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The DN method, referred to a gas chromatography (GC) method uses dinitrogen as a carrier gas, in combination with opaque static chamber, was widely used to measure grassland nitrous oxide (N 2 O) fluxes. However the N 2 O fluxes were positively biased by this method, as compared to the other GC methods. Currently, no study was conducted through simultaneous measurements of N 2 O fluxes by DN and other GC methods to correct the biased fluxes by the DN-based opaque static chamber measurement in grasslands. For this purpose, DN and DN-CO 2 methods (dinitrogen is also used as a carrier gas, and carbon dioxide as a make-up gas), both in combination with opaque static chambers, were compared through paired measurements in alpine pastures, including meadow as grazed pasture (MGP), ungrazed meadow (UGM), zokor mounds in meadow (ZMM), dung patches in meadow (DPM) and peat wetland as pasture (PWP). The DN method resulted in N 2 O fluxes about 11.1, 12.1 and 7.5 times higher (p < 0.05) in MGP, UGM and ZMM, respectively, while there was no significant difference between the two methods in DPM or PWP. All the paired fluxes with DN-CO 2 measurements >15 μg N m−2 h−1 showed positive correlations between the N 2 O fluxes measured by the two methods (p < 0.0001), whereas the other measurements showed a negative linear correlation of flux differences between the two methods versus DN-measured fluxes (p < 0.0001). We further developed correction approaches for DN-measured fluxes and validated these corrections using the data from this study or those observed previously in different terrestrial ecosystems by other studies. The estimated annual N 2 O emissions from grasslands in China would be reduced from 288.1 to 98.7–142.3 Gg N yr−1 (1 Gg = 109 g) if DN-measured fluxes were corrected using the approaches established in this study. We concluded that the DN method should be replaced by other GC methods or non-GC techniques to measure N 2 O fluxes from terrestrial ecosystems. Moreover, our study provides a valid approach to correct DN-measured N 2 O fluxes from global grasslands. X c denotes corrected DN-measured nitrous oxide (N 2 O) flux (μg N m−2 h−1). DN is a widely used gas chromatograph (GC) method that analyzes N 2 O with an electron capture detector (ECD), uses dinitrogen (N 2) as the carrier gas but does not use a make-up gas while not filtering samples using, e.g., ascarite. The correction approaches are established for measurements of DN in combination with opaque static chambers. In b, DN and Non-DN are the N 2 O fluxes obtained by DN and other GC-ECD methods, respectively, in different terrestrial ecosystems as non-hot cases. DN c1 , DN c2 and DN c3 are the DN-measured N 2 O fluxes corrected by (1) a previously developed approach for fertilized croplands, and the approaches established in this study based on (2) instantaneously fluxes and (3) annual and seasonal mean fluxes, respectively. Different capital letters above the bars indicate significant differences at p < 0.05. [Display omitted] • Measurements by DN, a widely used GC method, largely bias N 2 O fluxes of grasslands. • DN should be replaced by non-DN techniques to measure N 2 O emissions from soils. • Approach for correcting bias of DN-measured N 2 O fluxes is developed and validated. • This approach is applicable for correction of DN measurements from grasslands. [ABSTRACT FROM AUTHOR]

Abstract: An inventory of mercury emissions originating from waste incineration in China, including municipal solid waste, rural household waste and agricultural waste, was calculated for the period of 2004–2010. During this period, mercury emissions from waste incineration increased at an average annual rate of 3.9%, and reached 16.6 t y−1 by the end of 2010. From 2004 to 2010, the mercury emissions from rural household waste incineration accounted for 46.6% of the total waste emissions, followed by agricultural waste (30.7%) and municipal solid waste (22.7%). However, the growth rate of mercury emissions was largest for municipal solid waste incineration, with an annual rate of 37.3%, while the emissions from rural household waste showed a negative growth rate (−5.8%). The mercury emissions from waste combustion is projected to be 18.6 t y−1 by 2015, with the contribution of municipal solid waste, rural household waste and agricultural waste being 46.4%, 27.1% and 26.5%, respectively. [Copyright &y& Elsevier]

Abstract: Carbon dioxide (CO2) and carbon monoxide (CO) impact climate change and human health. The uncertainties in emissions inventories of CO2 and CO are primarily due to the large variation in measured emissions factors (EFs), especially to the lack of EFs from developing countries. China''s goals of reducing CO2 emissions require a maximum utilization of biomass fuels. Pelletized biomass fuels are well suited for the residential biomass market, providing possibilities of more automated and optimized systems with higher modified combustion efficiency (MCE) and less products from incomplete combustion. However, EFs of CO2 and CO from pellet biomass fuels are seldom reported, and a comparison to conventional uncompressed biomass fuels has never been conducted. Therefore, the objectives of this study were to experimentally determine the CO2 and CO EFs from uncompressed biomass (i.e., firewood and crop residues) and biomass pellets (i.e., pine wood pellet and corn straw pellet) under real residential applications and to compare the influences of fuel properties and combustion conditions on CO2 and CO emissions from the two types of biomass fuels. For the uncompressed biomass examples, the CO2 and CO EFs were 1649.4 ± 35.2 g kg−1 and 47.8 ± 8.9 g kg−1, respectively, for firewood and 1503.2 ± 148.5 g kg−1 and 52.0 ± 14.2 g kg−1, respectively, for crop residues. For the pellet biomass fuel examples, the CO2 and CO EFs were 1708.0 ± 3.8 g kg−1 and 4.4 ± 2.4 g kg−1, respectively, for pellet pine and 1552.1 ± 16.3 g kg−1 and 17.9 ± 10.2 g kg−1, respectively, for pellet corn. In rural China areas during 2007, firewood and crop residue burning produced 721.7 and 23.4 million tons of CO2 and CO, respectively. [Copyright &y& Elsevier]

Abstract: Due to the high costs and deployment difficulties associated with automated sampling technologies, few investigations have been published on atmospheric mercury in typical urban and rural areas in developing countries. In this study, a novel passive sampler for gaseous elemental mercury was developed and applied to characterize trends in atmospheric mercury levels across an urban–rural transect. The sampling transect originated in the city of Beijing and extended ∼150km southward into a rural region. Field deployment was conducted during September–October (autumn) and November–December (winter) in 2010. The mercury concentrations in air obtained using the passive sampler were consistent with synchronous automated measurements performed during the field deployment. The results demonstrated that atmospheric mercury concentrations increased along the urban–rural gradient in the following order in both of the two periods: urban>suburban>rural (populated)>rural (farmland). [Copyright &y& Elsevier]

Abstract: Objection: To study the pollution of atmospheric particles at winter in Beijing and compare the lung toxicity which induced by particle samples from different sampling sites. Method: We collected samples from two sampling points during the winter for toxicity testing and chemical analysis. Wistar rats were administered with particles by intratracheal instillation. After exposure, biochemically index, esimmunity indexes, histopathology and DNA damage were detected in rat pulmonary cells. Result: The elements with enrichment factors (EF) larger than 10 were As, Cd, Cu, Zn, S and Pb in the four experiment groups. The priority control of the total concentration of polycyclic aromatic hydrocarbons (PAHs) in PM10 and PM2.5 of Near-traffic source was much higher than that of Far-traffic source, it demonstrated that near the traffic source of PAHs pollution was heavier than that of Far-traffic source, as it was close to main roads Beiyuan Road, motor vehicle emissions were much higher. The pathology of lung showed that the degree of inflammation was increased with the particle diameter minished, it was the same as the detection of biochemical parameters such as lactate dehydrogenase (LDH), Total antioxidant status(T-AOC) and total protein (TP) in BALF and inflammation cytokine(interleukin-1, interleukin-6 and tumor necrosis factor-alpha) in lung homogenate. The indexes of DNA damage including the content of DNA and Olive empennage of PM2.5 were significant higher than that of PM10 at the same surveillance point (P < 0.05), near-traffic particles were higher than the far-traffic particles at the same diameter, (P < 0.05). Conclusion: Near-traffic area particles had certain pollution at winter in Beijing. Meanwhile, atmospheric particulate matters on lung toxicity were related to the particles size and distance related sites which were exposed: smaller size, more toxicity; nearer from traffic, more toxicity. [Copyright &y& Elsevier]

Abstract: Much rain and strong winds caused by a cold front occurred in Beijing during the period of Sep. 27 to Oct. 4, 2004 and led to sharp drops in maximum and mean concentrations of HONO, HCHO, O3, and NO2, i.e., the maximum concentrations were reduced by 5.9, 21.3, 45.6, and 44.4 ppb, respectively, and the mean concentrations were decreased by 4.0, 5.5, 30.3, and 32.3 ppb, respectively. For daily HO x production rates HONO photolysis was the largest contributor and over 90% contributions were from photolysis of HONO and HCHO. Large number and area percentages of soot aggregate from PM10, and high correlations between concentrations of PM10 and chemical formation of HONO suggested that heterogeneous reactions of NO2 on surfaces of soot aggregate could be a key source of HONO in the heavy traffic areas of Beijing during the night and should be considered in air quality simulations for such areas. [Copyright &y& Elsevier]

Fine particulate matter (PM 2.5 ) has attracted increasing attention due to its impacts on air quality and human health. As an important source of PM 2.5 , diesel vehicles are often the focus of research. In this study, we characterized the carbonaceous composition of PM 2.5 that is emitted from on-road China III diesel trucks (DTs). Organic carbon (OC), elemental carbon (EC), and PM 2.5 emission characteristics were determined for 17 China III DTs, including 6 light-duty diesel trucks (LDDTs), 5 medium-duty diesel trucks (MDDTs), and 6 heavy-duty diesel trucks (HDDTs), based on real-world measurements in Beijing, China, using a portable emissions measurement system (PEMS). The average distance-based PM 2.5 emission factors (EFs) (g km −1 ) generally increased and the average CO 2 -based PM 2.5 EFs (g (kg of CO 2 ) −1 ) generally decreased with increased vehicle size from LDDTs to MDDTs to HDDTs. The effects of driving conditions on the EFs for carbonaceous PM 2.5 were analyzed. The results show that distance-based and CO 2 -based EFs strongly depend on driving conditions. Generally, greater amounts of PM 2.5 and OC are emitted from non-highway driving cycles, and greater amounts of EC are emitted from highway driving cycles for vehicles of the same size. For LDDTs, MDDTs, and HDDTs, no significant differences were observed between vehicles with different EC/OC ratios; therefore, the EC/OC ratio is not useful for distinguishing between the emissions generated by differently sized vehicles. The EC/OC, OC/PM 2.5 , and EC/PM 2.5 mass ratios are strongly dependent on driving conditions for vehicles of the same size. The results of this study provide EFs for the carbonaceous composition of PM 2.5 that are more appropriate for China; these results will be helpful for improving policies that are designed to control the carbonaceous composition of PM 2.5 emitted from on-road DTs in China. [ABSTRACT FROM AUTHOR]

Primary nonferrous metal smelting is one of the most significant anthropogenic mercury emission sources. A spatially resolved mercury emission inventory over a long time span is essential for assessment of mercury source attribution and mercury transport modeling. In this study, based on updated technology-based emission factors, the atmospheric mercury emissions originating from primary zinc, lead and copper smelting in China were calculated. The inventory indicated that the total mercury emission from nonferrous metal smelting in China was 14.65 Mg in 2010, lower than the estimations in previous studies. The contributions of point and non-point sources were 23.3% and 76.7%, respectively. In 2010, the mercury emission from primary zinc, lead and copper smelting was 7.49, 6.05 and 1.10 Mg, respectively, and the Hg 2+ , Hg 0 and Hg P emissions were 8.10, 6.16 and 0.75 Mg, respectively. Spatially, the province with the largest emission was Sichuan, followed by Henan, Gansu, Shaanxi, Hunan and Yunnan provinces. The historical emissions were estimated based on dynamic emission factors that take the temporal technology changes into consideration. During 1949–2010, the cumulative mercury emission from China's nonferrous metal smelting was 323.0 Mg, of which the emission from lead smelting accounted for 44.6%, followed by zinc smelting (32.8%) and copper smelting (22.6%). From 1949 to 2010, the contribution of mercury emission from zinc smelting increased from 1.4% to 53.7%, while that from lead smelting showed a decreasing trend. For copper smelting, its contribution reached the maximum (40.1%) in 1987. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of the Coronavirus Disease 2019 (COVID-19) lockdown on air quality in cities in southwest China, a single particle aerosol mass spectrometer (SPAMS) and other online equipments were used to measure the air pollution in Chengdu, one of the megacities in this area, before and during the lockdown period. It was found that the concentrations of fine particulate matter (PM 2.5), nitric oxide (NO), nitrogen dioxide (NO 2), sulfur dioxide (SO 2) and carbon monoxide (CO) decreased by 38.6%, 77.5%, 47.0%, 35.1% and 14.1%, respectively, while the concentration of ozone (O 3) increased by 57.5% from the time before to the time during lockdown. All particles collected during the study period could be divided into eight categories: biomass burning (BB), coal combustion (CC), vehicle emissions (VE), cooking emissions (CE), Dust, K-nitrate (K–NO 3), K-sulfate (K–SO 4) and K-sulfate-nitrate (K-SN) particles, and their contributions changed significantly after the beginning of lockdown. Compared to before lockdown, the contribution of VE particles experienced the largest reduction (by 14.9%), whereas the contributions of BB and CE particles increased by 7.0% and 7.3%, respectively, during the lockdown period. Regional transmission was critical for pollution formation before lockdown, whereas the pollution that occurred during the lockdown period was caused mainly by locally emitted particles (such as VE, CE and BB particles). Weighted potential source contribution function (WPSCF) analysis further verified and emphasized the difference in the contribution of regional transmission for pollution formation before and during lockdown. In addition, the potential source area and intensity of the particles emitted from different sources or formation mechanisms were quite different. • Single aerosol particles during the COVID-19 lockdown were measured based on SPAMS. • The lockdown caused reductions in PM 2.5 , NO, NO 2 , SO 2 and CO, while increase in O 3. • Vehicle emission particles decreased the most (by 14.9%) during lockdown period. • Pollution formation mechanism before and during lockdown was completely different. [ABSTRACT FROM AUTHOR]

Abstract: Incorporated into the WRF–Chem model are the three HONO sources, i.e., the reaction of photo-excited NO2 with water (NO2 * chemistry), heterogeneous reactions on aerosol surfaces, and HONO emissions. Four case simulations were performed in Beijing, Tianjin, and Hebei Province (BTH region) in August of 2007. Results indicate that the NO2 * chemistry yields 30–50 ppb enhancements in daily maximum 1-h surface O3 concentrations in major cities and 3–10 ppb increases in monthly mean daily maximum 8-h surface O3 concentrations in most areas of the BTH region. Heterogeneous reactions on aerosol surfaces lead to 5–20 ppb decreases in monthly mean NOy concentrations in major cities over the BTH region. Heterogeneous reactions and HONO emissions are the largest, and the second largest contributor, accounting for ∼59% and 26% of simulated HONO concentrations, respectively. The three HONO sources produce enhancements in monthly mean daytime (10:00–17:00) concentrations of NOy (total reactive N-containing compounds), NO2, HNO3, HONO, and HOx being −1 to −5 ppb, −1 to −3 ppb, −0.3 to 0.5 ppb, 20–50 ppt, and 1–3 ppt, respectively. Comparison with observations shows that inclusion of the three HONO sources into the WRF–Chem model can considerably improve HONO and O3 simulations in the BTH region. For HONO the mean, the normal mean bias, the root mean square error, and the correlation coefficient is greatly improved from 0.04 to 0.56 ppb, from −97% to −39%, from 1.10 ppb to 0.51 ppb, and from −0.56 to 0.86, respectively, by comparison with the gas chemical mechanism only considered in the WRF–Chem model. This suggests that the three important HONO sources be included in air quality models, particularly in the areas with high emissions of NOx and particulate matter. [Copyright &y& Elsevier]