Karakteristik fluks karbon dan kesehatan DAS dari aliran sungai-sungai utama di Jawa

Abstract

Karbon merupakan unsur kunci dari kehidupan. Siklus karbon penting untuk memahami biosfer dan mekanisme dasarnya. Bertambahnya jumlah penduduk dan meningkatnya aktivitas pembangunan telah menyebabkan karbon di atmosfer semakin meningkat. Dalam siklus karbon tersebut, sungai merupakan komponen penting karena berfungsi sebagai pemindah lateral karbon organik dan inorganik dari daratan menuju lautan, baik dalam bentuk terlarut maupun partikulat. Sungai-sungai di Indonesia diperkirakan memasok karbon organik terlarut sekitar 21 TgC/tahun atau 10% dari total pasokan sungai-sungai di dunia (Baum et al., 2007). Kondisi sungai-sungai di Jawa memiliki karakteristik yang lebih kompleks karena jumlah penduduk yang besar, penggunaan lahan yang intensif, berkembangnya industri dan permukiman, pencemaran dan sebagainya akan berpengaruh terhadap karakteristik fluks karbon sungai. Penelitian dilakukan dengan tujuan: a) Mengkaji karakteristik fluks karbon dari sungai-sungai di Jawa; b) Mengidentifikasi pola kecenderungan dan watak hidrologi; dan c) Menemukan indikator kesehatan DAS. Penelitian ini bersifat eksploratif-investigatif yang dilakukan untuk memperoleh fakta-fakta dari fenomena-fenomena yang ada, mencari dan mengungkapkan keteranganketerangan secara faktual, serta membandingkan obyek penelitian dengan lainnya. Penelitian mengenai karakteristik fluks karbon merupakan penelitian dasar untuk menjawab permasalahan lingkungan, khususnya dalam menjelaskan state of the knowledge dari siklus karbon di Jawa.

Carbon derived from land, whether from natural or the result of human production and consumption will partially be dissolved by surface flow into the river and flows into the sea. Forms of carbon in the rivers are organic and inorganic in the form of dissolved and particulate matter. Watershed condition has great influenced on the river carbon fluxes. Carbon is very important as energy source for life in coastal waters and for the process of photosynthesis. There has not been extensive research yet on the relationship between the condition of watershed and carbon. Changes in river flow patterns have significant influence on the carbon cycle, particularly the flux of carbon from rivers. With regards to the above issue, this study aims to: a) assess characteristics of carbon flux from rivers in Java; b) identify trends and patterns in hydrological character; and c) identify level of catchment health as indicator of environmental degradation. This research is both exploratory and investigative to obtain facts of phenomena that exist, locate and disclose information in a factual, and compare with other research objects. The research on carbon flux is a kind of basic research conducted to address environmental problems, particularly in explaining state of knowledge of the carbon cycle that is always developing. Concentration of carbon and the dissolved organic carbon yield of rivers in Java is higher compared with the rivers in the world. The average concentration of dissolved organic carbon in Java about 11.15 mg/l, while the rivers in the world of 5.62 mg/l. This is influenced by a large population and watershed conditions that have degraded. Catchment health index shows most of the watersheds in Java are in critical condition. River which flows into the north of Java is in more critical condition than that into the south of Java. This phenomenon is also reflected in the distribution of carbon flux, where the flux of carbon going to the north of Java greater than that to the south. Some of the factors that cause smaller carbon export to the south of Java are among others: lower carbon concentration, river flow, watershed area, population density, and number of industries. The rivers in Java contributes dissolved organic carbon to the sea about 6.58% of the rivers in Indonesia, or about 0.66% of the rivers in the world. Export of carbon to the north of Java Island is greater than that to the south of Java Island. Based on calculations by the method of partial pressure of CO2 (pCO2), the rivers in Java has less than 4259 μatm. pCO2 of rivers in Java is greater than the rivers in the world, as an example of the Yangtze in China 1125 μatm, the Rhine in Europe 1268 μatm, and Amazon 3067 μatm. While the influence of carbon on the quality of river waters in the Java environment is still very difficult to determine. Up to now there has been unknown quality standard for carbon in the waters in the world. Carbon in the river can not be used as an indicator of the watershed health. To overcome damage to watersheds in Java, it is necessary for an integrated river basin management.