Physico-Chemical Characteristics Of Pinang River Estuary, Balik Pulau, Penang
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Date
2018-08
Authors
Nurul Ruhayu Mohd Rosli
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The Pinang River is located at the north-western of Penang Island. Its length
is approximately 6.5 km, with narrow and shallow upstream, but wider and deeper
downstream. This river supplies freshwater to nearly one-third of Balik Pulau
population. Unfortunately, anthropogenic effluent from agriculture, domestic and
aquaculture are being directly discharge into the river thus, deteriorating the water
quality. Therefore, this study was undertaken to determine the Pinang River estuarine
processes which involve the mixing of freshwater and seawater that may influence the
river hydrodynamic, biological, physical and chemical aspects. These characteristics
would possibly affect the estuarine water circulation, river transport time scales (i.e.
residence time and flushing time) and pollutants (i.e. nutrient and sediment
concentrations; and its loadings). Net ecosystem metabolism (NEM) status in Pinang
River was also evaluated in terms of ratio between photosynthesis and respiration.
Diurnal studies were carried out for 24 hours at two stations during two tidal cycles at
spring and neap tides and wet and dry season. A secondary data (from October 2007
until October 2008) on river discharge, salinity and volume along Pinang River were
utilised to determine the residence time and flushing time. Pinang River estuarine
system was considered as micro-tidal and partially stratified estuary. The flushing
time did not influence the residence time (R2=0.028) in Pinang River. This river
estuary experienced longer residence time (spring, dry: 17.77 – 42.86 hours; spring,
wet: 16.29 – 23.91 hours; neap, dry: 25.47 – 186.69 hours; neap, wet: 23.44 – 89.88
hours) and flushing time (spring, dry: 12.68 – 75.08 hours; spring, wet: 44.05 –186.79 hours; neap, dry: 15.69 – 107.75 hours; neap, wet: 9.90 – 222.73 hours) during
both tidal events. However during neap tide, the results were significantly higher than
spring tide (p<0.05). Only the flushing time showed significantly higher in wet
season at lower part of the river estuary (p<0.05). The nitrite (maximum 3.35 kg/h),
orthophosphate (maximum 18.85 kg/h) and sediment (86,837.86 kg/h) loadings were
significantly higher during neap tide in wet season (p<0.05). Meanwhile, the
ammonia (maximum 44.32 kg/h) and nitrate (maximum 15.96 kg/h) loadings were
high throughout the study. Besides tidal event and sedimentation problem, untreated
discharged from anthropogenic activities along the river may affect the river turbidity
and increase in biological oxygen demand (BOD5) (maximum 11.23 mg/L) which
leads the Pinang River estuarine system to be in heterotrophic condition
Description
Keywords
Natural history