PERANAN HUTAN MANGROVE SEBAGAI BIOFILTER DALAM PENGENDALIAN POLUTAN TIMBAL (Pb) DAN TEMBAGA (Cu) DI KAWASAN REHABILITASI MANGROVE CILACAP, JAWA TENGAH

GISKA PARWA M, Ni Putu Diana Mahayani, S.Hut., M.For.

2013 | Skripsi | KONSERV. SUMBER DAYA HUTAN

Kilang Minyak Cilacap yang menghasilkan limbah logam berat seperti Pb dan Cu terletak di seberang hutan mangrove di tepi Sungai Donan. Tujuan dari penelitian ini adalah (1) untuk mengetahui kualitas fisis dan kimiawi habitat perairan mangrove, kerapatan absolut vegetasi mangrove, (2) untuk mengetahui status mutu air dan status kondisi mangrove berdasarkan nilai kerapatan vegetasi mangrove, (3) untuk mengetahui peranan hutan mangrove sebagai biofilter dalam pengendalian polutan Pb dan Cu di kawasan rehabilitasi mangrove di tepi Sungai Donan, Cilacap. Lokasi penelitian terbagi menjadi empat zona pengamatan yaitu, zona kontrol (3 km dari sumber polutan), zona dalam (di sumber pencemar), zona tengah (satu km dari sumber pencemar), dan zona luar (muara). Pada tiap zona dibuat empat plot pemantauan kualitas fisis dan kimiawi perairan, kerapatan absolut vegetasi mangrove. Data yang diperoleh dianalisis dengan indeks pencemaran, kriteria baku kerusakan mangrove, analisis regresi untuk mengetahui pengaruh kerapatan absolut vegetasi mangrove terhadap konsentrasi polutan Pb dan Cu dalam air, substrat, daun, serta akar. Untuk mengetahui peranan hutan mangrove sebagai biofilter, digunakan analisis sidik ragam. Hasil penelitian ini menunjukkan bahwa rata-rata suhu perairan, salinitas, pH air, serta konsentrasi polutan Pb dan Cu dalam substrat hutan mangrove di tepi Sungai Donan masih dalam kisaran baku mutu yang diperbolehkan. Akan tetapi, rata-rata kandungan oksigen terlarut serta konsentrasi polutan Pb dan Cu dalam air telah melampaui baku mutu yang diperbolehkan. Status mutu air kawasan perairan mangrove di tepi Sungai Donan adalah tercemar ringan, padahal hutan mangrove di tepi Sungai Donan memiliki status kerapatan dengan kondisi baik sangat padat. Walapun konsentrasi polutan Pb dan Cu dalam air tidak berbeda signifikan, tetapi konsentrasi logam berat tersebut berkurang dari zona dalam hingga luaran, terutama konsentrasi logam berat Pb dalam substrat yang berkurang secara signifikan. Peranan hutan mangrove sebagai biofilter juga dibuktikan dengan terkandungnya logam berat Pb dan Cu dalam organ tumbuhan akar dan daun Rhizophora apiculata.

Cilacap Oil Refinery that produces heavy metal waste containing Pb and Cu is located across to the mangrove forests along Donan river banks. This study aimed to (1) to identify the physical and chemical quality of the mangrove aquatic habitat and the absolute density of mangrove vegetation, (2) to identify water quality status and to categorize the mangrove condition based on its vegetation density, (3) to recognize the role of mangrove forest as biofilters in controlling water pollutants of Pb and Cu that is predicted containing the mangrove rehabilitation areas along Donan River banks, Cilacap. The research site was grouped into four areas, which are control zone (three km before the point source), Inner Zone (at the point source), middle zone (one km point source), and outer zone (estuarine). Four plots were established to measure physical and chemical water quality and mangrove tree density. Data colected were then analyzed using Pollutan index and standard criteria of mangrove damages, regression model to identify the relationship between mangrove tree density and Pb and Cu concentration in the water, substrate, roots, and leaves of Rhizophora apiculata. Analysis of variance were applied among four zones to find out the role of mangrove as biofilters for those heavy metals. The results showed that the average of water temperature, salinity, pH, and the concentrations of Pb and Cu pollutants in the mangrove substrates were below the allowed water quality standards. However, the average of dissolved oxygen and the water concentrations of Pb and Cu have exceeded the allowed water quality standards. The water quality status was lightly-polluted, although the tree density was categorized as good conditions and highly-dense. Even though Pb and Cu concentration in the water was not significantly different, however, the concentrations of those heavy metals from the point source to the estuarine zones decreased, especially the concentration of Pb in the substrat highly reduced. Finally, the role of mangrove forest as biofilter was also recognized from the concentration of Pb and Cu detected in the roots and leaves of Rhizophora apiculata.

Kata Kunci : Rhizophora apiculata, Sungai Donan, Pb, Cu, biofilter