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431.
Shaibal Mukerjee Luther A. Smith Gary A. Norris Maria T. Morandi Melissa Gonzales Christopher A. Noble 《Journal of the Air & Waste Management Association (1995)》2013,63(3):307-319
Abstract This study evaluates the performance of Model 3300 Ogawa Passive Nitrogen Dioxide (NO2) Samplers and 3M 3520 Organic Vapor Monitors (OVMs) by comparing integrated passive sampling concentrations to averaged hourly NO2 and volatile organic compound (VOC) measurements at two sites in El Paso, TX. Sampling periods were three time intervals (3-day weekend, 4-day weekday, and 7-day weekly) for three consecutive weeks. OVM concentrations were corrected for ambient pressure to account for higher elevation. Precise results (<5% relative standard deviation, RSD) were found for NO2 measurements from collocated Ogawa samplers. Reproducibility was lower from duplicate OVMs for BTEX (benzene, toluene, ethylbenzene, and xylene isomers) VOCs (≥7% RSD for 2-day samples) with better precision for longer sampling periods. Comparison of Ogawa NO2 samplers with chemiluminescence measurements averaged over the same time period suggested potential calibration problems with the chemiluminescence analyzer. For BTEX species, generally good agreement was obtained between OVMs and automated-gas chromatograph (auto-GC) measurements. The OVMs successfully tracked increasing levels of VOCs recorded by the auto-GCs. 相似文献
432.
Tarek Abichou Jeremy Clark Jeffery Chanton Gary Hater Roger Green Doug Goldsmith 《Journal of the Air & Waste Management Association (1995)》2013,63(12):1403-1410
In the method termed “Other Test Method-10,” the U.S. Environmental Protection Agency has proposed a method to quantify emissions from nonpoint sources by the use of vertical radial plume mapping (VRPM) technique. The surface area of the emitting source and the degree to which the different zones of the emitting source are contributing to the VRPM computed emissions are often unknown. The objective of this study was to investigate and present an approach to quantify the unknown emitting surface area that is contributing to VRPM measured emissions. Currently a preexisting model known as the “multiple linear regression model,” which is described in Thoma et al. (2009), is used for quantifying the unknown surface area. The method investigated and presented in this paper utilized tracer tests to collect data and develop a model much like that described in Thoma et al. (2009). However, unlike the study used for development of the multiple linear regression model, this study is considered a very limited study due to the low number of pollutant releases performed (seven total releases). It was found through this limited study that the location of an emitting source impacts VRPM computed emissions exponentially, rather than linearly (i.e., the impact that an emitting source has on VRPM measurements decreases exponentially with increasing distances between the emitting source and the VRPM plane). The data from the field tracer tests were used to suggest a multiple exponential regression model. The findings of this study, however, are based on a very small number of tracer tests. More tracer tests performed during all types of climatic conditions, terrain conditions, and different emissions geometries are still needed to better understand the variation of capture efficiency with emitting source location. This study provides a step toward such an objective.
Implications The findings of this study will aid in the advancement of the VRPM technique. In particular, the contribution of this study is to propose a slight improvement in how the area contributing to flux is determined during VRPM campaigns. This will reduce some of the technique's inherent uncertainties when it is employed to estimate emissions from an area source under nonideal conditions. 相似文献
433.
Smits JE Bortolotti GR Baos R Jovani R Tella JL Hoffmann WE 《Environmental pollution (Barking, Essex : 1987)》2007,145(2):538-544
In 1998, the Aznalcóllar mine tailings dyke in southwestern Spain broke, flooding the Agrio-Guadiamar river system with acid tailings up to the borders of one of the largest breeding colonies of white storks in the western Palearctic, Dehesa de Abajo. Over the following years, a high proportion of nestlings developed leg defects not seen before the spill, prompting this study. Nestlings with deformed legs had significantly lower plasma phosphorous (P) and higher Ca:P ratios than non-deformed cohorts in the first two years, but in the third year, when more, younger birds were studied, plasma P ranged from much higher to much lower in the affected colony compared with reference birds. Coefficients of variation for phosphorous were 19% and 60%, in reference and contaminated colonies, respectively. Storks from the contaminated colony were unable to control P levels and Ca:P ratios within the narrow limits necessary for normal bone development. 相似文献
434.
Thu Nguyen Marcus Hilliard Gary T. Rochelle 《International Journal of Greenhouse Gas Control》2010,4(5):707-715
Amine volatility is a key screening criterion for amines to be used in CO2 capture. Excessive volatility may result in significant economic losses and environmental impact. It also dictates the capital cost of the water wash. This paper reports measured amine volatility in 7 m MEA (monoethanolamine), 8 m PZ (piperazine), 7 m MDEA (n-methyldiethanolamine)/2 m PZ (piperazine), 12 m EDA (ethylenediamine), and 5 m AMP (2-amino-2-methyl-1-propanol) at 40–60 °C with lean and rich loadings giving CO2 partial pressures of 0.5 and 5 kPa at 40 °C. The amine concentrations were chosen to maximize CO2 capture capacity at acceptable viscosity. At the lean loading condition (where volatility is of greatest interest), the amines are ranked in order of increasing volatility: 7 m MDEA/2 m PZ (6/2 ppm), 8 m PZ (8 ppm), 12 m EDA (9 ppm), 7 m MEA (31 ppm), and 5 m AMP (112 ppm). The apparent amine partial molar excess enthalpies in these systems were estimated to range from ~10 to 87 kJ/mol of amine. 相似文献
435.
When a mining company selects a site for development, the company begins a dialogue with the local community about receiving the necessary approvals for the mining permits. The dialogue focuses on how well the company can use science and technology to manage risk to the local environment, and on how much economic benefit will be gained by the local community for accepting the risk. A useful approach to better understand how the debate affects the outcome of the permitting effort is to use the method of “discourse communities and analysis”. This paper analyzes two efforts by Kennecott (Rio Tinto) and one by Exxon to develop base metal mine sites in the Upper Midwest of the USA. As the three case studies show, the local pro- and anti-mining discourse community members will not be changing their basic positions as the permitting of a new mine is debated. Accordingly, both communities are trying to convince undecided stakeholders rather than talking to each other. Both sides are using ever more sophisticated media methods to communicate their message to the undecided residents of the community. By winning the support of the majority of the undecided residents, political pressure can be used to sway the decision. 相似文献
436.
Temporal variation and persistence of bacteria in streams 总被引:1,自引:0,他引:1
Koirala SR Gentry RW Perfect E Schwartz JS Sayler GS 《Journal of environmental quality》2008,37(4):1559-1566
Better understanding of bacterial fate and transport in watersheds is necessary for improved regulatory management of impaired streams. Novel statistical time series analyses of coliform data can be a useful tool for evaluating the dynamics of temporal variation and persistence of bacteria within a watershed. For this study, daily total coliform data for the Little River in East Tennessee from 1 Oct. 2000 to 31 Dec. 2005 were evaluated using novel time series techniques. The objective of this study was to analyze the total coliform concentration data to: (i) evaluate the temporal variation of the total coliform, and (ii) determine whether the total coliform concentration data demonstrated any long-term or short-term persistence. For robust analysis and comparison, both time domain and frequency domain approaches were used for the analysis. In the time domain, an autoregressive moving average approach was used; whereas in the frequency domain, spectral analysis was applied. As expected, the analyses showed that total coliform concentrations were higher in summer months and lower in winter months. However, the more interesting results showed that the total coliform concentration exhibited short-term as well as long-term persistence ranging from about 4 wk to approximately 1 yr, respectively. Comparison of the total coliform data to hydrologic data indicated both runoff and baseflow are responsible for the persistence. 相似文献
437.
Mathematical modelling of the oxidation reduction redox potential (ORP) of an electrolyte has been carried out for a batch system comprising an electrochemical reactor and an electrolyte circuit containing a redox couple. The ORP can be useful to monitor the environmental impact of chemical species in solution that represent a risk to the environment. Considerations of four fundamental equations, namely, the Nernst equation, a mass balance, Faraday's laws of electrolysis and a first order kinetic equation, leads to an expression for the electrolyte redox potential as a function of the batch time, the electrical charge and the redox concentration. Such an expression facilitates graphical plots which can be used to estimate kinetic parameters, current efficiency and the relative redox concentration. The Ce(IV)/Ce(III) system has been chosen as a model reaction for electrolyte redox potential measurement in a batch recycle system consisting of a pumped flow through a divided FM01-LC parallel-plate electrochemical reactor (64cm(2) projected electrode area) and a well mixed tank (3600cm(3)). The differences between experimental and model predictions are discussed. 相似文献
438.
Thomas GO Farrar D Braekevelt E Stern G Kalantzi OI Martin FL Jones KC 《Environment international》2006,32(1):34-40
Chlorinated paraffins (also called polychlorinated n-alkanes -- PCAs) are a class of industrial chemicals comprising chlorinated straight chain hydrocarbons. They have a wide range of applications and are now found in a range of environmental compartments. We analysed a total of 25 human milk-fat samples, donated by 18 individuals from the urban London and more rural Lancaster areas in the UK, for short chain PCAs (C(10)-C(13) sPCAs) and medium chain PCAs (C(14)-C(17) mPCAs), using gas chromatography-ECNI high-resolution mass spectrometry. Our study confirms that trace quantities of PCAs can reach human milk-fat. sPCAs were detected in all but four samples, while mPCAs were detected in all samples. The median sPCA concentration was 180 ng/g fat (range of 49 to 820 ng/g fat -- detected values only) and the median mPCA concentration was 21 ng/g fat (range of 6.2 to 320 ng/g fat). No differences were noted in ranges of observed values for either sPCAs or mPCAs between samples from London and Lancaster. Most samples also exhibited similar patterns of sPCAs and mPCAs. One sample exhibited a different pattern for sPCAs and mPCAs, an observation that may be related to differences in exposure or biological factors for this individual. 相似文献
439.
Stephanie A. Freeman Jason Davis Gary T. Rochelle 《International Journal of Greenhouse Gas Control》2010,4(5):756-761
Concentrated, aqueous piperazine (PZ) is a novel solvent for carbon dioxide (CO2) capture by absorption/stripping. One of the major advantages of PZ is its resistance to thermal degradation and oxidation.At 135 and 150 °C, 8 m PZ is up to two orders of magnitude more resistant to thermal degradation than 7 m monoethanolamine (MEA). After 18 weeks at 150 °C, only 6.3% of the initial PZ was degraded, yielding an apparent first order rate constant for amine loss of 6.1 × 10?9 s?1. PZ was the most resistant amine tested, with the other screened amines shown in order of decreasing resistance: 7 m 2-amino-2-methyl-1-propanol, 7 m Diglycolamine®, 7 m N-(2-hydroxyethyl)piperazine, 7 m MEA, 8 m ethylenediamine, and 7 m diethylenetriamine. Thermal resistance allows the use of higher temperatures and pressures in the stripper, potentially leading to overall energy savings.Concentrated PZ solutions demonstrate resistance to oxidation compared to 7 m MEA solutions. Experiments investigating metal-catalyzed oxidation found that PZ solutions were 3–5 times more resistant to oxidation than MEA. Catalysts tested were 1.0 mM iron (II), 4.0–5.0 mM copper (II), and a combination of stainless steel metals (iron (II), nickel (II), and chromium (III)). Inhibitor A reduced PZ degradation catalyzed by iron (II) and copper (II). 相似文献
440.
Chemodynamics of heavy metals in long-term contaminated soils:Metal speciation in soil solution 总被引:2,自引:2,他引:2
The concentration and speciation of heavy metals in soil solution isolated from long-term contaminated soils were investigated. The
soil solution was extracted at 70% maximum water holding capacity (MWHC) after equilibration for 24 h. The free metal concentrations
(Cd2+, Cu2+, Pb2+, and Zn2+) in soil solution were determined using the Donnan membrane technique (DMT). Initially the DMT was
validated using artificial solutions where the percentage of free metal ions were significantly correlated with the percentages predicted
using MINTEQA2. However, there was a significant difference between the absolute free ion concentrations predicted by MINTEQA2
and the values determined by the DMT. This was due to the significant metal adsorption onto the cation exchange membrane used in
the DMT with 20%, 28%, 44%, and 8% mass loss of the initial total concentration of Cd, Cu, Pb, and Zn in solution, respectively.
This could result in a significant error in the determination of free metal ions when using DMT if no allowance for membrane cation
adsorption was made. Relative to the total soluble metal concentrations the amounts of free Cd2+ (3%–52%) and Zn2+ (11%–72%) in
soil solutions were generally higher than those of Cu2+ (0.2%–30%) and Pb2+ (0.6%–10%). Among the key soil solution properties,
dissolved heavy metal concentrations were the most significant factor governing free metal ion concentrations. Soil solution pH showed
only a weak relationship with free metal ion partitioning coefficients (Kp) and dissolved organic carbon did not show any significant
influence on Kp. 相似文献