Gas cleaning under extreme conditions of temperature and pressure

This paper reviews recent studies conducted in the first-named author's laboratory dealing with selection of filters for temperatures up to 1000°C and pressures of 20 bar. Quartz glass filters improved with alumina-silicates provide adequate stability for extreme conditions. Various conditions for this medium are discussed and test results are presented.     

Mitigation of azinphos-methyl in a vegetated stream: comparison of runoff- and spray-drift

The effectiveness of aquatic macrophytes in reducing runoff- and spray-drift-induced azinphos-methyl (AZP) input was compared in a vegetated stream. Water, sediment and plant samples were taken at increasing distances from a point of input during a spray-drift event and two runoff (10 and 22 mm/day) events. Peak concentrations of AZP decreased significantly (R2=0.99; p<0.0001; n=5) from 0.24 microg/l to 0.11 microg/l during the 10mm runoff event. No reduction took place during the 22 mm event. AZP concentrations were reduced by 90% following spray-drift input, with peak concentrations decreasing significantly (R2=0.93; p=0.0084; n=5) from 4.3 microg/l to 1.7 microg/l with increasing distance from the point of input. Plant samples taken after the spray-drift event showed increased AZP concentrations in comparison to before the event indicating sorption of the pesticide to the macrophytes. Although peak concentrations of AZP were as effectively mitigated during the 10mm runoff event as during the spray-drift event, predictive modelling revealed that maximum concentrations expected during a worst-case scenario 10mm runoff event (0 days after application) are an order of magnitude lower than what can be expected for a worst-case spray-drift and 22 mm runoff event, suggesting that spray-drift-derived pesticide concentrations are more effectively mitigated than those of runoff.     

Influence of vegetation in mitigation of methyl parathion runoff

A pesticide runoff event was simulated on two 10 m x 50 m constructed wetlands (one non-vegetated, one vegetated) to evaluate the fate of methyl parathion (MeP) (Penncap-M). Water, sediment, and plant samples were collected at five sites downstream of the inflow for 120 d. Semi-permeable membrane devices (SPMDs) were deployed at each wetland outflow to determine exiting pesticide load. MeP was detected in water at all locations of the non-vegetated wetland (50 m), 30 min post-exposure. MeP was detected 20 m from the vegetated wetland inflow 30 min post-exposure, while after 10d it was detected only at 10 m. MeP was measured only in SPMDs deployed in non-vegetated wetland cells, suggesting detectable levels were not present near the vegetated wetland outflow. Furthermore, mass balance calculations indicated vegetated wetlands were more effective in reducing aqueous loadings of MeP introduced into the wetland systems. This demonstrates the importance of vegetation as sorption sites for pesticides in constructed wetlands.     

A Biomimetic Approach to the Detection and Identification of Estrogen Receptor Agonists in Surface Waters Using Semipermeable Membrane Devices (SPMDs) and Bioassay-Directed Chemical Analysis (12 pp)

Goal, Scope and Background Some anthropogenic pollutants posses the capacity to disrupt endogenous control of developmental and reproductive processes in aquatic biota by activating estrogen receptors. Many anthropogenic estrogen receptor agonists (ERAs) are hydrophobic and will therefore readily partition into the abiotic organic carbon phases present in natural waters. This partitioning process effectively reduces the proportion of ERAs readily available for bioconcentration by aquatic biota. Results from some studies have suggested that for many aquatic species, bioconcentration of the freely-dissolved fraction may be the principal route of uptake for hydrophobic pollutants with logarithm n-octanol/water partition coefficient (log Kow) values less than approximately 6.0, which includes the majority of known anthropogenic ERAs. The detection and identification of freely-dissolved readily bioconcentratable ERAs is therefore an important aspect of exposure and risk assessment. However, most studies use conventional techniques to sample total ERA concentrations and in doing so frequently fail to account for bioconcentration of the freely-dissolved fraction. The aim of the current study was to couple the biomimetic sampling properties of semipermeable membrane devices (SPMDs) to a bioassay-directed chemical analysis (BDCA) scheme for the detection and identification of readily bioconcentratable ERAs in surface waters. Methods SPMDs were constructed and deployed at a number of sites in Germany and the UK. Following the dialytic recovery of target compounds and size exclusion chromatographic clean-up, SPMD samples were fractionated using a reverse-phase HPLC method calibrated to provide an estimation of target analyte log Kow. A portion of each HPLC fraction was then subjected to the yeast estrogen screen (YES) to determine estrogenic potential. Results were plotted in the form of 'estrograms' which displayed profiles of estrogenic potential as a function of HPLC retention time (i.e. hydrophobicity) for each of the samples. Where significant activity was elicited in the YES, the remaining portion of the respective active fraction was subjected to GC-MS analysis in an attempt to identify the ERAs present. Results and Discussion Estrograms from each of the field samples showed that readily bioconcentratable ERAs were present at each of the sampling sites. Estimated log Kow values for the various active fractions ranged from 1.92 to 8.63. For some samples, estrogenic potential was associated with a relatively narrow range of log Kow values whilst in others estrogenic potential was more widely distributed across the respective estrograms. ERAs identified in active fractions included some benzophenones, various nonylphenol isomers, benzyl butyl phthalate, dehydroabietic acid, sitosterol, 3-(4-methylbenzylidine)camphor (4-MBC) and 6-acetyl-1,1,2,4,4,7-hexamethyltetralin (AHTN). Other tentatively identified compounds which may have contributed to the observed YES activity included various polycyclic aromatic hydrocarbons (PAHs) and their alkylated derivatives, methylated benzylphenols, various alkylphenols and dialkylphenols. However, potential ERAs present in some active fractions remain unidentified. Conclusions and Outlook Our results show that SPMD-YES-based BDCA can be used to detect and identify readily bioconcentratable ERAs in surface waters. As such, this biomimetic approach can be employed as an alternative to conventional methodologies to provide investigators with a more environmentally relevant insight into the distribution and identity of ERAs in surface waters. The use of alternative bioassays also has the potential to expand SPMD-based BDCA to include a wide range of toxicological endpoints. Improvements to the analytical methodology used to identify ERAs or other target compounds in active fractions in the current study could greatly enhance the applicability of the methodology to risk assessment and monitoring programmes.     

Spray deposition of two insecticides into surface waters in a South African orchard area

Drift from pesticide spray application can result in contamination of nontarget environments such as surface waters. Azinphos-methyl (AZI) and endosulfan (END) deposition in containers of water was studied in fruit orchards in the Western Cape, South Africa. Additionally, attention was given to the contamination in farm streams, as well as to the resulting contamination of the subsequent main channel (Lourens River) approx. 25 km downstream of the tributary stream inlets. Spray deposit decreased with increasing distance downwind and ranged from 4.7 mg m(-2) within the target area to 0.2 mg m(-2) at 15 m downwind (AZI). Measured in-stream concentrations of both pesticides compared well with theoretical values calculated from deposition data for the respective distances. Furthermore, they were in the range of values predicted by an exposure assessment based on 95th-percentile values for basic drift deposition (German Federal Biological Research Centre for Agriculture and Forestry [BBA] and USEPA). Pesticide deposition in the tributaries was followed by a measurable increase of contamination in the Lourens River. Mortality of midges (Chironomus spp.) exposed for 24 h to samples obtained from the AZI trials decreased with decreasing concentrations (estimated LC50 from field samples = 10 microg L(-1) AZI; lethal distance: LD50 = 13 m). Mortality in the tributary samples averaged 11% (0.5-1.7 microg L(-1) AZI), while no mortality was discernible in the Lourens River samples (0.041 microg L(-1)). The sublethal endpoint failure to form tubes from the glass beads provided was significantly increased at all sites in comparison with the control (analysis of variance [ANOVA], Fisher's protected least significant difference [PLSD], p < 0.01).     

Seasonal dependence of the chiral composition of alpha-HCH in coastal deposition at the North Sea

The environmental pollutant alpha-HCH was analysed in seawater, air and bulk deposition samples from the North Sea. Enantioselective analyses of the sample extracts gave evidence of the change of the direction of net air-water gas transfer of the contaminant in dependence on the season. Due to warmer water surface temperatures during late summer to early autumn the equilibrium of alpha-HCH between air and water is dominated rather by volatilisation than deposition. The volatilisation of non-racemic alpha-HCH, as known to occur from seawater, changes the enantiomeric ratio in air, which is reflected in the observed ratio in rain that passes the air column.     

Interactions of organic compounds with wastewater dissolved organic matter: role of hydrophobic fractions

The role of structural fractions of dissolved organic matter (DOM) from wastewater in the sorption process of hydrophobic organic compounds is still not clear. In this study, DOM from two wastewater treatment plants (Lachish and Netanya, Israel) was fractionated to hydrophobic acid (HoA) and hydrophobic neutral (HoN) fractions. The fractions were characterized and their sorptive capabilities for s-triazine herbicides and polycyclic aromatic hydrocarbons (PAHs) were studied. For all sorbates, the binding to the HoN fractions was much higher than to HoA fractions. The HoA fractions were more polar than the HoN fractions, containing a higher level of carboxylic functionalities. However the higher binding coefficients of atrazine (2-chloro-4-ethylamine-6-isopropylamino-s-triazine) and ametryn [2-(ethylamino)-4-isopropylamino-6-methyl-thio-s-triazine] obtained for the HoN fractions suggest that their sorption is governed by hydrophobic-like interactions rather than H bonding. The values of binding coefficients of PAHs measured for the HoN fractions were within the range reported for humic acids and much higher than other fractions, suggesting that this fraction plays an important role in the overall sorption of these compounds by DOM. Higher sorption coefficients were measured for the Netanya DOM sample containing higher level of hydrophobic fractions (HoA + HoN) than the Lachish DOM, suggesting that the sorption of hydrophobic organic compounds by DOM is governed by the level of these structural substances. The evaluation of mobility of organic pollutants by wastewater irrigation requires not only assessment of the total carbon concentration but also, more importantly, the content of the hydrophobic fractions.     

Nickel and sulfur speciation of residual oil fly ashes from two electric utility steam-generating units

Representative duplicate fly ash samples were obtained from the stacks of 400- and 385-MW utility boilers (Unit A and Unit B, respectively) using a modified U.S. Environmental Protection Agency (EPA) Method 17 sampling train assembly as they burned 0.9 and 0.3 wt % S residual (No. 6 fuel) oils, respectively, during routine power plant operations. Residual oil fly ash (ROFA) samples were analyzed for Ni concentrations and speciation using inductively coupled plasma-atomic emission spectroscopy, X-ray absorption fine structure (XAFS) spectroscopy, and X-ray diffraction (XRD). ROFA deionized H2O extraction residues were also analyzed for Ni speciation using XAFS and XRD. Total Ni concentrations in the ROFAs were similar, ranging from 1.3-1.5 wt%; however, stack gas Ni concentrations in the Unit A were 0.990 microg/Nm3 compared with 0.620 microg/Nm3 for Unit B because of the greater residual oil feed rates employed at Unit A to attain higher 400-MW load conditions with a lower heating value oil. Ni speciation analysis results indicated that ROFAs from Unit A contain approximately 3 wt % NiSO4 x xH2O (where x is assumed to be 6 for calculation purposes) and appoximately 4.5 wt% of a Ni-containing spinel compound, similar in composition to (Mg,Ni)(Al,Fe)2O4. ROFAs from Unit B contain on average 2 wt% NiSO4 x 6 H20 and 1.1 wt% NiO. XAFS and XRD analyses did not detect any nickel sulfide compounds, including carcinogenic nickel subsulfide (Ni3S2) (XAFS detection limit is 5% of the total Ni concentration). In addition, XAFS measurements indicated that inorganic sulfate and organic thiophene species accounted for > 97% of the total S in the ROFAs. Unit A ROFAs contained much lower thiophene proportions because cyclone-separated ROFA reinjection is employed on this unit to collect and reburn the larger carbonaceous particles.     

Plant Community Structure in Relation to Long-Term Disturbance by Mechanized Military Maneuvers in a Semiarid Region

/ Mechanized military maneuvers are an intensive form of disturbance to plant communities in large areas throughout the world. Tracking by heavy vehicles can cause direct mortality and indirectly affect plant communities through soil compaction and by altering competitive relationships. We assessed the long-term condition of structural attributes of open woodland, grassland, and shrubland communities at Fort Carson, Colorado, in relation to levels of disturbance and soil texture. Covariate analyses were used to help separate the directional forcings by the chronic disturbance from the regenerative capacities in order to assess the relative resistance and resilience of the communities and to determine whether the continual disturbance-recovery processes balanced under current levels of utilization. All three communities responded differently to disturbance. In open woodlands, altered understory/overstory relationships were suggested by increased grass, forb, shrub, and total vegetation cover and smaller decreases in shorter than taller woody species with increasing levels of disturbance. Grassland communities generally displayed greater responses to disturbance than other communities, but temporal dynamics were often similar, indicating relatively less resistance but greater resilience of this community. Weed and exotic species increased both temporally and in relation to levels of disturbance in all three community types. Temporal trends in community-level indices of dissimilarity and diversity also indicate that rates of disturbance were greater than rates of recovery. Few variables were related to within-community differences in soil texture. While total aerial cover was temporally stable, changes in species composition and in basal cover in grasslands and shrublands suggest increasing erosion potential.