Assessing the contribution of global wildfire biomass burning to BaP contamination in the Arctic

Polycyclic aromatic hydrocarbons(PAHs)have become cause for growing concern in the Arctic ecosystems,partly due to their stable levels despite global emission reduction.Wildfire is considered one of the primary sources that influence PAH levels and trends in the Arctic,but quantitative investigations of this influence are still lacking.This study estimates the global emissions of benzo[a]pyrene(BaP),a congener of PAHs with high carcinogenicity,from forest and grassland fires from 2001 to 2020 and simulates the contributions of wildfire-induced BaP emissions from different source regions to BaP contamination in the Arctic.We find that global wildfires contributed 29.3%to annual averaging BaP concentrations in the Arctic from 2001 to 2020.Additionally,we show that wildfires contributed significantly to BaP concentrations in the Arctic after 2011,enhancing it from 10.1%in 2011 to 83.9%in 2020.Our results reveal that wildfires accounted for 94.2%and 50.8%of BaP levels in the Asian Arctic during boreal summer and autumn,respectively,and 74.2%and 14.5%in the North American Arctic for the same seasons.The source-tagging approach identified that local wildfire biomass emissions were the largest source of BaP in the Arctic,accounting for 65.7%of its concentration,followed by those of Northern Asia(17.8%)and Northern North America(13.7%).Our findings anticipate wildfires to play a larger role in Arctic PAH contaminations alongside continually decreasing anthropogenic emissions and climate warming in the future.

Antagonism between ambient ozone increase and urbanization-oriented population migration on Chinese cardiopulmonary mortality

Everincreasing ambient ozone(O3)pollution in China has been exacerbating cardiopulmonary premature deaths.However,the urban-rural exposure inequity has seldom been explored.Here,we assess populationcale 03 exposure and mortality burdens between 1990 and 2019 based on integrated pollution tracking and epidemiological evidence.We find Chinese population have been suffering from climbing 03 exposure by 4.3±2.8 ppb per decade as a result of rapid urbanization and growing prosperity of socioeconomic activities.Rural residents are broadly exposed to 9.8±4.1 ppb higher ambient O3 than the adjacent urban citizens,and thus urbaniza-tion-oriented migration compromises the exposure-associated mortality on total population.Cardiopulmonary excess premature deaths attributable to longterm 03 exposure,373,500(95%uncertainty interval[U]:240,600-510,900)in 2019,is underestimated in previous studies due to ignorance of cardiovascular causes.Future 03 pollution policy should focus more on rural population who are facing an aggravating threat of mortality risks to ameliorate environmental health injustice.

Emissions of parent, nitrated, and oxygenated polycyclic aromatic hydrocarbons from indoor corn straw burning in normal and controlled combustion conditions

Emission factors （EFs） of parent polycyclic aromatic hydrocarbons （pPAHs）, nitrated PAHs （nPAHs）, and oxygenated PAHs （oPAHs） were measured for indoor corn straw burned in a brick cooking stove under different burning conditions. The EFs of total 28 pPAHs, 6 nPAHs and 4 oPAHs were （7.9 ±3.4）, （6.5 ±1.6）×10^-3, and （6.1 ±1.4）×10^-1mg/kg, respectively. Fuel charge size had insignificant influence on the pollutant emissions. Measured EFs increased significantly in a fast burning due to the oxygen deficient atmosphere formed in the stove chamber. In both restricted and enhanced air supply conditions, the EFs of pPAHs, nPAHs and oPAHs were significantly higher than those measured in normal burning conditions. Though EFs varied among different burning conditions, the composition profiles and calculated isomer ratios were similar, without significant differences. The results from the stepwise regression model showed that fuel burning rate, air supply amount, and modified combustion efficiency were the three most significant influencing factors, explaining 72%-85% of the total variations.

Cohort-based long-term ozone exposure-associated mortality risks with adjusted metrics:A systematic review and meta-analysis

Long-term ozone(O_(3))exposure may lead to non-communicable diseases and increase mortality risk.However,cohort-based studies are relatively rare,and inconsistent exposure metrics impair the credibility of epidemiological evidence synthetization.To provide more accurate meta-estimations,this study updates existing systematic reviews by including recent studies and summarizing the quantitative associations between O_(3) exposure and cause-specific mortality risks,based on unified exposure metrics.Cross-metric conversion factors were estimated linearly by decadal observations during 1990-2019.

Influence of fuel mass load,oxygen supply and burning rate on emission factor and size distribution of carbonaceous particulate matter from indoor corn straw burning

The uncertainty in emission estimation is strongly associated with the variation in emission factor （EF）,which could be influenced by a variety of factors such as fuel properties,stove type,fire management and even methods used in measurements.The impacts of these factors are complicated and often interact with each other.Controlled burning experiments were conducted to investigate the influences of fuel mass load,air supply and burning rate on the emissions and size distributions of carbonaceous particulate matter （PM） from indoor corn straw burning in a cooking stove.The results showed that the EFs of PM （EFPM）,organic carbon （EFOC） and elemental carbon （EFEC） were independent of the fuel mass load.The differences among them under different burning rates or air supply amounts were also found to be insignificant （p 〉 0.05） in the tested circumstances.PM from the indoor corn straw burning was dominated by fine PM with diameter less than 2.1 μm,contributing 86.4%±3.9% of the total.The size distribution of PM was influenced by the burning rate and air supply conditions.On average,EF PM,EF OC and EF EC for corn straw burned in a residential cooking stove were （3.84±1.02）,（0.846±0.895） and （0.391±0.350） g/kg,respectively.EF PM,EF OC and EF EC were found to be positively correlated with each other （p 〈 0.05）,but they were not significantly correlated with the EF of co-emitted CO,suggesting that special attention should be paid to the use of CO as a surrogate for other incomplete combustion pollutants.

Air pollution and inhalation exposure to particulate matter of different sizes in rural households using improved stoves in central China

Household air pollution is considered to be among the top environmental risks in China.To examine the performance of improved stoves for reduction of indoor particulate matter（PM） emission and exposure in rural households, individual inhalation exposure to size-resolved PM was investigated using personal portable samplers carried by residents using wood gasifier stoves or improved coal stoves in a rural county in Central China.Concentrations of PM with different sizes in stationary indoor and outdoor air were also monitored at paired sites. The stationary concentrations of size-resolved PM in indoor air were greater than those in outdoor air, especially finer particles PM0.25. The daily averaged exposure concentrations of PM0.25, PM1.0, PM2.5 and total suspended particle for all the surveyed residents were 74.4 ± 41.1, 159.3 ± 74.3, 176.7 ± 78.1 and 217.9 ± 78.1 μg/m3,respectively. Even using the improved stoves, the individual exposure to indoor PM far exceeded the air quality guideline by WHO at 25 μg/m3. Submicron particles PM1.0 were the dominant PM fraction for personal exposure and indoor and outdoor air. Personal exposure exhibited a closer correlation with indoor PM concentrations than that for outdoor concentrations. Both inhalation exposure and indoor air PM concentrations in the rural households with gasifier firewood stoves were evidently lower than the reported results using traditional firewood stoves. However, local governments in the studied rural areas should exercise caution when widely and hastily promoting gasifier firewood stoves in place of improved coal stoves, due to the higher PM levels in indoor and outdoor air and personal inhaled exposure.

The Pedagogical,Linguistic,and Content Features of Popular English Language Learning Websites in China:A Framework for Analysis and Design

As increasing numbers of Chinese language learners choose to learn English online,there is a need to investigate popular websites and their language learning designs.This paper reports on the first stage of a study that analyzed the pedagogical,linguistic,and content features of 25 Chinese English Language Learning(ELL)websites ranked according to their value and importance to users.The website ranking was undertaken using a system known as PageRank.The aim of the study was to identify the features characterizing popular sites as opposed to those of less popular sites for the purpose of producing a framework for ELL website design in the Chinese context.The study found that a pedagogical focus with developmental instructional materials accommodating diverse proficiency levels was a major contributor to website popularity.Chinese language use for translations and teaching directives and intermediate level English for learning materials were also significant features. Content topics included Anglophone/Western and non-Anglophone/Eastern contexts. Overall, popular websites were distinguished by their mediation of access to and scaffolded support for ELL.

Global brown carbon emissions from combustion sources

Light-absorbing organic carbon(OC),sometimes known as Brown Carbon(BrC),has been recognized as an important fraction of carbonaceous aerosols substantially affecting radiative forcing.This study firstly developed a bottom-up estimate of global primary BrC,and discussed its spatiotemporal distribution and source contributions from 1960 to 2010.The global total primary BrC emission from both natural and anthropogenic sources in 2010 was 7.26(5.98-8.93 as an interquartile range)Tg,with 43.5%from anthropogenic sources.High primary BrC emissions were in regions such as Africa,South America,South and East Asia with natural sources(wild fires and deforestation)contributing over 70%in the former two regions,while in East Asia,anthropogenic sources,especially residential solid fuel combustion,accounted for over 80%of the regional total BrC emissions.Globally,the historical trend was mainly driven by anthropogenic sources,which increased from 1960 to 1990 and then started to decline.Residential emissions significantly impacted on emissions and temporal trends that varied by region.In South and Southeast Asia,the emissions increased obviously due to population growth and a slow transition from solid fuels to clean modern energies in the residential sector.It is estimated that in primary OC,the global average was about 20%BrC,but this ratio varied from 13%to 47%,depending on sector and region.In areas with high residential solid fuel combustion emissions,the ratio was generally twice the value in other areas.Uncertainties in the work are associated with the concept of BrC and measurement technologies,pointing to the need for more studies on BrC analysis and quantification in both emissions and the air.

Vertically-resolved indoor measurements of air pollution during Chinese cooking

Chinese cooking features several unique processes,e.g.,stir-frying and pan-frying,which represent important sources of household air pollution.However,factors affecting household air pollution and the vertical variations of indoor pollutants during Chinese cooking are less clear.Here,using low-cost sensors with high time resolutions,we measured concentrations of five gas species and particulate matter(PM)in three different sizes at multiple heights in a kitchen during eighteen different Chinese cooking events.We found indoor gas species were elevated by 21%-106%during cooking,compared to the background,and PMs were elevated by 44%-159%.Vertically,the pollutants concentrations were highly variable during cooking periods.Gas species generally showed a monotonic increase with height,while PMs changed more diversely depending on the cooking activity's intensity.Intense cooking,e.g.,stir-frying,pan-frying,or cooking on high heat,tended to shoot PMs to the upper layers,while moderate ones left PMs within the breathing zone.Individuals with different heights would be subject to different levels of household air pollution exposure during cooking.The high vertical variability challenges the current indoor standard that presumes a uniform pollution level within the breathing zone and thus has important implications for public health and policy making.