A 5-Year study of inland aquatic acidification at Semenyih Dam

A 5-year inland aquatic acidification study was conducted on surface water of Semenyih Dam from 2005 to 2009. This study is part of a continous acidification monitoring programme for Malaysia as a participatory country of EANET (East Asia Acid Monitoring Network). Water samples were taken every three months at selected points of the dam. Besides pH, temperature and electrical conductivity, these samples were also analysed for soluble ions using ion chromatography. The ions analysed include SO
4
^2-
, NO
3
⁻
, Cl
⁻
, NH
4
⁺
, Na
⁺
, K
⁺
, Ca
²⁺
and Mg
²⁺
. Basic pH, together with high acid neutralizing capacity (ANC) and alkalinity especially in 2005 and 2006 indicate Semenyih Dam was capable of neutralization any acidification due to anthropogenic activities. However, in 2008 and 2009, decreases in pH, alkalinity and ANC indicate surface water at Semenyih Dam was experiencing some acidification due to increases in acidifying species with respect to basic neutralizing cations.