Stimulation of reductive dechlorination of hexachlorobenzene in soil by inducing the native microbial activity

The reductive dechlorination and behaviour of ¹⁴C-hexachlorobenzene (HCB) was investigated in an arable soil. The activity of the native anaerobic microbial communities could be induced by saturating the soil with water. Under these conditions high rates of dechlorination were observed. After 20 weeks of incubation only 1% of the applied ¹⁴C-HCB could be detected in the fraction of extractable residues. Additional organic substances, like wheat straw and lucerne straw, however considerably delayed and reduced the dechlorination process in the soil. The decline of HCB was not only caused by dechlorination but also by the formation of non-extractable residues, whereby their amounts varied with time depending on the experimental conditions. Several dechlorination products were detected, indicating the following main HCB transformation pathway: HCB → PCB → 1,2,3,5-TeCB → 1,3,5-TCB → 1,3-DCB, with 1,3,5-TCB as main intermediate dechlorination product. The other TeCB-, TCB- and DCB-isomers were also detected in low amounts, showing the presence of more than one dechlorination pathway. Since the methane production rates were lowest when the dechlorination rates were highest, it can be assumed that methanogenic bacteria were not involved in the dechlorination process of HCB. The established ¹⁴C-mass balances show, that with increasing dechlorination and incubation times, the ¹⁴C-recoveries decreased.     

Development of emission factors for polycarbonate processing

Emission factors for selected volatile organic compounds (VOCs) and particulate emissions were developed while processing eight commercial grades of polycarbonate (PC) and one grade of a PC/acrylonitrile-butadiene-styrene (ABS) blend. A small commercial-type extruder was used, and the extrusion temperature was held constant at 304 degrees C. An emission factor was calculated for each substance measured and is reported as pounds released to the atmosphere/million pounds of polymer resin processed [ppm (wt/wt)]. Scaled to production volumes, these emission factors can be used by processors to estimate emission quantities from similar PC processing operations.     

Activity patterns in the terebellid polychaete <Emphasis Type="Italic">Eupolymnia nebulosa</Emphasis> assessed using a new image analysis system

The activity and surface sediment displacement by the terebellid polychaete Eupolymnia nebulosa were monitored, using new image acquisition and image analysis procedures. We used a video sensor mounted on a motorized table, to acquire adjacent images of the whole studied aquarium within about 2 s. These images were then grouped within a composite image acquired every 15 s. Consecutive composite images were compared to infer activity and surface sediment displacement. This procedure proved efficient for E. nebulosa as indicated by (1) the continuity of the tentacles within composite images, and (2) the direct comparison of images and detected activities. There were important temporal changes in the relative importance of the three main types of activity: feeding, tube-building and (both partial and total) emergence from the tube, accounting, respectively, for 75, 15 and 10% of the entire experiment duration. Activity intensity (cm² min^-1) was assessed through the surface of pixels with grey levels differing by more than 20 (on a 0–255 scale) between two consecutive images. Feeding was associated with low activity intensity, whereas tube-building and emergence from the tubes were associated with high activity intensities. Surface sediment displacement mostly resulted from tentacle activity both during feeding and tube-building and was almost zero when worms emerged from their tube. We used our experimental set up to assess spatial changes in activity intensity and particle displacements along the tentacles. Most of the activity occurred within the first 4–6 cm from the tube aperture. Particle loss during their transfer along the tentacles preferentially affected larger particles as postulated by the model of particle selection and transport in tentaculate deposit-feeders. Moreover, the speed of the particles along the tentacles correlated negatively with their size. This contributed to increase in the residence time of larger particles on the tentacles and thus, to further enhance their probability of being lost. The size distributions of particles during feeding and tube-building did not differ significantly although visual observations confirmed the preferential use of larger particles for tube-building. This suggests the existence of a sorting step occurring elsewhere than on the tentacles as already demonstrated for spionid polychaetes.     

Environmental auditing at the crossroads: The environmental auditing roundtable's response to ISO 14000

The Environmental Auditing Roundtable (EAR) is the single largest professional organization in the world, representing over 900 members. Built on a tradition of promoting environmental auditing through openly sharing experiences in the field of safety, health, and environmental auditing, the organization in recent years has significantly expanded its influence on auditing practices both nationally and internationally by monitoring audit activities and participating in the development of audit policy, regulation, standardization, and the certification of environmental auditors. This article describes the origin and evolution of the organization from meeting the needs of the membership to addressing the needs of external national and international stakeholders.     

Temporal changes in wetland landscapes of a section of the St. Lawrence River,Canada

Historical aerial photographs (from 1946 through 1983) were used to study and describe the nature and extent of changes in wetland vegetation of a section of the St. Lawrence River and to evaluate the relative importance of water level, fire, and vegetational development as causal factors of these historical changes. Data were encoded and analyzed using a geographical information system, autocorrelation, and Mantel tests. Results show three temporal patterns in wetland dynamics. First, some wetland zones have been reduced by human activities (urbanization, landfilling, canal dredging). The second group consists of wetland areas that remain stable and do not change over time. They are generally protected sites artificially maintained by water-level control. A third situation has occurred in the Lake Saint-François National Wildlife Area, where no significant wetland losses were detected, but where landscape structure has changed greatly. Modeling with Mantel tests suggests that, in the latter case, these changes in wetland landscape are related to the suppression of burning (fires set deliberately by Indians) since the purchase of the territory by the Canadian federal government. This situation has caused rapid replacement of wet meadows byAlnus rugosa scrub and a possible decline in habitat diversity.     

Trends and patterns in section 404 permitting requiring compensatory mitigation in Oregon and Washington,USA

The effects of permitting decisions made under Section 404 of the Clean Water Act for which compensatory mitigation was required were examined. Information was compiled on permits issued in Oregon (January 1977–January 1987) and Washington (1980–1986). Data on the type of project permitted, wetland impacted, and mitigation project were collected and analyzed. The records of the Portland and Seattle District Offices of the US Army Corps of Engineers and of Environmental Protection Agency Region X were the primary sources of information. The 58 permits issued during the years of concern in Oregon document impacts to 82 wetlands and the creation of 80. The total area of wetland impacted was 74 ha while 42 ha were created, resulting in a net loss of 32 ha or 43%. The 35 permits issued in Washington document impacts to 72 wetlands and the creation of 52. The total area of wetland impacted was 61 ha while 45 ha were created, resulting in a net loss of 16 ha or 26%. In both states, the number of permits requiring compensation increased with time. The area of the impacted and created wetlands tended to be ≤0.40 ha. Permitted activity occurred primarily west of the Cascade Mountains and in the vicinity of urban centers. Estuarine and palustrine wetlands were impacted and created most frequently. The wetland types created most often were not always the same as those impacted; therefore, local gains and losses of certain types occurred. In both states the greatest net loss in area was in freshwater marshes. This study illustrates how Section 404 permit data might be used in managing a regional wetland resource. However, because the data readily available were either incomplete or of poor quality, the process of gathering information was very labor intensive. Since similar analyses would be useful to resource managers and scientists from other areas, development of an up-to-date standardized data base is recommended.     

Emergency braking is affected by the use of cruise control

Objective: We compared the differences in the braking response to vehicle collision between an active human emergency braking (control condition) and cruise control (CC) or adaptive cruise control (ACC).

Methods: In 11 male subjects, age 22 to 67 years, we measured the active emergency braking response during manual driving using the accelerator pedal (control condition) or in condition mimicking CC or ACC. In both conditions, we measured the brake reaction time (BRT), delay to produce the peak braking force (PBD), total emergency braking response (BRT + PBD), and peak braking force (PBF). Electromyograms of leg and thigh muscles were recorded during braking. The tonic vibratory response (TVR), Hoffman reflex (HR), and M-waves were recorded in leg muscles to explore the change in sensorimotor control.

Results: No difference in PBF, TVR amplitude, HR latency, and H_max/M_max ratio were found between the control and CC/ACC conditions. On the other hand, BRT and PBD were significantly lengthened in the CC/ACC condition (240 ± 13 ms and 704 ± 70 ms, respectively) compared to control (183 ± 7 ms and 568 ± 36 ms, respectively). BRT increased with the age of participants and the driving experience shortened PBD and increased PBF.

Conclusions: In male subjects, driving in a CC/ACC condition significantly delays the active emergency braking response to vehicle collision. This could result from higher amplitude of leg motion in the CC/ACC condition and/or by the age-related changes in motor control. Car and truck drivers must take account of the significant increase in the braking distance in a CC/ACC condition.     

Soil Vapor Extraction and Chemical Oxidation to Remediate Chlorinated Solvents in Fractured Crystalline Bedrock: Pilot Study Results and Lessons Learned

A pilot study was completed at a fractured crystalline bedrock site using a combination of soil vapor extraction (SVE) and in‐situ chemical oxidation (ISCO) with Fenton's Reagent. This system was designed to destroy 1,1,1‐trichloroethane (TCA) and its daughter products, 1,1‐dichloroethene (DCE) and 1,1‐dichloroethane (DCA). Approximately 150 pounds of volatile organic compounds (VOCs) were oxidized in‐situ or removed from the aquifer as vapor during the pilot study. Largely as a result of chemical oxidation, TCA concentrations in groundwater located within a local groundwater mound decreased by 69 to 95 percent. No significant rebound in VOC concentration was observed in these wells. Wells located outside of the groundwater mound showed less dramatic decreases in VOC concentration, and the data show that vapor stripping and short‐term groundwater migration following the oxidant injection were the key processes at these wells. Although the porosity of the aquifer at the site is on the order of 2 percent or less, the pilot study showed that SVE could be an effective remedial process in fractured crystalline rock. © 2002 Wiley Periodicals, Inc.