Sedimentary Organic Matter and Phosphate along the Kapuas River (West Kalimantan, Indonesia)

Pei Sun Loh,Jough-Tai Wang,Chen-Tung Arthur Chen,Shu-Lun Wang,Jiann-Yuh Lou,Bing-Jye Wang,Gusti Z Anshari

doi:10.1155/2016/6874234

Abstract

This study assessed the sedimentary organic matter (OM) and phosphate along the world’s longest river on an island: the Kapuas River in West Kalimantan, Indonesia. The surface sediment was tested using the loss-on-ignition experiment to determine the % labile OM, % refractory OM, and % total OM and the Rp values (the ratio of refractory to total OM). The C/N ratios and the inorganic phosphate (IP), organic phosphate (OP), and total phosphate (TP) levels were also determined. The combination of high Rp values and low C/N ratios along the upper river indicated the possible presence of relatively degraded material; the low Rp values and high C/N ratios downstream were indicative of a fresher terrestrial signal. Sedimentary P levels were the highest along the densely populated areas downstream from the Kapuas River; the second highest along the midstream river, which is surrounded by oil palm plantations; and the lowest along the upper river, which is surrounded by forest. Higher levels of OM, IP, OP, and TP downstream along the Kapuas River indicated the presence of anthropogenic sources of OM and P.

Highlights

Rivers are major regulators of global climate change due to their role as contributors to atmospheric CO2 emissions [1, 2]
This study presents a profile of organic matter (OM) and P along a Southeast Asian tropical river for the purpose of further understanding the dynamics of the river
total phosphate (TP) showed a better correlation with inorganic phosphate (IP) (r > 0.9) and a poorer correlation with organic phosphate (OP) (r = 0.6 to 0.8), and IP showed good correlation with labile OM (p < 0.05)

Summary

Introduction

Rivers are major regulators of global climate change due to their role as contributors to atmospheric CO2 emissions [1, 2]. One of the consequences of increasing river runoff is increased nutrient discharge to coastal zones This has a significant impact, in areas that were already receiving a high input of nutrients from their surroundings [7]. In Indonesia, where there are few reservoirs, rivers still deliver a considerable amount of sediment to coastal zones [8] This has major consequences because Southeast Asia contains a vast area of peatland [9, 10], and peat soils tend to leach dissolved organic carbon (DOC) into rivers in quantities several orders of magnitude higher than nonpeat soils do. Tropical rivers are major sources of DOC to the oceans [11,12,13]; this leaching is exacerbated by global climate change because increased temperatures [14] and precipitation [15] have resulted in the increased export of DOC from peat soils into rivers and coastal zones.

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Discussion

Conclusion