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.     

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.     

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.     

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.     

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.     

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.     

Dissipation pattern and risk quotients assessment of amisulbrom in Korean melon cultivated in plastic house conditions

Amisulbrom formulated as suspension concentrate was applied at the rate recommended for Korean melon to determine the dissipation pattern (at two different sites), the pre-harvest residue limit (PHRL), and risk assessments. Samples collected over 10 days were extracted using liquid-liquid extraction (LLE) and cleaned up with solid-phase extraction (SPE) Florisil cartridge. Residual concentrations were determined using liquid chromatography-ultraviolet detector (LC-UVD) and confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The standard showed good instrument response linearity with a correlation coefficient (R ²) = 0.9999, and the recovery ranged from 87.5 to 93.7%. The dissipation half-life calculated from two different sites were found to be 7.0 and 8.8 days for sites 1 and 2, respectively. A PHRL graph constructed from the data indicated that if the residue levels were less than 0.55–0.59 mg/kg 3 days before harvest or less than 0.61–0.74 mg/kg 7 days before harvest, then they would be lower than the maximum residue limits (MRLs) at harvest. Risk assessments showed that the risk quotient (RQ) was 4.39–3.47% at 0 day, declined to 1.53–1.63% at 10 days. Therefore, the current data indicate that the amisulbrom can be applied safely to Korean melon; hence, it is unlikely to induce adverse health effects in consumers.     

Monitoring of ambient particles and heavy metals in a residential area of Seoul, Korea

In this study, ambient TSP, PM10, and PM2.5 in a residential area located in the northern part of Seoul were monitored every other month for 1 year from April 2005 to February 2006. The monthly average levels of TSP, PM10, and PM2.5 had ranges of 71∼158, 40∼106, and 28∼43 μg/m³, respectively. TSP and PM10 showed highest concentration in April; this seems to be due to Asian dust from China and/or Mongolia. However, the fine particle of PM2.5 showed a relatively constant level during the monitoring period. Heavy metals in PM 10 and PM2.5, such as Cr, As, Cd, Mn, Zn and Pb, were also analysed during the same period. The monthly average concentrations of heavy metal in PM2.5 were Cr:1.9∼22.7 ng/m³; As:0.9∼2.5 ng/m³; Cd: 0.6∼7 ng/m³; Mn:6.1∼22.6 ng/m³; Zn: 38.9∼204.8 ng/m³, and Pb: 21.6∼201.1 ng/m³. For the health risk assessment of heavy metals in ambient particles, excess cancer risks were calculated using IRIS unit risk. As a result, the excess cancer risks of chromium, cadmium, and arsenic were shown to be more than one per million based on the annual concentration of heavy metals, and chromium showed the highest excess cancer risk in ambient particles in Seoul.     

Characterization of metal aerosols in PM10 from urban, industrial, and Asian Dust sources

Metallic elements (As, Be, Ca, Cd, Co, Cr, Fe, K, Mn, Ni, Pb, Sb, Se, and Zn) in PM10 aerosols were determined at urban and industrial sites, which are affected by traffic and residential sources, metallurgical activity, and petrochemical and steel works. The effect of the long-range transported Asian Dust on the metal content of aerosols was also examined. At the urban sampling site, concentrations of As, Cd, Pb, Se, and Zn were assigned to road traffic and combustion sources, Ca and Fe to soil dust sources from long-range transported Asian Dusts, and Cr and Ni to metallurgical sources transported from the nearby industrial complex, based on Principal Component Analysis (PCA). Enhanced Cr and Ni concentrations at the metallurgical industrial site suggest that local emissions from metal-assembly facilities and manufacture of alloys contributed to elevated levels of those metals. We also observed that petrochemical activities contributed to increased levels of Sb and Zn. When Asian Dust events occurred, Ca, Fe, K, and Zn concentrations dramatically increased compared to values without the Asian Dust. Two different types of Asian Dust events were observed. For the Asian Dust event 1 (4/1/2007), the Fe and K concentrations were much higher by a factor of 2–3 than those for the Asian Dust event 2 (3/2/2008), while As, Mn, and Zn concentrations were significantly higher on the Asian Dust event 2. Backward trajectory analysis showed that for the Asian Dust event 2, the air mass had passed over the heavily industrialized zones in China during long-range transport to the current sampling site, suggesting that the As, Mn, and Zn may have originated from industrial sources.