Nutrients accumulation in drainage channel sediments

Abstract

The drainage channel network in Vojvodina, northern part of the Republic of Serbia, in total length of around 20,000 km, transfers excessive (under)ground waters from around 2.15 million ha of lowlands. Channels are mostly in direct connection with the surrounding arable agricultural land and are exposed to different run-off, leaching and/or wind erosion processes. Close to urban areas, some channel sections serve as recipients of unrefined sewage and industrial waste waters. Water flows and velocities, as well as the transportable capacity of fluvial materials (sediments) are relatively low. This, in combination with other natural and anthropogenic impacts, contributes to sediment generation in the drainage channel network. Based on around 100 sediment samples from 46 channels, concentrations of primary nutrients (N, P and K) were elaborated in this study. Detected concentrations of macronutrients in the channel sediments (e.g. N 1-1.2%, P 100-265 and K 100-380 mg 100 g(-1)) exceeded their content in surrounding arable land by a few fold. Also, significantly higher nutrient concentrations (in average by 50%) were detected in downstream (vs. upstream) channel sections. An excessive presence of observed elements in channel sediments, due to interactive processes between water and sediment material, can adversely influence the water quality and life conditions for channel biota and caused other negative environmental impacts such as eutrophication. These results clearly confirm that the processes of nutrient accumulation in channel sediments are greater than those in the surrounding, mostly intensively arable land areas. The erosion of unprotected agricultural areas and sediment transport as the most important pollution pathways from the drainage basin to channel network may be essential factors responsible for detected condition of nutrient accumulation.