Effect of coumaphos on cholinesterase activity,hematology, and biochemical blood parameters of bovines in tropical regions of Mexico

To assess the effect of coumaphos [O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl) O,O-diethyl phosphorothioate] exposure on physiological responses during bovine production, acetylcolinesterase (AChE) and butyrylcholinesterase (BuChE) activities were measured in whole blood, erythrocytes, and plasma of healthy male steers (Bos Taurus x Bos indicus) sprayed with coumaphos at a non-lethal dose of 1 mg kg^{? 1} body weight per day once every 14 (in vivo group) or 21 days (southern and central groups). Coumaphos topically administered at 1 mg/kg body weight per day to cattle under normal management practices in tropical areas produced a significant inhibition in erythrocyte (RBC) AChE and BuAChE activities when compared to baseline levels. RBC-AChE activity for the in vivo group decreased 71.3% (P < 0.05) and BuChE activity 59.1% (P < 0.05); RBC-AChE activity decreased 55.1% (P < 0.05) (southern group) and 43.4% (P < 0.05) (central group). Compared to the control specimens, steers from in vivo, southern, and central groups after 150 days of exposure had lower (P < 0.05) leukocyte count, absolute lymphocyte, erythrocyte, and platelet counts. Decreases in RBC-AChE activities correlated with decreased lymphocyte (r = 1.000, p = 0.01), erythrocyte (r = 1.000, p = 0.003), and platelet counts (r = 0.841, p = 0.036). Significantly increased BUN levels (P < 0.05) correlated with the decrease in RBC-AChE activities (r = ? 0.997, p = 0.047) and with the decrease in absolute red blood cell (r = ? 0.883, p = 0.020) and lymphocyte (r = ? 0.825, p = 0.043) counts; increased (P < 0.05) total plasma protein levels correlated with the decrease in RBC-AChE activities (r = ?0.998, p = 0.043), absolute red blood cell (r = ? 0.998, p = 0.040), lymphocyte (r = ? 0.893, p = 0.017), and platelet (r = -0.855, p = 0.030) counts. The physiological responses correlated with the erythrocyte acetylcholinesterase inhibition could be considered as early indicators or warning responses of bovine exposures to organophosphorus pesticides (OPs).     

Long-term trends in airborne SO2 in an air quality monitoring station in Seoul,Korea, from 1987 to 2013

Atmospheric concentration of sulfur dioxide (SO₂) was intermittently measured at an air quality monitoring (AQM) station in the Yong-san district of Seoul, Korea, between 1987 and 2013. The SO₂ level was compared with other important pollutants concurrently measured, including methane (CH₄), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO₂), ozone (O₃), and particulate matter (PM₁₀). If split into three different periods (period 1, 1987–1988, period 2, 1999–2000, and period 3, 2004–2013), the respective mean [SO₂] values (6.57 ± 4.29, 6.30 ± 2.44, and 5.29 ± 0.63 ppb) showed a slight reduction across the entire study period. The concentrations of SO₂ are found to be strongly correlated with other pollutants such as CO (r = 0.614, p = 0.02), which tracked reductions in reported emissions due to tighter emissions standards enacted by the South Korean government. There was also a clear seasonal trend in the SO₂ level, especially in periods 2 and 3, reflecting the combined effects of domestic heating by coal briquettes and meteorological conditions. Although only a 16% concentration reduction was achieved during the 27-year study duration, this is significant if one considers rapid urbanization, an 83.2% increase in population, and rapid industrialization that took place during that period.

Implications: Since 1970, a network of air quality monitoring (AQM) stations has been operated by the Korean Ministry of Environment (KMOE) for routine nationwide monitoring of air pollutant concentrations in urban/suburban areas. To date, the information obtained from these stations has provided a platform for analyzing long-term trends of major pollutant species. In this study, we examined the long-term trends of SO₂ levels and relevant environmental parameters monitored continuously in the Yong-san district of Seoul between 1987 and 2013. The data were analyzed over various time scales (i.e., monthly, seasonal, and annual intervals). The results obtained from this study will allow us to assess the effectiveness of abatement strategy and to predict future concentrations trends in association with future abatement strategies and technologies.     

Photochemical air pollutant levels and ozone phytotoxicity in the region of Mesogia–Attica, Greece

The levels of photochemical air pollutants: O₃, NO and NO₂, were monitored in Athens and in the neighbouring region of the Mesogia plain (Spata, Artemis and Markopoulo) from 1 May–31 August 2000. Phytodetection of ozone was also conducted using bioindicator plants of Bel-W3 and Zichnomirodata (KK6/5) tobacco varieties. The average maximum daily O3 concentration was 60–75 ppb, while the 24 hour average ranged from 40–65 ppb. The AOT40 (ppb hours) index was very high in Athens (16 679 over 121 days), Spata (16 325 over 110 days), Artemis (8093 over 22 days) and Markopoulo (18 646 over 113 days), suggesting potentially phytotoxic ozone levels. The ozone bioindicator plants of Bel-W3 and KK6/5 tobacco varieties were highly injured in all regions confirming the phytotoxicity of those ozone levels. The levels of NO and NO₂ recorded at the three stations, in the Mesogia plain, were considerably lower than those occurring in Athens. The data presented here provide important background information concerning pollution levels in the Mesogia plain shortly before the operation of the new international airport 'Eleftherios Venizelos' in this region (March 2001).     

Nitric oxide emission from a typical vegetable field in the Pearl River Delta, China

Croplands contribute to atmospheric nitric oxide (NO), but very limited data are available about NO fluxes from intensively managed croplands in China. In this study, NO fluxes were measured in a typical vegetable field planted with flowering Chinese cabbage (Brassica campestris L. ssp. Chinensis var. utilis Tsen et Lee), which is the most widely cultivated vegetable in Guangdong province, south China. NO emission drastically increased after nitrogen fertilizer application, and other practices involving loosening the soil also enhanced NO emission. Mean NO emission flux was 47.5 ng N m⁻² s^–1 over a complete growth cycle. Annual NO emission from the vegetable field was about 10.1 kg N ha⁻¹ yr⁻¹. Fertilizer-induced NO emission factor was estimated to be 2.4%. Total NO emission from vegetable fields in Guangdong province was roughly estimated to be 11.7 Gg N yr⁻¹ based on the vegetable field area and annual NO emission rate, and to be 13.3 Gg N yr⁻¹ based on fertilizer-induced NO emission factor and background NO emission. This means that NO emission from vegetable fields was approximately 6% of NO_x from commercial energy consumption in Guangdong province.     

Investigation of adsorption characteristics of four toxic gases (nitric oxide,nitrogen dioxide,sulfur dioxide,and hydrogen chloride) on the inner surface of nickel-coated manganese steel cylinders and aluminum cylinders

To develop standard toxic gas mixtures, it is essential to identify adsorption characteristics of each toxic gas on the inner surface of a gas cylinder. Thus, this study quantified adsorbed amounts of the four toxic gases (nitric oxide [NO], nitrogen dioxide [NO₂], sulfur dioxide [SO₂], and hydrogen chloride [HCl]) on the inner surface of aluminum cylinders and nickel-coated manganese steel cylinders. After eluting adsorbed gases on the inside of cylinders with ultrapure water, a quantitative analysis was performed on an ion chromatograph. To evaluate the reaction characteristics of the toxic gases with cylinder materials, quantitative analyses of nickel (Ni), iron (Fe), and aluminum (Al) were also performed by inductively coupled plasma optical emission spectrometry (ICP-OES). It was found that the amounts of NO, NO₂, and SO₂ adsorbed on the inner surface of aluminum cylinders were less than 1.0% at the level of 100 μmol/mol mixing ratio, whereas the signal for most heavy metal elements were below their respective detection limits. This study found that the amounts of HCl adsorbed on the inner surface of nickel-coated manganese steel cylinders were less than 5% at the level of 100 μmol/mol mixing ratio, whereas Ni (86 μmol) and Fe (28 μmol) were detected in the same cylinders. It was revealed that the adsorption mainly took place via the reaction of HCl with inner surface material of nickel-coated manganese steel cylinders. On the other hand, in the case of aluminum cylinders, the amounts of the adsorption were determined to be less than 1% at the level of HCl 100 μmol/mol mixing ratio, whereas most of Ni, Fe, and Al were detected at levels similar to their limits of detection. As a result, this study found that aluminum cylinders are more suitable for preparing HCl gas mixtures than nickel-coated manganese steel cylinders.

Implications: To develop a standard toxic gas mixture, it is essential to understand the adsorption characteristics of each toxic gas inside a gas cylinder. It was found that the amounts of NO, NO₂, and SO₂ adsorbed inside aluminum cylinders were less than 1.0% at the level of 100 μmol/mol mixing ratio. The amounts of HCl adsorbed inside nickel-coated manganese steel cylinders were less than 5% at the level of 100 μmol/mol mixing ratio, whereas those inside aluminum cylinders were less than 1%, indicating that aluminum cylinders are more suitable for preparing HCl gas mixtures.     

Removal of nitric oxide in a biotrickling filter under thermophilic condition using Chelatococcus daeguensis

The development of a thermophilic biotrickling ?lter (BTF) system to inoculate a newly isolated strain of Chelatococcus daeguensis TAD1 for the effective treatment of nitric oxide (NO) is described. A bench-scale BTF was run under high concentrations of NO and 8% O₂ in thermophilic aerobic environment. A novel aerobic denitrifier Chelatococcus daeguensis TAD1 was isolated from the biofilm of an on-site biotrickling filter and it showed a denitrifying capability of 96.1% nitrate removal rate in a 24 h period in aerobic environment at 50 °C, with no nitrite accumulation. The inlet NO concentration fluctuated between approximately 133.9 and 669.6 mg m-3 and kept on a steady NOx removal rate above 80% in an oxygen stream of 8%. The BTF system was able to consistently remove 80–93.7% NO when the inlet NO was 535.7 mg m-3 in an oxygen stream of 2–20%. The biological removal efficiency of NO at 50 °C is higher than that at 25 °C, suggesting that the aerobic denitri?er TAD1 display well denitrification performance under thermophilic condition. Starvation for 2, 4 and 8 days resulted in the re-acclimation times of Chelatococcus daeguensis TAD1 ranging between 4 and 16 hours. A longer recovery time than that for weekend shutdown will be required when a longer starvation occurs. The results presented here demonstrate the feasibility of biotrickling ?lter for the thermophilic removal of NOx from gas streams.

Implications A novel denitrifier Chelatococcus daeguensis TAD1 was isolated from an on-site biotrickling filter in aerobic environment at 50 °C. To date, C. daeguensis has not been previously reported to be an aerobic denitrifier. In this study, a thermophilic biotrickling ?lter system inoculated with Chelatococcus daeguensis TAD1 for treatment of nitric oxide is developed. In coal-fired power plants, influent flue gas stream for nitrogen oxides (NO_x) removal typically exhibit temperatures between 50 and 60 °C. Traditionally, cooling gases to below 40 °C prior to biological treatment is inevitable, which is costly. Therefore, the application of thermophilic microorganisms for the removal of nitric oxide (NO) at this temperature range would offer great savings and would greatly extend the applicability of biofilters and biotrickling filters. Until now there has not been any study published about thermophilic biological treatment of NO under aerobic condition.     

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in breast milk from the Pacific Northwest

Breast milk samples from 40 first-time mothers from the Pacific Northwest of the US and Canada were analyzed for polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs). Total PBDEs (summation operator PBDEs), calculated by summing values for the 12 PBDEs congeners analyzed, ranged from 6 to 321 ppb (lipid weight) (mean=96 ppb; median=50 ppb). In approximately 40% of the women (15/40), summation operator PBDEs>100 ppb lw in their milk, and four samples had levels >250 ppb lw. PBDE 47 was the dominant congener in most samples, whereas PBDE 153 was predominant in a few (3/40). summation operator PCBs were calculated by summing values for the 82 PCB congeners analyzed, and ranged from 49 to 415 ppb (lipid weight) (mean=147 ppb; median=126 ppb). approximately 30% of the mothers (13/40) have summation operator PBDEs> summation operator PCBs in their milk samples, and approximately 65% (25/40) have BDE 47>PCB 153 in breast milk samples, with BDE 47 averaging 3-fold greater levels than PCB 153. Clearly, the lower brominated PBDEs are surpassing PCBs as a major environmental concern in North America, and are likely affecting significant portions of the populations in these regions. PBDEs have become a major persistent organic pollutant. However, there are no positive correlations between levels of summation operator PBDEs and summation operator PCBs, or between levels of PBDE 47 and PCB 153, suggesting there may be some differences in exposure pathways for PBDEs and PCBs in humans.     

Engineered biochar composites with zeolite,silica, and nano-zerovalent iron for the efficient scavenging of chlortetracycline from aqueous solutions

Date palm waste–derived biochar (DBC) was produced through pyrolysis (600 °C) and modified with zeolite (Z-DBC), silica (S-DBC), or nano-zerovalent iron (nZVI-DBC) to design efficient sorbents. The pristine and engineered biochars were characterized by SEM, XRD, BET, TGA, CHNS-O, and FTIR to investigate the surface, structural, and mineralogical composition. The nZVI-DBC exhibited lowest pH (6.15) and highest surface area (220.92 m² g⁻¹), carbon (80.55%), nitrogen (3.78%), and hydrogen (11.09%) contents compared with other biochars. Isotherm sorption data for chlortetracycline (CTC) removal from aqueous solutions was described well by Langmuir and Redlich–Peterson isotherms showing the highest fitness (R² values in the range of 0.88–0.98 and 0.88–0.99, respectively). Langmuir predicted maximum CTC adsorption capacity was in order of nZVI-DBC (89.05 mg g⁻¹) > S-DBC (45.57 mg g⁻¹) > Z-DBC (30.42 mg g⁻¹) > DBC (28.19 mg g⁻¹). Kinetics adsorption data was best described by power function model (R² = 0.93–0.99), followed by interaparticle diffusion (R² = 0.85–0.96) model. The nZVI-DBC performed outclass by removing 98% of CTC, followed by S-DBC (68%), Z-DBC (35%), and DBC (36%). Chemisorption, H-bonding, and interaparticle diffusion were the operating mechanisms for CTC adsorption onto DBC, S-DBC, and Z-DBC, while π-π electron donor–accepter interactions and redox reactions augmented these mechanisms for highest CTC adsorption onto nZVI-DBC. Therefore, nZVI-DBC may serve as an efficient green technology for the removal of CTC from aqueous solutions and to reduce surface date palm waste pollution.

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VOC concentrations measured in personal samples and residential indoor,outdoor and workplace microenvironments in EXPOLIS-Helsinki,Finland

Thirty target volatile organic compounds (VOC) were analyzed in personal 48-h exposure samples and residential indoor, residential outdoor and workplace indoor microenvironment samples as a component of EXPOLIS-Helsinki, Finland. Geometric mean residential indoor concentrations were higher than geometric mean residential outdoor concentrations for all target compounds except hexane, which was detected in 40% of residential outdoor samples and 11% of residential indoor samples, respectively. Geometric mean residential indoor concentrations were significantly higher than personal exposure concentrations, which in turn were significantly higher than workplace concentrations for compounds that had strong residential indoor sources (d-limonene, alpha pinene, 3-carene, hexanal, 2-methyl-1-propanol and 1-butanol). 40% of participants in EXPOLIS-Helsinki reported personal exposure to environmental tobacco smoke (ETS). Participants in Helsinki that were exposed to ETS at any time during the 48-h sampling period had significantly higher personal exposures to benzene, toluene, styrene, m,p-xylene, o-xylene, ethylbenzene and trimethylbenzene. Geometric mean ETS-free workplace concentrations were higher than ETS-free personal exposure concentrations for styrene, hexane and cyclohexane. Geometric mean personal exposures of participants not exposed to ETS were approximately equivalent to time weighted ETS-free indoor and workplace concentrations, except for octanal and compounds associated with traffic, which showed higher geometric mean personal exposure concentrations than any microenvironment (o-xylene, ethylbenzene,benzene, undecane, nonane, decane, m,p-xylene, and trimethylbenzene). Considerable differences in personal exposure concentrations and residential levels of compounds with mainly indoor sources suggested differences in product types or the frequency of product use between Helsinki, Germany and the United States.     

Differences between Weekday and Weekend Air Pollutant Levels in Atlanta; Baltimore; Chicago; Dallas–Fort Worth; Denver; Houston; New York; Phoenix; Washington,DC; and Surrounding Areas

Abstract

We evaluated day-of-week differences in mean concentrations of ozone (O₃) precursors (nitric oxide [NO], nitrogen oxides [NO_x], carbon moNO_xide [CO], and volatile organic compounds [VOCs]) at monitoring sites in 23 states comprising seven geographic focus areas over the period 1998– 2003. Data for VOC measurements were available for six metropolitan areas in five regions. We used Wednesdays to represent weekdays and Sundays to represent weekends; we also analyzed Saturdays. At many sites, NO, NO_x, and CO mean concentrations decreased at all individual hours from 6:00 a.m. to 3:00 p.m. on Sundays compared with corresponding Wednesday means. Statistically significant (p < 0.01) weekend decreases in ambient concentrations were observed for 92% of NO_x sites, 89% of CO sites, and 23% of VOC sites. Nine-hour (6:00 a.m. to 3:00 p.m.) mean concentrations of NO, NO_x, CO, and VOCs declined by 65, 49, 28, and 19%, respectively, from Wednesdays to Sundays (median site responses). Despite the large reductions in ambient NO_x and moderate reductions in ambient CO and VOC concentrations on weekends, ozone and particulate matter (PM) nitrate did not exhibit large changes from week-days to weekends. The median differences between Wednesday and Sunday mean ozone concentrations at all monitoring sites ranged from 3% higher on Sundays for peak 8-hr concentrations determined from all monitoring days to 3.8% lower on Sundays for peak 1-hr concentrations on extreme-ozone days. Eighty-three percent of the sites did not show statistically significant differences between Wednesday and weekend mean concentrations of peak ozone. Statistically significant weekend ozone decreases occurred at 6% of the sites and significant increases occurred at 11% of the sites. Average PM nitrate concentrations were 2.6% lower on Sundays than on Wednesdays. Statistically significant Sunday PM nitrate decreases occurred at one site and significant increases occurred at seven sites.     

Comparative effect of thymol or its glucose conjugate,thymol-β-d-glucopyranoside,on Campylobacter in avian gut contents

Campylobacter jejuni is an important human food-borne pathogen that can contaminate meat and poultry during processing. Consequently, strategies are sought to reduce the carriage of C. jejuni in food animals before they arrive at the abattoir. Thymol is a natural product that reduces survivability of Campylobacter in vitro, but its rapid absorption from the proximal alimentary tract limits its bactericidal efficacy in vivo. Thymol-β-d-glucopyranoside is more resistant to absorption than free thymol, but its administration to chickens has not been reported. In the present studies, 1 mM thymol-β-d-glucopyranoside was shown to exhibit near equal anti-Campylobacter activity as 1 mM thymol when incubated anaerobically in avian crop or cecal contents in vitro, resulting in reductions of 1.10–2.32 log₁₀ colony forming units mL^?1 in C. jejuni concentrations after 24 h incubation. In a follow-up live animal study, oral administration of thymol-β-d-glucopyranoside, but not free thymol, significantly lowered (>10-fold) recovery of Campylobacter from the crop of market-aged broilers when compared to placebo-treated controls (n = 6 broilers/treatment). Neither thymol-β-d-glucopyranoside nor thymol affected recovery of Campylobacter from cecal contents of the treated broilers. These results indicate that rapid absorption or passage of free thymol from the crop precluded its anti-Campylobacter activity at this site and throughout the entire gastrointestinal tract. Conversely, lower recovery of Campylobacter from the crop of birds treated with thymol-β-d-glucopyranoside indicates this conjugate was retained and able to be hydrolyzed to biologically active free thymol at this site as intended, yet was not sufficiently protected to allow passage of efficacious amounts of the intact glycoside to the lower gut. Nevertheless, these results warrant further research to see if higher doses or encapsulation of thymol-β-d-glucopyranoside or similar glycosides may yield an efficacious additive to reduce carriage of Campylobacter as well as other pathogens throughout the avian gut.     

Removal of toxic ions (chromate, arsenate, and perchlorate) using reverse osmosis, nanofiltration, and ultrafiltration membranes

Rejection characteristics of chromate, arsenate, and perchlorate were examined for one reverse osmosis (RO, LFC-1), two nanofiltration (NF, ESNA, and MX07), and one ultrafiltration (UF and GM) membranes that are commercially available. A bench-scale cross-flow flat-sheet filtration system was employed to determine the toxic ion rejection and the membrane flux. Both model and natural waters were used to prepare chromate, arsenate, and perchlorate solutions (approximately 100 μg L⁻¹ for each anion) in mixtures in the presence of other salts (KCl, K₂SO₄, and CaCl₂); and at varying pH conditions (4, 6, 8, and 10) and solution conductivities (30, 60, and 115 mS m⁻¹). The rejection of target ions by the membranes increases with increasing solution pH due to the increasingly negative membrane charge with synthetic model waters. Cr(VI), As(V), and rejection follows the order LFC-1 (>90%) > MX07 (25–95%)  ESNA (30–90%) > GM (3–47%) at all pH conditions. In contrast, the rejection of target ions by the membranes decreases with increasing solution conductivity due to the decreasingly negative membrane charge. Cr(VI), As(V), and rejection follows the order CaCl₂ < KCl  K₂SO₄ at constant pH and conductivity conditions for the NF and UF membranes tested. For natural waters the LFC-1 RO membrane with a small pore size (0.34 nm) had a significantly greater rejection for those target anions (>90%) excluding (71–74%) than the ESNA NF membrane (11–56%) with a relatively large pore size (0.44 nm), indicating that size exclusion is at least partially responsible for the rejection. The ratio of solute radius (r_i,s) to effective membrane pore radius (r_p) was employed to compare ion rejection. For all of the ions, the rejection is higher than 70% when the r_i,s/r_p ratio is greater than 0.4 for the LFC-1 membrane, while for di-valent ions (, , and ) the rejection (38–56%) is fairly proportional to the r_i,s/r_p ratio (0.32–0.62) for the ESNA membrane.     

Particle size distribution and anion content at a traffic site in Sha-Lu, Taiwan.

Ambient air particle concentrations were sampled by two total suspended particle (TSP) samplers, PM10/PM2.5 specific sampler and micro-orifice uniform deposit impactor (MOUDI) during July-October 2000 at a traffic sampling site in central Taiwan. The average TSP concentration (194 microg/m3) was about a factor of two higher than that of the fraction <2.5 microm (93.2 microg/m3). The mean level of the fraction <10 microm collected by MOUDI (93.2 microg/m3) was about 1 1/2 times higher than that of the size class <2.5 microm (43.8 microg/m3). Furthermore, this fraction showed a certain correlation with the TSP concentration. The particle size distribution was bimodal in the ambient air at the traffic site. The major peaks appear at particle diameters between 0.56-1.0 and 3.2-5.6 microm. The percentages of anions contained in TSP were 0.24% F-, 13.7% Cl, 0.52% Br, 12.0% NO-, 18.9% NO2-, and 54.6% SO2-. The Cl-, NO2-, and NO3- size distributions were all unimodal and the major peaks appeared at 3.2-5.6 microm. The SO2 size distribution was bimodal, with major peaks at 0.32-0.56 and 3.2-5.6.     

Nitric oxide emissions from conventional vegetable fields in southeastern China

We conducted multi-year observations of nitric oxide (NO) fluxes from typical vegetable fields in the Yangtze River delta, which is located in southeastern China. Flux measurements were performed manually twice per week at intervals of 2–3 days, in both fertilized and unfertilized fields, over an investigation period of 1448 days (September 2004–August 2008). In total, twelve vegetable-growing periods and a short fallow period were investigated. On average, the NO fluxes from the fertilized plots were 21 times higher than fluxes from the unfertilized plots (p < 0.001). Peak NO emissions usually occurred soon after the addition of nitrogenous fertilizer. Peak emissions took place during about 15% of the whole investigation time, but contributed to approximately 89% of the total NO release. The annual background NO emissions (from fields without nitrogen amendment) were observed at 0.290 ± 0.019 (standard deviation of 3 observations) kg N ha^?1. The total amounts of NO emitted during the individual vegetable-growing periods correlated positively and exponentially with the products of seasonal mean soil temperatures and nitrogen addition rates (R² = 0.87, p < 0.001). The mean direct NO emission factor (EF_d, the loss rate of fertilizer nitrogen via NO emissions) for the four-year period was determined to be 0.51% ± 0.11% (standard error of 3 observations). The EF_ds of individual vegetable-growing seasons ranged from 0.05% to 1.24%, varying linearly and positively with the products of seasonal mean soil temperatures and nitrogen addition rates (R² = 0.58, p < 0.01). The observed interaction of soil temperature and nitrogen addition on NO emission in seasonal totals and EF_ds occurred in soils with moisture contents ranging from 55% to 100% water-filled pore space (mean: 79%; standard deviation: 9%). The results of this study indicate that when other conditions remain relatively stable, the direct emission factor, a key parameter for compiling an inventory of NO emissions from vegetable fields, may vary with not only soil temperature but also nitrogen addition.     

Introduction to the Air & Waste Management Association's 29th Annual Critical Review

Abstract

On-road mobile sources contribute substantially to ambient air concentrations of the carcinogens 1,3-butadiene, benzene, and polycyclic aromatic hydrocarbons (PAHs). The current study measured benzene and 1,3-butadiene at the Baltimore Harbor Tunnel tollbooth over 3-hr intervals on seven weekdays (n = 56). Particle-bound PAH was measured on a subset of three days. The 3-hr outdoor 1,3-butadiene levels varied according to time of day and traffic volume. The minimum occurred at night (12 a.m.–3 a.m.) with a mean of 2 µg/m³ (SD = 1.3, n = 7), while the maximum occurred during the morning rush hour (6 a.m.–9 a.m.) with a mean of 11.9 µg/m³ (SD = 4.6, n = 7). The corresponding traffic counts were 1413 (SD = 144) and 16,893 (SD = 692), respectively. During the same intervals, mean benzene concentration varied from 3 µg/m³ (SD = 3.1, n = 7) to 22.3 µg/m³ (SD = 7.6, n = 7). Median PAH concentrations ranged from 9 to 199 ng/m³. Using multivariate regression, a significant association (p < 0.001) between traffic and curbside concentration was observed. Much of the pollutant variability (1,3-butadiene 62%, benzene 77%, and PAH 85%) was explained by traffic volume, class, and meteorology. Results suggest >2-axle vehicles emit 60, 32, and 9 times more PAH, 1,3-butadiene, and benzene, respectively, than do 2-axle vehicles. This study provides a model for estimating curbside pollution levels associated with traffic that may be relevant to exposures in the urban environment.     

Consistency of Ozone and Nitrogen Oxides Standards at Tropospherically Relevant Mixing Ratios

Abstract

The absolute accuracy and long‐term precision of atmospheric measurements hinge on the quality of the instrumentation and calibration standards. To assess the consistency of the ozone (O₃) and nitrogen oxides (NO_x) standards maintained at the National Institute of Standards and Technology (NIST), these standards were compared through the gas‐phase titration of O3 with nitric oxide (NO). NO and O₃ were monitored using chemiluminescence and UV absorption, respectively. Nitrogen dioxide (NO₂) was monitored directly by laser‐induced fluorescence and indirectly by catalytic conversion to NO, followed by chemiluminescence. The observed equivalent loss of both NO and O₃ and the formation of NO₂ in these experiments was within 1% on average over the range of 40–200 nmol mol^?1 of NO in excess O3, indicating that these instruments, when calibrated with the NIST O₃ and NO standards and the NO₂ permeation calibration system, are consistent to within 1% at tropospherically relevant mixing ratios of O₃. Experiments conducted at higher initial NO mixing ratios or in excess NO are not in as good agreement. The largest discrepancies are associated with the chemiluminescence measurements. These results indicate the presence of systematic biases under these specific conditions. Prospects for improving these experiments are discussed.