Piet Seuntjens

Research on the Spatial Variability of Three Sediment Types in Flanders

Sediments have a natural heterogeneity that is seldom considered in sampling strategies. All physical, chemical and biological characteristics can have an unsuspectedly great variability within a few centimeters of distance (Baudo, 1990). One sediment sample will reveal the sediment characteristics at the sample site, and from this it is possible to make predictions about the situation near the site (Hankanson, 1992). To characterize sediment quality in running waters, ussualy mixed samples are taken to describe the quality of a sampling zone. But the question remains how many sampling units are necessary to make a representative mixed sample? A second problem remains the distance between the different sampling zones.

Model-based Scenario Analysis of the Impact of Remediation Measures on Metal Leaching from Soils Contaminated by Historic Smelter Emissions

A spatially distributed model for leaching of Cd from the unsaturated zone was developed for the Belgian-Dutch transnational Kempen region. The model uses as input land-use maps, atmospheric deposition data, and soil data and is part of a larger regional model that simulates transport of Cd in soil, groundwater, and surface water. A new method for deriving deposition from multiple sites was validated using soil data in different wind directions. Leaching was calculated for the period 1890 to 2010 using a reconstruction of metal loads in the region. The model was able to reproduce spatial patterns of concentrations in soil and groundwater and predicted the concentration in shallow groundwater adequately well for the purpose of evaluating management options. For 42% of the data points, measurements and calculations were within the same concentration class. The model was used for forecasting under a reference scenario, an autonomous development scenario including climate change, and a scenario with implementation of remediation measures. The impact of autonomous development (under the most extreme scenario of climatic change) amounted to an increase of 10% in cumulative Cd flux after 100 yr as compared with the reference scenario. The impact of remediation measures was mainly local and is less pronounced (i.e., only 3% change in cumulative flux at the regional scale). The integrated model served as a tool to assist in developing management strategies and prioritization of remediation of the wide-spread heavy metal contamination in the region.

Spatial variability in characteristics and trace metal levels in sediments from watercourses

Assessing sediment quality requires sampling designs which address variability. Often however, only one sample or composited sample is collected at a sample site. Existing studies on sediment variability or sampling strategies primarily concern lake or marine sediments. Two rivers and one canal were sampled to assess sediment variability. Further, it was determined if sediment contamination in running water could be predicted by using visual criteria and/or knowledge of the presence of depositional and erosion areas. Metal concentrations and sediment characteristics were measured in different visually distinct areas of the river. At all sample sites the coefficient of variance was relatively high for most sediment characteristics (1.4‐ > 100%) and metal levels (15.3–63.6%). In one river the majority of sediment characteristics variation was between two sediment types and detected by visually distinct differences. Significant differences in cadmium and zinc concentrations were also detected. Contrary to wh...

Development of an Integrated Contaminated Sediments Assessment Approach in Flanders

The pollution of surface waters in Flanders has led to the accumulation of a variety of toxic chemicals in the sediments and to an overall deterioration of sediment and surface water quality. In addition, toxic chemicals can bioaccumulate in the biota, transferring toxicity up the food chain. This knowledge caused the Flemish government to undertake a large integrated research programme concerning contaminated sediments. The aim of the project is to develop a methodology to characterise and classify contaminated sediments in Flemish surface waters. In total six university laboratories and three scientific institute laboratories are involved. The assessment method uses a combination of chemical and biological testing.