Sources, Ionic Composition and Acidic Properties of Bulk and Wet Atmospheric Deposition in the Eastern Middle Adriatic Region

Abstract

Atmospheric bulk and wet deposition samples were collected simultaneously at the background coastal site in the Eastern Middle Adriatic region in order to assess the impact of major ions (Cl^-, NO₃^-, SO₄^2-, Na⁺, K⁺, NH₄⁺, Mg²⁺, Ca²⁺) on deposition acidity and distinguish the main sources. Higher ion levels were observed during the cold period, especially for Cl^-, Na⁺, Mg²⁺ and K⁺. Dust intrusion caused significant increases in levels of Ca²⁺, Mg²⁺ and K⁺, while open-fire events increased the levels of K⁺. Deposition acidity showed seasonal differences as well as the influence of dust intrusion. Low ionic balance ratios indicated acidic deposition properties and the presence of organic anions. The highest neutralization ability was found for Ca²⁺, Na⁺ and NH₄⁺. Several natural (marine, crustal) and anthropogenic sources were determined, as well as the formation of secondary aerosols. Wet deposition was characterized by higher contribution of sea salt fraction compared to bulk deposition and lower contribution of crustal fraction.

Keywords: deposited matter; dust intrusion; major ions; open-fire events.

Figure 1

Average temperature, humidity, precipitation and wind speed determined during the sampling period in 2019.

Figure 2

Average bulk deposition fluxes during the sampling campaign from February to July 2019 at the Middle Adriatic coastal site.

Figure 3

Average (a) deposition fluxes and (b) equivalent concentrations of ions in bulk deposition during the sampling campaign from February to July 2019 at the Middle Adriatic coastal site.

Figure 4

Average contributions of each ion to the bulk deposition mass during the sampling campaign from February to July 2019 at the middle Adriatic coastal site.

Figure 5

Average (a) deposition fluxes and (b) equivalent concentrations of ions in wet deposition during the sampling campaign from February to July 2019 at the middle Adriatic coastal site.

Figure 6

Average pH of bulk and wet deposition during the sampling campaign from February to July 2019 at the middle Adriatic coastal site.

Figure 7

The average ratio of ionic neutralization potential (NP) to the acidification potential (AP) and average neutralization factors (NF) of individual cations in (a) bulk and (b) wet deposition during cold and warm seasons and special events.

Figure 8

Ion balance of bulk (●) and wet (▲) deposition, expressed as Σanions-to-Σcations equivalent ratio.

Figure 9

Determined contribution of crustal fraction (CF), sea-salt fraction (SSF) and anthropogenic fraction (AF) in (a) bulk and (b) wet deposition to the overall investigated period as well as during different seasons and specific events in the middle Adriatic region.