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.
Highlights
Holocene beach ridges and present shore ridges are typical landforms in a wave dominated coastal area along the coastal plains of east coast of Peninsular Malaysia
The results indicated that fecal coliform (FC) Most Probable Number (MPN) were higher during drier periods than wet periods
As a whole, the surface water was the most polluted by FC followed by the beach ridge
Summary
They have a narrow and elongated shape and could be a few hundred meters wide and few kilometres long (Raj et al, 2007; Roslan et al, 2010; Parham, 2016). Some of them are in a strand plain set up, while some could be delineated as a set of individual units separated by well defined swales These series of beach ridges or strand plains are usually parallel or almost parallel to the modern coastline. There were more than six village wells on the beach ridge, it is not possible to sample all of them because of the work load involved and accessibility issues (some wells were located inside bathrooms and kitchens).
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