Bulletin of the Geological Society of Malaysia, Volume 71, May 2021, pp. 203 – 213

Rainfalls and salinity effects on fecal coliform Most Probable Number (MPN) Index distribution in a beach ridge-shore ridge system in Mengabang Telipot, Terengganu, Malaysia

Edlic Sathiamurthy^1,*, Kwa Kian Min², Muhammad Zulhilmi Ishak², Lalitha Nagappan², Yong Jaw Chuen¹
1 Faculty of Science and Marine Environment, University Malaysia Terengganu, 20130 Kuala Nerus, Terengganu, Malaysia
2 Faculty of Ocean Engineering Technology and Informatics, University Malaysia Terengganu, 20130 Kuala Nerus, Terengganu, Malaysia
* Corresponding author email address: edlic@umt.edu.my

Abstract: A Holocene beach ridge and present day shore ridge system located in a rural area north east of Kuala Terengganu was studied. The relation between fecal coliform (FC) MPN Index (Most Probable Number) distribution with rainfalls and saline intrusions into the unconfined aquifer of the beach ridge–shore ridge system was examined. The probable primary source of the pollutants was also investigated in order to highlight the susceptibility of such aquifers to pollution. Six sampling sessions were made from September 2009 to January 2010. Three represent drier conditions and the other 3, heavier rainfalls corresponding to the northeast monsoon season. This sampling period represent a condition when this area was still not subjected to major coastal erosions and subsequent rock revetment work. Altogether, water samples were taken from 13 wells and 3 river stations. Physical-chemical measurements were made in-situ, while FC was tested at UMT laboratory. Essentially, the results indicated that the groundwater in the unconfined aquifer layer of the beach ridge was moderately to highly polluted with FC (up to 1600 MPN). In contrast, the shore ridge was only slightly polluted, whereas river stations had mixed conditions but generally worse than the beach ridge and shore ridge. These phenomena could be associated with salinity spatial-temporal variations. Samples from heavy rainfall conditions indicated lower pollution levels compared to drier conditions. This phenomenon could be associated with the availability of more infiltrated atmospheric water to dilute pollutants in a high hydraulic conductivity environment as the ridges are made of fine to coarse sands. The results underscore the sensitivity of such environment to pollution transport and distribution and hence implied special attention with regards to water resource management.

Keywords: Beach ridge, shore ridge, fecal coliform

DOI: https://doi.org/10.7186/bgsm71202116