Characteristics of school children's personal exposure to ultrafine particles in Heshan, Pearl River Delta, China - A pilot study.

BACKGROUND: There is a significant lack of scientific knowledge on population exposure to ultrafine particles (UFP) in China to date. This paper quantifies and characterises school children's personal UFP exposure and exposure intensity against their indoor and outdoor activities during a school day (home, school and commuting) in the city of Heshan within the Pearl River Delta (PRD) region, southern China. METHODS: Time-series of UFP number concentrations and average size were measured over 24?h for 24 children (9-13?years old), using personal monitors over two weeks in April 2016. Time-activity diaries and a questionnaire on the general home environment and potential sources of particles at home were also collected for each participating child. The analysis included concurrently measured size distributions of ambient UFP at a nearby fixed reference site (Heshan Supersite). RESULTS: Hourly average UFP concentrations exhibited three peaks in the morning, midday and evening. Time spent indoors at home was found to have the highest average exposure (1.26?×?104?cm-3 during sleeping) and exposure intensity (2.41). While there is always infiltration of outdoor particles indoors (from nearby traffic and general urban background sources), indoor exposure at home was significantly higher than outdoor exposure. Based on the collected questionnaire data, this was considered to be driven predominantly by adults smoking and the use of mosquito repellent incense during the night. Outdoor activities at school were associated with the lowest average exposure (6.87?×?102?cm-3) and exposure intensity (0.52). CONCLUSION: Despite the small sample size, this study characterised, for the first time, children's personal UFP exposure in a city downwind of major pollution sources of the PRD region in China. Particularly, the results highlighted the impact of smoking at home on children's exposure. While the study could not apportion the specific contributions of second hand-smoking and mosquito coil burning, considering the prevalence of smokers among the parents who smoke at home, smoking is a very significant factor. Exposure to second-hand smoke is avoidable, and these findings point out to the crucial role of government authorities and public health educators in engaging with the community on the role of air quality on health, and the severity of the impact of second-hand smoke on children's health

Heterogeneous N2O5 reactions on atmospheric aerosols at four Chinese sites : improving model representation of uptake parameters

Heterogeneous reactivity of N2O5 on aerosols is a critical parameter in assessing NOx fate, nitrate production, and particulate chloride activation. Accurate measurement of its uptake coefficient (gamma N2O5) and representation in air quality models are challenging, especially in the polluted environment. With an in situ aerosol flow-tube system, the gamma N2O5 was directly measured on ambient aerosols at two rural sites in northern and southern China. The results were analyzed together with the gamma N2O5 derived from previous field studies in China to obtain a holistic picture of gamma N2O5 uptake and the influencing factors under various climatic and chemical conditions. The field-derived or measured gamma N2O5 was generally promoted by the aerosol water content and suppressed by particle nitrate. Significant discrepancies were found between the measured gamma N2O5 and that estimated from laboratory-determined parameterizations. An observation-based empirical parameterization was derived in the present work, which better reproduced the mean value and variability of the observed gamma N2O5. Incorporating this new parameterization into a regional air quality model (WRF-CMAQ) has improved the simulation of N2O5, nitrogen oxides, and secondary nitrate in the polluted regions of China.Peer reviewe

Particle Growth and Variation of Cloud Condensation Nucleus Activity on Polluted Days with New Particle Formation: A Case Study for Regional Air Pollution in the PRD Region, China

New particle formation (NPF) events on polluted days at a regional supersite in the Pearl River Delta (PRD) region and its impact on the abundance and properties of cloud condensation nuclei (CCN) were investigated. Nucleation and subsequent significant growth of nanoparticles on a regional scale was observed and representative events on 2 and 6 October 2013 were chosen in this study. The measurements showed that the primary components of the particles were sulfate, ammonium, and organics as they were added continuously to secondary aerosol mass and that particles show inversion from growth to shrink if the particles comprise primarily of organics due to evaporation of semi-volatile species under favorable meteorological conditions. The effective hygroscopicity parameter. of fine particles on 2 October composed of sulfate, nitrate and ammonium (kappa = 0.26-0.42) was larger than that of fine particles on 6 October containing more organics (kappa = 0.19-0.36). Particles in the nucleation mode were observed to grow rapidly to the CCN sizes and dominate the CCN number concentrations at a water vapor supersaturation (S) over 0.46%. At an S range of 0.26-0.86%, the CCN number concentrations reached maximum values of (1.3-2.6) x 10(4) cm(-3) after the NPF event on 2 October. The sulfate component in the particles was found to increase significantly, about 50% higher than that before NPF. Results from events on 6 October showed a significant increase of the organic component and the CCN number concentrations after the NPF event were comparable or slightly lower than those before the event. Nevertheless, the average CCN number concentrations scaled with EC mass concentration with S over 0.46% in the daytime of 2 and 6 October were significantly higher than those on a non-NPF event day.National Natural Science Foundation of China [41303075, U1301234]; major national scientific instrument and equipment development project [2013YQ060569]; Pearl River New Star project on science and technology in Guangzhou [201506010079]SCI(E)[email protected]

Science policy interplay: Air quality management in the Pearl River Delta region and Hong Kong

The information provided by the scientific studies and control measures implemented in the Pearl River Delta (PRD) region of China reveals that tremendous progress has been made in the understanding of regional air pollution issues and the deployment of mitigation measures for alleviating these problems. Given the unparalleled rapid economic growth in the PRD over the past two decades, such progress was only made possible by strong, science-based support and the partnerships between government and research institutions in the region and overseas. Researchers from these partnership programs and related studies have deployed cutting-edge expertise and experience in various crucial mainland China and mainland China/Hong Kong-level projects. China recognizes the importance of protecting the environment and cleaning up the air in the pursuit of sustainable growth and economic development. To avoid falling into a cycle of event-driven clean-up efforts, China has recently taken a major step and updated the national ambient air quality standards. Clearly, China is implementing an increasing number of evidence-based policies to address air pollution problems. Thus, to bring a fresh impetus at a national level, the PRD must maintain and augment the Hong Kong-mainland collaborative momentum, inducing a "whole-China" effort to clean up air pollution. To strengthen the science-based support system and ensure continuous and concerted effort in implementing the regional multi-pollutant control strategy, there must be an over-arching and integral Hong Kong-Guangdong science consortium framework supporting the formulation of regional policy and control measures built on common goals under the "one country, two systems" principle. The "PRD Approach" of the air quality management regime reflected regional cooperative efforts in synchronous air pollutant control, catalyzed the crucial role of information disclosure and subtly transformed the air quality management approach to overcome the nation's new air pollution challenges. (C) 2013 Elsevier Ltd. All rights reserved

Comparisons of Anatomical Characteristics and Transcriptomic Differences between Heterografts and Homografts in Pyrus L.

Pear (Pyrus L.) is an important temperate fruit worldwide, and grafting is widely used in pear vegetative propagation. However, the mechanisms of graft healing or incompatibility remain poorly understood in Pyrus. To study the differences in graft healing in Pyrus, the homograft “Qingzhen D1/Qingzhen D1” and the heterograft “QAUP-1/Qingzhen D1” as compatibility and incompatibility combinations were compared. Anatomical differences indicated the healing process was faster in homografts than in heterografts. During the healing process, four critical stages in graft union formation were identified in the two types of grafts. The expression of the genes associated with hormone signaling (auxin and cytokinins), and lignin biosynthesis was delayed in the healing process of heterografts. In addition, the PbBglu13 gene, encoded β-glucosidase, was more highly up-regulated in heterografts than in homografts to promote healing. Meanwhile, the most of DEGs related starch and sucrose metabolism were found to be up-regulated in heterografts; those results indicated that cellulose and sugar signals were also involved in graft healing. The results of this study improved the understanding of the differences in the mechanisms of graft healing between homografts and heterografts

Estimation of Size-Resolved Ambient Particle Density Based on the Measurement of Aerosol Number, Mass, and Chemical Size Distributions in the Winter in Beijing

Simultaneous measurements of aerosol size, distribution of number, mass, and chemical compositions were conducted in the winter of 2007 in Beijing using a Twin Differential Mobility Particle Sizer and a Micro Orifice Uniform Deposit Impactor. Both material density and effective density of ambient particles were estimated to be 1.61 ± 0.13 g cm^–3 and 1.62 ± 0.38 g cm^–3 for PM_1.8 and 1.73 ± 0.14 g cm^–3 and 1.67 ± 0.37 g cm^–3 for PM₁₀. Effective density decreased in the nighttime, indicating the primary particles emission from coal burning influenced the density of ambient particles. Size-resolved material density and effective density showed that both values increased with diameter from about 1.5 g cm^–3 at the size of 0.1 μm to above 2.0 g cm^–3 in the coarse mode. Material density was significantly higher for particles between 0.56 and 1.8 μm during clean episodes. Dynamic Shape Factors varied within the range of 0.95–1.13 and decreased with particle size, indicating that coagulation and atmospheric aging processes may change the shape of particles