The Effects of Land Use on Concentrations of Nutrients and Selected Metals in Bottom Sediments and the Risk Assessment for Rivers of the Warta River Catchment, Poland

Michał Fiedler

doi:10.3390/land10060589

Abstract

Changes in the environment, aiming at agricultural intensification, progressive urbanisation and other forms of anthropopression, may cause an increase in soil erosion and a resulting increase in the pollution inflow to surface water. At the same time, this results in increased nutrient pollution of bottom sediments. In this study, the concentrations of total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC), calcium (Ca), iron (Fe) and potassium (K) were analysed using bottom sediment samples collected at 39 sites located along the entire length of the Warta River and its tributaries. Agricultural use of land adjacent to rivers was found to significantly degrade sediment quality, while anthropogenic land use (as defined by Corine Land Cover classification—CLC), unlike previous studies, reduces the pollution loads in the bottom sediments. Forest use also contributes to the reduction of the pollution load in sediments. It was found that the significance of the relationship between pollutant concentrations and land use depends on the length of the river–land interface. According to the analyses, the level of correlation between the analysed constituents depends on the use of land adjacent to rivers. The impact of agricultural land use has the strongest effect in the 1 km zone and 5 km in the case of anthropogenic land use. The results showed that the variability of total phosphorus TP concentrations is strongly correlated with the variability of iron concentrations. SPI values indicate that the risk to sediment quality is low due to TOC and Fe concentrations. In contrast, the risk of sediment pollution by TN and TP shows greater differentiation. Although the risk is negligible for 40% of the samples, at the same time, for 33% of the samples, a very high risk of pollution with both TN and TP was found.

Highlights

River sediments are an important part of the cycling of materials in the aquatic ecosystem
This study aims to analyse the spatial variability of total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC), Ca, Fe and K concentrations and their interrelationships in bottom sediments of the Warta River and its tributaries
The TOC values measured in 1998–2000 are similar to those measured in bottom sediments of the Oder, which is a receiving body for the water of the Warta River, when they ranged from 0.2% d.m. to

Summary

Introduction

River sediments are an important part of the cycling of materials in the aquatic ecosystem. The understanding of the pollution processes of river bottom sediments is of great importance because it can be an indicator of the ecological health of waters [1]. Sediments can accumulate pollutants and act as a buffer to absorb and release pollutants into the aquatic environment [2] Loads of constituents such as carbon, nitrogen and phosphorus in bottom sediments and their interrelationships enable identification of the sources of organic matter and its transformations. The ratios of these constituents are affected by several environmental factors such as climate [3,4], terrestrial inflows, morphometry and use of adjacent areas [5] or the mineralogical composition of sediments [6]. Biochemical and biological transformations taking place in sediments and at the water–sediment interface [7,8], as well as the hydrodynamic processes of sediment transport in riverbeds [9], are of great importance for concentrations and mutual proportions of constituents that can be found in bottom sediments

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