[en] The adverse impact of climate change-associated extreme weather events is becoming more significant globally, particularly the flood impact on coastal and low-lying areas such as the Pearl River Delta (PRD). This study applied the framework to obtain order-of-magnitude estimations of human damages from future flood disasters caused by sea level rise for Hong Kong and the PRD region in southern China by 2050 and 2100. The assessment framework employs statistical analysis to combine global historical flood damage data with national development indicators and local sea level characteristics to assess the potential damages. Following the terminology of the Intergovernmental Panel on Climate Change Special Report on Extreme Events, the three determinants of disaster risk (climate extreme, exposure and vulnerability) are quantified in our framework. It is found that without adaptation, sea level rise will significantly increase the flood risk in this region. For instance, in the PRD region, with a 75-cm sea level rise by 2100, the deaths and displacements from a 100-year flood are estimated to be around 200 and 1.5 million, respectively. Our results provide motivation for regional authorities to adopt a long-term adaptation plan to reduce exposure and vulnerability to flooding, thus managing the risks in this region. Furthermore, with appropriate datasets available, our framework allows the assessment of the effects of flooding in other areas and/or the quantitative evaluation of potential losses from other climate-related hazards such as heat waves.

[en] Shipping activities contribute to degraded air quality and premature mortalities worldwide, but previous assessments of their health impact have not yet differentiated contributions from domestic and international shipping at the global level. The impacts of domestic shipping can affect different populations, and domestic and international shipping emissions are governed under different regulatory systems. Thus, a consistent global analysis comparing the health impacts from domestic and international shipping could inform policy making in attempts to coordinate policies across multiple scales to address the health burden of shipping emissions. In this study, we create bottom-up global ship emission inventories based on ship activity records from the automatic identification system, and then apply the GEOS-Chem atmospheric model and global exposure mortality model to quanitfy shipping-related PM_2.5-concentrations and associated mortalities. We also quantify the public health benefits under different control scenarios including the 2020 0.5% sulphur cap, a post-2020 0.1% sulphur cap, and a post-2020 Tier III NO_x standard. We find that 94 200 (95% confidence interval: 84 800–103 000) premature deaths were associated with PM_2.5 exposure due to maritime shipping in 2015, of which 83% were associated with international shipping activities and 17% with domestic shipping. Although the global health burdens of ship emissions are dominated by international shipping, the fraction varies by region: 44% of shipping-related premature deaths in China come from domestic shipping activities. We estimate about 30 200 (27 200–33 000) avoided premature deaths per year under a scenario consistent with a 2020 0.5% sulphur cap. We find that a post-2020 Tier III NO_x standard would have greater benefits than a post-2020 0.1% sulphur cap, with the two policies reducing annual shipping-attributable PM_2.5-related premature deaths by 33 300 (30 100–36 400) and 5070 (4560–5540), respectively. (letter)

[en] As one of the most notorious atmospheric pollutants, NO_x not only promotes the formation of ozone but also has adverse health effects on humans. It is therefore of great importance to study the sources of NO_x and its effects on human health. The Comprehensive Air Quality Model (CAMx) modeling system and ozone source apportionment technology (OSAT) were used to study the contribution of NO_x from different emission sources over southern China. The results indicate that heavy duty diesel vehicles (HDDVs) and industrial point sources are the two major local NO_x sources, accounting for 30.8% and 18.5% of local NO_x sources, respectively. In Hong Kong, marine emissions contributed around 43.4% of local NO_x in 2011. Regional transport is another important source of this pollutant, especially in February and November, and it can contribute over 30% of ambient NO_x on average. Power plant point emission is an significant regional source in Zhuhai, Zhongshan and Foshan. The total emission sources are estimated to cause 2119 (0–4405) respiratory deaths and 991 (0–2281) lung cancer deaths due to long-term exposure to NO_x in the Pearl River Delta region. Our results suggest that local governments should combine their efforts and vigorously promote further reduction of NO_x emissions, especially for those sources that make a substantial contribution to NO_x emissions and affect human health: HDDV, LDGV, industrial point sources and marine sources. - Highlights: • WRF-CAMx modeling system with OSAT was used to study the source of NO_x over Pearl River Delta region in China. • The results indicated that local emission and regional transportation are important contributors for NO_x in this region. • Heavy duty diesel vehicle, marine emission and industrial point source are three important contribution sectors. • Long-term exposure to NO_x is estimated to cause 2119 respiratory deaths and 991 lung cancer deaths in PRD during 2011. - Result indicated that heavy duty diesel vehicle and industrial point source make a substantial contribution to ambient NO_x concentration in this region.

[en] Highlights: • Proposed an BIM-based CFD approach for sensitivity analysis on validated floor • Door gap size >3% of door panel stimulates sharp increase in air velocity in gaps. • Without MVAC system, zonal temperature variation is more sensitive to solar heat. • Addition of occupants shows CO₂ concentration is more sensitive than temperature. • The studied influence factors should be considered in other thermal comfort studies. Computational fluid dynamics (CFD) is a powerful tool for performing indoor airflow analysis. The simulation results are usually validated with measurement results for accuracy in reflecting reality. When conducting CFD for simulating air flow in a multiple-zone indoor environment with different boundary conditions in different regions, the validation of the CFD model becomes sophisticated. To improve the accuracy of the simulation, boundary conditions need to be adjusted based on how significant the influence factors are affecting the multi-zone CFD model, which few studies have been conducted on. The objective of this study is to investigate the impact of influence factors on temperature and carbon dioxide concentration distribution of a validated CFD model of a typical office floor using ANSYS Fluent. This study provides insights on how to fine-tune a complex model to reflect the actual air flow and how the air quality and human comfort in different zones on the same floor could be affected by influence factors. The influence factors investigated are: (1) size of door gaps, (2) solar radiation and (3) number and orientation of occupants. The velocity variations caused by different door gap sizes were studied for improving multi-zone simulation accuracy by adjusting door gap sizes. To study the significant impact of solar heat on multi-zone environment, the sensitivity of different regions of the office floor to solar heat amount and distribution was analyzed by conducting solar analysis under different weather conditions. Impact of occupants on temperature and carbon dioxide concentration distributions in multi-zone environment were investigated by considering different numbers and facing directions of occupants in different regions of the office floor. In addition, this study demonstrates how to modify the influence factors efficiently using building information modeling (BIM).

[en] Highlights: • Air Parcel Residence Time (APRT) is investigated to identify potential emission control regions. • The APRT and traditional emission control methods are compared. • The APRT in the seasonal cycle and on regional air pollution days is analyzed. • Population exposure to air parcels (PEAP) on regional air pollution days is investigated. -- Abstract: In this study, the concept of air parcel residence time was raised and the APRT was investigated to study its potential application in air pollution prevention and control in the Pearl River Delta (PRD) region. The APRT in the PRD region was defined as the total period for which an air parcel stays within the PRD region. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to calculate the hourly APRT in 2012, 2014, and 2015 based on forward trajectories from 16,720 starting locations. The seasonal APRT results revealed that long APRT was mainly distributed in southern PRD in the summer half year, but in northeastern PRD in the winter half year. This is related to the prevailing wind directions in the summer and winter monsoons. Moreover, the comparison of APRT in different years revealed that the dispersion condition was relatively poor in fall in 2012 and throughout 2014 but was relatively favorable in 2015, which also corresponded to the pollutant concentrations. The APRT calculated from regional air pollution days indicated that the emission reduction strategy should be implemented in the key areas, namely the eastern and central Guangzhou, western Huizou, and the border between Foshan and Jiangmen, and the construction of new factories should not be allowed in these areas. Compared to the APRT, which was investigated to trace the air pollution source, population exposure to air parcels (PEAP) was investigated to orient the influence of path-and-time-weighted sources to population. Consequently, a high PEAP was found to be distributed mainly in the central Guangzhou and Shenzhen and scattered in other urban areas.

[en] Highlights: • Health risk tradeoffs between decreased NO₂ and increased O₃ concentrations. • Lower NO₂ concentrations offset short-term health risk for higher O₃ concentrations. • Short-term health risk for the mixture of NO₂ and O₃ decreased at roadside stations. • Overall health risk related to four AQHI pollutants (NO₂, O₃, SO₂ and PM) decreased. The reduction of NO_x emissions in a VOC-limited region can lead to an increase of the local O₃ concentration. An evaluation of the net health effects of such pollutant changes is therefore important to ascertain whether the emission control measures effectively improve the overall protection of public health. In this study, we use a short-term health risk (added health risk or AR) model developed for the multi-pollutant air quality health index (AQHI) in Hong Kong to examine the overall health impacts of these pollutant changes. We first investigate AR changes associated with NO₂ and O₃ changes, followed by those associated with changes in all four AQHI pollutants (NO₂, O₃, SO₂, and particulate matter (PM)). Our results show that for the combined health effects of NO₂ and O₃ changes, there is a significant reduction in AR in urban areas with dense traffic, but no statistically significant changes in other less urbanized areas. The increase in estimated AR for higher O₃ concentrations is offset by a decrease in the estimated AR for lower NO₂ concentrations. In areas with dense traffic, the reduction in AR as a result of decreased NO₂ is substantially larger than the increase in AR associated with increased O₃. When additionally accounting for the change in ambient SO₂ and PM, we found a statistically significant reduction in total AR everywhere in Hong Kong. Our results show that the emission control measures resulting in NO₂, SO₂, and PM reductions over the past decade have effectively reduced the AR over Hong Kong, even though these control measures may have partially contributed to an increase in O₃ concentrations. Hence, efforts to reduce NOx, SO₂, and PM should be continued.

[en] Highlights: • Door-side PM_2.5 concentrations typically increase when train doors open. • Train in-cabin PM_2.5 concentrations are lower than ambient PM_2.5 concentration. • Underground metro train in-cabin PM_2.5 concentrations are higher than above-ground. • Ambient PM_2.5 infiltration into cabins is higher for above-ground than underground. • Non-ambient sources contributed around half of PM_2.5 inside the underground metro. The objectives of this study were to: (1) evaluate PM_2.5 inflow to metro train cabins when doors open at stations; (2) assess the spatial and temporal variability in PM_2.5 exposure concentration; and (3) quantify the relationship between in-cabin concentration versus outdoor and non-ambient PM_2.5. We measured in-cabin PM_2.5 concentrations using portable monitors at the door-side and center of a train cabin simultaneously on a Hong Kong metro line. In addition, platform and in-cabin pollutant concentrations near a train door were simultaneously measured. Short-term spikes in PM_2.5 concentrations typically occur near train doors when doors open, related to inflow of ambient air aboveground and tunnel air underground. In-cabin PM_2.5 exposure concentrations are typically lower away from the doors when the doors open. PM_2.5 concentrations inside train cabins and on station platform operating above-ground are more influenced, compared to underground, by outdoor PM_2.5. Moreover, non-ambient sources contribute approximately 50% of train in-cabin and station platform PM_2.5 concentrations during underground operation. The results help more accurately quantify commuting PM_2.5 exposure on a metro system, and can be used to improve population-based exposure simulation models.

[en] Highlights: • PM_2.5 concentrations have shown a sharply decreasing trend during the period from 2013 to 2017 in China. • The premature mortality associated with PM_2.5 concentrations dropped from 1,078,800 in 2014 to 962,900 in 2017. • The health cost avoided in 2017 as a result of the reduction of PM_2.5 concentrations amounted to 1.58% of the national GDP. • The mortality density in dense urban areas is much higher than that in rural area. • The urban migration can increase the premature mortality caused by PM_2.5 indirectly. -- Abstract: In this study, the trend of PM_2.5 concentrations and its adverse health effects in China from 2001 to 2017 are estimated utilizing 1-km high-resolution annual satellite-retrieved PM_2.5 data. PM_2.5 concentrations for most of the provinces/cities remained stable from 2001 to 2012; however, following the issue of the Air Pollution Prevention and Control Action Plan (APPCAP) by the central government of China, a dramatic decrease in PM_2.5 concentrations from 2013 to 2017 occurred. Premature mortality caused by PM_2.5 dropped from 1,078,800 in 2014 to 962,900 in 2017. The PM_2.5 caused 17-year average mortality ranges from 3800 in Hainan Province to 124,800 in Henan Province. The health cost benefits gained by the reduction of PM_2.5 pollution amounted to US $193,800 in 2017 (compared to the costs due to PM_2.5 concentrations in 2013), amounting to 1.58% of the total national GDP. The impacts of urbanization on PM_2.5 concentration and mortality are analyzed. The PM_2.5 concentration and its induced mortality density in dense urban areas are much higher than those in rural areas. The aggravation of PM_2.5 associated premature mortality in urban areas is mainly due to the larger amount of emissions and to urban migration, and 6500 deaths in 2014 could have been avoided were the population ratios in dense-urban/normal-urban/rural areas to be reversed to the ones in 2001. It is recommended that people with respiratory-related diseases live in rural areas, where the pollutant concentration is relatively low.

[en] Recently, portable monitors have been increasingly used to quantify air pollutant concentrations at high spatiotemporal resolution. A sampling campaign was conducted to measure the fine particulate matter (PM_2.5) and carbon monoxide (CO) exposure concentrations in transport microenvironments (TMEs) in Hong Kong in January and June 2015 using TSI DustTrak and Q-Trak portable monitors. The objectives were to: (1) calibrate DustTrak and Q-Trak; (2) evaluate variability between seasons and microenvironments; (3) estimate indoor/outdoor relationships; and (4) determine minimum sample size. Calibration equations, obtained through side-by-side measurement against stationary reference methods in winter and summer, were applied to correct the measured PM_2.5 data set. In general, PM_2.5 concentrations in all TMEs were significantly higher in winter than in summer. The mean PM_2.5 concentration in winter was lower for underground sections of the Mass Transit Railway (MTR) metro system (31 μg/m³) than for other TMEs, whereas in summer TMEs had mean PM_2.5 concentrations in the range of 10–15 μg/m³, with above-ground MTR train as an exception, at 23 μg/m³. PM_2.5 concentrations measured in TMEs were strongly correlated with nearby air quality monitoring stations (AQMSs) measurements in winter, but in summer there was little correlation. The minimum sample size estimates varied more among TMEs in summer versus winter because of the differences in PM_2.5 concentration distributions related to changes in ambient PM_2.5 concentrations and ventilation practices. This study provides a feasible protocol on the calibration and application of portable monitors in TME air quality measurement and develops a method for estimating minimum sample size. - Highlights: • Portable monitors were calibrated through side-by-side comparison against stationary reference methods. • Step-by-step standard operation procedures for portable measurement were developed. • Transport microenvironment (TME) PM_2.5 concentrations in Hong Kong are significantly higher in winter than in summer. • The TME PM_2.5 concentrations in Hong Kong are correlated to ambient levels in winter, not in summer. • A method for estimating minimum sample size is demonstrated.

[en] We report the discovery of a circumstellar debris disk viewed nearly edge-on and associated with the young, K1 star BD+45° 598 using high-contrast imaging at 2.2 μm obtained at the W.M. Keck Observatory. We detect the disk in scattered light with a peak significance of ∼5σ over three epochs, and our best-fit model of the disk is an almost edge-on ∼70 au ring, with inclination angle ∼87°. Using the NOEMA interferometer at the Plateau de Bure Observatory operating at 1.3 mm, we find resolved continuum emission aligned with the ring structure seen in the 2.2 μm images. We estimate a fractional infrared luminosity of L _IR/L _tot $\simeq <!--\; ???\; -->6_{-<!--\; ???\; -->1}^{+2}$ × 10⁻⁴, higher than that of the debris disk around AU Mic. Several characteristics of BD+45° 598, such as its galactic space motion, placement in a color–magnitude diagram, and strong presence of lithium, are all consistent with its membership in the β Pictoris Moving Group with an age of 23 ± 3 Myr. However, the galactic position for BD+45° 598 is slightly discrepant from previously known members of the β Pictoris Moving Group, possibly indicating an extension of members of this moving group to distances of at least 70 pc. BD+45° 598 appears to be an example from a population of young circumstellar debris systems associated with newly identified members of young moving groups that can be imaged in scattered light, key objects for mapping out the early evolution of planetary systems from ∼10–100 Myr. This target will also be ideal for northern-hemisphere, high-contrast imaging platforms to search for self-luminous, planetary mass companions residing in this system.