[Analysis of O3 Sources in Yulin City in Summer Based on WRF-CMAQ/ISAM Model].

In order to have a clearer understanding of the sources of ozone pollution in Yulin City in summer and put forward scientific governance suggestions, the WRF-CMAQ model was used to simulate the O3 concentration in Yulin City and surrounding areas (including Taiyuan City, Xi'an City, Yinchuan City, Hohhot City, and other provincial capital cities) in July 2019. Using the ISAM module, the sources of O3 and its precursors NOx and VOCs in a heavy pollution process in Yulin City were quantified. The results showed that on heavy pollution days, the O3 in Yulin City mainly came from the long-distance transmission outside the simulation area (55.5%), followed by the photochemical reaction of precursors in the simulation area (20.6%, 10.0%, 5.0%, 2.3%, and 2.1%, respectively, in Yulin City, Shanxi Province, Inner Mongolia Autonomous Region, and Shaanxi Province, 1.2% in Gansu Province, Ningxia Hui Autonomous Region, and Henan Province in total), and initial conditions (0.3%); the remaining sources (23.6%) could not be successfully labeled. Yulin City is in the VOCs control area, and its VOCs were composed of paraffin (76.5%), ketones (9.2%), and other types of VOCs (14.3%). The VOCs came from the emission of pollution sources in the simulation area (45.6%, 22.0%, 11.4%, 6.3%, and 5.1%, respectively, in Yulin City, Shanxi Province, Inner Mongolia Autonomous Region, and Shaanxi Province, 0.8% in Gansu Province, Ningxia Hui Autonomous Region, and Henan Province in total) and the long-distance transmission outside the simulation area (27.9%); the remaining 26.5% were not successfully marked. This research showed that to control the O3 pollution in Yulin, not only should the local VOCs emissions be controlled, but the overall planning of VOCs emissions in the peripheral areas should also be done well.

[Analysis of Causes and Sources of Summer Ozone Pollution in Rizhao Based on CMAQ and HYSPLIT Models].

As a typical coastal city, O3 pollution in Rizhao has become increasingly serious in recent years. In order to explore the causes and sources of O3 pollution, IPR process analysis and ISAM source tracking tools based on the CMAQ model were used, respectively, to quantify the contributions of different physicochemical processes and different source tracking areas to O3 in Rizhao. Additionally, by comparing the differences between O3-exceeding days and non-exceeding days, combined with the HYSPLIT model, the regional transportation path of O3 in Rizhao was explored. The results showed that the concentrations of O3, NOx, and VOCs near the coastal areas of Rizhao and Lianyungang were significantly increased on O3 exceedance days compared with those on non-exceedance days. This was mainly because Rizhao was the convergence zone of western, southwestern, and eastern winds on exceedance days, which facilitated the transport and accumulation of pollutants. Process analysis showed that the transport process (TRAN) contribution to the near-surface O3 near the coastal areas of Rizhao and Lianyungang increased significantly on the exceedance days, whereas the contribution to most areas to the west of Linyi decreased. Photochemical reaction (CHEM) had a positive contribution to the O3 concentration in Rizhao during the daytime at all heights, and TRAN had a positive contribution at 0-60 m above the ground, and mainly had a negative contribution above 60 m. The contributions of CHEM and TRAN at 0-60 m above the ground would increase significantly on exceedance days, which was approximately twice that on the non-exceedance days. Source analysis showed that the local sources in Rizhao were the main contribution sources of NOx and VOCs, with the contribution rates of 47.5% and 58.0%, respectively. O3 mainly came from the contribution outside the simulation area (67.5%). The O3 and precursor contributions of the western cities of Rizhao (Weifang, Linyi, etc.) and the southern cities (Lianyungang, etc.) would increase significantly on the days of exceeding the standard. The transportation path analysis showed that the number of exceedances accounted for the largest proportion (11.8%) in the path from the west of Rizhao, which was the main transportation channel of O3 and precursors in Rizhao. This was verified through process analysis and source tracking results, and such trajectories accounted for 13.0% of the total number of trajectories, and their main routes were in the Shaanxi, Shanxi, Hebei, and Shandong regions.

Residue 544 in domain III of the Bacillus thuringiensis Cry1Ac toxin is involved in protein structure stability.

A unique residue W544 in the beta18-beta19 loop of the Bacillus thuringiensis Cry1Ac toxin has been implicated in its toxicity. In this study, the effects of mutations at this residue on protein stability during protease treatment, UV irradiation, and preservation were examined. Residue 544 of Cry1Ac was involved in maintaining structural stability, and substitution of a polar group at this position was unfavorable to protein stability. One mutant, W544F, produced larger crystals and was more stable. This mutant showed greater resistance to UV radiation than the wild type Cry1Ac but retained equal toxicity. This is the first report showing that residue 544 in the Cry1Ac domain III plays a significant role in toxin structural stability. Our W544F mutant is a significant development in terms of field applications of Cry1Ac toxin.