Sediment quality assessment in the delta of rivers Rhine and Meuse based on field observations, bioassays and food chain implications

Abstract

The quality of sediment was assessed in 46 sites in the delta of the rivers Rhine and Meuse (The Netherlands) by means of physical-chemical analysis, field observations on the macrobenthic community structure, accumulation studies and bioassays using Chironomus riparius, Daphnia magna and P hotobacterium phosphoreum. The results of chemical analyses were classified using national criteria for sediment quality. Results of field studies and bioassays were classified using criteria derived from research in reference areas or based on data from literature. Risk assessment was carried out according to the sediment quality triad and by means of multi criteria analysis (MCA). The Triad approach was used to demonstrate causal relations between effects on the macrozoobenthos community structure, effects demonstrated in bioassays and sediment pollution. This was done by making a comparison of sediment contamination levels with toxicity data from literature for the test organisms of the bioassays. Using the MCA method, for each site a numerical value was derived for total environmental risk in the present situation, based on observed effects. In this way, a relative risk ranking of all sites was realized. The MCA values for the present situation were also compared with MCA scores based on estimated risks after remediation in 1995, in order to set priorities for sites where remediation is expected to cause a significant reduction in environmental risk. In most of the 46 sites studied so far, the macrofauna community was poorly developed, judged by a low number of benthic species, low abundances and a high dominance of species regarded as relatively tolerant to chemical pollution. In bioassays high sediment toxicity was demonstrated for 24 sites. Using the sediment quality triad approach, 25 sites were identified as areas where pollution can be held responsible for the effects observed in the field. From a comparison of contaminant concentrations in different types of food with maximum tolerable risk levels, and the application of a bioaccumulation model it was concluded that the sediment pollution also implies high risks for plant-, benthos-or fish-eating birds (secondary poisoning of top predators). In the Nieuwe Merwede highest MCA risk scores were found for shallow parts where highly polluted sediments are found. It is concluded that the sediment quality triad and the MCA provide additional information which can be used to establish priorities for remedial action. Based on an ecotoxicological evaluation of the improved quality of new sediments that will be deposited after removal of the polluted sediments in the Nieuwe Merwede, it is concluded that in this upstream part of the Rhine delta remedial action will be effective.

Tail Moment versus Tail Length—Application of an In Vitro Version of the Comet Assay in Biomonitoring for Genotoxicity in Native Surface Waters Using Primary Hepatocytes and Gill Cells from Zebrafish (Danio rerio)

“…Even though overall pollution parameters are declining in many rivers of Europe and actual contaminant concentrations are below concentrations with acute e!ects (Den Besten et al, 1995;MuK ller et al, 1993;Vargas et al, 1995), there is still an urgent need for biomonitoring, since the number of manmade chemicals released into the environment is still growing. Furthermore, rising drinking water consumption rates in developed countries will require the direct use of rivers as a source for drinking water at increasing rates.…”

Biological and chemical monitoring after pilot remediations in the delta of the rivers Rhine and Meuse

“…Bioassays with D. magna were carried out in sediment pore water according to standard methods for sediment toxicity tests as described by Maas et al (1993) andDen Besten et al (1995). Mortality and reproduction were used as end points.…”

Confounding Factors in Bioassays with Freshwater and Marine Organisms

“…In The Netherlands bioassays are used for assessing ecological risks of waste water, surface water, and groundwater as well as sediments, soils, or dredged material (e.g., Den Besten et al, 1995;Stronkhorst et al, 1996;Tonkes, 1997). Many such samples do not ful"ll the basic ecological demands and will be quali"ed as &&toxic.''…”