Effect of Motor-Vehicle Emissions on Biochemical and Morphological Characteristics Indicating the State of English Oak Trees

We examined the vital condition of the common oak (Quercus robur L.) in plantations of different categories in Dnipro-city. In the investigated plantations, differences in the individual resistance of plants were recorded. The patterns of changes in the pigmented complex of leaves exposed to atmospheric pollution from motor vehicle emissions were studied in connection with the life state of oak trees. The content of chlorophyll a had, in all variants of the experiment, significantly higher values than chlorophyll b. Chlorophyll a accounted for 52.4–75.0% of the total content of chlorophylls, and chlorophyll b (25.0–47.6%). Regardless of the level of air pollution, relatively healthy oak plants were characterized by a high content of pigments activity in the photosynthetic apparatus of the leaves. A chronic moderate influence of motor vehicle emissions had a positive effect on the content of green pigments and carotenoids. Increase in the intensity of transport emissions resulted in a significant reduction in the accumulation of chlorophylls and to an increase in carotenoids. The stability of the chlorophyll a / chlorophyll b ratio under the influence of motor vehicle emissions was been registered. Only severely damaged common oak trees showed a decrease of this parameter by 29.3% compared with healthy and moderately weakened specimens of oak. The values of the coefficients of variation in the content of chlorophylls, their amounts and ratios, as well as carotenoids were low and represent less than 19.0%, while the amplitude of the variability of the studied parameters of the pigment complex, depending on the life state of plants and the intensity of transport emissions, was quite significant: the highest fluctuations in the сontent indexes were recorded for chlorophyll a, the sum of chlorophylls a + b in trees from the park area and the area with a medium level of pollution, chlorophyll b only in oaks from the street with an average level of air pollution by transport emissions. The smallest variability was a characteristic of the ratio of chlorophylls a / b and the content of carotenoids. Low values of the ratio of the sum of chlorophylls a + b to carotenoids (4.3–5.2) indicate the stress state of oak plants in urban environments.

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Quantifying Air Pollutant Variations during COVID-19 Lockdown in a Capital City in Northwest China

Atmosphere ◽

10.3390/atmos12060788 ◽

2021 ◽

Vol 12 (6) ◽

pp. 788

Author(s):

Rong Feng ◽

Hongmei Xu ◽

Zexuan Wang ◽

Yunxuan Gu ◽

Zhe Liu ◽

...

Keyword(s):

Air Pollution ◽

Air Quality ◽

Rural Areas ◽

Vehicle Emissions ◽

Motor Vehicle ◽

Northwest China ◽

Air Pollutant ◽

Capital City ◽

Air Pollution Control ◽

Motor Vehicle Emissions

In the context of the outbreak of coronavirus disease 2019 (COVID-19), strict lockdown policies were implemented to control nonessential human activities in Xi’an, northwest China, which greatly limited the spread of the pandemic and affected air quality. Compared with pre-lockdown, the air quality index and concentrations of PM2.5, PM10, SO2, and CO during the lockdown reduced, but the reductions were not very significant. NO2 levels exhibited the largest decrease (52%) during lockdown, owing to the remarkable decreased motor vehicle emissions. The highest K+ and lowest Ca2+ concentrations in PM2.5 samples could be attributed to the increase in household biomass fuel consumption in suburbs and rural areas around Xi’an and the decrease in human physical activities in Xi’an (e.g., human travel, vehicle emissions, construction activities), respectively, during the lockdown period. Secondary chemical reactions in the atmosphere increased in the lockdown period, as evidenced by the increased O3 level (increased by 160%) and OC/EC ratios in PM2.5 (increased by 26%), compared with pre-lockdown levels. The results, based on a natural experiment in this study, can be used as a reference for studying the formation and source of air pollution in Xi’an and provide evidence for establishing future long-term air pollution control policies.

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