Impacts of meteorology and precursor emission change on O_(3) variation in Tianjin, China from 2015 to 2021

Deterioration of surface ozone (O_(3)) pollution in Northern China over the past few years received much attention.For many cities,it is still under debate whether the trend of surface O_(3)variation is driven by meteorology or the change in precursors emissions.In this work,a time series decomposition method (Seasonal-Trend decomposition procedure based on Loess (STL)) and random forest (RF) algorithm were utilized to quantify the meteorological impacts on the recorded O_(3)trend and identify the key meteorological factors affecting O_(3)pollution in Tianjin,the biggest coastal port city in Northern China.After “removing” the meteorological fluctuations from the observed O_(3)time series,we found that variation of O_(3)in Tianjin was largely driven by the changes in precursors emissions.The meteorology was unfavorable for O_(3)pollution in period of 2015-2016,and turned out to be favorable during 2017-2021.Specifically,meteorology contributed 9.3μg/m^(3)O_(3)(13%) in 2019,together with the increase in precursors emissions,making 2019 to be the worst year of O_(3)pollution since 2015.Since then,the favorable effects of meteorology on O_(3)pollution tended to be weaker.Temperature was the most important factor affecting O_(3)level,followed by air humidity in O_(3)pollution season.In the midday of summer days,O_(3)pollution frequently exceeded the standard level (>160μg/m^(3)) at a combined condition with relative humidity in 40%-50%and temperature>31℃.Both the temperature and the dryness of the atmosphere need to be subtly considered for summer O_(3)forecasting.

Impact of Cold Spells on Ischemic Stroke Severity and Clinical Outcomes in Tianjin, China

There are several studies on the impact of extreme weather on the incidence and mortality of stroke, but the research on the effect of extreme weather events on severity and outcome of ischemic stroke is scarce. This study aimed to evaluate the impact of cold spells on the severity and clinical outcomes of patients with initial acute ischemic stroke in a hospital-based study. We enrolled 553 patients with initial ischemic stroke during the cold seasons between 2016 and 2019. Patients were separated into the mild stroke group and moderate-to-severe stroke group according to the National Institutes of Health Stroke Scale(NIHSS) of the U.S., and good outcome group and poor outcome group according to modified Rankin Scale(mRS) scores. There are nine different definitions of cold spells according to intensities and duration time. After adjustment for climate factors, air quality index, and common risk factors, it is found that cold spells were associated with moderate-to-severe neurological deficits and clinical outcomes in overall ischemic stroke patients. Furthermore, the delay effect for stroke severity started at the beginning of the cold wave(Lag 0) and lasted up to 14 days(Lags 0–14). In addition, when a cold spell was set as a daily mean temperature < 3rd or 5th percentile and with a duration ≥ 2 or 3 consecutive days, cold spells had a significant impact on clinical outcomes, and there was a definite delay effect of at least 7 days(Lags 0–7) and it lasted up to 14days(Lags 0–14). At last, we concluded that cold spells may be a contributory factor for more severe neurological deficits and worse outcomes in patients with initial ischemic stroke.

Impact of meteorological condition changes on air quality and particulate chemical composition during the COVID-19 lockdown

Stringent quarantine measures during the Coronavirus Disease 2019(COVID-19)lockdown period(January 23,2020 to March 15,2020)have resulted in a distinct decrease in anthropogenic source emissions in North China Plain compared to the paralleled period of 2019.Particularly,22.7%decrease in NO_(2)and 3.0%increase of O_(3)was observed in Tianjin,nonlinear relationship between O_(3)generation and NO_(2)implied that synergetic control of NOx and VOCs is needed.Deteriorating meteorological condition during the COVID-19 lockdown obscured the actual PM2.5 reduction.Fireworks transport in 2020 Spring Festival(SF)triggered regional haze pollution.PM2.5 during the COVID-19 lockdown only reduced by 5.6%in Tianjin.Here we used the dispersion coefficient to normalize the measured PM2.5(DN-PM2.5),aiming to eliminate the adverse meteorological impact and roughly estimate the actual PM2.5 reduction,which reduced by 17.7%during the COVID-19 lockdown.In terms of PM2.5 chemical composition,significant NO_(3)−increase was observed during the COVID-19 lockdown.However,as a tracer of atmospheric oxidation capacity,odd oxygen(Ox=NO_(2)+O_(3))was observed to reduce during the COVID-19 lockdown,whereas relative humidity(RH),specific humidity and aerosol liquid water content(ALWC)were observed with noticeable enhancement.Nitrogen oxidation rate(NOR)was observed to increase at higher specific humidity and ALWC,especially in the haze episode occurred during 2020SF,high air humidity and obvious nitrate generation was observed.Anomalously enhanced air humidity may response for the nitrate increase during the COVID-19 lockdown period.