Search

Ozone (O3) is of great importance to air quality in the Yangtze River Delta (YRD) region, China. Focusing on surface O3 in the YRD, its spatiotemporal characteristics, meteorological driving factors, and health impacts are investigated based on surface O3 observations in this study. We find that from 2015 to 2019, most cities failed to meet the national standards and O3 pollution mainly occurred in warm seasons (April‐September). Surface O3 in the YRD increased in the recent years, so did tropospheric column O3. Spatially, surface shows a significant positive autocorrelation over the YRD except for 2019, and high O3 values mainly gather in the central of the YRD. The first two empirical orthogonal functions (EOFs) of O3 accounted for 37.4% and 20.0% of the total variance in O3, respectively, with their spatial patterns characterized by the same phase and west and east contrast, respectively. The EOF1 is related to the change in radiation and the EOF2 is attributed to regional transport by prevailing westerly wind. Downward UV radiation, temperature and u wind are crucial factors. The premature mortality caused by O3 for respiratory disease in the YRD is estimated to be 5,889 cases per year. Furthermore, we find that premature mortality is more sensitive to O3 concentration than population, suggesting that controlling peak O3 concentration can bring great health benefits. Key Points: Spatiotemporal characteristics of ozone were investigated based on satellite data and observation network dataThe main meteorological driving factors of ozone were captured using EOF analysisThe premature mortality attributed to ozone was estimated with epidemiological exposure response functions [ABSTRACT FROM AUTHOR]

The natural emissions of ozone precursors (NO x and VOCs) are sensitive to climate. Future climate change can impact O 3 concentrations by perturbing these emissions. To better estimate the variation of natural emissions under different climate conditions and understand its effect on surface O 3 , we model the present and the future air quality over the Yangtze River Delta (YRD) region by running different simulations with the aid of the WRF-CALGRID model system that contains a natural emission module. Firstly, we estimate the natural emissions at present and in IPCC A1B scenario. The results show that biogenic VOC emission and soil NO x emission over YRD in 2008 is 657 Gg C and 19.1 Gg N, respectively. According to climate change, these emissions in 2050 will increase by 25.5% and 11.5%, respectively. Secondly, the effects of future natural emissions and meteorology on surface O 3 are investigated and compared. It is found that the variations in meteorological fields can significantly alter the spatial distribution of O 3 over YRD, with the increases of 5–15 ppb in the north and the decreases of −5 to −15 ppb in the south. However, only approximately 20% of the surface O 3 increases caused by climate change can be attributed to the natural emissions, with the highest increment up to 2.4 ppb. Finally, Ra (the ratio of impacts from NO x and VOCs on O 3 formation) and H 2 O 2 /HNO 3 (the ratio between the concentrations of H 2 O 2 and HNO 3 ) are applied to study the O 3 sensitivity in YRD. The results show that the transition value of H 2 O 2 /HNO 3 will turn from 0.3 to 0.5 in 2008 to 0.4–0.8 in 2050. O 3 formation in the YRD region will be insensitive to VOCs under future climate condition, implying more NO x need to be cut down. Our findings can help us understand O 3 variation trend and put forward the reasonable and effective pollution control policies in these famous polluted areas. [ABSTRACT FROM AUTHOR]

Abstract Fine particle (PM 2.5) and ozone (O 3) are major air pollutants in China, especially in developed city clusters. A comprehensive field campaign, the Campaign on Air Pollution and Urban Meteorology in Yangtze River Delta (CAPUM-YRD), eastern China is carried out in 2016 to enhance the understanding of regional PM 2.5 and O 3 pollution. Two super sites in Shanghai, one in Hangzhou, as well as nineteen national monitoring stations in Nanjing and Hefei jointly participate in the campaign. In this study, regional PM 2.5 and O 3 pollution episodes are characterized based on summer and winter experiments during the CAPUM-YRD. Further, trajectory simulation and source apportionment technology in Comprehensive Air Quality Model with Extensions (CAMx) are applied to explore the source of the pollution episodes. We find that regional synchronous PM 2.5 pollution episodes (over 120 μg/m3) occur frequently in YRD. Secondary inorganic and carbonaceous components account for a major proportion (70–80%) in PM 2.5. Nitrate concentration is significantly higher (lower) than sulfate in winter (summer). The secondary conversion of sulfur and nitrogen increases alongside elevated PM 2.5 levels, with a maximum ratio of 0.28 and 0.18 in winter, respectively. Source apportionment results suggest that the contribution of emissions within YRD dominates in PM 2.5 (over 60%) compared to other regions. The inter-regional transport from the north-northwest in eastern China can contribute over 20% to PM 2.5 in YRD, with a maximum of 28.4% in Nanjing. Under the transport by enhanced northerly winds, PM 2.5 concentrations may increase explosively, with observed peak values in Hefei (312.6 μg/m3) and Nanjing (255.7 μg/m3). Moreover, high levels and remarkable spatial heterogeneity of O 3 are observed over YRD in summer, with daily maximum 8-h average O 3 above 300 μg/m3 in Nanjing. The occurrence of O 3 pollution episodes is significantly impacted by favorable weather conditions and transport at multiple spatial scales. Regional contribution results demonstrate that super-regional transport is prominent (29.4–50.7%) in O 3 pollution, especially in coastal cities like Shanghai (30.3–63.0%). Our results suggest that enhanced regional collaboration and efforts are of extreme necessity in long-term and optimized control of severe PM 2.5 and O 3 pollution in YRD. Highlights • Regional severe PM 2.5 and O 3 episodes over YRD during a comprehensive field observation campaign were characterized. • Particulate and ozone source apportionment technology were applied to explore the sources of PM 2.5 and O 3. • Qualitative and quantitative contributions of different source regions to PM 2.5 and O 3 in YRD were investigated. [ABSTRACT FROM AUTHOR]

The Yangtze River Delta (YRD) region has experienced a rapid urbanization process accompanied with economic development during last decades. To investigate impacts of urbanization on regional climate and air quality, two-month (January and July 2010) simulations with two different land-use scenarios (USGS and MODIS land-use types) are conducted using the Advanced Weather Research and Forecasting/Chemistry (WRF/Chem) modeling system in this study. Results show that the conversion of vegetated and irrigated cropland into urban type significantly changes 2-m temperature and 10-m wind speed, which are obtained from differences of two simulations based on significance t-test at 95% confidence level. Changes of land-use cause an increase in 2-m temperature with maximum (minimum) value of 2.3 °C (0.9 °C) over urbanized area, a decrease in 10-m wind speed with magnitude of 0.6–1.2 m s −1 for both the two months. Planetary boundary layer height (PBLH) differences show a maximum increase of 425 m during daytime in July, and the increases are about 100 m during nighttime for both January and July. Urbanization reduces near-surface PM 10 concentration due to increase of PBLH, with maximum decrease of 57.6 μg m −3 during nighttime in July. The biggest increase of O 3 is around 6.8 ppb during daytime in July and the difference is about 1.7–2.3 ppb in January. Vertical profiles show that PM 10 concentrations decrease due to increase of mixing height during both daytime and nighttime. While for O 3 concentration, urbanization causes an increase during daytime due to higher air temperature and decrease of wind speed and leads to a decrease during nighttime. Overall, influences of urbanization on climate and air quality are important and significant over YRD region, which must be considered in any climate and air quality assessment. [ABSTRACT FROM AUTHOR]

Yangtze River Delta (YRD) region has experienced a remarkable urbanization during the past 30years, and regional climate change and air pollution are becoming more and more evident due to urbanization. Impacts of urban canopy on regional climate and air quality in dry- and wet-season are investigated in this paper, utilizing the Weather Research and Forecasting/Chemistry (WRF/Chem) model. Four regimes of urban canopy schemes with updated USGS land-use data in actual state of 2004 base on MODIS observations are examined: (1) SLAB scheme that does not consider urban canopy parameters (the control experiment in this paper); (2) a single-layer urban model with a fixed diurnal profile for anthropogenic heat (UCM); (3) multilayer urban canopy model (BEP-Building effect parameterization); (4) multilayer urban models with a building energy model including anthropogenic heat due to air conditioning (BEP+BEM). Results show that, compared with observations, the best 2-m temperature estimates with minimum bias are obtained with SLAB and BEP+BEM schemes, while the best 10-m wind speed predictions are obtained with BEP and BEP+BEM scheme. For PM10 and ozone predictions, BEP+BEM scheme predicted PM10 well during January, while the best estimate of PM10 is obtained with UCM scheme during July, BEP+BEM and SLAB schemes best estimated ozone concentrations for both the two months. Spatial differences of meteorological factors between canopy schemes and control scheme show that compared with SLAB scheme, BEP and BEP+BEM schemes cause an increase of temperature with differences of 0.5°C and 0.3°C, respectively, UCM scheme simulates lower temperature with decrease of 0.7°C during January. In July, all the canopy experiments calculates lower air temperature with reduction of 0.5°C–1.6°C. All the canopy experiments compute lower 10-m wind speed for both January and July. Decreases were 0.7m/s (0.8m/s) with UCM, 1.7m/s (2.6m/s) with BEP, and 1.8m/s (2.3m/s) with BEP+BEM schemes in January (July), respectively. For chemical field distributions, results show that, compared with SLAB scheme, UCM scheme calculates higher PM10 concentration in both January and July, with the differences of 22.3% (or 24.4μg/m3) in January, and 31.4% (or 17.4μg/m3) in July, respectively. As large as 32.7% (or 18.3 μg/m3) of PM10 increase is found over Hangzhou city during July. While 18.6% (or 22.1 μg/m3) and 16.7% (or 24.6 μg/m3) of PM10 decreases are fund in BEP and BEP+BEM schemes during January. Compared with control experiment during January, 6.5% (or 2.6ppb) to 10.4% (4.2ppb) increases of ozone are computed over mage-cities by canopy experiments. All the three canopy schemes predict lower ozone concentrations and as large as 30.2% (or 11.2ppb) decrease is obtained with UCM scheme, and 16.5% (6.2ppb) decrease with BEP scheme during July. The SLAB scheme is suitable for real-time weather forecast while multiple urban canopy scheme is necessary when quantify the urbanization impacts on regional climate. [ABSTRACT FROM AUTHOR]