Impact of heat waves (HWs) on air pollution

(case study for HWs episode in July-August 2010 in the

Kiev city (Ukraine)

Prof. Sergiy Snizhko,

Dr. Olga Shevchenko

Taras Shevchenko University,

Kiev, Ukraine

Kiev has a population of 3,14 millions and occupies an area of

more than 840 square kilometers

Sources of air pollution in Kiev

The main sources of air pollution in Kiev are cars. In Kiev, road transport

provides almost 90% of all harmful emissions into the atmosphere.

Road

transport

90%

Industry

10%

Increasing of numbers of vehicles in the city

Number of vehicles in the city has increased from 426 thousand units in 2000 to

825 thousand units in 2013. In the same time amount the incoming pollutants into

the atmosphere from road transport increased from 160 thousand tons in 2000 to

236 thousand tons in 2010.

426

562

692

778

820 822803 815 825

300

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500

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800

900

1998 2000 2002 2004 2006 2008 2010 2012 2014

Years

Cars, th

ou

san

d u

nit

s

Temporal dynamics of main pollutants

concentrations in the ambient air in the city of Kiev

NO2 = 0,0018x + 0,0684

R2 = 0,208

Formaldehyde = 0,0005x + 0,0013

R2 = 0,5954

0,00

0,02

0,04

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0,12

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

NO

2,m

g/m

3

0,000

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0,006

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Fo

rmal

deh

yde,

mg

/m3

NO2

FormaldehydeIn Kiev were detected a significant

increasing in the concentration of

some pollutants, especially NO2 (by

50%) and formaldehyde (by 200%)

due to the increasing number of road

transport in the city.

Mean annual concentrations of formaldehyde in the air have increased in last period 3

times and concentrations of NO2 increased in 1,5-2,0 times.

High concentrations of nitrogen dioxide in the air contribute to the formation of

photochemical smog. During HWs periods by accelerating photochemical processes it take

part as ozone-precursor in photochemical reactions.

Our study of HWs in Ukraine (Shevchenko et al., 2014) for the period 1911-2011 indicate,

that in contrast to other decades, the number of HW episodes was highest for almost all

stations in the decade 2001–2010. Heat wave in summer 2010 was very intensitive (the more

intensitive HW was observed just once).

A period of more than 5 consecutive days with daily Ta,max more than 5 ◦C above

the mean daily Ta,max for the normal climatic period 1961–1990 is dicated as a

HEAT WAVE (according to the recommendation of the IPCC).

HWs in July-August 2010 in Kiev

In this study we analyze interactions between meteorology and chemistry for second biggest HW.

During second HW excess of the average daily temperature was at least 5°C;

- about 10 days this excess reached 8-10°C;

- maximal daily temperature reached 38,2°C (8.08.2010).

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T m

ax d

aily, o

C

11 days 18 days

During July-August 2010 in Kiev

were observed two HWs:

1) from 14.07 to 24.07.2010 (11

days);

2) 31.07–17.08.2010 (18 days).

Heat waves and air pollution Under meteorological point of view HW are generally associated with quasi-stationary anticyclonic circulation anomalies, which produce subsidence, clear skies, warm-air advection and prolonged hot conditions in the near-surface atmosphere (Fischer et al ., 2007; Barriopedro et al ., 2011).

During HWs periods in urban areas created ideal conditions for the

accumulation of a number of pollutants and formation of photochemical

smog.

First, temperature increases favored the chemical production of ozone

in the troposphere.

Second, low atmospheric humidity reduced ozone destruction, as well as

the production of the hydroxyl radical, which destroys several air

pollutants, including ozone precursors.

Third, the vegetation was affected by high temperature and the lack of

precipitation, which led to a substantial reduction in the removal by dry

deposition to the Earth’s surface of ozone and other compounds

Air quality monitoring net in Kiev

Three stations are on the left bank of the

Dnipro river (monitoring station 3, 4 and

9), station 15 is situated on the Venetian

island of Dnipro river and 12 stations are

situated on the right bank of the Dnipro

and represents air quality in the central

part of the city.

Measurement of basic air pollutants

makes 4 times per day (at 01, 07, 13, 19

hours).

Stations 6,7

Main precursor of ground-level ozone - NO2 : spatial

distribution of mean annual concentrations in air of

the city Kiev, Ukraine

Source: Snizhko S., Shevchenko O. (2011) 0,085 mg/m3 - 0,20 mg/м3

Interactions between meteorology and chemistry

during heat waves episode in July-August 2010

All plots shows sufficient increasing both substances during period of HW. Contentration of

formaldehyde increases with increasing temperature and reaches a maximum in the hottest days

of this period.

Content of NO2 raised at the beginning of the HW and then slightly decreases.

This behavior of NO2 may be connected with his participation in photochemical processes.

Statistical estimation of the impact of HW on air pollution

To estimate the impact of HW on air pollution we have performed a comprehensive analysis of climatic

characteristics and some air pollutants, in particular NO2, formaldehyde.

Statistical analysis shoved high positive correlation between temperature indexes and concentrations of

pollutants. This can means that oscillation of both substances in the time determined by the same

dominant meteorological factor.

Index of T max daily may be a good descriptor of coupled impact of meteorological factor on

ozone formation processes in the ground level layer of air.

The impact of temperature on formaldehyde formation confirms a significant value coefficients of

correlations between Tmax day and formaldehyde concentration (r=0,588). This relationship was

approximated by linear regression equation.

Graphical approximation of relationship between

formaldehyde, NO2 and air temperature

The above data indicate that concentration of formaldehyde depend on temperature and

concentration of NO2. Using the PC-Program “Statistica” we have calculated the

relationship between formaldehyde accumulation and leading ozone precursor NO2 and

air temperature and have got relative good approximation of this relationship in form of

3D Contour Plot

Two combination of temperature and NO2 concentrations tend to formation of highest concentrations of formaldehyde

3D contour plot presents distribution of probably formaldehyde concentration in bright range of air temperature (T max daily) from 18,0 to 42,0oC and NO2 concentration from 0,05 to 0,40 mg/m3. Probability of formation highest concentrations of formaldehyde is possible in two cases:

- highest concentrations of NO2 in range 0,20-0,40 mg/m³ and relatively low for

summer HW episode temperature in range from 18,0 to 23,0°C;

- relatively low concentrations of NO2 in range 0,05-0,20 mg/m³ and very height

temperature – 35,0–42,0oC.

Statistical model of temporal dynamics of

formaldehyde during HW

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mg/

m3

Formaldehyde (monitoring dates)

Formaldehyde forecast

For approximation relationship between formaldehyde, NO2 and air temperature we have

calculated an equation of multiple linear regression:

Formaldehyde (mg/m3) = 0,001577+0,011329 NO2 (mg/m3)+0,000648 T max day (oC).

Results of retrospective

forecast calculation using this

this equation and monitoring

dates from station 6 shows

satisfactory results.

Conclusions 1. In Kiev have been detected a significant increasing of the concentration of some

pollutants, especially NO2 (by 50%) and formaldehyde (by 200%) due to the

increasing number of road transport in the city.

2. Have been detected sufficient increasing NO2 and formaldehyde during period of

HW. Concentration of formaldehyde increases with increasing temperature and

reaches a maximum in the hottest days of this period. Concentration of NO2 raised

at the beginning of the HW and then slightly decreases.

3. The impact of temperature on formaldehyde formation confirms a significant value

coefficients of correlations between Tmax daily and formaldehyde concentration

(r=0,588).

4. Was developed statistical model of temporal dynamics of formaldehyde during

HW.

This model can use as statistical model for short-time expert assessment of

formaldehyde accumulation in urban air during HW cases if not available a more

modern numerical forecast models.

17

Thank you for your attention!