. In this work, a standardized, portable fluorescence method for the determination of trace beryllium in workplace samples, i.e., air filters and dust wipes, was validated through intra- and inter-laboratory testing. The procedure entails extraction of beryllium in 1% ammonium bifluoride (NH(4)HF(2), aqueous), followed by fluorescence measurement of the complex formed between beryllium ion and hydroxybenzoquinoline sulfonate (HBQS). The method detection limit was estimated to be less than 0.02 microg Be per air filter or wipe sample, with a dynamic range up to greater than 10 microg. The overall method accuracy was shown to satisfy the accuracy criterion (A< or = +/-25%) for analytical methods promulgated by the US National Institute for Occupational Safety and Health (NIOSH). Interferences from numerous metals tested (in >400-fold excess concentration compared to that of beryllium) were negligible or minimal. The procedure was shown to be effective for the dissolution and quantitative detection of beryllium extracted from refractory beryllium oxide particles. An American Society for Testing and Materials (ASTM) International voluntary consensus standard based on the methodology has recently been published. 相似文献
576.
Kari E. Gunson Anthony P. Clevenger Adam T. Ford John A. Bissonette Amanda Hardy 《Environmental management》2009,44(2):268-277
Wildlife-vehicle collisions (WVCs) pose a significant safety and conservation concern in areas where high-traffic roads are
situated adjacent to wildlife habitat. Improving transportation safety, accurately planning highway mitigation, and identifying
key habitat linkage areas may all depend on the quality of WVC data collection. Two common approaches to describe the location
of WVCs are spatially accurate data derived from global positioning systems (GPS) or vehicle odometer measurements and less
accurate road-marker data derived from reference points (e.g., mile-markers or landmarks) along the roadside. In addition,
there are two common variable types used to predict WVC locations: (1) field-derived, site-specific measurements and (2) geographic
information system (GIS)-derived information. It is unclear whether these different approaches produce similar results when
attempting to identify and explain the location of WVCs. Our first objective was to determine and compare the spatial error
found in road-marker data (in our case the closest mile-marker) and landmark-referenced data. Our second objective was to
evaluate the performance of models explaining high- and low-probability WVC locations, using congruent, spatially accurate
(<3-m) and road-marker (<800-m) response variables in combination with field- and GIS-derived explanatory variables. Our WVC
data sets were comprised of ungulate collisions and were located along five major roads in the central Canadian Rocky Mountains.
We found that spatial error (mean ± SD) was higher for WVC data referenced to nearby landmarks (516 ± 808 m) than for data
referenced to the closest mile-marker data (401 ± 219 m). The top-performing model using the spatially accurate WVC locations
contained all explanatory variable types, whereas GIS-derived variables were only influential in the best road-marker model
and the spatially accurate reduced model. Our study showed that spatial error and sample size, using road-marker data for
ungulate species, are important to consider for model output interpretation, which will impact the appropriate scale on which
to apply modeling results. Using road-marker references <1.6 km or GPS-derived data locations may represent an optimal compromise
between data acquisition costs and analytical performance.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
577.
Anthony R. Olsen Joseph Sedransk Don Edwards Carol A. Gotway Walter Liggett Stephen Rathbun Kenneth H. Reckhow Linda J. Yyoung 《Environmental monitoring and assessment》1999,54(1):1-45
The United States funds a number of national monitoring programs to measure the status and trends of ecological and natural resources. Each of these programs has a unique focus; the scientific objectives are different as are the sample designs. However, individuals and committees, all well aware of the cost of ecological monitoring, have called for more effective monitoring programs. The objective of this paper is to summarize existing programs' statistical designs and discuss potential alternatives for improvement in national monitoring. Can we improve the current situation by providing an overall framework for the design or analysis of data from these disparate surveys? First, the paper summarizes the objectives of these surveys, compares and contrasts their survey designs as currently implemented, and determines what variables they collect. Through this process we identify commonalities and issues that impact our ability to combine information across one or more of the surveys. Three potential alternatives are presented, leading to comprehensive monitoring in the United States. 相似文献
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