Capital and Operating Costs of Selected Air Pollution Control Systems-III

Pollution control systems will normally require some auxiliary equipment to capture and carry the gas stream to the control device. In general, this auxiliary equipment will consist of a hood or similar device to isolate and collect the pollutant-laden gas, ductwork to convey the gas stream to the control device, and dampers to control and modulate the flow. In this article, the equipment cost of canopy hoods, ducting, and dampers will be considered, together with their effect on the size, cost, and operation of the control device.     

Assessment of lead uptake in reptilian prey species

As part of an investigation determining the trophically available fraction of metals in a model terrestrial food web, i.e., invertebrate prey to Western fence lizards (Sceloporus occidentalis), we evaluated the ability of several invertebrate prey to bioaccumulate lead and to form metals-rich granules, which are hypothesized to be non-available to predators. Crickets (Acheta domestica), tenebroid beetle larvae (Tenebrio molitor), and isopods (Porcellio scaber) were selected as model prey organisms. Lack of standard exposure methodologies for these species has presented a barrier to trophic transfer evaluations, as each species has particular requirements that create challenges for designing exposure conditions. We were able to devise exposure conditions for all three species that allow long-term exposure studies. All prey organisms accumulated lead from contaminated food, and for all species the majority of the accumulated Pb was associated with the exoskeleton (>50%), with metals-rich granules accounting for most of the remaining accumulated lead.     

New methodology to investigate potential contaminant mass fluxes at the stream-aquifer interface by combining integral pumping tests and streambed temperatures

The spatial pattern and magnitude of mass fluxes at the stream-aquifer interface have important implications for the fate and transport of contaminants in river basins. Integral pumping tests were performed to quantify average concentrations of chlorinated benzenes in an unconfined aquifer partially penetrated by a stream. Four pumping wells were operated simultaneously for a time period of 5 days and sampled for contaminant concentrations. Streambed temperatures were mapped at multiple depths along a 60m long stream reach to identify the spatial patterns of groundwater discharge and to quantify water fluxes at the stream-aquifer interface. The combined interpretation of the results showed average potential contaminant mass fluxes from the aquifer to the stream of 272microgm(-2)d(-1) MCB and 71microgm(-2)d(-1) DCB, respectively. This methodology combines a large-scale assessment of aquifer contamination with a high-resolution survey of groundwater discharge zones to estimate contaminant mass fluxes between aquifer and stream.     

Distribution and variability of redox zones controlling spatial variability of arsenic in the Mississippi River Valley alluvial aquifer, southeastern Arkansas

Twenty one of 118 irrigation water wells in the shallow (25-30 m thick) Mississippi River Valley alluvial aquifer in the Bayou Bartholomew watershed, southeastern Arkansas had arsenic (As) concentrations (<0.5 to 77 microg/L) exceeding 10 microg/L. Sediment and groundwater samples were collected and analyzed from the sites of the highest, median, and lowest concentrations of As in groundwater in the alluvial aquifers located at Jefferson County, Arkansas. A traditional five-step sequential extraction was performed to differentiate the exchangeable, carbonate, amorphous Fe and Mn oxide, organic, and hot HNO(3)-leachable fraction of As and other compounds in sediments. The Chao reagent (0.25 M hydroxylamine hydrochloride in 0.25 M HCl) removes amorphous Fe and Mn oxides and oxyhydroxides (present as coatings on grains and amorphous minerals) by reductive dissolution and is a measure of reducible Fe and Mn in sediments. The hot HNO(3) extraction removes mostly crystalline metal oxides and all other labile forms of As. Significant total As (20%) is complexed with amorphous Fe and Mn oxides in sediments. Arsenic abundance is not significant in carbonates or organic matter. Significant (40-70 microg/kg) exchangeable As is only present at shallow depth (0-1 m below ground surface). Arsenic is positively correlated to Fe extracted by Chao reagent (r=0.83) and hot HNO(3) (r=0.85). Arsenic extracted by Chao reagent decreases significantly with depth as compared to As extracted by hot HNO(3). Fe (II)/Fe (the ratio of Fe concentration in the extracts of Chao reagent and hot HNO(3)) is positively correlated (r=0.76) to As extracted from Chao reagent. Although Fe (II)/Fe increases with depth, the relative abundance of reducible Fe decreases noticeably with depth. The amount of reducible Fe, as well as As complexed to amorphous Fe and Mn oxides and oxyhydroxides decreases with depth. Possible explanations for the decrease in reducible Fe and its complexed As with depth include historic flushing of As and Fe from hydrous ferric oxides (HFO) by microbially-mediated reductive dissolution and aging of HFO to crystalline phases. Hydrogeochemical data suggests that the groundwater in the area falls in the mildly reducing (suboxic) to relatively highly reducing (anoxic) zone, and points to reductive dissolution of HFO as the dominant As release mechanism. Spatial variability of gypsum solubility and simultaneous SO(4)(2-) reduction with co-precipitation of As and sulfide is an important limiting process controlling the concentration of As in groundwater in the area.     

Rooting response in stem cuttings from five species of mangrove trees: effect of auxins and enzyme activities

An experiment was conducted to optimise rooting in stem cuttings of the mangrove tree species Bruguiera parviflora, Cynometra iripa, Excoecaria agallocha, Heritiera fomes and Thespesia populnea. Cuttings were girdled or non-girdled and treated with the auxins indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) and naphthalene-acetic acid (NAA) and amylase, IAA-oxidase, peroxidase and polyphenol oxidase activities were measured. The best rooting performance (in terms of root number) was in stem cuttings of E. agallocha followed by C. iripa and H. fomes when treated with IBA + NAA. IAA and IBA combinations were more effective in T. populnea and B. parvifolia. Variations in rooting response were markedly reflected in amylase, IAA-oxidase, peroxidase and polyphenol oxidase activities. Sharp increases in amylase and polyphenol-oxidase activities were associated with enhanced rooting in E. agallocha, C. iripa and H. fomes. On the contrary, lowered IAA-oxidase and peroxidase activities favoured rooting in T. populnea and B. parviflora. A higher number of roots occurred in pre-girdled cuttings in comparison to non-girdled cuttings. Received: 30 March 1999 / Accepted: 6 October 1999     

Male-male competition ensures honest signaling of male parental ability in the three-spined stickleback (Gasterosteus aculeatus)

The importance of socially imposed costs for the evolution and maintenance of honest sexual signals has received less attention than other costs. Here I show that male-male competition can increase the honesty of sexual signaling in relation to male parental ability in a species with flexible signaling. When four three-spined stickleback (Gasterosteus aculeatus) males were allowed to court a female first separately and then in competition, red nuptial coloration under competition reflected male parental ability more accurately than red coloration when separated. Parental ability was determined as the ability of the male to raise a clutch of eggs to the hatching stage under interaction with other breeding and non-breeding males. The increased honesty under competition was probably due to subordinate males of poor parental ability decreasing their color expression under interaction to reduce the risk of fights with superior males. However, socially imposed costs of signaling were probably not the main factors maintaining honest signaling, as red coloration reflected male parental ability also in the absence of competition, although less accurately. Nevertheless, the small-scale differences that male-male competition induced can significantly facilitate adaptive female choice and have large impacts on sexual selection. Received: 7 July 2000 / Revised: 31 August 2000 / Accepted: 4 September 2000     

Straßenversiegelung in Deutschland und ihre Beinflussung der Umwelt im Vergleich mit anderen OECD-Ländern

Since the increasing awareness of environmental damage, attention has focussed on the problems caused by the extension of car traffic. The number of cars has permanently increased over the years and is predicted to continue in the future. The number of cars registered worldwide already passed the number of 500 million in the year 1988 (OECD, 1995). Two major problems are linked to the increase in car traffic: The air pollution by engine conbustion and the so-called sealing of the ground by pavements. The streets dramatically cut into coherent areas, separate biotopes, animal and plant populations (BBR, 1998). Facts about grund sealing in Germany are presented and compared to those of other OECD-countries. Environmental consequences are discussed.     

Quantifying RDX biodegradation in groundwater using δ15N isotope analysis

Isotope analysis was used to examine the extent of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) biodegradation in groundwater along a ca. 1.35-km contamination plume. Biodegradation was proposed as a natural attenuating remediation method for the contaminated aquifer. By isotope analysis of RDX, the extent of biodegradation was found to reach up to 99.5% of the initial mass at a distance of 1.15–1.35 km down gradient from the contamination sources. A range of first-order biodegradation rates was calculated based on the degradation extents, with average half-life values ranging between 4.4 and 12.8 years for RDX biodegradation in the upper 15 m of the aquifer, assuming purely aerobic biodegradation, and between 10.9 and 31.2 years, assuming purely anaerobic biodegradation. Based on the geochemical data, an aerobic biodegradation pathway was suggested as the dominant attenuation process at the site. The calculated biodegradation rate was correlated with depth, showing decreasing degradation rates in deeper groundwater layers. Exceptionally low first-order kinetic constants were found in a borehole penetrating the bottom of the aquifer, with half life ranging between 85.0 to 161.5 years, assuming purely aerobic biodegradation, and between 207.5 and 394.3 years, assuming purely anaerobic biodegradation.The study showed that stable isotope fractionation analysis is a suitable tool to detect biodegradation of RDX in the environment. Our findings clearly indicated that RDX is naturally biodegraded in the contaminated aquifer. To the best of our knowledge, this is the first reported use of RDX isotope analysis to quantify its biodegradation in contaminated aquifers.