A new study carried out by researchers from the Hebrew University on two districts with the highest air pollution in Israel, Gush Dan and Haifa, while taking meteorological conditions into account, reveals for the first time the effect of a significant reduction in economic activity on the quality of the environment. The research findings revealed that the maximum relative contribution of the closure to the total change in pollutants was up to 26%, and together with the meteorological conditions up to 47%
The corona closures led to a sharp and drastic reduction in land, sea and air transportation, and industrial activity, and therefore there was a decrease in air pollution throughout Israel and even in other countries - there is no doubt about that. But what is the scope and size of this decrease, and what is the effect of the entire period of quarantine on the quality of the air we breathe? A new study they conducted Two researchers from the Hebrew University - Dr. Sharit Agami from the Department of Economics and Prof. Uri Dayan from the Department of Geography, who was published in the scientific magazine Atmospheric Environment, Worked on testing the impact of the first lockdown (on 2.5.20 - 8.3.20) due to the corona virus on air pollution in Israel, taking into account meteorological conditions that also have an effect on the amount of concentrations themselves. The study focused on the areas of Gush Dan and Haifa, two districts with high air pollution in Israel. Both districts include transportation and industrial activity, where air pollution in Gush Dan is mainly contributed by transportation, while in Haifa it is mainly due to industrial activity. Where was there a more significant decrease in air pollution?
The study consisted of two phases. In the first stage, the difference in the average concentration of pollutants in 2020 during the period of closure was examined, compared to the average in the corresponding period in 2019. In the second stage, the effect of the closure on the total amount of pollutants will be examined, as well as an assessment of this effect when adding the effect of the meteorological conditions that prevailed during the closure. The calculations in the first stage showed a significant decrease in the concentration of all pollutants in the air, except for an increase in ozone concentration. Specifically, registered decrease in particles in air whose diameter is less than 2.5 micrometers (PM2.5), known as fine respirable particles capable of penetrating the lungs, at a rate of 18% in Gush Dan, and 10% in Haifa. Also, there was a 19% decrease in carbon monoxide in Gush Dan, whose main source today is mainly from vehicle engines that burn hydrocarbons such as gasoline, compared to a 4% decrease in Haifa. The apparent reason for the higher decrease in these two pollutants in Gush Dan compared to Haifa is that the air pollution in Gush Dan mainly stems from transportation compared to Haifa.
For nitrogen oxides (total nitrogen monoxide and nitrogen dioxide) which increase the risk of respiratory diseases - in Haifa there was a 46% decrease in nitrogen dioxide concentration, compared to a 40% decrease in Gush Dan, but for other nitrogen oxides a similar decrease in concentrations was detected in Haifa and Gush Dan. For example, sulfur dioxide (SO2) emitted from the burning of sulfur-containing fossil fuels, such as coal, fuel oil and diesel fuel - are burned mainly in power plants and refineries, hence the explanation for the significant decrease of 57% in its concentration in Haifa compared to a much more moderate decrease of 14% in Gush Dan.
The monitoring stations located in the largest population centers in the country measure these air pollutants continuously. There are three types of air pollution monitoring stations - general, transport and industrial. In comparing the decrease in the amount of pollutant concentrations according to station types, The highest decrease was measured at the transport stations. Also, in a complex chemical process called titration, nitrogen oxides are consumed for the formation of ozone, so the decline in nitrogen oxide concentrations during the quarantine period was characterized by an increase in ozone concentration at a rate of 5% and 13% in Haifa and Gush Dan respectively. The results of reducing activity throughout the economy and their effect on ozone concentrations are not surprising, according to the researchers, since results close to the findings obtained in the current study can be obtained in Israel even on the weekends, during which transportation is more limited (public, for example, does not operate).
To what extent do the meteorological factors affect the findings? The calculations from the second stage of the study showed that the effect of the closure alone in terms of the explained variance of the amount of concentrations was greater in Gush Dan compared to Haifa, in most of the monitoring stations that were taken into account. Despite this it is important to note that The most prominent effect was the blockade effect on the benzene concentration (a toxic and carcinogenic organic compound, coming from vehicle exhaust gases and industrial areas), with an explained variance of 39% in the Hadar neighborhood in Haifa. Excluding the effect on benzene, the effect on the other pollutants was at most 26%. However, with the addition of meteorological conditions (temperature, speed and wind direction) that prevailed during the closure, the total relative contribution of the closure increases, ranging between 47%-7% in Haifa, compared to 41%-3% in Gush Dan. That is, the sharp decrease in transportation and industrial activity explained only up to 26% of the decrease in the amount of pollutant concentrations, but the addition of meteorological conditions indicates a significant change in the closure effect, which is reflected in the percentage of explained variance which almost doubled, reaching a dramatic rate of 47%.
"To the best of our knowledge, this study is the first to be carried out in Israel to quantitatively assess the effect of the lockdown on air quality," the researchers conclude. "These surprising results highlighted the necessity to examine, in a follow-up study, the impact of transportation and industry separately, as well as to emphasize in detail the accompanying meteorological conditions during times of closure which greatly influence, as this study indicated, the change in the concentration of pollutants in the environment of urban centers Large as received in Haifa and Gush Dan".
