Atmospheric oxalic acid and related secondary organic aerosols inQinghai Lake, a continental background site in Tibet Plateau

Summertime PM2.5 aerosols collected from Qinghai Lake (3200ma.s.l.), a remote continental site in the northeastern part of Tibetan Plateau, were analyzed for dicarboxylic acids (C2-C11), ketocarboxylic acids and &alpha;-dicarbonyals. Oxalic acid (C2) is the dominant dicarboxylic acid in the samples, followed by malonic, succinic and azelaic acids. Total dicarboxylic acids (231&plusmn;119ngm-3), ketocarboxylic acids (8.4&plusmn;4.3ngm-3), and &alpha;-dicarbonyls (2.7&plusmn;2.1ngm-3) at the Tibetan background site are 2-5 times less than those detected in lowland areas such as 14 Chinese megacities. Compared to those in other urban and marine areas enhancements in relative abundances of C2/total diacids and diacids-C/WSOC of the PM2.5 samples suggest that organic aerosols in the region are more oxidized due to strong solar radiation. Molecular compositions and air mass trajectories demonstrate that the above secondary organic aerosols in the Qinghai Lake atmosphere are largely derived from long-range transport. Ratios of oxalic acid, glyoxal and methylglyoxal to levoglucosan in PM2.5 aerosols emitted from household burning of yak dung, a major energy source for Tibetan in the region, are 30-400 times lower than those in the ambient air, which further indicates that primary emission from biomass burning is a negligible source of atmospheric oxalic acid and &alpha;-dicarbonyls at this background site.</p

Estimation of Gas-Particle Partitioning Coefficients (K-p) of Carcinogenic Polycyclic Aromatic Hydrocarbons in Carbonaceous Aerosols Collected at Chiang-Mai, Bangkok and Hat-Yai, Thailand

To assess environmental contamination with carcinogens, carbonaceous compounds, water-soluble ionic species and trace gaseous species were identified and quantified every three hours for three days at three different atmospheric layers at the heart of Chiang-Mai, Bangkok and Hat-Yai from December 2006 to February 2007. A DRI Model 2001 Thermal/Optical Carbon Analyzer with the IMPROVE thermal/optical reflectance (TOR) protocol was used to quantify the organic carbon (OC) and elemental carbon (EC) contents in PM10. Diurnal and vertical variability was also carefully investigated. In general, OC and EC mass concentration showed the highest values at the monitoring period of 21.00-00.00 as consequences of human activities at night bazaar coupled with reduction of mixing layer, decreased wind speed and termination of photolysis at nighttime. Morning peaks of carbonaceous compounds were observed during the sampling period of 06:00-09:00, emphasizing the main contribution of traffic emission in the three cities. The estimation of incremental lifetime particulate matter exposure (ILPE) raises concern of high risk of carbonaceous accumulation over workers and residents living close to the observatory sites. The average values of incremental lifetime particulate matter exposure (ILPE) of total carbon at Baiyoke Suit Hotel and Baiyoke Sky Hotel are approximately ten times higher than those air samples collected at Prince of Songkla University Hat-Yai campus corpse incinerator and fish-can manufacturing factory but only slightly higher than those of rice straw burning in Songkla province. This indicates a high risk of developing lung cancer and other respiratory diseases across workers and residents living in high buildings located in Pratunam area. Using knowledge of carbonaceous fractions in PM10, one can estimate the gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs). Dachs-Eisenreich model highlights the crucial role of adsorption in gas-particle partitioning of low molecular weight PAHs, whereas both absorption and adsorption tend to account for gas-particle partitioning of high molecular weight PAHs in urban residential zones of Thailand. Interestingly, the absorption mode alone plays a minor role in gas-particle partitioning of PAHs in Chiang-Mai, Bangkok and Hat-Yai.</p

Effects of Grazing on Ecosystem CO2 Exchange in a MeadowGrassland on the Tibetan Plateau During the Growing Season

Effects of human activity on ecosystem carbon fluxes (e.g., net ecosystem exchange (NEE), ecosystem respiration (R eco), and gross ecosystem exchange (GEE)) are crucial for projecting future uptake of CO2 in terrestrial ecosystems. However, how ecosystem that carbon fluxes respond to grazing exclusion is still under debate. In this study, a field experiment was conducted to study the effects of grazing exclusion on R eco, NEE, and GEE with three treatments (free-range grazing (FG) and grazing exclusion for 3 and 5&nbsp;years (GE3 and GE5, respectively)) in a meadow grassland on the Tibetan Plateau. Our results show that grazing exclusion significantly increased NEE by 47.37 and 15.84&nbsp;%, and R eco by 33.14 and 4.29&nbsp;% under GE3 and GE5 plots, respectively, although carbon sinks occurred in all plots during the growing season, with values of 192.11, 283.12, and 222.54&nbsp;g&nbsp;C&nbsp;m&minus;2 for FG, GE3, and GE5, respectively. Interestingly, grazing exclusion increased temperature sensitivity (Q 10) of R eco with larger increases at the beginning and end of growing season (i.e., May and October, respectively). Soil temperature and soil moisture were key factors on controlling the diurnal and seasonal variations of R eco, NEE, and GEE, with soil temperature having a stronger influence. Therefore, the combined effects of grazing and temperature suggest that grazing should be taken into consideration in assessing global warming effects on grassland ecosystem CO2 exchange.</p

Carbonaceous Aerosol Characteristics in Outdoor and Indoor Environments of Nanchang, China, during Summer 2009

A study of carbonaceous aerosol was initiated in Nanchang, a city in eastern China, for the first time. Daily and diurnal (daytime and nighttime) PM(2.5) (particulate matter with aerodynamic diameter &lt;= 2.5 mu m) samples were collected at an outdoor site and in three different indoor environments (common office, special printing and copying office, and student dormitory) in a campus of Nanchang University during summer 2009 (5-20 June). Daily PM(10) (particulate matter with aerodynamic diameter &lt;= 10 mu m) samples were collected only at the outdoor site, whereas PM(2.5) samples were collected at both indoor and outdoor sites. Loaded PM(2.5) and PK(10) samples were analyzed for organic and elemental carbon (OC, EC) by thermal/optical reflectance following the Interagency Monitoring of Protected Visual Environments-Advanced (IMPROVE-A) protocol. Ambient mass concentrations of PM(10) and PM(2.5) in Nanchang were compared with the air quality standards in China and the United States, and revealed high air pollution levels in Nanchang. PM(2.5) accounted for about 70% of PM(10), but the ratio of OC and EC in PM(2.5) to that in PK(10) was higher than 80%, which indicated that OC and EC were mainly distributed in the fine particles. The variations of carbonaceous aerosol between daytime and nighttime indicated that OC was released and formed more rapidly in daytime than in nighttime. OC/EC ratios were used to quantify secondary organic carbon (SOC). The differences in SOC and SOC/OC between daytime and nighttime were useful in interpreting the secondary formation mechanism. The results of (1) OC and EC contributions to PM(2.5) at indoor sites and the outdoor site; (2) indoor-outdoor correlation of OC and EC; (3) OC-EC correlation; and (4) relative contributions of indoor and outdoor sources to indoor carbonaceous aerosol indicated that OC indoor sources existed in indoor sites, with the highest OC emissions in 12 (the special printing and copying office), and that indoor EC originated from outdoor sources. The distributions of eight carbon fractions in emissions from the printer and copier showed obviously high OC1 (&gt; 20%) and OC2 (similar to 30%), and obviously low EC1-OP (a pyrolyzed carbon fraction) (&lt; 10%), when compared with other sources.</p

Numerical Simulation of the Micro Environment in the Han Yang Mausoleum Museum

As a first underground museum in the world, whole sealed glass system is adopted in the Han Yang Mausoleum Museum to protect relics from the destruction by microbe and pollution in the atmosphere and to provide visitors a wonderful environment for enjoying the fantastic artwork closely from different angles. This study shows that, this method cannot completely stop relics from the destruction. The main reason is that, in the museum, the microbe growth and pollution spread are fairly significant to affect the protection of relics. This study numerically simulates the micro environment in the museum, including air movement, temperature and relative humidity by using the CFD software Fluent. The major findings are summaried as the followes: there are four air cyclones; temperature is getting lower from one side to another; and relative humidity profile is reversed, especially at the surface. This numerical result provides useful information for the protection of relics.</p

Elemental compositions of PM2.5 and TSP in Lijiang, southeastern edge of Tibetan Plateau during pre-monsoon period

PM2.5 and total suspended particulate (TSP) samples were collected at Lijiang, southeastern Tibetan Plateau, China. Sixteen elements (Al, Si, S, K, Ca, Cr, Mn, Ti, Fe, Ni, Zn, As, Br, Sb, Pb and Cu) were analyzed to investigate their elemental compositions during the pre-monsoon period. The results showed that Ca was the most abundant element in both PM2.5 and TSP samples. The enrichment factors (EFs) of Si, Ti, Ca, Fe, K and Mn were all below 10 for both PM2.5 and TSP, and these elements also had lower PM2.5/TSP ratios (0.32-0.34), suggesting that they were mainly derived from crustal sources. Elements Cu, Zn, S, Br and Sb showed strong enrichment in PM2.5 and TSP samples, with their PM2.5/TSP ratios ranging from 0.66 to 0.97, indicating that they were enriched in the fine fractions and influenced by anthropogenic sources. Analysis of the wind field at 500 hPa and calculations of back trajectories indicated that Al, Si, Ca, Ti, Cr, Mn and Fe can be influenced by transport from northwestern China during the dust-storm season, and that S, K, Ni, Br and Pb reached high concentrations during westerly transport from south Asia. Combined with the principle component analysis and correlation analysis, elements of PM2.5 samples were mainly from crustal sources, biomass burning emissions and regional traffic-related sources.</p

Effect of Quaternary climatic change on modern hydrologicalsystems in the southern Chinese Loess Plateau

A systematic study was conducted to investigate the permeability, porosity, grain size, water content, mass percentage of carbonate, and magnetic susceptibility of representative Middle Pleistocene loess-palaeosol layers (from L1 to S5) on the Chinese Loess Plateau. The average infiltration rate of the loess (0.93&nbsp;mm/min) was higher than the palaeosol (0.62&nbsp;mm/min), and the porosity of loess was higher than that of palaeosol. The loess layers have greater water-bearing capacity and, therefore, they are more likely to form aquifers while the palaeosol layers are more prone to form aquitards. The greater permeability and the larger water-bearing space of the loess layers are largely the result of lower intensity pedogenesis due to the colder/drier climatic conditions at the time these sediments were deposited. Conversely, the weaker permeability and lesser water-bearing capacity of the palaeosol layers can be explained by the greater pedogenesis during the warmer/wetter climatic conditions. The studies demonstrate a compelling relationship between Pleistocene climate and modern hydrological systems in the southern Chinese Loess Plateau.</p

Climate effect of black carbon aerosol in a Tibetan Plateau glacier

In the Tibetan Plateau, the black carbon (BC) concentration in surface snow and snow pits has received much attention, whereas the seasonal behavior of aerosol-in-snow concentration, vertical profile, meltscavenging, and enrichment have received relatively little attention. Here we investigate these processes and their impacts on radiative forcing on the Muji glacier in the westernmost Tibetan Plateau during the 2012 snowmelt season. Increasing impurity concentrations were mostly due to post-deposition effects rather than new deposition. On 5 July, BC concentrations in the surface snow were higher than those of fresh snow, implying enrichment via sublimation and/or melting of previous snow. Fresh snow contained 25 ng g 1 BC on 27 July; afterward, BC gradually increased, reaching 730.6 ng g 1 in September. BC, organic carbon (OC), and dust concentrations co-varied but differed in magnitude. Melt-scavenging efficiencies were estimated at 0.19 &plusmn; 0.05 and 0.04 &plusmn; 0.01 for OC and BC, respectively, and the BC in surface snow increased by 20e25 times depending on melt intensity. BC-in-snow radiative forcing (RF) was approximately 2.2 W m 2 for fresh snow and 18.1e20.4 W m 2 for aged snow, and was sometimes reduced by the presence of dust.</p