Chemical composition and sources of PM2.5 and TSP collected at Qinghai Lake during summertime

PM2.5 and total suspended particulate (TSP) samples were collected from June to September 2010 at Qinghai Lake, northeastern Tibetan Plateau. The concentrations of major water-soluble ions, 10 elements, elemental carbons (ECs) and organic carbons (OCs) were quantified. Mass concentrations of PM2.5 and TSP were 21.27&plusmn;10.70&mu;gm-3 and 41.47&plusmn;20.25&mu;gm-3, respectively, and the mean ratio of PM2.5/TSP was 0.51. The greatest anion and cation in both PM2.5 and TSP samples were SO42- and Ca2+, respectively. Crustal elements, such as Ca, Fe and K, were the main elements in our aerosol samples, and their enrichment factors (EFs) were lower than 10. EFs for Pb, As, and Zn were greater than 10, indicating that they were influenced by anthropogenic sources. EC concentrations were 0.33&plusmn;0.17&mu;gm-3 and 0.47&plusmn;0.28&mu;gm-3, whereas OC concentrations were 1.49&plusmn;0.63&mu;gm-3 and 2.30&plusmn;0.95&mu;gm-3 in PM2.5 and TSP, respectively. Based on the calculated ratios of EC/TC and K+/EC, most of the ECs were found to be related to biomass burning emissions. Because of the pollution from local sources, the ratios of OC/EC were 4.77&plusmn;1.32 and 5.23&plusmn;1.39 in PM2.5 and TSP, respectively, which were lower than those of other remote sites. Salt particles produced by the salty lake reacted with acid gases and caused most of the nitrates and a small fraction of sulfate to be distributed in coarse mode; Cl deficit was also observed in our aerosol samples. Results of backward trajectories and correlation analysis show that the concentrations of SO42-, OCs, As, Pb, and Zn, were influenced by the long-distance transport from eastern China.</p

Comparison and implications of PM2.5 carbon fractionsin different environments

The concentrations of PM2.5 carbon fractions in rural, urban, tunnel and remote environments were measured using the IMPROVE thermal optical reflectance (TOR) method. The highest OC1 and EC1 concentrations were found for tunnel samples, while the highest OC2, OC3, and OC4 concentrations were observed for urban winter samples, respectively. The lowest levels of most carbon fractions were found for remote samples. The percentage contributions of carbon fractions to total carbon (TC) were characterized by one peak (at rural and remote sites) and two peaks (at urban and tunnel sites) with different carbon fractions, respectively. The abundance of char in tunnel and urban environments was observed, which might partly be due to traffic-related tire-wear. Various percentages of optically scattering OC and absorbing EC fractions to TC were found in the four different environments. In addition, the contribution of heating carbon fractions (char and soot) indicated various warming effects per unit mass of TC. The ratios of OC/EC and char/soot at the sites were shown to be source indicators. The investigation of carbon fractions at different sites may provide some information for improving model parameters in estimating their radiative effects.</p

Characteristics of surface ozone at an urban site of Xi'an in Northwest China

Surface ozone concentrations in Xi&#39;an, China were monitored from March 23, 2008 to January 12, 2009 using the Model ML/EC9810 ozone analyzer. The daily average O(3) ranged from &lt;1 ppb to 64.2 ppbv with an annual average of 16.0 ppbv. The seasonal average of O(3) in summer (32.5 ppbv) was more than 10 times higher than that in winter (3.0 ppbv). A significant positive correlation was found between ozone concentration and ambient temperature, indicating that the intensity of solar radiation was one of the several major factors controlling surface ozone production. Using the NOAA HYSPLIT 4 trajectory model, the three longest O(3) pollution episodes were found to be associated with the high biogenic volatile organic carbon (BVOC) emissions from the vegetation of Qinling Mountains. No significant weekday and weekend difference in O(3) levels was detected due to the non-significant change in NO(x) emissions. O(3) depletion by NO emission directly emitted from vehicles, low oxygenated VOC concentrations, and low-level solar radiation caused by high aerosol loading all contributed to the low levels of O(3) found in Xi&#39;an compared to other cities and rural areas.</p

Indoor and Outdoor Chemical Components of PM2.5 in the Rural Areas ofNorthwestern China

A case study of indoor and outdoor fine particles (PM2.5) was undertaken for rural areas in northwestern China, and quantitative data was obtained on their chemical composition including carbon fractions, water soluble ions, and elements. OM (organic matter), sulfate, and geological material dominated PM2.5, followed by nitrate and ammonium, which accounted for 78&ndash;85% of the mass for indoor and outdoor environments. The variations of the carbon fractions indicated that four OC factions and EC1 were more abundant in winter than in summer. SO4 2&minus; contributions were the highest of the ionic species for indoor and outdoor environments (about 40% of total ions in winter and 53% in summer), followed by NO3 &minus; (about 23% in winter and 14% in summer). The integrated results from the ratios of K+/OC, K+/EC, and as well as the EF (enrichment factor) values for K, Cl, S and Pb, indicate that the biofuel contributions were significant in the rural area. The indoor/outdoor ratios and correlations of the components were also investigated. The results for the indoor and outdoor PM2.5 sources showed that biomass burning in summer was the dominant primary source (31% for indoor and 44% for outdoor), and those for winter were coal combustion (21% for indoor and 29% for outdoor) and biomass burning (24% for indoor and 16% for outdoor). Due to the local patterns of energy consumption, the discussion presented in this work could give implications for future strategies to improve rural air quality.</p

Measuring and Modeling Black Carbon (BC) Contamination in the SE Tibetan Plateau,

Black carbon (BC) concentrations were measured in the southeast (SE) Tibetan Plateau along the valley of the Yarlung Tsangpo River during winter (between November, 2008 and January, 2009). The measured mean concentration (0.75 &mu;g m&minus;3) is significantly higher than the concentrations (0.004&ndash;0.34 &mu;g m&minus;3) measured in background and remote regions of the globe, indicating that Tibetan glaciers are contaminated by BC particles in the Plateau. Because BC particles play important roles for the climate in the Tibetan Plateau, the sources and causes of the BC contamination need to be understood and investigated. In this study, a mesocale dynamical model (WRF) with BC particle modules is applied for analyzing the measurement. The analysis suggests that the major sources for the contamination in the SE Plateau were mainly from the BC emissions in eastern Indian and Bangladesh. Because of the west prevailing winds, the heavy emissions in China had no significant effects on the SE Plateau in winter. Usually, the high altitude of the Himalayas acts a physical wall, inhibiting the transport of BC particles across the mountains to the plateau. This study, however, finds that the Yarlung Tsangpo River valley causes a &#39;leaking wall&#39;, whereby under certain meteorological conditions, BC particles are being transported up onto the glacier. This too causes variability of BC concentrations (ranging from 0.3 to 1.5 &mu;g m&minus;3) in a time scale of a few days. The analysis of the variability suggests that the &ldquo;leaking wall&rdquo; effect cannot occur when the prevailing winds were northwest winds, during which the BC transport along the valley of the Yarlung Tsangpo River was obstructed. As a result, large variability of BC concentration was observed due to the change of prevailing wind directions.</p

Physiochemical characteristics ofindoor PM2.5 with combustion ofdried yak dung as biofuel in TibetanPlateau, China

People inhabiting the Tibetan Plateau rely for survival on the yak, the region&rsquo;s native cattle. One of the important products of yak is dung, which has been served as cooking and heating fuels in the traditional Tibetan pastoralist society for several thousand years. The indoor air quality (IAQ) at eight residential homes with altitudes ranging from 3212 m to 4788 m was investigated in November 2012 to obtain a shot-term profile of emission from combustion of dried yak dung as biofuel in pastoral and agro-pastoral regions on the Tibetan Plateau. The indoor temperature, relative humidity, CO2 and mass concentrations of PM2.5 were monitored for around a 4-h period (5 kg dried fuel was consumed) at each site. Filter-based aerosol samples were also collected to characterize their elemental compositions, water-soluble ions, carbonaceous species and individual particle morphologies. The results showed that combustion of solid biomass fuel in cast-iron stove is the preliminary source of indoor particulate pollution. The average indoor and outdoor PM2.5 mass concentrations were 330.7 and 29.1 lg/m3, respectively. Individual particle analysis showed that most of the particles in smoke from dung burning were in the submicrometer size range. Regular and irregular organic balls and soot aggregates were the predominant species in the smoke (&gt;90% in numbers). The data set in this study can provide significant basis for IAQ and epidemiology study on the Tibetan Plateau.</p

Chemical composition of PM2.5 at a high–altitude regional backgroundsite over Northeast of Tibet Plateau

Aerosol samples were collected from a site near Qinghai Lake (QHL) on the northeastern margin of the Tibetan Plateau (TP) to investigate PM2.5 mass levels and chemical composition, especially their seasonal patterns and sources. The PM2.5 ranged from 5.7 to 149.7&nbsp;&mu;g m&ndash;3, and it was predominately crustal material (-40% on average). The combined mass of eight water&ndash;soluble inorganic ions ranged from 1.0 to 41.5&nbsp;&mu;g m&ndash;3, with the largest contributions from SO42&ndash; NO3-, and Ca2+. Low abundances of organic carbon (OC, range: 1.0 to 8.2&nbsp;&mu;g m&ndash;3) and elemental carbon (EC, 0.2 to 2.3&nbsp;&mu;g m&ndash;3) were found in QHL. Weak seasonality in the OC/EC ratio (4.5&plusmn;2.0) indicated simple and stable sources for carbonaceous particles. The water&ndash;soluble ions, OC and EC accounted for ~30%, 10% and 2% of the PM2.5, respectively. Water&ndash;soluble organic carbon (WSOC, range: 0.5 to 4.3&nbsp;&mu;g m&ndash;3) accounted for 47.8% of the OC. Both OC and WSOC were positively correlated with water&ndash;soluble K+(r=0.70 and 0.73 respectively), an indicator of biomass burning. Higher WSOC and stronger correlations between WSOC and EC in spring and winter compared with summer and autumn are evidence for primary biomass burning aerosols. The concentrations of mass and major compositions were 2&ndash;10 times higher than those for some TP or continental background sites but much lower than urban areas. Compared with particles produced from burning yak dung (a presumptive source material), PM2.5 had higher SO42&ndash;/OC ratios. The higher ratios were presumed as a result of fossil fuel combustion. After excluding data for dust storms events, the relative percentages of OM, EC, K+, NH4+, NO3&ndash; and mineral dust showed little difference among seasons despite different monsoons dominated in four seasons; implying that the PM2.5 sources were relatively stable. The results from QHL evidently reflect regional cha racteristics of the aerosol.</p

Indoor air quality at five site museums of Yangtze River civilization

The Yangtze River civilization, dating back to more than 7 thousand years ago, is one of the most historic culture aggregates in China. For long-term conservation of archaeological artifacts and historical ruins along the Yangtze River, indoor air quality at five site museums were investigated during summer and winter. Unstable microclimate conditions were observed at all five museums. The maximal seasonal variations in temperature and relative humidity were 25.7 C and 40.0%, respectively. The mass concentration of PM2.5 inside the museums remained at high levels, ranging from 33.9 to 79.6 mg/m3 in winter and from 52.8 to 113.0 mg/m3 in summer. Organic matter (OM) constituted a major fraction (39.3% e53.9% in summer, 22.1%e27.8% in winter) of total PM2.5. The results showed that besides short-term fluctuation and seasonal variation in microclimate conditions, infiltration of gaseous and particulate air pollutants should be of increasing concern at museums in Southern China.</p

Indoor air quality at five site museums of Yangtze River civilization

The Yangtze River civilization, dating back to more than 7 thousand years ago, is one of the most historic culture aggregates in China. For long-term conservation of archaeological artifacts and historical ruins along the Yangtze River, indoor air quality at five site museums were investigated during summer and winter. Unstable microclimate conditions were observed at all five museums. The maximal seasonal variations in temperature and relative humidity were 25.7 C and 40.0%, respectively. The mass concentration of PM2.5 inside the museums remained at high levels, ranging from 33.9 to 79.6 mg/m3 in winter and from 52.8 to 113.0 mg/m3 in summer. Organic matter (OM) constituted a major fraction (39.3% e53.9% in summer, 22.1%e27.8% in winter) of total PM2.5. The results showed that besides short-term fluctuation and seasonal variation in microclimate conditions, infiltration of gaseous and particulate air pollutants should be of increasing concern at museums in Southern China.</p

Chemical composition, sources, and deposition fluxes of water-soluble inorganic ions obtained from precipitation chemistry measurements collected at an urban site in northwest China

Precipitation samples were collected at an urban site in Xi&#39;an, northwest China during March to November in 2009 and were then analyzed to determine the pH and concentrations of water-soluble inorganic ions (Na(+), NH(4)(+), K(+), Mg(2+), Ca(2+), SO(4)(2-), NO(3)(-), Cl(-), and F(-)) in precipitation. The pH of precipitation ranged from 4.1 to 7.6 for all of the samples with an annual volume-weighted mean of 6.4. While a large portion of the precipitation events were weakly acidic or alkaline, around 30% of the precipitation events in the autumn were strongly acidic. Precipitation events with air masses from the northeast and the southeast were weakly acidic while those with air masses from the northwest and the southwest were alkaline. SO(4)(2-), Ca(2+), NH(4)(+), and NO(3)(-) were dominant ions in the precipitation, accounting for 37%, 25%, 18%, and 9%, respectively, of the total analyzed ions. Ca(2+) and NH(4)(+) were found to be the major neutralizers of precipitation acidity; however, the contribution of Mg(2+), although much lower than those of Ca(2+) and NH(4)(+), was important, in many cases, in changing the precipitation from weakly acidic to weakly alkaline. Enrichment factor analysis confirmed that SO(4)(2-) and NO(3)(-) were produced from anthropogenic sources, Ca(2+), K(+), and 80% Mg(2+) were from crustal sources, and Na(+), Cl(-), and &sim;20% of Mg(2+) were from marine sources. The annual wet depositions were estimated to be 3.5 t km(-2) per year for sulfur; 2.3 t km(-2) per year for nitrogen, of which 0.8 t km(-2) per year was oxidized nitrogen and 1.5 t km(-2) per year was reduced nitrogen; and 3.0 t km(-2) per year for Ca(2+).</p