Indoor/Outdoor Relationships for Organic and Elemental Carbon in PM2.5 at Residential Homes in Guangzhou, China

Nine residential areas were selected in this study (three homes in urban areas, three homes near roadsides, and three homes in industrial zones) to evaluate the indoor and outdoor relationship and carbonaceous species characteristics of PM2.5 in Guangzhou, China, during summer and winter 2004. Daily (24 h) average PM2.5 samples were collected on pre-fired quartz-fiber filters with low-volume samplers and analyzed by the thermal optical reflectance (TOR) method following the Interagency Monitoring of PROtected Visual Environments (IMPROVE) protocol. The average indoor and outdoor concentrations of PM2.5 were 88.8 mu g/m(3) and 99.1 mu g/m(3), respectively. The average indoor OC and EC concentrations were 21.7 mu g/m(3), and 7.6 mu g/m(3), respectively, accounting for an average of 25.5% and 8.9% indoor PM2.5 mass, respectively. The average indoor and outdoor OC/EC ratios were 3.4 and 3.0, respectively. The average I/O ratios of PM2.5, OC and EC were 0.91, 1.02 and 0.96, respe! ctively. Poor indoor-outdoor correlations were observed for OC in the summer (R-2 = 0.18) and winter (R-2 = 0.33), while strong correlations (R-2 &gt; 0.8) were observed for EC during summer and winter. OC and EC were moderately correlated (R-2 = 0.4) during summer, while OC and EC correlated well during winter, with a correlation coefficient of 0.64 indoors and 0.75 outdoors. Similar distributions of eight carbon fractions in indoor and outdoor TC pointed to the contributions of motor vehicle exhaust and coal-combustion sources. A simple estimation indicates that about ninety percent of carbonaceous particles in indoor air result from penetration of outdoor pollutants, and indoor sources contribute only ten percent of the indoor carbonaceous particles.</p

Elemental and morphological analyses of filter tape deposits from a beta attenuation monitor

An hourly average PM10 concentration of 1402 mu g m(-3) was registered at 1400 Pacific Standard Time (PST), 1/11/2007, on the beta attenuation monitor (BAM) at a North Las Vegas, Nevada sampling site. The high PM10 concentration at similar to 1245-similar to 1331 PST was a microscale event, limited strictly to the PM10 sampler; it did not affect the adjacent PM2.5 concentrations. A method was developed for retrospective compositional analysis of BAM glass-fiber filter tape sample deposits. Sample punches were submitted for optical examination, followed by elemental and morphological analyses with X-ray fluorescence (XRF) and scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDS) analyses, respectively. Geological samples surrounding the sampling site were acquired to establish source profiles and identify source markers. Although blank levels for many elements were high on the glass-fiber filter tape from the BAM, they were consistent enough to allow background subtraction from the deposit concentrations for most chemical components. Chemical mass balance (CMB) receptor model source apportionment for the event closely matched the paved road dust sample collected adjacent to the sampling site. It is likely that this high mass event was the result of environmental vandalism. This study demonstrates the feasibility of analyzing BAM filter tape deposits for source attribution, especially for short-duration fugitive dust events. Filter tapes should be time-stamped and immediately retained after an event for future analysis.</p

Winter and Summer Characteristics of Airborne Particles Inside Emperor Qin's Terra-Cotta Museum, China: A Study by Scanning Electron Microscopy-Energy Dispersive X-Ray Spectrometry

Day- and nighttime total suspended particulate matter was collected inside and outside Emperor Qin&#39;s Terra-Cotta Museum in winter and summer 2008. The purpose was to characterize the winter and summer differences of indoor airborne particles in two display halls with different architectural and ventilation conditions, namely the Exhibition Hall and Pit No. 1. The morphology and elemental composition of two season samples were investigated using scanning electron microscopy and energy dispersive X-ray spectrometry. It is found that the particle size, particle mass concentration, and particle type were associated with the visitor numbers in the Exhibition Hall and with the natural ventilation in Pit No. 1 in both winter and summer. Evident winter and summer changes in the composition and physicochemical properties of the indoor suspended particulate matters were related to the source emission and the meteorological conditions. Particle mass concentrations in both halls were higher in winter than in summer. In winter, the size of the most abundant particles at the three sites were all between 0.5 and 1.0 mu m, whereas in summer the peaks were all located at less than 0.5 mu m. The fraction of sulfur-containing particles was 2-7 times higher in winter than in summer. In addition to the potential soiling hazard, the formation and deposition of sulfur-containing particles in winter may lead to the chemical and physical weathering of the surfaces of the terra-cotta statues.</p

Stratospheric ozone, global warming, and the principle of unintended consequences-An ongoing science and policy story

Supplemental Materials: Supplemental materials are available for this paper. Go to the publisher&#39;s online edition of the Journal of the Air &amp; Waste Management Association.</p

Measurement System Evaluation for Upwind/Downwind Sampling of Fugitive Dust Emissions

Eight different PM(10) samplers with various size-selective inlets and sample flow rates were evaluated for upwind/downwind assessment of fugitive dust emissions from two sand and gravel operations in southern California during September through October 2008. Continuous data were acquired at one-minute intervals for 24 hours each day. Integrated filters were acquired at five-hour intervals between 1100 and 1600 PDT on each day because winds were most consistent during this period. High-volume (hivol) size-selective inlet (SSI) PM(10) Federal Reference Method (FRM) filter samplers were comparable to each other during side-by-side sampling, even under high dust loading conditions. Based on linear regression slope, the BGI low-volume (lovol) PQ200 FRM measured similar to 18% lower PM(10) levels than a nearby hivol SSI in the source-dominated environment, even though tests in ambient environments show they are equivalent. Although the TSI DustTrak DRX PM(10) concentrations did not equal those from the hivol SSI, both instruments were highly correlated (R = 0.9) at the two downwind sites. Multiple size ranges from the TSI DustTrak DRX and Grimm optical particle counters (OPC) allowed the identification of spatial non-uniformity for sources within and outside the facilities. Narrow dust plumes were only detected by some of the continuous instruments across the sampler array. Upwind PM(10) concentrations at one of the locations were higher than the downwind concentrations owing to a high concentration of industrial and vehicular activities. The shorter-duration measurements and quantification of super-coarse (&gt; 10 mu m) particles with high deposition velocities available from optical particle counters is needed to evaluate the effects of local emissions on both upwind and downwind samples.</p

Chemical Composition of Indoor and Outdoor Atmospheric Particles at Emperor Qin's Terra-cotta Museum, Xi'an, China

Indoor particles and microclimate were measured in summer (August 2004) and winter (January 2005) periods inside and outside Emperor Qin&#39;s Terra-Cotta Museum in Xi&#39;an, China. Indoor temperature ranged from 21.9 degrees C to 32.4 degrees C in summer and from 0 degrees C to 5.3 degrees C in winter. Relative humidity varied from 56% to 80% in summer and from 48% to 78% in winter. The number concentrations of particles were lower (0.3-1.0 mu m) in summer, and were higher (1.0-7.0 mu m) in winter. The average indoor PM(2.5) and TSP concentrations were 108.4 +/- 30.3 mu g/m(3) and 172.4 +/- 46.5 mu g/m(3) in summer and were 242.3 +/- 189.0 mu g/m(3) and 312.5 +/- 112.8 mu g/m(3) in winter, respectively. Sulfate, organic matter, and geological material dominated indoor PM(2.5), followed by ammonium, nitrate, and elemental carbon. Several milligram of sulfate particles can deposited in the museum per square meter each year based on the dry deposition estimate. High concentrations of acidic particles suspended inside the museum and their depositions have high risk for the erosion of the terra-cotta figures.</p

PM2.5 and PM10-2.5 chemical composition and source apportionmentnear a Hong Kong roadway

Twenty-four-hour PM2.5 and PM10 samples were collected simultaneously at a highly trafficked roadside site in Hong Kong every sixth day from October 2004 to September 2005. The mass concentrations of PM2.5, PM10-2.5 (defined as PM10 &minus; PM2.5), organic carbon (OC), elemental carbon (EC), water-soluble ions, and up to 25 elements were determined. Investigation of the chemical compositions and potential sources revealed distinct differences between PM2.5 and PM10-2.5. The annual average mass concentrations were 55.5 &plusmn; 25.5 and 25.9 &plusmn; 15.7 g/m3 for PM2.5 and PM10-2.5, respectively. EC, OM (OM = OC &times; 1.4), and ammonium sulfate comprised over &sim;82% of PM2.5, accounting for &sim;29%, &sim;27%, and &sim;25%, respectively, of the PM2.5 mass. Low OC/EC ratios (less than 1) for PM2.5 suggested that fresh diesel-engine exhaust was a major contributor. Seven sources were resolved for PM2.5 by positive matrix factorization (PMF) model, including vehicle emissions (&sim;29%), secondary inorganic aerosols (&sim;27%), waste incinerator/biomass burning (&sim;23%), residual oil combustion (&sim;10%), marine aerosols (&sim;6%), industrial exhaust (&sim;4%), and resuspended road dust (&sim;1%). EC and OM comprised only &sim;19% of PM10-2.5. The average OC/EC ratio of PM10-2.5 was 7.8 &plusmn; 14.2, suggesting that sources other than vehicular exhaust were important contributors. The sources for PM10-2.5 determined by the PMF model included &sim;20% traffic-generated resuspension (e.g., tire dust/brake linear/petrol evaporation), &sim;17% locally resuspended road dust, &sim;17% marine aerosols, &sim;12% secondary aerosols/field burning, and &sim;11% vehicle emissions.</p

Comparison of Elemental Carbon in Lake Sediments Measured by Three Different Methods and 150-Year Pollution History in Eastern China

Concentrations of elemental carbon (EC) were measured in a 150 yr sediment record collected from Lake Chaohu in Anhui Province, eastern China, using three different thermal analytical methods: IMPROVE_A thermal optical reflectance (TOR), STN_thermal optical transmittance (TOT), and chemothermal oxidation (CTO). Distribution patterns for EC concentrations are different among the three methods, most likely due to the operational definition of EC and different temperature treatments prescribed for each method. However, similar profiles were found for high-temperature EC fractions among different methods. Historical soot(ToR) (high-temperature EC fractions measured by the IMPROVE_A TOR method) from Lake Chaohu exhibited stable low concentrations prior to the late 1970s and a sharp increase thereafter, corresponding well with the rapid industrialization of China in the last three decades. This may suggest that high-temperature thermal protocols are suitable for differentiating between soot and other carbon fractions. A similar soot(ToR) record was also obtained from Lake Taihu (similar to 200 km away), suggesting a regional source of soot. The ratio of char(ToR) (low-temperature EC fraction measured by the IMPROVE_A TOR method, after correction for pyrolysis) to sootToR in Lake Chaohu shows an overall decreasing trend, consistent with gradual changes in fuel use from wood burning to increasing fossil fuel combustions. Average higher char(ToR)/soot(ToR) was observed in Lake Taihu than in Lake Chaohu in the past 150 years, consistent with the longer and more extensive industrialization around the Taihu region.</p