In recent years, natural attenuation (NA) has evolved into a possible remediation alternative, especially in the case of BTEX spills. In order to be approved by the regulators, biodegradation needs to be demonstrated which requires efficient site investigation and monitoring tools. Three methods--the Integral Groundwater Investigation method, the compound-specific isotope analysis (CSIA) and a newly developed combination of both--were used in this work to quantify at field scale the biodegradation of o-xylene at a former gasworks site which is heavily contaminated with BTEX and PAHs. First, the Integral Groundwater Investigation method [Schwarz, R., Ptak, T., Holder, T., Teutsch, G., 1998. Groundwater risk assessment at contaminated sites: a new investigation approach. In: Herbert, M. and Kovar, K. (Editors), GQ'98 Groundwater Quality: Remediation and Protection. IAHS Publication 250, pp. 68-71; COH 4 (2000) 170] was applied, which allows the determination of mass flow rates of o-xylene by integral pumping tests. Concentration time series obtained during pumping at two wells were used to calculate inversely contaminant mass flow rates at the two control planes that are defined by the diameter of the maximum isochrone. A reactive transport model was used within a Monte Carlo approach to identify biodegradation as the dominant process for reduction in the contaminant mass flow rate between the two consecutive control planes. Secondly, compound-specific carbon isotope analyses of o-xylene were performed on the basis of point-scale samples from the same two wells. The Rayleigh equation was used to quantify the degree of biodegradation that occurred between the wells. Thirdly, a combination of the Integral Groundwater Investigation method and the compound-specific isotope analysis was developed and applied. It comprises isotope measurements during the integral pumping tests and the evaluation of delta13C time series by an inversion algorithm to obtain spatially integrated mean isotope values at the control planes. It was shown that the Rayleigh equation is applicable to spatially integrated mean isotope values in order to obtain the mean biodegradation between the consecutive control planes. All three approaches yielded consistently a 98-99% degradation of o-xylene. 相似文献
AbstractWe investigated the anaerobic degradation of tetracycline antibiotics (tetracycline [TC], oxytetracycline [OTC] and chlortetracycline [CTC]) in swine, cattle, and poultry manures. The manures were anaerobically digested inside polyvinyl chloride batch reactors for 64?days at room temperature. The degradation rate constants and half-lives of the parent tetracyclines were determined following first-order kinetics. For CTC the fastest degradation rate was observed in swine manure (k?=?0.016?±?0.001 d?1; half-life = 42.8?days), while the slowest degradation rate was observed in poultry litter (k?=?0.0043?±?0.001 d?1; half-life = 161?days). The half-lives of OTC ranged between 88.9 (cattle manure) and 99.0?days (poultry litter), while TC persisted the longest of the tetracycline antibiotics studied with half-lives ranging from 92.4?days (cattle manure) to 330?days (swine manure). In general, the tetracyclines were found to degrade faster in cattle manure, which had the lowest concentrations of organic matter and metals as compared to swine and poultry manures. Our results demonstrate that tetracycline antibiotics persist in the animal manure after anaerobic digestion, which can potentially lead to emergence and persistence of antibiotic resistant bacteria in the environment when anaerobic digestion byproducts are land applied for crop production. 相似文献
In situ methods are needed to evaluate the effectiveness of chemical amendments at enhancing reductive dechlorination rates in groundwater that is contaminated with the priority pollutant, trichloroethene (TCE). In this communication, a method that utilizes single-well, “push–pull” tests to quantify the effects of chemical amendments on in situ reductive dechlorination rates is presented and demonstrated. Five push–pull tests were conducted in each of five monitoring wells located in a TCE-contaminated aquifer at the site of a former chemical manufacturing facility. Rates for the reductive dechlorination of the fluorinated TCE-surrogate, trichlorofluoroethene (TCFE), were measured before (test 1) and after (test 5) three successive additions (tests 2–4) of fumarate. Fumarate was selected to stimulate the growth and activity of indigenous microorganisms with the metabolic capability to reduce TCFE and TCE. In three wells, first-order rate constants for the reductive dechlorination of TCFE increased by 8.2–92 times following fumarate additions. In two wells, reductive dechlorination of TCFE was observed after fumarate additions but not before. The transformation behavior of fumarate was also monitored following each fumarate addition. Correlations between the reductive dechlorination of TCFE and the reduction of fumarate to succinate were observed, indicating that these reactions were supported by similar biogeochemical conditions at this site. 相似文献
Emissions from fugitive dust due to erosion of “natural” wind-blown surfaces are an increasingly important part of PM10 (particulate matter with sizes of 10 μm aerodynamic diameter) emission inventories. These inventories are particularly important to State Implementation Plans (SIP), the plan required for each state to file with the Federal government indicating how they will comply with the Federal Clean Air Act (FCAA). However, techniques for determining the fugitive dust contribution to over all PM10 emissions are still in their developmental stages. In the past, the methods have included field monitoring stations, specialized field studies and field wind-tunnel studies. The measurements made in this paper allow for systematic determination of PM10 emission rates through the use of an environmental boundary layer wind tunnel in the laboratory. Near surface steady-state concentration profiles and velocity profiles are obtained in order to use a control volume approach to estimate emission rates. This methodology is applied to soils retrieved from the nation's single largest PM10 source, Owens (dry) Lake in California, to estimate emission rates during active storm periods. The estimated emission rates are comparable to those obtained from field studies and lend to the validity of this method for determining fugitive dust emission rates. 相似文献
The emissions of selected flame retardants were measured in 1- and 0.02-m3 emission test chambers and 0.001-m3 emission test cells. Four product groups were of interest: insulating materials, assembly foam, upholstery/mattresses, and electronics equipment. The experiments were performed under constant environmental conditions (23°C, 50% RH) using a fixed sample surface area and controlled air flow rates. Tris (2-chloro-isopropyl)phosphate (TCPP) was observed to be one of the most commonly emitted organophosphate flame retardants in polyurethane foam applications. Depending on the sample type, area-specific emission rates (SERa) of TCPP varied between 20 ng m−2 h−1 and 140 μg m−2 h−1.The emissions from electronic devices were measured at 60°C to simulate operating conditions. Under these conditions, unit specific emission rates (SERu) of organophosphates were determined to be 10–85 ng unit−1 h−1. Increasing the temperature increased the emission of several flame retardants by up to a factor of 500. The results presented in this paper indicate that emissions of several brominated and organophosphate flame retardants are measurable. Polybrominated diphenylethers exhibited an SERa of between 0.2 and 6.6 ng m−2 h−1 and an SERu of between 0.6 and 14.2 ng unit−1 h−1. Because of sink effects, i.e., sorption to chamber components, the emission test chambers and cells used in this study have limited utility for substances low vapour pressures, especially the highly brominated compounds; hexabromocyclododecane had an SERa of between 0.1 and 29 ng m−2 h−1 and decabromodiphenylether was not detectable at all. 相似文献
Objective: This study aimed to investigate the social and hospital costs of patients treated at a public hospital who were motorcycle crash victims.
Method: This prospective study was on 68 motorcycle riders (drivers or passengers), who were followed up from hospital admission to 6 months after the crash. A questionnaire covering quantitative and qualitative questions was administered.
Results: Motorcycle crash victims were responsible for 12% of the institution's hospital admissions; 54.4% were young (18–28 years of age); 92.6% were the drivers; 91.2% were male; and 50% used their motorcycles as daily means of transportation. Six months afterward, 94.1% needed help from someone; 83.8% had changed their family dynamics; and 73.5% had not returned to their professional activities. Among the injuries, 94.7% had some type of fracture, of which 53.5% were exposed fractures; 35.3% presented temporary sequelae; and 32.4% presented permanent sequelae. They used the surgical center 2.53 times on average, with a mean hospital stay of 18 days. The per capita hospital cost of these victims’ treatment was US$17,481.50.
Conclusion: The social and hospital costs were high, relative to the characteristics of a public institution. Temporary or permanent disability caused changes to family dynamics, as shown by the high numbers of patients who were still away from their professional activities more than 6 months afterward. 相似文献