Thermal Oxidation Kinetics of Selected Organic Compounds

A thermal oxidizer destroys organic pollutants by oxidation to CO₂ and water. Time, temperature, and turbulence, govern the performance of a thermal oxidizer just as they do all other combustion devices. To achieve a desired degree of destruction, a higher temperature allows the use of a shorter residence time and vice versa. For most organics, a thermal oxidizer designed at 1400°-1500°F with 0.1 to 0.3 seconds residence time is normally enough to obtain nearly complete destruction.¹ However, some chemicals require more extreme conditions. These time-temperature requirements can be determined from kinetic rate studies.     

Spatial and behavioral interactions between a native and introduced salamander species

Behavioral interactions with native species may influence the invasiveness of introduced species. The salamanders Plethodon glutinosus and P. jordani in the eastern United States share many life history traits and demonstrate complex interspecific interactions that range geographically from competitive exclusion to sympatry. P. jordani was introduced to Mountain Lake Biological Station, Virginia, USA, between the years 1935 and 1945. We tested whether competition for space may influence the invasion of P. jordani into native P. glutinosus habitat by utilizing data from natural distributions, a field experiment, and controlled laboratory experiments. No environmental variables differed where P. glutinosus and P. jordani were collected in the field at the site of P. jordani introduction. In the field experiment, P. glutinosus was more fully exposed during foraging bouts in cages shared with heterospecifics as opposed to ones shared with conspecific salamanders. Condition (mass relative to body length) of salamanders at the end of the 3 months did not differ between conspecific and heterospecific treatments. In the laboratory, P. glutinosus most often attained the single burrow in the arena, but residency status had no effect. Species cohabited the burrow 50% of the time. Pair-wise encounters in the laboratory indicated that both species spend less than 20% of the time in aggressive behaviors as juveniles. Adults showed no behavior interpreted by us as aggression during pair-wise encounters. Received: 19 December 1999 / Accepted: 18 March 2000     

Urban Agriculture：A Transitional Mechanism for Reducing Environmental Degradation and Fossil Fuel over Dependence

With the increasing population in the urban cities of the world,the demand for food from distant areas has been on the rise but at the expense of scarce natural resources like oil,water and forest,etc.However,producing food locally in urban centers provides a sustainable mechanism of reducing the carbon,food or ecological footprints of these cities in particular and environmental degradation in general.It creates a circular metabolic system in which the natural inputs are efficiently harnessed rather than the linear metabolic system in which resources flow in and wastes flow out.This article analyzes some urban agricultural local initiatives in urban centers of the worlds that promote a circular metabolic systems and proposes the procedure that can be adopted to promote urban agriculture.     

Effect of amendment C:N ratio on plant richness, cover and metal content for acidic Pb and Zn mine tailings in Leadville, Colorado

Biosolids and woody debris were applied with target C:N ratios of 8:1 to 50:1 to phytotoxic, acidic, high metal mine tailings to test the effect of amendment C:N ratio on native plant restoration. Total soil C decreased over time indicating an active microbial community. The 8:1 treatment initially had no growth, the highest plant cover for the final sampling (86.8+/-13.8%) and the lowest number of species (3.33+/-0.4). The greatest number of species was in the 30:1 treatment (5.44+/-0.45). Plant cover increased over time for all treatments from 44.7% in 2001 to 71% in 2005. This response was consistent across all except for the 30:1 treatment, which showed a slight decrease in the final year (65+/-11%). Volunteer species and evidence of animal grazing were observed in all amended plots. Results indicate that a C:N ratio>/=20:1 increased species diversity.     

First compound-specific chlorine-isotope analysis of environmentally-bioaccumulated organochlorines indicates a degradation-relatable kinetic isotope effect for DDT

Compound-specific chlorine-isotope analysis (CSIA-Cl) of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDT) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethene (p,p'-DDE) in blubber from Baltic Grey seal (Halichoerus grypus) was performed in order to investigate if a kinetic isotope effect (KIE) could be observed concomitant to environmental degradation of DDT. The delta(37)Cl of p,p'-DDT and p,p'-DDE were -0.69 +/- 0.21 per thousand and -2.98 +/- 0.57 per thousand (1s igma, n = 3), respectively. Both samples were enriched relative to the hypothesized initial isotope composition (-4.34 per thousand), thus indicating a composite KIE associated with the degradation mechanisms pertaining to DDT. An isotope fractionation factor for degradation of dichloromethane, from the literature, was adapted and modified for use in the calculation of DDT degradation. A subsequent simplified Rayleigh distillation model of the DDT chlorine-isotope composition yielded an estimated fraction (f) of 7 +/- 2% of released DDT presently remaining as undegraded compound in the environment. The consistency between the result of the Rayleigh model (f approximately 7%) and the use of the DDT/(DDT + DDE) ratio as a measure of DDT degradation ( approximately 10% undegraded DDT) suggests that the KIE of DDT degradation may be significant, and that the novel approach of CSIA-Cl may be a valuable tool for degradation/persistence studies of lipophilic organochlorines in the environment.     

Responses of juvenile sea bass, Dicentrarchus labrax, exposed to acute concentrations of crude oil, as assessed by molecular and physiological biomarkers

In the present study, juvenile sea bass were exposed for 48 and 96 h to an Arabian light crude oil and their responses were assessed at the molecular and physiological levels. The aim of the study was therefore to assess (i) the short term effects of crude oil exposure by the measurement of several molecular biomarkers, (ii) the consequences of this short term exposure on fish health by using growth and condition indices measured after a decontamination period of 28 and 26 d in seawater. Hydrocarbon petroleum concentrations was monitored during the 96 h experiments and an increase of PAH concentrations were found in fish following both exposure times. An 7-ethoxyresorufin-O-deethylase (EROD) induction was observed after 48 h of exposure, while a significant decrease in the sea bass specific growth rate in length and for the RNA:DNA ratio was observed 28 d after that exposure ceased. The EROD induction doubled after the 96 h exposure, and a significant increase in GST activities was observed. A significant decrease in the specific growth rates, the otolith recent growth, the RNA:DNA ratio and the Fulton’s K condition index were then observed in sea bass 26 d after the 96 h exposure to mechanically dispersed crude oil compared to the control. The present study shows that growth and condition indices can prove useful in assessing fish health status following an oil spill. Their complementary analysis with sensitive molecular biomarkers as EROD could improve the determination of oil spill impact on fish populations.     

Perfluoroalkyl chemicals in vacuum cleaner dust from 39 Wisconsin homes

Perfluoroalkyl chemicals (PFCs) have been used as surfactants and stain repellants in a variety of consumer products for more than 50 years and there is growing concern regarding their persistence and toxicity. Human exposure to these chemicals is essentially universal in North America and researchers have linked them to a variety of health problems ranging from higher rates of cancer, to developmental and reproductive problems, and higher cholesterol levels. Major exposure pathways are food and water ingestion, dust ingestion via hand to mouth transfer. In an effort to assess residential exposure, the Wisconsin Department of Health Services tested vacuum cleaner contents from thirty-nine homes for 16 perflouroalkyl chemicals. PFOS, PFOA, PFHxS, PFHpA and PFNA were found in all of the vacuum dust samples and dust from eight homes contained all 16 PFCs included in our analysis. The most commonly detected compounds were perfluorooctanesulfonate (PFOS), perfluorohexanesulfonate (PFHxS) and perfluorooctanoic acid (PFOA) which together made up 70% of the total PFC residues in dust from these homes. Summed PFC concentrations in these dust samples ranged from 70 to 2513 ng/g (median 280 ng/g). Our investigation suggests that these chemicals may be ubiquitous contaminants in US homes.     

Unregulated greenhouse gas and ammonia emissions from current technology heavy-duty vehicles

The study presents the measurement of carbonyl, BTEX (benzene, toluene, ethyl benzene, and xylene), ammonia, elemental/organic carbon (EC/OC), and greenhouse gas emissions from modern heavy-duty diesel and natural gas vehicles. Vehicles from different vocations that included goods movement, refuse trucks, and transit buses were tested on driving cycles representative of their duty cycle. The natural gas vehicle technologies included the stoichiometric engine platform equipped with a three-way catalyst and a diesel-like dual-fuel high-pressure direct-injection technology equipped with a diesel particulate filter (DPF) and a selective catalytic reduction (SCR). The diesel vehicles were equipped with a DPF and SCR. Results of the study show that the BTEX emissions were below detection limits for both diesel and natural gas vehicles, while carbonyl emissions were observed during cold start and low-temperature operations of the natural gas vehicles. Ammonia emissions of about 1 g/mile were observed from the stoichiometric natural gas vehicles equipped with TWC over all the driving cycles. The tailpipe GWP of the stoichiometric natural gas goods movement application was 7% lower than DPF and SCR equipped diesel. In the case of a refuse truck application the stoichiometric natural gas engine exhibited 22% lower GWP than a diesel vehicle. Tailpipe methane emissions contribute to less than 6% of the total GHG emissions.

Implications: Modern heavy-duty diesel and natural gas engines are equipped with multiple after-treatment systems and complex control strategies aimed at meeting both the performance standards for the end user and meeting stringent U.S. Environmental Protection Agency (EPA) emissions regulation. Compared to older technology diesel and natural gas engines, modern engines and after-treatment technology have reduced unregulated emissions to levels close to detection limits. However, brief periods of inefficiencies related to low exhaust thermal energy have been shown to increase both carbonyl and nitrous oxide emissions.     

Evaluation of Multi-level Social Learning for Sustainable Landscapes: Perspective of a Development Initiative in Bergslagen, Sweden

To implement policies about sustainable landscapes and rural development necessitates social learning about states and trends of sustainability indicators, norms that define sustainability, and adaptive multi-level governance. We evaluate the extent to which social learning at multiple governance levels for sustainable landscapes occur in 18 local development initiatives in the network of Sustainable Bergslagen in Sweden. We mapped activities over time, and interviewed key actors in the network about social learning. While activities resulted in exchange of experiences and some local solutions, a major challenge was to secure systematic social learning and make new knowledge explicit at multiple levels. None of the development initiatives used a systematic approach to secure social learning, and sustainability assessments were not made systematically. We discuss how social learning can be improved, and how a learning network of development initiatives could be realized.