Rapid change in nitrate and sulfate concentrations observed in early stage of precipitation and their deposition processes

Abstract

The concentrations of H +, nitrate (NO 3), and sulfate (SO]-) in rainwater and their temporal changes were analyzed on the basis of continuous observation from 1 July 1991 to 30 June 1992 at a suburb of Nagoya, Japan. The yearly average for pH was 4.4. In general, an increasing pH with increase in precipitation amount was observed for rain events. Relatively high pH rainwater was sometimes observed at the beginning of rainfall, even though high concentrations of NO 3 and SOlwere involved. The high pH values were considered to be caused by the neutralization process with particulate matter containing cations. The yearly averaged ratio of equivalent concentration of nitrate to sulfate (N/S) in rainwater was 0.58. In the early stage of rain, the N/S value was usually more than 1.0 due to the difference of scavenging process between NOr and SO]-. High values of N/S ranging from 5 to 10 were found under the atmospheric conditions of calm winds and low humidity, during which it is possible that atmospheric particles float for a long time in the air before a rain event. The adsorption of NO~-in the early stage of rainfall by particulate matter was suggested from the difference in scavenging processes of NO 3 and SO]-. A possible scavenging process, called limb cloud scavenging, is presented to explain the interaction of particles and nitrate ions at the early stage of rain. In limb cloud scavenging, the repeated migration of cloud particles or raindrops between the inside and outside of clouds increases the absorption of ions to a highly condensed level, thus increasing the N/S value of rainwater. The influence of global scale seasonal phenomena with large amounts of particulates, such as typhoons or Asian dust storms, was also studied.

Seasonal Changes in the Concentrations of Major Cations and Anions in Precipitations in Urban Nagoya, Japan

“…The averaged pH was 4.4 and ion concentrations of NO3-and 5042-were 28.2 and 48.3 ,ueq. 1-1, respectively (Minoura and Iwasaka, 1996). Considering the overestimation of pH obtained in the JEA Phase-I Study and comparing the pH obtained in the precedent observation, the pH obtained in this study was higher and the ion concentrations were lower than the values usually observed in the Nagakute area.…”

La Lluvia Ácida Y Los Ecosistemas Forestales

“…Even in regions not subject to industrial pollution, atmospheric moisture is exposed to varying amounts of naturally-occurring acids, so precipitation has a pH of about 5. However, in regions encompassing centers of human activity that can extend for hundreds of kilometers, the pH of precipitation is lower, 3.5 to 4.5 or sometimes even less (Mohnen, 1988;Minoura and Iwasaka. 1996).…”

“…Incluso en regiones no sometidas a contaminación industrial, la humedad atmosférica se ve expuesta a cantidades variables de ácidos de origen natural; de este modo las precipitaciones tienen un pH de alrededor de 5. Sin embargo, en las regiones que se extienden alrededor de centros de actividad humana, y que pueden llegar a cientos de kilómetros, el pH de la precipitación es más bajo, de 3.5 a 4.5 o aun menor ocasionalmente (Mohnen, 1988;Minoura, y Iwasaka. 1996).…”

“…In some heavily industrialized regions, the hydrogen chloride gas released into the atmosphere produces hydrochloric acid, which can also be a component of acid rain. For this reason, environmentalists have succeeded in making acid rain a matter of national and international interest (Minoura and Iwasaka, 1996).…”

Composição iônica majoritária de águas de chuva no centro da cidade de São Paulo

“…Pesquisas mais detalhadas abrangem, Cl e Mg 2+ e, eventualmente, metais pesados e espécies orgânicas como ácidos carboxílicos [5][6][7][8][9][10] . É importante destacar que em países da Europa e América do Norte existem programas de monitoramento envolvendo redes de amostragem cobrindo um ou mais países, obtendo-se avaliações tanto espaciais quanto temporais da composição química das águas de chuva e seus efeitos em diferentes ecossistemas (lagos, florestas e solos) [11][12][13][14][15] . No Brasil, ao contrário do hemisfério norte, os dados disponíveis sobre deposição úmida originam-se de iniciativas isoladas ou de grupos de pesquisadores em algumas regiões e por períodos de tempo limitados 10,[16][17][18][19][20][21][22][23][24][25][26][27][28][29] .…”