Fog Water, Throughfall, and Bulk Precipitation Chemistry and a Newly Developed Methodology for the Estimation of Fog Water Deposition

Fog water, throughfall, and bulk precipitation were collected at the site neighboring to coastal and urbanized area in Japan. Fog water was collected by using string type passive fog collector. Fog water was strongly influenced by the sea salt components presumably due to drizzle. Furthermore, fog water would be acidified by acid-related nitrate species like HNO₃ gas in ambient air; however, fog water was neutralized well as shown below. Throughfall selectively included non-sea salt chloride (nss-Cl⁻) among the three media: fog water, throughfall, and bulk precipitation, likely due to a dry deposition of nss-Cl⁻ species on canopy. The pH values for fog water, throughfall, and bulk precipitation, were 5.28, 5.97, and 5.73, respectively. Those were typically higher compared with other previous observations, meaning that all media were neutralized well. In particular, fog water was dominantly neutralized by nss-Mg²⁺ and nss-Ca²⁺. The supply of nitrogen (NO₃⁻-N + NH₄⁺-N) via throughfall showed the seasonality, higher in winter and summer. We considered a new and simple methodology to evaluate/estimate the deposition amount of fog water. We applied our new methodology to our present observation and obtained a good agreement with the result heretofore used.