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13 pags., 7 figs. ; Severe and persistent haze events in northern China, characterized by high loading of fine aerosol especially of secondary origin, negatively impact human health and the welfare of ecosystems. However, current knowledge cannot fully explain the formation of this haze pollution. Despite field observations of elevated levels of reactive halogen species (e.g., BrCl, ClNO, Cl, HBr) at several sites in China, the influence of halogens (particularly bromine) on haze pollution is largely unknown. Here, for the first time, we compile an emission inventory of anthropogenic bromine and quantify the collective impact of halogens on haze pollution in northern China. We utilize a regional model (WRF-Chem), revised to incorporate updated halogen chemistry and anthropogenic chlorine and bromine emissions and validated by measurements of atmospheric pollutants and halogens, to show that halogens enhance the loading of fine aerosol in northern China (on average by 21%) and especially its secondary components (∼130% for secondary organic aerosol and ∼20% for sulfate, nitrate, and ammonium aerosols). Such a significant increase is attributed to the enhancement of atmospheric oxidants (OH, HO, O, NO, Cl, and Br) by halogen chemistry, with a significant contribution from previously unconsidered bromine. These results show that higher recognition of the impact of anthropogenic halogens shall be given in haze pollution research and air quality regulation. ; This study received funding from the European Research Council Executive Agency under the European Union's Horizon 2020 Research and Innovation Programme (Project ERC-2016- COG 726349 CLIMAHAL) and the Hong Kong Research Grants Council (Project T24-504/17-N and APolyU502/16). CU team is funded by NSF AGS-1822664. X.F. acknowledges the financial support of the Scientific Research Start-up Funds from Tsinghua Shenzhen International Graduate School (QD2021015C). The development and maintenance of the WRF-Chem model are conducted by NOAA/ESRL/GSD in active collaboration with other institutes. Computing resources, support, and data storage were provided by the Climate Simulation Laboratory at NCAR's Computational and Information Systems Laboratory (CISL), sponsored by the NSF.

In Southeast Asia, environmental issues become an annual agenda in every regional meeting such as the Transboundary Haze Pollution (THP) issues. The domino effect that resulted from this phenomenon has become increasingly complex, including the degradation of natural resources, health problems for living things, to stretched diplomatic relations between regional countries. ASEAN formulated the Agreement on Transboundary Haze and Pollution (AATHP) as the basic law for addressing this issue since 2003 and has been fully ratified by entire ASEAN member countries in 2015 marked by the ratification of Indonesia as the last ratification among ASEAN membership. This research attempt to explain the phenomenon by utilizing a qualitative method with descriptive analysis to conclude the factors and challenges faced by ASEAN during the implementation of AATHP from 2015 to 2019. Through the approach of regionalism, environmental security, soft law characteristics in international agreements, and fiqh al-biah, this research concluded that the implementation of AATHP is considered to have an insignificant effect in overcoming the transboundary haze issue.Keyword: ASEAN, AATHP, transboundary haze pollution, soft law

Toxic 'haze' from fires, often burning over dry peatland in Indonesia, has affected millions across Indonesia, Singapore and Malaysia, as well as parts of the Philippines and Thailand. For Singapore in particular, this slash-and-burn method of clearing land in Indonesia to cultivate crops such as oil palm has been an annual problem since 1972. However, 2015 stands out as the year Singapore experienced one of its worst episodes of haze pollution. Air quality based on the Pollutant Standards Index (PSI) plummeted to the 'very unhealthy' and 'hazardous ranges' for close to 50 days. Singapore suffered an estimated SGD $700 million in economic losses in 2015 as a result of, inter alia, the closure of schools, hotels, tourist attractions and major sporting events. Moreover, the large quantities of carbon dioxide released set back Southeast Asia's efforts to mitigate climate change. A scientific study has shown that the 2015 fires in Indonesia released nearly one gigaton of greenhouse gases. Daily emissions during that haze period were even higher than that of all the European Union member states put together.

Long-term exposure to haze pollution will not only affect citizens&rsquo ; health and shorten their life expectancy, but also cause unpredictable economic losses. In addition, it has become the focus of worldwide concern whether and how institutional quality affects haze pollution. In this study, we explored the impacts of political corruption on haze pollution in 139 global countries. We employed a geographical detector model to identify the driving factors of spatial differentiation in global haze pollution. In addition, corruption degree and per capita gross domestic production (GDP) were used as threshold variables to analyze whether there is a nonlinear relationship between corruption and haze pollution. The main results are as follows. (1) The corruption perception index (CPI) was negatively correlated with haze pollution and had a strong and stable explanatory power for the heterogeneity of haze pollution. Besides, the degree of corruption had a significant triple threshold effect on haze pollution. When the CPI crossed the double threshold value, strengthening institutional quality could inhibit haze pollution. (2) Per capita GDP significantly determined how institutional quality exerted an effect on haze pollution, which was also a key factor affecting spatial heterogeneity of PM2.5 concentration. In high-income countries, choosing a more honest ruling party could substantially reduce haze pollution, while in low-income countries, an incompetent government could increase the degree of haze pollution. (3) The &ldquo ; Matthew effect&rdquo ; was manifested in our study. It indicated that the higher was the level of economic development, the lower was the severity of haze pollution. Based on these results, we state that policy makers cannot simply alleviate haze pollution through anti-corruption construction. For low-income countries, ensuring economic growth is the prerequisite for the substantial alleviation of haze pollution. On the contrary, high-income countries should pay more attention to the integrity of government institutions and strengthen the awareness of anti-corruption.

This study takes a network perspective to examine the spatial spillover effects of haze pollution in Cheng-Yu urban agglomeration which is the fourth largest urban agglomeration and a comprehensive demonstration zone of new urbanization in China. Firstly, we use Granger causality test to construct haze pollution spatial association network, and then we apply social network analysis to reveal the structural characteristics of this network. The results show that: haze pollution in Cheng-Yu urban agglomeration is a complex multithreaded network. Chongqing, Chengdu, Guang'an, Luzhou, Deyang and Nanchong are the centers of the network, sending and transmitting the most relationships. The haze pollution spatial association network can be divided into net beneficiary block, net overflow block, bilateral overflow block and broker block. These four blocks present obvious geographical distribution characteristics and are partly related to the difference of urbanization. The above results contribute by illustrating the current spatial spillover situation of haze pollution and provide a theoretical foundation for the government that it should simultaneously consider cities' statues and their spatial spillover effects in the network rather than simple geographic proximity when formulating future haze pollution control policies in urban agglomeration.