Air pollutant concentrations near three Texas roadways, part II: Chemical characterization and transformation of pollutants

Spatial gradients of vehicular emitted air pollutants were measured in the vicinity of three roadways in the Austin, Texas area: (1) State Highway 71 (SH-71), a heavily traveled arterial highway dominated by passenger vehicles; (2) Interstate 35 (I-35), a limited access highway north of Austin in Georgetown; and (3) Farm to Market Road 973 (FM-973), a heavily traveled surface roadway with significant truck traffic. A mobile monitoring platform was used to characterize the gradients of CO and NO_x concentrations with increased distance from each roadway, while concentrations of carbonyls in the gas-phase and fine particulate matter mass and composition were measured at stationary sites upwind and at one (I-35 and FM-973) or two (SH-71) downwind sites. Regardless of roadway type or wind direction, concentrations of carbon monoxide (CO), nitric oxide (NO), and oxides of nitrogen (NO_x) returned to background levels within a few hundred meters of the roadway. Under perpendicular wind conditions, CO, NO and NO_x concentrations decreased exponentially with increasing distance perpendicular to the roadways. The decay rate for NO was more than a factor of two greater than for CO, and it comprised a larger fraction of NO_x closer to the roadways than further downwind suggesting the potential significance of near roadway chemical processing as well as atmospheric dilution. Concentrations of most carbonyl species decreased with distance downwind of SH-71. However, concentrations of acetaldehyde and acrolein increased farther downwind of SH-71, suggesting chemical generation from the oxidation of primary vehicular emissions. The behavior of particle-bound organic species was complex and further investigation of the size-segregated chemical composition of particulate matter (PM) at increasing downwind distances from roadways is warranted. Fine particulate matter (PM_2.5) mass concentrations, polycyclic aromatic hydrocarbons (PAHs), hopanes, and elemental carbon (EC) concentrations generally exhibited concentrations that decreased with distance downwind of SH-71. Concentrations of organic carbon (OC) increased from upwind concentrations immediately downwind of SH-71 and continued to increase further downwind from the roadway. This behavior may have primarily resulted from condensation of semi-volatile organic species emitted from vehicle sources with transport downwind of the roadway.     

Hormesis and plant biology

A database has been developed that demonstrates experimental evidence of hormesis. It includes information from a broad range of biological models, including plants, and information on study design, dose-response features, and physical/chemical properties of the agents. An assessment of plant hormetic dose responses is presented based on greater than 3000 plant endpoints. Plant hormetic dose responses were observed for numerous endpoints including disease incidence, reproductive indices, mutagenic endpoints, various metabolic parameters, developmental processes, and a range of growth indicators. Quantitative features of these dose responses typically display a maximum stimulatory response less than two-fold greater than controls and a width of the stimulatory response usually less than 10-fold in dose range. The database establishes that hormetic dose responses commonly occur in plants, are broadly generalizable, and have quantitative features similar to hormetic dose responses found for animals.     

Maternal allocation of lipid classes and fatty acids with seasonal egg production in Atlantic cod (Gadus morhua) of wild origin

A suite of characteristics is often used to assess egg quality as these properties potentially play important roles in progeny survival and growth. Our objective was to assess egg characteristics including lipid biocomposition of an iteroparous, batch-spawning teleost of wild origin. Maternal allocation to egg number was generally dome-shaped (5 of 8 females) and egg size declined over the breeding season for eight breeding pairs of wild Atlantic cod (Gadus morhua) (n = 43 batches). Egg lipid composition ranged considerably among females and between egg batches within females (e.g., phospholipids 40–86 %; polar 47–87 % and neutral lipids 15–52 % of total lipids; polyunsaturated fatty acids 16–50 % of total fatty acids). Principal component analyses revealed significant inter-relationships among maternal traits, batch sequence and fecundity, and egg size and composition. Seasonal trends with regard to lipid deposition were variable; three females showed consistent declines in lipid parameters (μg egg⁻¹) with both batch number and egg diameter, one female showed consistent increase and the four remaining females showed no trend. The three females that exhibited seasonal declines in egg lipid content were characterized as having high fertilization success (>75 %). Our findings highlight the variability in lipid allocation to eggs of batch spawners of wild origin and characterize the composition of endogenous reserves available during embryogenesis and yolk sac larval stages.     

Neue Reaktor-Technologien

It is doubtful that large-scale industrial utilization of the fast breeding reactor will ever be possible. It is, however, probable that the thorium reactor, for which three plans already exist, will be realized. There is enough thorium to supply thorium reactors up to the next glacial period.     

Chromium speciation and fractionation in ground and surface waters in the vicinity of chromite ore processing residue disposal sites

Chromium concentrations of up to 91 mg l(-1) were found by ICP-OES for ground water from nine boreholes at four landfill sites in an area of S.E. Glasgow/S. Lanarkshire where high-lime chromite ore processing residue (COPR) from a local chemical works had been deposited from 1830 to 1968. Surface water concentrations of up to 6.7 mg l(-1) in a local tributary stream fell to 0.11 mg l(-1) in the River Clyde. Two independent techniques of complexation/colorimetry and speciated isotope dilution mass spectrometry (SIDMS) showed that Cr was predominantly (>90%) in hexavalent form (CrVI) as CrO4(2-), as anticipated at the high pH (7.5-12.5) of the sites. Some differences between the implied and directly determined concentrations of dissolved CrIII, however, appeared related to the total organic carbon (TOC) content. This was most significant for the ground water from one borehole that had the highest TOC concentration of 300 mg l(-1) and at which < 3% of Cr was in the form of CrVI. Subsequent ultrafiltration produced significant decreases in Cr concentration with decreasing size fractions, e.g. <0.45 microm, < 100 kDa, <30 kDa and < 1 kDa by the tangential-flow method. As this appeared related more to concentrations of humic substances than of TOC per se, horizontal bed gel electrophoresis of freeze-dried ultrafilter retentates was carried out to further characterise the CrIII-organic complex. This showed for the main Cr-containing fraction, 100 kDa-0.45 microm, that the Cr was associated with a dark brown band characteristic of organic (humic) matter. Comparison of gel electrophoresis and FTIR results for ultrafilter retentates of ground water from this borehole with those for a borehole at another site where CrVI predominated suggested the influence of carboxylate groups, both in reducing CrVI and in forming soluble CrIII-humic complexes. The implications of this for remediation strategies (especially those based on the addition of organic matter) designed to reduce highly mobile and carcinogenic Cr(VI)O4(2-) to the much less harmful CrIII as insoluble Cr(OH)3 are discussed.     

Examples of the role of analytical chemistry in environmental risk management research

Analytical chemistry is an important tier of environmental protection and has been traditionally linked to compliance and/or exposure monitoring activities for environmental contaminants. The adoption of the risk management paradigm has led to special challenges for analytical chemistry applied to environmental risk analysis. Namely, methods developed for regulated contaminants may not be appropriate and/or applicable to risk management scenarios. This paper contains examples of analytical chemistry applied to risk management challenges broken down by the analytical approach and analyte for some selected work in our laboratory. Specific techniques discussed include stable association complex electrospray mass spectrometry (cESI-MS), gas chromatography-mass spectrometry (GC-MS), split-flow thin cell (SPLITT) fractionation and matrix-assisted laser desorption time of flight mass spectrometry (MALDI-ToF-MS). Specific analytes include haloacetic acids (HAA9), perchlorate, bromate, triazine degradation products, metal-contaminated colloids and Cryptosporidium parvum oocysts.     

Performance of poly(vinyl alcohol) gel columns on the ion chromatographic determination of perchlorate in fertilizers

Interest in possible sources of perchlorate (ClO4) that could lead to environmental release has been heightened since the Environmental Protection Agency placed this anion on its Contaminant Candidate List for drinking water. Although recent investigations have suggested that fertilizers are minor contributors to environmental perchlorate contamination overall, there is still interest in screening commercial products for possible contamination and quantitating perchlorate when it is found. Ion chromatography (IC) has been used for this application owing to its speed, low detection limits, widespread availability, and moderate ruggedness relative to other techniques. However, fertilizer matrixes complicate the IC analysis relative to potable water matrixes. In this study, the performance of poly(vinyl alcohol) gel resin IC columns (100 mm and 150 mm) was evaluated for fertilizer matrixes using method EPA/600/R-01/026. The NaOH eluent included an organic salt, sodium 4-cyanophenoxide. Detection was by suppressed conductivity. A set of 55 different field samples representing 48 products and previously used by the EPA to assess occurrence of perchlorate in fertilizers (EPA/600/R-01/049) was reanalyzed on the 150 mm column. The 100 mm column was used to further investigate the positive hits. Both columns gave satisfactory performance in fertilizer matrixes, with spike recoveries (+/- 15%), assured reporting levels (0.5-225 microg g(-1) except for one at 1,000 microg g(-1)), accuracy (relative error < 30% always and most < 15%), and precision [injection-to-injection reproducibility < 3% relative standard deviation (RSD)] comparable to those reported in other studies. Performance did not vary substantially between column lengths. Lastly, the results of this investigation provided further evidence in support of the conclusions that had been reached previously by the EPA on the occurrence of perchlorate in fertilizers.     

South Pole Antarctica observations and modeling results: New insights on HOx radical and sulfur chemistry

Measurements of OH, H₂SO₄, and MSA at South Pole (SP) Antarctica were recorded as a part of the 2003 Antarctic Chemistry Investigation (ANTCI 2003). The time period 22 November, 2003–2 January, 2004 provided a unique opportunity to observe atmospheric chemistry at SP under both natural conditions as well as those uniquely defined by a solar eclipse event. Results under natural solar conditions generally confirmed those reported previously in the year 2000. In both years the major chemical driver leading to large scale fluctuations in OH was shifts in the concentration levels of NO. Like in 2000, however, the 2003 observational data were systematically lower than model predictions. This can be interpreted as indicating that the model mechanism is still missing a significant HO_x sink reaction(s); or, alternatively, that the OH calibration source may have problems. Still a final possibility could involve the integrity of the OH sampling scheme which involved a fixed building site. As expected, during the peak in the solar eclipse both NO and OH showed large decreases in their respective concentrations. Interestingly, the observational OH profile could only be approximated by the model mechanism upon adding an additional HO_x radical source in the form of snow emissions of CH₂O and/or H₂O₂. This would lead one to think that either CH₂O and/or H₂O₂ snow emissions represent a significant HO_x radical source under summertime conditions at SP. Observations of H₂SO₄ and MSA revealed both species to be present at very low concentrations (e.g., 5 × 10⁵ and 1 × 10⁵ molec cm^?3, respectively), but similar to those reported in 2000. The first measurements of SO₂ at SP demonstrated a close coupling with the oxidation product H₂SO₄. The observed low concentrations of MSA appear to be counter to the most recent thinking by glacio-chemists who have suggested that the plateau's lower atmosphere should have elevated levels of MSA. We speculate here that the absence of MSA may reflect efficient atmospheric removal mechanisms for this species involving either dynamical and/or chemical processes.