SEBARAN SPASIAL EKOLOGI NITROGEN DI DANAU TONDANO PROVINSI SULAWESI UTARA

Sofia Wantasen, Ir.,M.Si., Prof. Dr. Sudarmadji, M.Eng.Sc.

2012 | Disertasi | S3 Ilmu Lingkungan

Penelitian ini bertujuan untuk 1). Mengkaji transformasi dari Nitrogen menjadi Nitrat, Nitrit, Ammonia dan konsentrasinya di inlet Danau Tondano, di Danau Tondano dan outlet Danau Tondano. 2). Mengkaji dampak sebaran dan transformasi Nitrogen terhadap lingkungan hidup yaitu kualitas air (lingkungan abiotik) serta flora akuatik (lingkungan biotik). 3). Menggambarkan sebaran spasial Nitrogen total dan transformasinya (Nitrat, Nitrit, Ammonia) di Danau Tondano. Lokasi pengambilan sampel kualitas air dilakukan di Inlet Danau Tondano, di Danau Tondano dan outlet Danau Tondano. Pengambilan titik sampel di inlet Danau Tondano adalah untuk mendapatkan keterwakilan sampel air dari muara sungai, outlet dari saluran irigasi, drainase permukiman yang menjadi inlet Danau Tondano. Jumlah sampel di inlet Danau Tondano adalah 25 sampel, di Danau Tondano 24 sampel dan di outlet danau adalah 5 sampel, sehingga total sampel di Danau Tondano adalah 29 sampel. Waktu pengambilan sampel adalah tanggal 10 November 2008 sampai dengan 19 Pebruari 2009, dengan kondisi cuaca adalah musim hujan. Pengambilan sampel kualitas air dilakukan dengan menggunakan metode composite sampling, kecerahan air danau dengan Metode Cakram Seichi Disk dan pengambilan sampel sosial ekonomi dan budaya sebanyak 30 responden, dilakukan dengan menggunakan metode survey purposive sampling. Variabel penelitian adalah nitrat, nitrit, ammonia, pH air, suhu, DO, kekeruhan, kecerahan, serta Klorofil-a sebagai parameter biotik. Metode pengambilan sampel air Danau Tondano mengacu ( APHA, 2005). Data yang diperoleh dalam penelitian ini, dianalisis menggunakan empat cara analisis. Cara yang pertama adalah analisis laboratorium, ditujukan untuk mengetahui sifat fisik dan kimia sampel air di inlet Danau Tondano, Danau Tondano dan di outlet Danau Tondano, kedua menggunakan metode Keseimbangan Massa Nitrogen (Nitrogen Mass Balance). Ketiga adalah analisis grafik dan statistik, dan cara keempat adalah cara analisis spasial dan kelingkungan. Hasil penelitian menunjukkan bahwa konsentrasi Nitrogen (Nitrat, Nitrit, Ammonia di inlet Danau Tondano (input) sangat tinggi sedangkan keluaran/output rendah. Hal ini menunjukkan bahwa sebagian besar nutrien tertinggal di dalam danau, menyebabkan terjadinya eutrofikasi Danau Tondano. Status trofik Danau Tondano secara absolut adalah pada taraf eutrof bahkan sudah mengarah ke Hipereutrof. Nitrogen mengalami transformasi menjadi Nitrat, Nitrit, Ammonia di inlet Danau Tondano dan di Danau Tondano. Transformasi Nitrogen di inlet Danau Tondano didominasi oleh NO3, dan di permukaan Danau Tondano didominasi oleh NH3, di perairan Danau Tondano pada kedalaman 5 (lima) meter didominasi oleh NO3 dan Transformasi Nitrogen di kedalaman 10 meter didominasi oleh NH3, diikuti oleh NO3, NO2. Sebaran spasial Nitrogen total terdapat dalam 10 kelas; Sebaran Nitrat, Nitrit, Ammonia di permukaan, kedalaman 5 m dan kedalaman 10 m adalah 9 kelas.

The Purposes of this study were 1) to study the transformation of Nitrogen into Nitrate, Nitrite, Ammonia and their concentration in inlet, in-lake and outlet of Tondano Lake. 2). To assess the Nitrogen distribution and transformation impacts on abiotic environments (water quality degradation) as well as biotic environments (aquatic plants). 3). To describe the spatial distribution of total nitrogen and its transformation (Nitrate, Nitrite, Ammonia) in Tondano Lake. Location of water quality sample were at the inlet of the lake, in the lake and the outlet of the Lake Tondano. Water quality sample was taken at the inlet of the lake in order to get representation of condition of the rivers, irrigation channel, and drainage housing which flow to the Lake Tondano. The number of samples at the inlet of the Lake Tondano was 25 samples. Total samples from the lake were 29 samples, it was 24 samples from the lake and from the outlet of the lake was five samples. Sampling time from 10 November to 19 Pebruary 2009, rainy season. Water quality sampling done by using composite sampling, lake water brightness with a Disk Seichi Method, and socioeconomic and culture survey carried out by using purposive sampling method. Research variable were Nitrate, Nitrite, Ammonia, pH, water, temperature, DO, turbidity, brightness, and Chlorophyll-a as a biotic parameters. Method of water sampling refered to APHA (2005). Data obtained in this study were analyzed using four-way analysis. The first way was the analysis of laboratory, aimed to determine the physical and chemical properties of water samples at the inlet of the Lake Tondano, Tondano Lake and at the outlet of the Lake Tondano, the second way Nitrogen Mass Balance method. The third way was the statistical analysis using graphs and calculation, and the fourth way was Spatio Ecology Analysis. Results showed that the concentration of nitrogen (Nitrate, Nitrite, Ammonia) at the inlet of the Lake Tondano (input) was very high, while the output was low. This showed that the majority of nutrients left in the lake, causing eutrophication of Lake Tondano. The trophic level of Lake Tondano was Eutrof even lead to hipereutrof. Nitrogen was transformed into nitrate, nitrite, ammonia in inlet, in-lake, and outlet of Tondano Lake. Transformed Nitrogen in inlet of the Lake Tondano was dominated by nitrate. In the lake at the surface, transformed nitrogen was dominated by NH3, while at a depth of five meters was dominated by NO3. Transformation of nitrogen at a depth of 10 meters was dominated by NH3, followed by NO3, NO2. Spatial distribution of total nitrogen could be grouped into 10 class; spatial distribution of Nitrate, Nitrite, Ammonia at the surface, at a depth of 5 m and a depth 10 m could be grouped into nine class.

Kata Kunci : Sebaran Spasial Ekologi, Nitrogen, Danau Tondano.