The effect of weathering in the Buyukmelen River basin on the geochemistry of suspended and bed sediments and the hyrogeochemical characteristics of river water, Duzce, Turkey

摘要

The Buyukmelen River is expected to be a water source that can supply the drinking water needs of Istanbul until 2040. The drinking and utility water needs of Istanbul are to transport water from the Buyukmelen River to Istanbul via pipeline and pump it into the Alibeykoy and Omerli reservoirs when their water levels drop. The Buyukmelen River is located in the province of Duzce in 170 km east of Istanbul and its water basin is approximately 2250 km2. The Buyukmelen River flows muddy in the rainy season and into the Black Sea.rnThe chemical compositions of natural waters alter due to interaction with geological formations, physical and chemical weathering of various rocks and the effects of mining and agricultural production. A research was conducted at the Buyukmelen River basin to determine the effects of hydrological processes. Therefore, the samples of rocks, soil, stream water, suspended and bed sediment were collected from the Buyukmelen River basin. Geochemical and water chemistry analyses of samples were performed at ALS Chemex laboratories, Canada.rnThe bed sediments contain quartz, calcite, plagioclase, amphibole and clay minerals. The clay minerals in the suspended and bed sediment samples are kaolinite, smectite and illite.rnThe water samples collected from the Aksu, Kucukmelen, Asarsu and Ugursuyu streams and the Buyukmelen River in winter (December 2005) and summer (June 2006) periods are rich in Ca and HCO_3 ions. The ions most abundant in rainfall sample are HCO_3 and Na. The ion compositions of surface waters have increased due to the weathering of limestone, agglomerate and volcanic sandstones, light acidic rainfall, semi-arid Black Sea climate in the Buyukmelen basin. The suspended sediment amount of the Buyukmelen River in the rainy season (December 2005) is 174 mg/l.rnAccording to the water contamination regulation of Turkey, the Buyukmelen Rivers belongs to quality class 4 based on Al ion and to quality class 3 based on Fe ion in winter period, and to quality class 2 based on Mn concentration in summer period.rnChemical index of alteration (CIA) indices observed in the suspended and bed sediments (average of 55) suggest that their source area underwent moderate degrees of chemical weathering processes. According to Upper Continental Crust (UCC) values, the suspended sediment was rich in elements such as Fe_2O_3, CaO, MgO, MnO, TiO_2, P_2O_5, V, Cr, Co, Cu, Zn, As, Cd, Sb, Hg and Pb. The element concentrations of the suspended sediments were related to size fractionation, mainly of clay content. The mentioned enrichment was contributed by agglomerate, basalt, volcanic sandstone and graywacke from rocks in the study area. Source of ions such as Al, Fe, Mn, Ba, Cr, Co, Cu, Ni, Ti and Hg and major in the Buyukmelen River is interaction with rocks such as the agglomerate, basalt, andesite, volcanic sandstone and graywacke.rnAs suggested by Singh et al. (2005), before weathering of some rocks in the Buyukmelen River basin, it was determined that they were graywacke and literanite based on the geochemistry of the suspended and bed sediments.