TINGKAT PENCEMARAN MERKURIPADA LAHAN BEKAS TAMBANG EMAS RAKYAT DI KALIMANTAN BARAT DAN BIOREMEDIASI IN SITU UNTUK PEMULIHANNYA

WINARDI, Ibu Prof. Dra. A. Endang Sutariningsih Soetarto, M.Sc., Ph.D.,

2020 | Disertasi | DOKTOR ILMU LINGKUNGAN

Kegiatan Penambangan Emas Tanpa Ijin (PETI) dilakukan masyarakat secara tradisional di Kalimantan Barat, menyebabkan lahan kritis dan tercemar merkuri. Metode pemulihan lahan yang efektif, sehingga bebas dari cemaran belum ditemukan. Salah satu cara pemulihan lahan adalah bioremediasi mikroba (microbial bioremediation) dengan memanfaatkan aktivitas bakteri indigenous secara in situ. Program pemulihan lahan secara alami sangat diperlukan yang memberikan nilai tambah dengan melibatkan partisipasi masyarakat. Penelitian ini bertujuan: (1). Menganalisis konsentrasi merkuri pada lahan bekas PETI; (2). Meneliti aktivitas bakteri indigenous toleran merkuri sebagai agensia bioremediasi; (3). Meneliti pengaruh stimulasi, musim dan pH terhadap aktivitas populasi bakteri indigenous (4). Mengimplementasi bioremediasi in situ berbasis masyarakat untuk pemulihan lahan. Penelitian ini dilaksanakan di Desa Mandor, Kecamatan Mandor, Kabupaten Landak, Provinsi Kalimantan Barat yang merupakan wilayah pertambangan tradisional. Penelitian ini dilakukan melalui pendekatan eksperimen pada lahan pasca tambang dan dilakukan dalam dua tahap kegiatan, yaitu: tahap penelitian lapangan dan laboratorium; dan tahap implementasi di lahan bekas tambang dengan melibatkan masyarakat secara langsung. Penelitian diawali dengan penelitian lapangan yang meliputi penelitian fisik, kimia dan biologi lahan dan karakteristik masyarakat di sekitar lokasi penelitian. Metode yang digunakan adalah observasi lapangan, berupa: pengamatan dan pencatatan; dokumentasi; kuesioner; dan wawancara. Tahap berikutnya adalah penelitian laboratorium terdiri dari: analisis fisika kimia tanah, potensi mikroba tanah untuk bioremediasi dan factor lingkungan yang mempengaruhi aktivitas bakteri indigenous tanah. Penelitian strategi bioremediasi dilakukan dengan menggunakan tes plot, memanfaatkan aktivitas bakteri indigenous tanah secara in situ dengan stimulasi dan rekayasa factor lingkungan. Strategi bioremediasi pada kondisi optimal dipilih untuk diimplementasi oleh masyarakat. Metoderekaman proses dan wawancara digunakan dalam tahap implementasi. Hasil penelitian menunjukkan bahwa konsentasi merkuri total ketiga lahan bekas tambang dengan lama pembiaran: t>10; 5<t<10; t<5 relatif rendah, masing-masing 83,56 ���µg/kg; 249,79 ���µg/kg; 124,47 ���µg/kg (<300 ���µg/kg) dan tidak dipengaruhi oleh lama pembiaran lahan.Populasi bakteri dari lahan bekas tambang mampu tumbuh dalam media basal dengan penambahan HgCl2 hingga 5 mg/l. Bakteri dari lahan bekas tambang yang lebih lama mampu beradaptasi lebih baik. Konsentrasi merkuri di alam meningkatkan kemampuan bakteri beradaptasi untuk melakukan transformasi merkuri. Musim penghujan terjadi stimulasi aktivitas bakteri indigenous dengan penambahan nutrien, aerasi melalui pembajakan dan pH yang tepat. Kadar air dan pH tanah meningkatkan aktivitas bakteri indigenous untuk menurunkan konsentrasi merkuri selama penelitian. Partisipasi masyarakat di lokasi penelitian dinilai cukup aktif (76%) sehingga memberikan nilai positif dalam pelaksanaan bioremediasi. Partisipasi yang diharapkan, didasari atas pemahaman kesadaran untuk hidup bebas dari pencemaran dan pelestarian lingkungan danbukan didasarkan atas kepentingan pragmatis sekedar meningkatkan pendapatan. Masyarakat Desa Mandor pada dasarnya memerlukan dorongan dan motivasi untuk melakukan kegiatan pemulihan lahan dan pemanfaatannya. Pemulihan lahan bekas tambang emas tradisional harus dijabarkan dalam bentuk peraturan daerah sebagai upaya pengelolaan lingkungan berdasarkan pendekatan teknologi, sosial ekonomi dan kelembagaan.

Illegal Gold Mining (IGM) activities are carried out traditionally by the community in West Kalimantan, Indonesia, and they have been reported as the cause of critical land and mercury contamination. Nevertheless, effective methods of land recovery have not been found. One way to restore contaminated land is by in situ microbial bioremediation that utilizes the activity of indigenous bacteria. A natural land recovery program is urgently needed, and community participation provides added values to this program. This research was designed to (1) analyze the mercury concentrations in abandoned IGM lands, (2) examine the activity of mercury-resistant indigenous bacteria as a bioremediation agent, (3) evaluate the effects of stimulation, season, and pH on the activity of indigenous bacterial populations, and (4) implement community-based in situ bioremediation for land recovery. This research was conducted in Mandor Village, MandorSubdistrict, Landak Regency, West Kalimantan Province, which has been a traditional mining area. It used the duration or age of post-mining land abandonment as an approach and was carried out in two stages, namely (1) field research and laboratory analysis and (2) the implementation phase on abandoned mine land by directly involving the local people. The field research included observing the physical, chemical, and biological properties of the land and the characteristics of the community around the research site. This stage employed observation and recording, documentation, questionnaire, and interview. Meanwhile, the laboratory analysis identified the soil chemical and physical characteristics, the potential of soil microbes as bioremediation agents, and environmental factors that affect the activity of indigenous soil bacteria. Research on in situ bioremediation strategy made use of the activity of indigenous soil bacteria when exposed to various stimulations and engineered environmental factors. Then, the local community was asked to implement a bioremediation strategy that had been proven to produce an optimal result. Process recording and interview methods were employed in the implementation phase. The results showed that the total mercury concentrations found in mine lands abandoned for <5 years, 5-10 years, and >10 years were relatively low (<300 ���µg/kg): 83.56 ���µg/kg, 249.79 ���µg/kg, and 124.47 ���µg/kg, respectively. These figures indicate that the length of mine abandonment does not affect the amount of mercury left in the soil. Soil bacterial isolates from abandoned IGM land grew on basal media enriched with 5 mg/l of HgCl2. Compared to recently abandoned mine lands, bacteria isolated from older mined lands had better adaptability. The presence of mercury in nature increases the adaptability and capacity of bacteria to transform mercury. In the rainy season, the activity of indigenous bacteria can be stimulated by nutrient addition, aeration (plowing), and pH neutralization. Moisture content and soil pH determine the activity of indigenous bacteria in reducing mercury concentrations. Aside from proper stimulation, the successful implementation of bioremediation depends on community participation, which was considered active and positively contributing to land recovery in the study (76%). Participation is expected to be based on a thorough understanding or awareness of living free of pollution and environmental preservation instead of mere pragmatic interests to earn a higher income. The village community needs encouragement and motivation to carry out land recovery and make use of its benefits. Therefore, the recovery of land in abandoned traditional gold mines must be incorporated and defined in regional regulations as part of environmental management based on technological, socio-economic, and institutional approaches.

Kata Kunci : in situ bioremediation, illegal gold mining, mercury, indigenous bacteria, land recovery.