Performance evaluation of an in situ nitrous acid measurement system and continuous measurement of nitrous acid in an indoor environment

Nitrous acid (HONO) may cause adverse effects to mucous membranes and lung function when people are exposed to higher HONO concentrations than those present in typical indoor residential environments. Therefore, determination of HONO concentration in indoor environments is required to investigate occurrences of high HONO levels. In this work, a high-time-resolution measurement system was utilized to better understand the levels and dynamic behavior of HONO in an indoor environment. The performance of the in situ HONO analyzer applied to this work was evaluated using a 12-hr integrated annular denuder technique under ambient conditions. Both methods for the measurements of HONO were in good agreement, with a regression slope of 0.84, an intercept of 0.09, and correlation coefficient (r2) of 0.67. Indoor HONO and nitrogen oxide concentrations were also observed for approximately 5 days in winter in the living room of an apartment that had a gas range for cooking in the kitchen. Investigation of the relationships among nitric oxide (NO), nitrite (NO2), and HONO concentrations suggests that HONO production during combustion could be the result of direct emission, whereas the heterogeneous NO2 chemistry during the background period and after combustion was the possible pathway of HONO production. Controlled combustion experiments, performed at a burning rate of 50% valve setting, show peak HONO concentrations during the unvented combustion to be approximately 8-10 times higher than background levels depending on the time of day. At a burning rate setting of 50%, the peak concentration of HONO during unvented combustion was found to be 33-37% higher than those from "weak" (airflow = 340 m3/hr) and "strong" (airflow = 540 m3/hr) vented combustions. The decay rate of the HONO concentrations for the unvented combustion conditions was approximately 2-fold higher in the daytime than in the nighttime and significantly less than those of NO and NO2.     

Measurement of real time black carbon for investigating spot loading effects of Aethalometer data

Measurements of real-time continuous PM_2.5 black carbon (BC) concentrations were made using a single-wavelength Aethalometer (@880 nm) in three different environments, i.e., an indoor office, a residential indoor living room and an urban site, to evaluate the difference in temporal behaviors of BC particles and investigate the optical shadowing effect in the Aethalometer BC data. An empirical method was used for correcting the optical saturation effect on the original BC data obtained from the measurements at the three sites. Also, the elemental carbon (EC) concentrations from 24-h filter-based measurements of PM_2.5 particles were determined using a thermal optical transmittance (TOT) method at the same urban site for comparison with the Aethalometer BC results. Transient events of BC were often observed for period of a few hours at all sites, reaching a maximum level of 27.3 μg m^?3 at the urban site. The diurnal cycles of the BC concentrations observed at the two indoor environments were found to be considerably affected by the air exchange rate, occupants' behavior patterns and nearby traffic emissions. The time-series plots of the Aethalometer data showed obvious discontinuities at the filter spot change, and a rise in the apparent BC concentrations after filter tape advances. Also, the relationship between the attenuation and BC concentration was found to be non-linear at all sites. The empirical approach presented here demonstrated a definite improvement in the continuity of the BC data across the time gaps of each tape advance. The compensated BC concentration was 1.10–1.23 times greater than the raw BC data, depending on the observation sites, with the highest difference observed between the raw and compensated BC data at an indoor office near a small traffic road. The 24-h integrated EC concentration was approximately 12% higher than the original 24-h average BC concentration and 6% lower than the loading compensated BC concentration, showing that the loading compensation process accounted for the saturation effect of the filter tape.     

Determinants of exposure to fine particulate matter (PM2.5) for waiting passengers at bus stops

This research evaluates commuter exposure to particulate matter during pre-journey commute segments for passengers waiting at bus stops by investigating 840 min of simultaneous exposure levels, both inside and outside seven bus shelters in Buffalo, New York. A multivariate regression model is used to estimate the relation between exposure to particulate matter (PM_2.5 measured in μg m^?3) and three vectors of determinants: time and location, physical setting and placement, and environmental factors. Four determinants have a statistically significant effect on particulate matter: time of day, passengers’ waiting location, land use near the bus shelter, and the presence of cigarette smoking at the bus shelter. Model results suggest that exposure to PM_2.5 inside a bus shelter is 2.63 μg m^?3 (or 18 percent) higher than exposure outside a bus shelter, perhaps due in part to the presence of cigarette smoking. Morning exposure levels are 6.51 μg m^?3 (or 52 percent) higher than afternoon levels. Placement of bus stops can affect exposure to particulate matter for those waiting inside and outside of shelters: air samples at bus shelters located in building canyons have higher particulate matter than bus shelters located near open space.     

Concurrent sorption of antimony and lead by iron phosphate and its possible application for multi-oxyanion contaminated soil

Environmental Science and Pollution Research - Concurrent stabilization of oxyanions such as antimony (Sb), arsenic (As), and heavy metals including lead (Pb) and manganese (Mn) in contaminated...     

Environmental impact minimization of a total wastewater treatment network system from a life cycle perspective

Synthesis of distributed wastewater treatment plants (WTPs) has focused on cost reduction, but never on the reduction of environmental impacts. A mathematical optimization model was developed in this study to synthesize existing distributed and terminal WTPs into an environmentally friendly total wastewater treatment network system (TWTNS) from a life cycle perspective. Life cycle assessment (LCA) was performed to evaluate the environmental impacts of principal contributors in a TWTNS. The LCA results were integrated into the objective function of the model. The mass balances were formulated from the superstructure model, and the constraints were formulated to reflect real wastewater treatment situations in industrial plants. A case study validated the model and demonstrated the effect of the objective function on the configuration and environmental performance of a TWTNS. This model can be used to minimize environmental impacts of a TWTNS in retrofitting existing WTPs in line with cleaner production and sustainable development.     

Kinetics of the reduction of hexavalent chromium with the brown seaweed Ecklonia biomass

The dead biomass of the brown seaweed, Ecklonia sp., is capable of reducing toxic Cr(VI) into less toxic or nontoxic Cr(III). However, little is known about the mechanism of Cr(VI) reduction by the biomass. The objective of this work was to develop a kinetic model for Cr(VI) biosorption, for supporting our mechanism. The reduction rate of Cr(VI) increased with increasing total chromate concentration, [Cr(VI)], and equivalent concentration of organic compounds, [OCs], and decreasing solution pH. It was found that the reduction rate of Cr(VI) was proportional to [Cr(VI)] and [OCs], suggesting the simple kinetic equation -d[Cr(VI)]/dt=k[Cr(VI)][OCs]. When considering the consumption of organic compounds due to the oxidation by Cr(VI), an average rate coefficient of 9.33 (+/-0.65)microM(-1)h(-1) was determined, at pH 2. Although the function of the pH could not be expressed in a mechanistic manner, an empirical model able to describe the pH dependence was obtained. It is expected that the developed rate equation could likely be used for design and performance predictions of biosorption processes for treating chromate wastewaters.     

TCDD alters PKC signaling pathways in developing neuronal cells in culture

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is known to induce neurodevelopmental deficits such as poor cognitive development and motor dysfunction. However, the mechanism of TCDD-mediated neurotoxicity remains unclear. Since PKC signaling is one of the most pivotal events involved in neuronal function and development, we analyzed the effects of TCDD on the PKC signaling pathway in cerebellar granule cells derived from PND-7 rat brain. Immunoblot analysis revealed the presence of PKC-alpha, betaII, delta, epsilon, lambda and iota in both cytosol and membrane fractions of cerebellar granule cells, but PKC-gamma was below the detectable level. TCDD induced a significant translocation of PKC-alpha, -betaII and -epsilon from cytosol to membrane fraction (p<0.05) and a marginal translocation of PKC-delta at high dose only (p<0.1). It also increased RACK-1, an adaptor protein for PKC, in a dose-dependent manner. Exposure to TCDD induced a dose-dependent increase of both [3H] PDBu binding and the intracellular calcium level. The results suggest that the selective PKC isozymes and RACK-1 are involved in TCDD-mediated signaling pathway and these proteins may be possible molecular targets in neuronal cells for TCDD exposure. Our study provides basic data to understand mechanism of TCDD-induced neurotoxicity with respect to PKC signaling pathway and a scientific basis for improving the health risk assessment of neurotoxicants by identifying intracellular target molecules in neuronal cells.     

Polycyclic aromatic hydrocarbons in bulk PM2.5 and size-segregated aerosol particle samples measured in an urban environment

To analyze polycyclic aromatic hydrocarbons (PAHs) at an urban site in Seoul, South Korea, 24-hr ambient air PM_2.5 samples were collected during five intensive sampling periods between November 1998 and December 1999. To determine the PAH size distribution, 3-day size-segregated aerosol samples were also collected in December 1999. Concentrations of the 16 PAHs in the PM_2.5 particles ranged from 3.9 to 119.9 ng m⁻³ with a mean of 24.3 ng m⁻³.An exceptionally high concentration of PAHs(∼120 ng m⁻³) observed during a haze event in December 1999 was likely influenced more by diesel vehicle exhaust than by gasoline exhaust, as well as air stagnation, as evidenced by the low carbon monoxide/elemental carbon (CO/EC) ratio of 205 found in this study and results reported by previous studies. The total PAHs associated with the size-segregated particles showed unimodal distributions. Compared to the unimodal size distributions of PAHs with modal peaks at < 0.12 μm measured in highway tunnels in Los Angeles (Venkataraman and Friedlander, 1994), four- to six-ring PAHs in our study had unimodal size distributions, peaking at the larger size range of 0.28–0.53 μm, suggesting the coagulation of freshly emitted ultrafine particles during transport to the sampling site. Further, the fraction of PAHs associated with coarse particles(> 1.8 μm) increased as the molecular weight of the PAHs decreased due to volatilization of fine particles followed by condensation onto coarse particles.     

Analysis of the effects diclofenac has on Japanese medaka (Oryzias latipes) using real-time PCR

The expression levels of cytochrome P450 1A, p53 and vitellogenin were investigated in three different tissues of male medaka fish after exposure to diclofenac that is one of the main concerns among pharmaceuticals frequently found in sewage treatment plant (STP) effluents. The results showed that cytochrome P450 1A, p53 and vitellogenin were highly expressed in tissue-specific gene expression patterns after exposure to 8 mg/l and 1 μg/l of diclofenac. These elevated expression levels of three biomarkers suggested that diclofenac has potential to cause cellular toxicity, p53-related genotoxicity and estrogenic effects. It is also noteworthy that diclofenac has the potential to cause these effects even at an environmentally relevant concentration of diclofenac, 1 μg/l.