ANALYSIS OF THE PH OF DAILY RAINFALL AT A RURAL SITE IN HONG-KONG, 1989-1993

Citation
R. Sequeira et Mr. Peart, ANALYSIS OF THE PH OF DAILY RAINFALL AT A RURAL SITE IN HONG-KONG, 1989-1993, Science of the total environment, 159(2-3), 1995, pp. 177-183
Citations number
13
Categorie Soggetti
Environmental Sciences
ISSN journal
00489697
Volume
159
Issue
2-3
Year of publication
1995
Pages
177 - 183
Database
ISI
SICI code
0048-9697(1995)159:2-3<177:AOTPOD>2.0.ZU;2-B
Abstract
Daily bulk precipitation samples have been collected and their pH meas ured since April 1989 at a rural site, Kadoorie Agricultural Research Centre (KARC), in the central New Territories, Hong Kong. The frequenc y distribution of this population (N = 470) indicates a quasi-log norm al distribution up until December, 1993. This is perhaps one of the lo ngest daily pH-records available and it has climatological significanc e for the future. The annual median and the running, volume-weighted p H values (year end) are presented and they indicate collectively an an nually oscillating pattern for which there is no obvious explanation a t present. The annual volume-weighted pH values for 1990-1993 are 4.53 , 4.30, 5.04 and 4.32 and the corresponding running volume-weighted pH values are 4.53, 4.39, 4.57 and 4.50. Most of the daily observations indicate acidity on the Sorensen scale as expected, and there appears to be no seasonal pattern to pH or amount of rainfall. Also, the volum e of rainfall appears to exhibit no simple relationship with the acidi ty of the rainfall. On the other hand, there is, apparently, an anthro pogenic component of acid in Hong Kong if the increase in free hydroge n ion concentration measured at the site is not entirely due to orogra phic reduction of alkaline dust present at relatively lower elevations in Hong Kong. Thus, there is some evidence that in contrast to the vo lume-weighted pH in the mid-4's at Kadoorie, the pH of local backgroun d rainfall in the territory of Hong Kong may be approximately 4.8, whi le that of regional background (unpolluted) rainfall is probably brack eted by pH approximately 5-5.5.