Gas-particle partitioning of low-molecular-weight organic acids in suburban Shanghai: Insight into measured Henry's law constants dependent on relative humidity.

Low-molecular-weight (LMW) organic acids are among the most abundant water-soluble organic compounds, but their gas-particle partitioning mechanism remains unclear. In the present study, LMW organic acids were measured using a URG 9000D Ambient Ion Monitor in suburban Shanghai. The average concentrations of formic acid, acetic acid, oxalic acid, and methanesulfonic acid (MSA) in PM2.5 were 405 ± 116, 413 ± 11, 475 ± 266, and 161 ± 54 ng m-3, respectively. The particle fraction exceeded 30 % for formic acid and acetic acid. Model predictions underestimated the particle-phase monocarboxylic acids (MCAs) from the factor of 102 at the highest RH to 107 at the lowest RH. The average measured intrinsic Henry's law constants (Hmea) for formic acid, acetic acid, oxalic acid, and MSA were 3.8 × 107, 4.5 × 107, 8.7 × 108, and 3.4 × 107 mol L-1 atm-1, respectively, approximately four orders of magnitude higher than their literature-based intrinsic Henry's law constants (Hlit) for MCAs and approximately four orders of magnitude lower than Hlit, MSA. The ratio of Hmea /Hlit for MCAs ranged over three orders of magnitude, depending on relative humidity. The strong deviations at low RHs are attributed to the dominance of absorption by the organic phase. The discrepancy at the highest RH possibly relates to surfactant effects and dimer formation. We used Hmea as a model input for the first time to estimate the phase partitioning of particulate MCAs, finding that >80 % of MCAs resided in the organic phase under dry conditions. We propose parameterizing Hmea as model input to predict the multiphase partitioning of MCAs.

Dual isotopic evidence of δ15N and δ18O for priority control of vehicle emissions in a megacity of East China: Insight from measurements in summer and winter.

The source apportionment and main formation pathway of nitrate aerosols in China are not yet fully understood. In this study, PM2.5 samples were collected in Shanghai in the summer and winter of 2019. Water-soluble inorganic ions and isotopic signatures of stable nitrogen (δ15N-NO3-) and stable oxygen (δ18O-NO3-) in PM2.5 were determined. The results showed that NO3- was less important in summer (NO3-/SO42- = 0.4 ± 0.8), while it became the dominant species in winter (52.1 %). The average values of δ15N-NO3- and δ18O-NO3- in summer were + 2.0 ± 6.1 ‰ and 63.3 ± 9.4 ‰ respectively, which were significantly lower than those in winter (+7.2 ± 3.4 ‰ and 88.3 ± 12.1 ‰), indicating discrepancies between NOx sources and nitrate formation pathways. Both δ15N-NO3- and δ18O-NO3- were elevated at night, demonstrating that N2O5 hydrolysis contributed to the nocturnal nitrate increase even in summer. The contribution of the OH oxidation pathway to nitrate aerosols averaged at 70.5 ± 17.0 % in summer and N2O5 hydrolysis dominated the nitrate production in winter (approximately 80 %). On average, vehicle exhaust, coal combustion, natural gas burning, and soil emission contributed 50.7 %, 21.5 %, 15.9 %, and 11.9 %, respectively, to nitrate aerosols in summer, and contributed 56.8 %, 23.9 %, 13.6 %, and 5.7 %, respectively, to nitrate production in winter. Notably, natural gas burning is a non-negligible source of nitrate aerosols in Shanghai. In contrast to an inverse correlation between δ15N-NO3- and PM2.5, the value of δ18O-NO3- was positively correlated with nitrate concentration and aerosol liquid water content (ALWC) in winter, suggesting that explosive growth of nitrate was driven by continuous accumulation of N-depleted NOx and rapid N2O5 hydrolysis under calm and humid conditions. To continuously improve air quality, priority control should be given to vehicle emissions as the dominant source of NOx and volatile organic compounds (VOCs) in Shanghai.

Characteristics and sources of PM2.5-bound elements in Shanghai during autumn and winter of 2019: Insight into the development of pollution episodes.

Elemental composition of PM2.5 dispersed in the atmosphere has received increasing attention due to its health effect and catalytic activities. In this study, the characteristics and source apportionment of PM2.5-bound elements were investigated using hourly measurements. K is the most abundant metal element, followed by Fe > Ca > Zn > Mn > Ba > Pb > Cu > Cd. With an average of 8.8 ± 4.1 ng m-3, Cd was the only element whose pollution level exceeded the limits of Chinese standards and WHO guidelines. The concentrations of As, Se, and Pb doubled in December compared to November, indicating a large increase in coal consumption in winter. The enrichment factors of As, Se, Hg, Zn, Cu, Cd, and Ag were larger than 100, indicating that anthropogenic activities greatly affected them. Ship emissions, coal combustion, soil dust, vehicle emissions, and industrial emissions were identified as major sources of trace elements. In November, the pollution from coal burning and industrial activities was significantly reduced, demonstrating the remarkable achievement of coordinated control measures. For the first time, hourly measurements of PM2.5-bound elements and secondary sulfate and nitrate were used to investigate the development of dust and PM2.5 events. During a dust storm event, secondary inorganic salts, potentially toxic elements, and crustal elements sequentially reached peak concentrations, indicating different source origins and formation mechanisms. During the winter PM2.5 event, the sustained increase of trace elements was attributed to the accumulation of local emissions, while regional transport was responsible for the explosive growth before the end of the event. This study highlights the important role of hourly measurement data in distinguishing local accumulation from regional and long-range transport.

Characteristics of annual mold variations and association with childhood allergic symptoms/diseases via combining surveys and home visit measurements.

The presence of dampness and visible molds leads to concerns of poor indoor air quality which has been consistently linked with increased exacerbation and development of allergy and respiratory diseases. Due to the limitations of epidemiological surveys, the actual fungal exposure characteristics in residences has not been sufficiently understood. This study aimed to characterize household fungal diversity and its annual temporal and spatial variations. We developed combined cross-sectional survey, repeated air sampling around a year, and DNA sequencing methods. The questionnaire survey was conducted in 2019, and 4943 valid cases were received from parents; a follow-up case-control study (11 cases and 12 controls) was designed, and onsite measurements of indoor environments were repeated in typical summer, transient season, and winter; dust from floor and beddings in children's room were collected and ITS based DNA sequencing of totally 68 samples was conducted. Results from 3361 children without changes to their residences since birth verified the significant associations of indoor dampness/mold indicators and prevalence of children-reported diseases, with increased adjusted odd ratios (aORs) >1 for studied asthma, wheeze, allergic rhinitis, and eczema. The airborne fungal concentrations from air sampling were higher than 1000 CFU/m3 in summer, regardless of indoors and outdoors, indicating an intermediate pollution level. The DNA sequencing for dust showed the Aspergillus was the predominant at genus level and the Aspergillus_penicillioides was the most common at species level; while the fungal community and composition varied significantly in different homes and seasons, according to α and ß diversity analyses. The comprehensive research methods contribute to a holistic understanding of indoor fungal exposure, including the concentrations, seasonal variations, community, and diversity, and verifies the relations with children's adverse health outcomes. The study further elucidates the role of microbiome in human health, which helps setting health-protective thresholds and managing mold treatments in buildings, to promote indoor air quality and human well-beings.

Evaluating the effect of building construction periods on household dampness/mold and childhood diseases corresponding to different energy efficiency design requirements.

Despite concerns about building dampness and children' health, few studies have examined the effects of building energy efficiency standards. This study explored the connections between self-reported household dampness and children' adverse health outcomes across buildings corresponding to construction periods (pre-2001, 2001-2010, post-2010). Significant differences of dampness-related indicators were found between buildings; the prevalence was remarkable in pre-2001 buildings. The prevalence of lifetime-ever doctor-diagnosed diseases for children was significantly associated with building dampness (adjust odd ratios > 1), but was not affected by construction periods. The hygrothermal performance for a typical residence was simulated, varying in U-values of envelopes and air change rates. The simulated performance improvement increased indoor temperatures in 2001-2010 and post-2010 buildings. The frequency with higher indoor relative humidity was higher in pre-2001 buildings, leading to the highest values for maximum mold index (Mmax ) on wall surface, especially in winter. Compared to buildings in 2001-2010, increased insulation and lower air change rate led to a relatively higher relative humidity in post-2010 buildings, adversely increasing the Mmax values. The findings addressed the positive and negative role of building standard development, which help suggesting appropriate environmental and design solutions to trade-off energy savings and dampness/mold risk in residences.

Associations of household dampness with asthma, allergies, and airway diseases among preschoolers in two cross-sectional studies in Chongqing, China: Repeated surveys in 2010 and 2019.

Many studies have investigated the associations between household damp indicators, and allergies and respiratory diseases in childhood. However, the findings are rather inconsistent. In 2010, we conducted a cross-sectional study of preschoolers aged three-six years in three urban districts of Chongqing, China. In 2019, we repeated this cross-sectional study with preschoolers of the same ages and districts. Here, we selected data for 2935 and 2717 preschoolers who did not change residences since birth in the 2010 and 2019 studies, respectively. We investigated associations of household damp indicators with asthma, allergic rhinitis, pneumonia, eczema, wheeze, and rhinitis in childhood in the two studies. The proportions of residences with household damp indicators and the prevalence of the studied diseases (except for allergic rhinitis) were significantly lower in 2019 than in 2010. In the two-level (district-child) logistic regression analyses, household damp exposures that showed by different indicators were significantly associated with the increased odds of lifetime-ever asthma (range of adjusted odds ratio (AOR): 1.69-3.50 in 2019; 1.13-1.90 in 2010), allergic rhinitis (1.14-2.39; 0.67-1.61), pneumonia (1.09-1.64; 1.21-1.59), eczema (0.96-1.83; 0.99-1.56), wheeze (1.64-2.79; 1.18-1.91), rhinitis (1.43-2.71; 1.08-1.58), and current (in the past 12 months before the survey) eczema (0.46-2.08; 0.99-1.48), wheeze (0.97-2.86; 1.26-2.07) and rhinitis (1.34-2.25; 1.09-1.56) in most cases. The increased odds ratios (ORs) of most diseases had exposure-response relationships with the cumulative number (n) of household damp indicators in the current and early residences. Our results indicated household damp exposure could be a risk factor for childhood allergic and respiratory diseases, although the magnitudes of these effects could be different in different studies.