The variability and intrinsic remediation of a BTEX plume in anaerobic sulphate-rich groundwater

Data from long-term groundwater sampling, limited coring, and associated studies are synthesised to assess the variability and intrinsic remediation/natural attenuation of a dissolved hydrocarbon plume in sulphate-rich anaerobic groundwater. Fine vertical scale (0.25- and 0.5-m depth intervals) and horizontal plume-scale (>400 m) characteristics of the plume were mapped over a 5-year period from 1991 to 1996. The plume of dissolved BTEX (benzene, toluene, ethylbenzene, xylene) and other organic compounds originated from leakage of gasoline from a subsurface fuel storage tank. The plume was up to 420 m long, less than 50 m wide and 3 m thick. In the first few years of monitoring, BTEX concentrations near the point of leakage were in approximate equilibrium with non-aqueous phase liquid (NAPL) gasoline. NAPL composition of core material and long-term trends in ratios of BTEX concentrations in groundwater indicated significant depletion (water washing, volatilisation and possibly biodegradation) of benzene from residual NAPL after 1992. Large fluctuations in BTEX concentrations in individual boreholes were shown to be largely attributable to seasonal groundwater flow variations. A combination of temporal and spatial groundwater quality data was required to adequately assess the stationarity of plumes, so as to allow inference of intrinsic remediation. Contoured concentration data for the period 1991 to 1996 indicated that plumes of toluene and o-xylene were, at best, only partially steady state (pseudo-steady state) due to seasonal groundwater flow changes. From this analysis, it was inferred that significant remediation by natural biodegradation was occurring for BTEX component plumes such as toluene and o-xylene, but provided no conclusive evidence of benzene biodegradation. Issues associated with field quantification of intrinsic remediation from groundwater sampling are highlighted. Preferential intrinsic biodegradation of selected organic compounds within the BTEX plume was shown to be occurring, in parallel with sulphate reduction and bicarbonate production. Ratios of average hydrocarbon concentrations to benzene for the period 1991 to 1992 were used to estimate degradation rates (half-lives) at various distances along the plume. The estimates varied with distance, the narrowest range being, for toluene, 110 to 260 days. These estimates were comparable to rates determined previously from an in situ tracer test and from plume-scale modelling.     

Identifikation der kfz-bürtigen Schadstoffbelastung mit Hilfe der Verh?ltnisse der stabilen Isotope von Kohlenstoff und Schwefel

Zusammenfassung  Reifen-, Ru?-, Motoren?l-, Asphalt-, Plastik- und Lackproben aus dem Stra?enverkehr wurden auf ihre Kohlenstoff- und Schwefel-isotopenverh?ltnisse mit dem Ziel untersucht, die Frage zu beant-worten, ob diese Isotopenverh?ltnisse als Indikatoren für die Belastungssituation und die Schadstoffquellen bei der Untersuchung von stra?ennahen B?den eingesetzt werden k?nnen. Die δ¹¹C-Werte der technischen Substrate lagen zwischen-30‰ und-18‰ relativ zum PDB-Standard, Dabei zeigte sich aufgrund der unterschiedlichen Herstellungsverfahren eine deutliche Abgrenzung der Substrate untereinander. Asphalt hatte Werte zwischen-23 und-18‰, Ru? zwischen -27 und -22‰ Die Ru?proben unterschieden sich je nach Art des verwendeten Kraftstoffs. Plastik, Lack und Motor?le zeigten ?hnliche δ¹³C-Werte, die zwischen-30 und-27‰ lagen. Reifen haben relativ konstante δ¹³C-Werte um -26‰ Der Einflu? des Stra?enverkehrs auf die δ¹³C-Werte im Stra?ensediment und in stra?ennahen B?den konnte anhand verschiedener Kohlenstoffspezies an einem Transekt an einer Landstra?e aufgezeigt werden. Ein Vergleich mit verkehrstypischen Schwermetallemissionen ergab bei einzelnen Kohlenstoffspezies einen ?hnlichen Verlauf der Schwermetallkonzentrationen und der δ¹³C-Werte. Die δ³⁴S-Werte lagen zwischen -6 und +8‰ relativ zum CDT-Standard. Eine Abgrenzung der Substrate in ihren δ¹⁴S-Werten war hierbei nicht m?glich.      

Development of a black carbon-inclusive multi-media model: application for PAHs in Stockholm

A multi-media model was developed for predicting the fate of organic chemicals in the Greater Stockholm Area, Sweden, and applied to selected polycyclic aromatic hydrocarbons (PAHs). Although urban models have been previously developed, this model is novel in that it includes sorption to pyrogenically-derived particles, commonly termed "black carbon" (BC), within the model structure. To examine the influence of BC sorption on environmental fate of PAHs, two versions of the model were generated and run: one in which sorption to BC was included and one in which BC sorption was excluded. The inclusion of BC sorption did not cause any significant variations to air levels, but it did cause an average 20-30% increase in sediment concentrations related to increased sediment solids partitioning. The model also predicted reduced advective losses out of the model domain, as well as chemical potential to diffuse from sediments, whilst total chemical inventory increased. In all cases, the lighter PAHs were more affected by BC inclusion than their heavier counterparts. We advocate the addition of sorption to BC in future multi-media fate and exposure models, which as well as influencing fate will also alter (lower) chemical availability and, thus, wildlife exposure to hydrophobic chemicals. A quantification of the latter was derived with the help of the soot-inclusive model version, which estimated a lowering of dissolved water concentrations between five and >200 times for the different PAHs of this study.     

When the type of move matters: employee outcomes under various relocation situations

The type of job change associated with relocation and the type of relocation decision were examined as predictors of post‐move attitudes and intentions. Employees who relocated for a lateral or downward job change reported lower perceived organizational support and higher turnover intentions than those who relocated for a promotion. Further, those taking downward moves or moving involuntarily had lower perceptions of support and higher intentions to quit than lateral relocators and voluntary relocators, respectively. Copyright © 2000 John Wiley & Sons, Ltd.     

Demonstration of a high field electrostatically enhanced venturi scrubber on a magnesium furnace fume emission

A 566 m³/m (20,000 acfm) permanent installation demonstration system, consisting of the Air Pollution Systems' High Intensity Ionizer and a variable throat venturi scrubber (called the Scrub-E) has been installed on a magnesium recovery furnace. The furnace produces submicron fume particles of MgO, MgCl₂, and ZrCl₄. The system is designed to demonstrate the effectiveness of the High Intensity Ionizer versus high venturi pressure drop on the furnace emissions. The High Intensity Ionizer array operates stably at field strengths of 10–15 kV/cm and at velocities in excess of 18 m/sec (60 fps) while maintaining high charging efficiencies. The report covers the system design, technology, applications, and project developments. An Environmental Protection Agency proposed charged droplet Scrub-E is also discussed covering the design, technology, and proposed demonstration program.     

Plutonium in sheep faeces as an indicator of deposition on vegetation

In order to study the deposition on vegetation of plutonium arising from the testing of nuclear weapons and discharges from nuclear facilities, sheep faeces were collected from the South-west and North of England. The plutonium content of faeces has been shown to be a reproducible and sensitive indicator of deposition on herbage and, with this technique, plutonium discharged from the Sellafield Works of British Nuclear Fuels LImited can be detected 60 km from the site. On moorland pastures the concentration of ^239+240Pu in faeces, expressed as activity per gram of ash, is roughly equal numerically to the deposit of plutonium on 1 m² of vegetation.Some of the plutonium ingested by a grazing sheep is absorbed and the highest concentrations are found in liver. The liver of a sheep grazing on pasture where the ^239+240Pu concentration in faeces was about 2 pCi (74 mBq) g⁻¹ of ash, was found to contain <1% of the Generalised Derived Limit for mutton and offal, and the meat <0·001%.     

An appraisal of emissions control requirements in the California South Coast Air Basin

The purpose of this study is to evaluate the effect of reductions of reactive organic gases (ROG) and NO_x emissions on short-term O₃ and NO₂ concentrations and annual average NO₂ concentrations in the California South Coast Air Basin. Short-term air quality predictions were obtained by applying the Systems Applications Airshed Model to summer O₃ and autumn NO₂ episodes. Effects of emission controls on annual NO₂ concentrations were estimated using CDM and a new parcel tracking model NOXTRAK. Results for the summer O₃ episode indicate that ROG emission reduction in an effective means for reducing peak O₃ concentrations. NO_x emission reduction imposed in addition to ROG emission reductions are counterproductive in reducing peak O₃ concentrations. The modeling results also suggest that attainment of the 1-h federal O₃ standard requires ROG emission reductions on the order of 80% from 1987 levels. Results for the autumn NO₂ episode indicate that NO_x emission reductions approximating those recommended in a proposed Air Quality Management Plan (about 22%) will result in only small (about 5%) reductions in the peak NO₂ concentrations. ROG emission reduction may be more effective than NO_x emission reduction in reducing the peak NO₂ concentration. For the episode studied, a reduction of 36% in ROG emissions is estimated to result in a reduction in peak NO₂ concentrations commensurate with that required to attain the 1-h state NO₂ standard. Model calculations also indicate that the federal NO₂ standard may not be meet by 1987 at one or two stations, but may blosely approached.     

Design,measurement and evaluation of photovoltaic pumping system for rural areas in Oman

In the present paper, the optimum design of a PV system used to operate a water pumping system was determined for Oman. The system design focused on the environmental conditions of Sohar city. The implementation and measurement of the designed system are presented to prove the effectiveness of the proposed system. The results show that the system can provide the required power at peak hours, leading to a substantial reduction in the sizing of the PV system. Consequently, the investment capital costs 2400 USD, and the cost of energy is equal to 0.309 USD/kWh. Furthermore, the results indicate that the system annual yield factor is 2024.66 kWh/kWp and that the capacity factor is 23.05 %, which is encouraging since the latter is typically 21 %. The system capital cost and the cost of energy are worth comparing to a diesel generator. A comparison is made between the proposed system and several others in the literature. The comparison indicated that the system cost of energy is promising.     

Diatoms in bottom sediments as indicators of pollution of urban aquatic ecosystems

Analysis of the concentrations of chemical elements and the composition of diatoms in the surface layer of bottom sediments has been performed in a small reservoir at the mouth of dammed river to evaluate the levels of pollution and the impact of toxicants on diatom communities of the river ecosystem. Data on interrelations between the concentrations of chemical elements and the relationship between inorganic pollution and accumulation of diatoms in bottom sediments as an indicator of development of the diatom assemblage have been obtained using linear correlation analysis and graphical plotting.     

The holocene dynamics of vegetation and environmental conditions on the eastern slope of the Northern Urals

Consideration is given to changes in the vegetation and climatic conditions on the eastern slope of the Northern Urals in the second half of the Holocene as reconstructed on the basis of integrated palynological, botanical, paleocarpological, and radiocarbon analysis of material from a peat bog section in the floodplain of the Loz’va River. The results show that the northern taiga zone of the study region in the period between approximately 5000 and 700 years BP was occupied by forests of southern taiga facies, as the climate was significantly warmer than it is today.