Impact of drought conditions on air pollution over Turkey

As a natural disaster, drought affects many sectors such as agriculture and hydrology, as well as having an effect on air quality. In terms of air pollution, drought can reduce wet scavenging of pollutants and change their chemical production/loss and lifetime. This study investigates the relationship between drought events and air pollutants in Turkey. As a drought indicator, the Standardized Precipitation-Evapotranspiration Index (SPEI)-1 monthly values for dry (SPEI < -0.99), normal (-0.99 < SPEI < 0.99) and wet (SPEI < 0.99) conditions were used to investigate the changes in PM10, PM2.5, O-3 concentration levels. Monthly mean PM10 values of 80 stations for the period 2010-2018, PM2.5 and O-3 values of 10 and 12 stations, respectively, were used for the analysis throughout the 2014-2018 period. According to the results, while frequency occurrence of normal conditions decreased in the last period (2010-2018) when compared to the first (1901-2009), drought conditions have significantly increased in each region of Turkey in the last decade. Highest increase in drought events occurred in the inner/southern parts of Turkey. In dry events, while PM10 levels of the stations show above-normal values, highest regional increase in PM10 was found in the Central Anatolia (CAR), Mediterranean (MeR), Aegean (AR) and Marmara (MR) regions of the country. In fall, high daily temperatures and cloudless days in CAR and MeR regions are seen under deep surface low over continental Europe and surface high over Caspian Sea, which result in severe dryness events and associated high PM10 values in the air quality stations. On the other hand, as a consequence of the expanding Asiatic monsoon low to the eastern part of Turkey, significant amount of moisture is transferred from the Eastern Mediterranean Sea surface to the CAR and MeR regions by southerly flows (wetness SPEI conditions in fall) and cause to appear below-normal PM10 values in the southern stations.