Particle size distribution and air pollution patterns in threeurban environments in Xi’an, China

Three urban environments, office, apartment and restaurant, were selected to investigate the indoor and outdoor air quality as an inter-comparison in which CO2, particulate matter (PM) concentration and particle size ranging were concerned. In this investigation, CO2 level in the apartment (623 ppm) was the highest among the indoor environments and indoor levels were always higher than outdoor levels. The PM10 (333 lg/m3), PM2.5 (213 lg/m3), PM1 (148 lg/m3) concentrations in the office were 10&ndash;50 % higher than in the restaurant and apartment, and the three indoor PM10 levels all exceeded the China standard of 150 lg/m3. Particles ranging from 0.3 to 0.4 lm, 0.4 to 0.5 lm and 0.5 to 0.65 lm make largest contribution to particle mass in indoor air, and fine particles number concentrations were much higher than outdoor levels. Outdoor air pollution is mainly affected by heavy traffic, while indoor air pollution has various sources. Particularly, office environment was mainly affected by outdoor sources like soil dust and traffic emission; apartment particles were mainly caused by human activities; restaurant indoor air quality was affected by multiple sources among which cooking-generated fine particles and the human steam are main factors.</p

Primary PM2.5 and trace gas emissions from residential coal combustion: assessing semi-coke briquette for emission reduction in the Beijing-Tianjin-Hebei region, China

In response to severe haze pollution, the Chinese State Council set PM2.5 improvement targets for the Beijing-Tianjin-Hebei (BTH) region in 2013. To achieve the targets for the residential sector, semi-coke briquettes are being considered as a replacement for traditional raw coals with the help of financial subsidy, but information on the emission from them and the impacts on the air quality is limited. Laboratory experiments were conducted to determine emission factors (EFs) for a typical semi-coke briquette, its parent material (bituminous raw-coal-chunk) and three types of traditional coals (bituminous raw-coal-chunk, anthracite raw-coal-chunk and anthracite coal-briquette) extensively used in BTH. Compared with the parent material, significant lower EFs of primary PM2.5, organic carbon (OC), element carbon (EC), the sum of 16 polycyclic aromatic hydrocarbon components (PAHs), SO42−, NO3−, hazardous trace elements (HTEs) and NOx were found in semi-coke briquette. A scenario for the BTH region in 2015 in which raw coals were replaced with the semi-coke briquette showed that amounts of pollutants emitted from residential coal combustion could decrease by 91.6% for primary PM2.5, 94.0% for OC, 99.6% for EC, 99.9% for PAHs, 94.2% for NO3−, 45.6% for HTEs, 70.9% for NOx and 22.3% for SO2. However, SO42− loadings evidently would increase if raw coals were replaced with either semi-coke briquette or anthracite coal-briquette. Geographic distributions of modeled reductions were developed to identify emission-reducing hot-spots and aid in the development of clean energy policies. Replacement of traditional raw coals with the semi-coke briquette apparently could lead to significant environmental improvements in BTH and other regions in China

Quantification of nitrated-polycyclic aromatic hydrocarbons in atmospheric aerosol samples with in-injection port thermal desorption-gas chromatography/negative chemical ionization mass spectrometry method

In-injection port thermal desorption (TD) was extended in determination of particulate phase nitrated-polycyclic aromatic hydrocarbons (N-PAHs) on filter samples coupled with a gas chromatography/negative ion chemical ionization-mass spectrometry (GC/NCI-MS). The experimental and analytical parameters were optimized with standard testing and ambient samples. Fourteen of the most abundant N-PAHs in ambient airs were included for their quantification. A desorption temperature of 280 °C for 10 min was sufficient to transfer entire target compounds from injection port to the analytical system. Good linearity (R2 >0.995) on the calibrations for each analyte was achieved. The limit of detections (LODs) ranged from 46.5 to 152.3 pg per filter sample, which were 4–66% better than solvent extraction (SE) approach. Method precision, repeatability and reproducibility, determined by replicate analyses of calibration standards and ambient samples, were less than 6% for target compounds. Validation of the method were conducted with two batches of a total of 30 ambient aerosol-loaded filters using our TD and the traditional SE approaches. Reasonably good agreement (R2 = 0.98) by the two methods was demonstrated for most of N-PAHs, except for 9-nitrophenanthrene and 6-nitrobenzo(a)pyrene. The in-injection port TD can improve laboratory efficiency and reduce solvent-based costs for the measurement of N-PAHs

Spatial distributions and sequestrations of organic carbon and black carbon in soils from the Chinese loess plateau

Concentrations of soil organic carbon (SOC), black carbon (BC), char, and soot in topsoils (0-20 cm) and vertical soil profiles (0-100 cm) from the Chinese Loess Plateau (CLP) were investigated. Objectives of the study were to establish the spatial distributions and estimate the sequestrations of these substances. The SOC, BC, char and soot concentrations were higher in the eastern and southeastern parts of the plateau and lower in the north, which is consistent with the patterns of economic development and energy consumption. The highest average SOC concentration was found in the clayey loess zone, followed by the loess and sandy loess zones. Similar trends were observed for BC, char and soot, suggesting interactions with clay and silt are potentially important influences on DC and BC. The SOC contents in topsoils varied from 0.31 to 51.81 g kg(-1), with a mean value of 6.54 g kg(-1), while BC and char concentrations were 0.02 to 5.5 g kg(-1) and 0.003 to 4.19 g kg(-1), respectively, and soot ranged from 0.01 to 132 g kg(-1). Unlike SOC, both BC and char decreased with soil depth, whereas soot showed little variation with depth. BC and char were correlated in the topsoils, and both correlated moderately well with SOC (R-2=0.60) and soot (R-2= 0.53). The SOC pools sequestered in the 0 to 20 cm and 0 to 100 cm depths were estimated to be 0.741 and 3.63 Pg, respectively, and the BC pools sequestered in the 0 to 20 cm and 0 to 100 cm depths were 0.073 and 0.456 Pg, respectively. Therefore the quantity of carbon stored in the sediments of the CLP evidently exceeds 10(9) tons. The char contained in the upper 20 cm layer was 0.053 Pg, which amounted to 72.5% of the BC in that layer.</p

Characterization of atmospheric organic and elemental carbon of PM2.5 in a typical semi-arid area of northeastern China

In the spring of 2006, daily particulate matter (PM2.5) aerosol samples were collected in Tongyu, a semi-arid area in northeastern China. The concentrations of organic carbon (OC) and elemental carbon (EC) were determined with a thermal/optical carbon analyzer in the filter samples. The average concentrations of OC and EC in PM2.5 were 14.1 &plusmn; 8.7 and 2.0 &plusmn; 1.3 &mu;g/m3, respectively. A good correlation between OC and EC was observed during the spring season, suggesting that they might be derived from similar sources. The correlation between OC and K+ was high (R = 0.74), and the K+/OC ratio, as determined from their linear regression slope, reached 2.57. The good correlation and high K+/OC ratio indicated that biomass-burning was probably one of the major sources of OC in this region. The concentrations of estimated secondary organic carbon (SOC) in PM2.5 in Tongyu ranged from below the detection limit to 26.1 &mu;g/m3 (mean, 5.9 &mu;g/m3). The percentages of SOC in OC and in PM2.5 mass were 42.0% and 2.1%, respectively. The SOC concentrations during dust storm (DS) periods were higher than those during non-dust storm (NDS) ones, suggesting that chemical reaction processes involving gas-particle conversion occurred during the long-distance transport of aerosol particles.</p

Microscale spatial distribution and health assessment of PM2.5-boundpolycyclic aromatic hydrocarbons (PAHs) at nine communities inXi'an, China

Spatial variability of polycyclic aromatic hydrocarbons (PAHs) associated with fine particulate matter (PM2.5) was investigated in Xi&#39;an, China, in summer of 2013. Sixteen priority PAHs were quantified in 24-h integrated air samples collected simultaneously at nine urban and suburban communities. The total quantified PAHs mass concentrations ranged from 32.4 to 104.7&nbsp;ng&nbsp;m&minus;3, with an average value of 57.1&nbsp;&plusmn;&nbsp;23.0&nbsp;ng&nbsp;m&minus;3. PAHs were observed higher concentrations at suburban communities (average: 86.3&nbsp;ng&nbsp;m&minus;3) than at urban ones (average: 48.8&nbsp;ng&nbsp;m&minus;3) due to a better enforcement of the pollution control policies at the urban scale, and meanwhile the disorganized management of motor vehicles and massive building constructions in the suburbs. Elevated PAH levels were observed in the industrialized regions (west and northwest of Xi&#39;an) from Kriging interpolation analysis. Satellite-based visual interpretations of land use were also applied for the supporting the spatial distribution of PAHs among the communities. The average benzo[a]pyrene-equivalent toxicity (&Sigma;[BaP]eq) at the nine communities was 6.9&nbsp;&plusmn;&nbsp;2.2&nbsp;ng&nbsp;m&minus;3 during the sampling period, showing a generally similar spatial distribution to PAHs levels. On average, the excess inhalation lifetime cancer risk derived from &Sigma;[BaP]eq indicated that eight persons per million of community residents would develop cancer due to PM2.5-bound PAHs exposure in Xi&#39;an. The great in-city spatial variability of PAHs confirmed the importance of multiple points sampling to conduct exposure health risk assessment.</p