Significant Increase in Ammonia Emissions in China: Considering Nonagricultural Sectors Based on Isotopic Source Apportionment.

Isotopic source apportionment results revealed that nonagricultural sectors are significant sources of ammonia (NH3) emissions, particularly in urban areas. Unfortunately, nonagricultural sources have been substantially underrepresented in the current anthropogenic NH3 emission inventories (EIs). Here, we propose a novel approach to develop a gridded EI of nonagricultural NH3 in China for 2016 using a combination of isotopic source apportionment results and the emission ratios of carbon monoxide (CO) and NH3. We estimated that isotope-corrected nonagricultural NH3 emissions were 4370 Gg in China in 2016, accounting for an increase in the total NH3 emissions from 7 to 31%. As a result, compared to the original NH3 EI, the annual emissions of total NH3 increased by 35%. Thus, in comparison to the simulation driven by the original NH3 EI, the WRF-Chem model driven by the isotope-corrected NH3 EI has reduced the model biases in the surface concentrations and dry deposition flux of reduced nitrogen (NHx = gaseous NH3 + particulate NH4+) by 23 and 31%, respectively. This study may have wide-ranging implications for formulating targeted strategies for nonagricultural NH3 emissions controls, making it facilitate the achievement of simultaneously alleviating nitrogen deposition and atmospheric pollution in the future.

A New Index Developed for Fast Diagnosis of Meteorological Roles in Ground-Level Ozone Variations.

China experienced worsening ground-level ozone (O3) pollution from 2013 to 2019. In this study, meteorological parameters, including surface temperature (T 2 ), solar radiation (SW), and wind speed (WS), were classified into two aspects, (1) Photochemical Reaction Condition (PRC = T 2 × SW) and (2) Physical Dispersion Capacity (PDC = WS). In this way, a Meteorology Synthetic Index (MSI = PRC/PDC) was developed for the quantification of meteorology-induced ground-level O3 pollution. The positive linear relationship between the 90th percentile of MDA8 (maximum daily 8-h average) O3 concentration and MSI determined that the contribution of meteorological changes to ground-level O-3 varied on a latitudinal gradient, decreasing from ∼40% in southern China to 10%-20% in northern China. Favorable photochemical reaction conditions were more important for ground-level O3 pollution. This study proposes a universally applicable index for fast diagnosis of meteorological roles in ground-level O3 variability, which enables the assessment of the observed effects of precursor emissions reductions that can be used for designing future control policies. ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available in the online version of this article at 10.1007/s00376-021-1257-x.

Potential impact of industrial transfer on PM2.5 and economic development under scenarios oriented by different objectives in Guangdong, China.

For sustainable regional development, industrial transfer is an important trend that will potentially change the spatial and temporal pattern of air pollution and economic development. Aiming to better regulate industrial transfer and guide policy-making, this study proposes an assessment framework for industrial transfer that combines precise enterprise data, GIS technology and a 3-D air quality model. Taking Guangdong Province as an example, this study simulates the redistribution of 4015 high-pollution and high-energy-consumption (double-high) enterprises in the Pearl River Delta (PRD) to surrounding areas, and the potential impact on air quality is further evaluated. Three mutually independent transfer scenarios with different objectives are designed-ENV (ENVironment), ENT (ENTerprise), and GOV (GOVernment)-which aim to maximize benefits from the standpoint of the residents of Guangdong, the enterprises themselves, and local governments, respectively. Results show that Western Guangdong (WG), Northern Guangdong (NG), and Eastern Guangdong (EG) would be the primary transfer-in regions under the ENV, ENT, and GOV scenarios due to different resource endowment. Controlled by the different scenarios, the redistribution of enterprises presented different characteristics regarding the transport of pollutant emissions and economic added value between the PRD and surrounding areas. The average concentration of PM2.5 and the related population-weighted concentrations (PWC) showed a slight decrease over the PRD (-0.75 to -0.62 µg/m3 and -0.35 to -0.49 µg/m3 per person) but increased dramatically in surrounding areas under the three scenarios (0.46-7.68 µg/m3 and 0.07-4.44 µg/m3 per person). The transfer of double-high enterprises could potentially decrease the industrial fossil fuel consumption intensity (fossil energy consumption per unit of industrial GDP) of most of the cities while exacerbating pollution intensity (concentration of PM2.5 per unit of industrial GDP), reflecting the huge gap in the regional industrial development pattern in Guangdong Province at this stage, and illustrating the importance of emission control of these enterprises for improvement of regional air quality in the future. The research perspective on industrial transfer proposed in this study could provide a reference for future studies.

Synergistic effects of biogenic volatile organic compounds and soil nitric oxide emissions on summertime ozone formation in China.

Natural emissions play a key role in modulating the formation of ground-level ozone (O3), especially emissions of biogenic volatile organic compounds (BVOCs) and soil nitric oxide (SNO), and their individual effects on O3 formation have been previously quantified and evaluated. However, their synergistic effects remain unclear and have not yet been well assessed. By applying the Weather Research and Forecasting (WRF) model coupled with the Chemistry-Model of Emissions of Gases and Aerosols from Nature (WRF/Chem-MEGAN) model, this study reveals that in the presence of sufficient BVOC emissions, which act as a fuel, SNO emissions act as a fuel additive and promote the chemical reactions of BVOCs and the subsequent production of O3. Consequently, the synergistic effects of BVOC and SNO emissions on summertime O3 production surpassed the sum of their individual effects by as much as 10-20 µg m-3 in eastern China in 2014. In order to reduce O3 concentration to a level corresponding to no natural emissions of BVOC or SNO (i.e., the BASE scenario), the anthropogenic volatile organic compound (AVOC) emissions in the scenario considers BVOC and SNO emissions must be reduced by 1.76 times that of the BASE scenario. This study demonstrates that the synergistic effects of BVOC and SNO emissions can impede ground-level O3 regulation and can subsequently impose stricter requirements on anthropogenic precursor emission control in China. The results of this study can also inform efforts in other regions that are still combating ground-level O3 pollution.

[Nonlinear Response Relationship Between Ozone and Precursor Emissions in the Pearl River Delta Region Under Different Transmission Channels].

With the rapid development of urbanization, ozone (O3) pollution is an ongoing occurrence in the Pearl River Delta (PRD) region in China. The effective control of O3 pollution is a great challenge owing to the nonlinear relationship between O3 and precursor emissions and the effect of meteorological conditions. Based on the regional air quality model CAMx-OSAT (ozone source apportionment technology), O3 formation regimes were determined, and inter-city transportation across PRD was quantified under different transmission channels. The results showed that spatial differences were observed for the O3 formation regimes under different transmission channels. The VOCs-sensitive regime was mainly located in the central areas of the PRD region, and the NOx-sensitive regime was distributed in the suburban areas of the PRD regions under calm wind conditions. When the northeast wind was prevailing, the polluted air mass of the urban agglomeration was transmitted southwesterly downward, resulting in the downwind areas being transformed to VOCs-sensitive; the upwind areas were still NOx-sensitive. Under the southeast wind, the VOCs-sensitive regime had a banding distribution along the southeast-northwest direction, and the remaining areas were NOx-sensitive. With the influence of transmission channels, downwind cities were significantly affected by the transmission of upwind urban agglomerations (41%-87%), whereas the local formation was the main contributor under the calm wind conditions (60%-87%). To explore the relationship between O3 and precursor emissions, a series of sensitivity tests were designed. The results showed that maximized areas (20%-36%) with reductions in O3 can be achieved by reducing VOCs and NOx in the corresponding sensitive regimes, and the maximized level with the reduction in O3 can be fulfilled by reducing VOCs in the VOCs-sensitive regime. For the typical city Jiangmen, the area that met the standard increased the most under the calm wind (11%) and southeast wind (8%) conditions when VOCs and NOx were reduced in the corresponding sensitive regimes. Additionally, under northeast wind conditions, reducing VOCs in the VOCs-sensitive regime can more effectively control O3, as the area up to the standard increased by 140%.

Assessment of background ozone concentrations in China and implications for using region-specific volatile organic compounds emission abatement to mitigate air pollution.

Mitigation of ambient ozone (O3) pollution is a great challenge because it depends heavily on the background O3 which has been poorly evaluated in many regions, including in China. By establishing the relationship between O3 and air temperature near the surface, the mean background O3 mixing ratios in the clean and polluted seasons were determined to be 35-40 and 50-55 ppbv in China during 2013-2019, respectively. Simulations using the chemical transport model (i.e., the Weather Research and Forecasting coupled with Chemistry model, WRF/Chem) suggested that biogenic volatile organic compounds (VOC) emissions were the primary contributor to the increase in the background O3 in the polluted season (BOP) compared to the background O3 in the clean season (BOC), ranging from 8 ppbv to 16 ppbv. More importantly, the BOP continuously increased at a rate of 0.6-8.0 ppbv yr-1 during 2013-2019, while the non-BOP stopped increasing after 2017. Consequently, an additional 2%-16% reduction in anthropogenic VOC emissions is required to reverse the current O3 back to that measured in the period from 2013 to 2017. The results of this study emphasize the importance of the relative contribution of the background O3 to the observed total O3 concentration in the design of anthropogenic precursor emission control strategies for the attainment of O3 standards.

Ozone control strategies for local formation- and regional transport-dominant scenarios in a manufacturing city in southern China.

Given the leveling off of fine particulate matter (PM2.5), ground-level ozone (O3) pollution has become one of the most significant atmospheric pollution issues in the Pearl River Delta (PRD) region in China, especially in the manufacturing city of Dongguan, which faces more severe O3 pollution. The development of strategies to control O3 precursor emissions, including volatile organic compounds (VOCs) and nitrogen oxide (NOx), depends to a large extent on the source region of the O3 pollution. In this study, by combining the Weather Research and Forecasting model coupled with chemistry (WRF-Chem), the Empirical Kinetic Modeling Approach (EKMA), and the Flexible Particle model (FLEXPART), more effective strategies of controlling O3 precursor emissions were identified under two typical types of O3 pollution episodes: local formation (LF)-dominant (8-12 September 2019) and regional transport (RT)-dominant (23-27 October 2017) episodes, distinguished by the WRF-FLEXPART model. During the LF-dominant episode, the EKMA revealed that the O3 formation in Dongguan was in a transitional regime, and the abatement of solvent use-VOCs emissions in the key area of Dongguan was more effective in reducing O3 levels, with an emission reduction benefit 1.7 times that of total VOCs emission sources throughout Dongguan. With respect to the RT-dominant episode, the reduction in VOCs emissions in the local region did not effectively curb O3 pollution, although the photochemical regime of the O3 formation in Dongguan was VOCs-limited. A 50% reduction in NOx emissions in the upwind regions (parts of Guangzhou and Huizhou) effectively decreased the O3 concentration in Dongguan by 17%. The results of this study emphasize the importance of the source region of O3 pollution in the implementation of effective O3 control strategies and provide valuable insights for region-specific precursor emission policy formulation, not only in Dongguan, but also in other regions facing severe O3 pollution.

[Characteristics and Meteorological Factors of Complex Nonattainment Pollution of Atmospheric Photochemical Oxidant (Ox) and PM2.5 in the Pearl River Delta Region, China].

Based on the atmospheric pollutant data from twelve monitoring sites in the Guangdong-Hong Kong-Macao Pearl River Delta Regional Air Quality Monitoring Network, the mass concentration trends of atmospheric photochemical oxidants (Ox, NO2+O3) and PM2.5 during 2013-2017 were studied. The complex nonattainment pollution of Ox and PM2.5 is defined as the daily average mass concentration of NO2 and PM2.5 and daily maximum 8 h average (O3 MDA8) mass concentration of O3 simultaneously that exceeds the Chinese grade Ⅱ national air quality standard. The characteristics and meteorological factors that influence the complex nonattainment pollution of Ox and PM2.5 at different types of areas were analyzed. The results indicate that from 2013 to 2017, the annual average mass concentration of PM2.5 in the Pearl River Delta (PRD) region decreased from (44±7) µg·m-3 to (32±4) µg·m-3, which met the annual standard for three consecutive years. The annual average mass concentration of Ox decreased from (127±14) µg·m-3 in 2013 to (114±12) µg·m-3 in 2016 and then showed a general rebound trend to (129±13) µg·m-3 in 2017 when O3 concentrations increased significantly (10 µg·m-3). The proportion of pollution processes with O3 as the primary pollutant increased from 33% in 2013 to 78% in 2017, and the regional characteristics of simultaneous pollution in multiple cities have been highlighted. The complex nonattainment pollution of Ox and PM2.5 occurred 60 times during the study period, primarily in urban sites (78%) and suburban sites (22%). The largest number of days of complex nonattainment pollution occurred in autumn (52%) because of strong solar radiation that was conducive to ozone formation, and consequently, the high oxidization of the atmosphere promoted the secondary generation of PM2.5. The weather conditions that caused the complex nonattainment pollution in the PRD mainly include outflow-high-pressures (43%), subtropical-high-pressures(30%), and tropical-depressions (27%). In terms of specific meteorological conditions, when the temperature was in the range of 20-25℃ and relative humidity was in the range of 60%-75%, the proportion of complex nonattainment pollution was the highest (22%). When O3 pollution was substantial, the high relative humidity and low wind speed during the nighttime caused the concentration of NO2 and PM2.5 to rise significantly, and then the high temperatures during the day aggravated the complex nonattainment pollution.

Meteorological variations impeded the benefits of recent NOx mitigation in reducing atmospheric nitrate deposition in the Pearl River Delta region, Southeast China.

The trends and variability of atmospheric nitrogen deposition in the Pearl River Delta (PRD) region for the period 2008-2017 were investigated by integrating ground- and satellite-based observations and a chemical transport model, in order to gauge the effects of emission reductions and meteorological variability. We show that dry deposition observation of oxidized nitrogen decreased at the rate of 2.4% yr-1 for a moderate reduction in NOx emissions by 27% in the past decade, while reduced nitrogen presented an increase at the rate of 2.3% yr-1 despite no regulated interventions for NH3 emissions, which is likely related to changes in atmospheric gas-particle partitioning of NH3 as reductions in SO2 and NOx emissions. These results coincide with the trends in ground-level concentrations of oxidized and reduced nitrogen compounds in the atmosphere during 2008-2017. The changes in annual deposition fluxes of total oxidized and reduced nitrogen are not statistically significant trends and largely related with the inter-annual variability in their corresponding wet depositions, which reflects combined effects of variability in precipitation amount, and changes in atmospheric nitrogen compounds which dominates wet deposition of the oxidized and reduced forms. The meteorological conditions can mask 34% and 25% decrease in total oxidized and reduced nitrogen deposition on the decadal timescale, respectively. We conclude that meteorology-driven variability probably have masked the full response of oxidized nitrogen deposition to NOx emissions reduction. Our results also imply that persistent and integrated emission control strategies on NOx and NH3 are needed to effectively reduce total nitrogen deposition fluxes towards the critical limit in the PRD region.

[Professor HE Tianyou's clinical experience of acupuncture and medicine on intractable facial paralysis].

Professor HE Tianyou's unique understanding and treatment characteristics for intractahle facial paralysis are introduced. In clinical practice professor HE highly values acupoint selection and manipulation application, and integrates Chinese and western medicine to flexibly choose acupoints and formulate prescriptions according to syndrome differentiation and location differentiation, besides, he creates several specialized manipulation methods including "tug-of war opposite acupuncture method" and "tractive flash cupping". Based on strengthening body and dredging collaterals. more attention is given on stimulation to local paralyzed facial nerves; meanwhile acupuncture and medication are combined to improve clinical efficacy. During the treatment, the important role of psychological counseling on patient's anxiety is emphasized, and comprehensive treatment is given physically and psychologically in order to achieve the purpose of total rehabilitation.