Sains Malaysiana 47(4)(2018): 651-659

http://dx.doi.org/10.17576/jsm-2018-4704-02

Distribution and Behaviour of Nitrogen Compounds in the Surface Water of Sungai Terengganu Estuary, Southern Waters of South China Sea, Malaysia

(Taburan dan Perlakuan Sebatian Nitrogen di Permukaan Air Muara Sungai Terengganu, Perairan Selatan Laut China Selatan, Malaysia)

SUHAIMI SURATMAN^1,2*, AZYYATI ABDUL AZIZ1¹, NORHAYATI MOHD TAHIR^1,2

& LEE HIN LEE³

¹Institute of Oceanography and Environment, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu Darul Iman Malaysia

²Institute of Tropical Biodiversity and Sustainable Development, Universiti Malaysia Terengganu,

21030 Kuala Nerus, Terengganu Darul Iman, Malaysia

³School of Marine and Environment Sciences, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu Darul Iman Malaysia

⁴Water Quality and Environment Research Centre, National Hydraulic Research Institute for Malaysia, 43300 Seri Kembangan, Selangor Darul Ehsan, Malaysia

Diserahkan: 30 Disember 2016/Diterima: 27 Oktober 2017

ABSTRACT

A study was carried out to determine the distribution and behaviour of nitrogen (N) compounds (nitrite, nitrate, ammonia, dissolved and particulate organic nitrogen) in Sungai Terengganu estuary (TRE). Surface water samples were collected during ebb neap and spring tides for the longitudinal survey along the salinity gradient. The results indicated that all N compounds behave non-conservatively with addition during both tidal cycles, except for nitrate which exhibited removal behaviour during spring tide. In general, higher concentration of N compounds was observed during spring tide compared to neap tide. It is suggested that during spring tide, stronger water turbulence resulted in resuspension of nutrients in bottom sediment and lead to the increase in N compounds concentrations in the surface water. The diurnal survey for the freshwater station showed that the concentrations of N compounds follow the ebb and flood variations, whereas for the coastal station the reverse trend was observed. Comparisons with a previous study under similar tidal conditions show there was an increase in nitrite and ammonia concentrations in TRE, which was probably due to increase in discharge from the rapid development activities around this area. In addition, the presence of a breakwater at the lower part of the estuary may also contribute to the high nutrient content in the estuary due to restricted outflow of nutrients to the coastal area. Overall, the results from this study highlighted the importance of monitoring the N compounds for future protection of the estuary.

Keywords: Distribution and behaviour; nitrogen compounds; spring-neap tides; Sungai Terengganu estuary; surface water

ABSTRAK

Suatu kajian telah dijalankan untuk menentukan taburan dan perlakuan sebatian nitrogen (N) (nitrit, nitrat, ammonia, nitrogen organik terlarut dan partikulat) di muara Sungai Terengganu (TRE). Sampel permukaan air telah diambil sepanjang cerun saliniti ketika air surut semasa pasang-surut perbani dan purnama. Keputusan kajian menunjukkan semua sebatian N berkelakuan tidak konservatif iaitu tambahan untuk kedua-dua kitaran pasang-surut, kecuali nitrat yang menunjukkan perlakuan singkiran semasa pasang-surut purnama. Secara umumnya, kepekatan sebatian N adalah tinggi semasa pasang-surut purnama berbanding pasang-surut perbani. Adalah dicadangkan semasa pasang-surut purnama, berlakunya kegeloraan air yang kuat menyebabkan nutrien dalam sedimen di dasar sungai akan terampai dan seterusnya meninggikan kepekatan sebatian N di permukaan air. Persampelan diurnal untuk stesen air tawar menunjukkan kepekatan sebatian N mengikut variasi air pasang dan surut, manakala untuk stesen di kawasan pantai, corak yang bertentangan adalah diperhatikan. Perbandingan dengan kajian terdahulu di kawasan dan keadaan pasang- surut yang sama, menunjukkan terdapatnya peningkatan kepekatan nitrit dan ammonia di TRE yang mungkin disebabkan bertambahnya pembuangan daripada aktiviti-aktiviti pembangunan yang pesat di sekitar kawasan kajian. Tambahan lagi, kehadiran benteng pemecah ombak di kawasan hilir muara mungkin turut menyumbang kepada tingginya kandungan nutrien di dalam muara disebabkan pergerakan keluar nutrien ke kawasan pantai yang terhad. Secara keseluruhannya, keputusan daripada kajian ini menekankan kepentingan pemantauan sebatian N untuk pemeliharaan muara sungai pada masa hadapan.

Kata kunci: Muara Sungai Terengganu; pasang surut perbani-purnama; permukaan air; sebatian nitrogen; taburan dan perlakuan

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*Pengarang untuk surat-menyurat; email: miman@umt.edu.my