SOURCE IDENTIFICATION AND IMPACT OF MULTIPLE
STRESSORS ON SURFACE WATER QUALITY AT THE
CATCHMENT-SCALE
Post doc Ursula .S. McKnight1
PhD studerende Jes J. Rasmussen2
Professor Poul L. Bjerg1
PhD studerende Nanna .I. Thomsen1
PhD studerende Maria Loinaz1
Cand. scient. Mikael Emil Olsson1
Professor Brian Kronvang2
Lektor Philip J. Binning1
1
2
DTU Miljø, Danmarks Tekniske Universitet
Danmarks Miljøundersøgelser, Århus Universitet
RESUME
Der er gennemført en større undersøgelser af forskellige stressfaktorers påvirkning af den
kemiske og økologiske vandkvalitet i et grundvandsopland ved Hove på Sjælland. Der er
udvalgt vandløbslokaliteter i området, som er undersøgt for en lang række fysiske, kemiske
og økologiske parametre og forhold. Lokaliteterne er prøvetaget i foråret 2010 og i august
2010. De 13 lokaliteter repræsenterer så vidt muligt 1. ordens vandløb, som fortrinsvis
formodes at være påvirket af en af følgende stressfaktorer: forurenede grunde, landbrugsdrift
og diffus urban påvirkning. Der er også en markant vandindvinding og et enkelt
spildevandsrensningsanlæg i området. Vandvindingen sker primært omkring 3. og 4. ordens
vandløb, så der er set bort fra denne stressfaktor i undersøgelsen. De foreløbige resultater
viser, at der er et tydeligt aftryk fra pesticider på vandløbene i Hove oplande. Der er fundet
pesticider, som direkte kan relateres til marksprøjtning i foråret 2010. Der er ved alle
målinger også fundet gamle pesticider, der kan relateres til påvirkning fra grundvand
(punktkilder eller diffuse kilder). Resultaterne fra undersøgelsen er ved at blive evalueret, og
de foreløbige konklusioner vil blive præsenteret på ATV’s Vingsted møde 2011.
INTRODUCTION
Micropollutants and nutrients from a range of sources are well-known stressors that may
cause a decline in groundwater and surface water quality and biodiversity of freshwater ecosystems (McKnight et al., 2010; Bacey and Spurlock, 2007). Effectively reducing cumulative
impacts on groundwater-dependent aquatic ecosystems clearly requires an understanding of
the different pressures that can be present in a particular catchment.
Ecosystem stressors include physical habitat degradation (e.g. channelization), diffuse
sources (pesticide and nutrient applications on agricultural fields), sewage effluents (micropollutants, organic matter, nutrients) including urban discharges from scattered settlements, contaminated sites (pesticides, chlorinated solvents, gasoline compounds and other
pollutants) and water abstraction.
The purpose of this study was twofold: to (1) identify the main stressors at catchment scale,
and if possible discriminate sources from each other; (2) evaluate the chemical impact and
stream ecosystem status represented by benthic macroinvertebrates.
MATERIAL AND METHODS
The study was conducted on first-order stream reaches within the Hove study catchment
near Copenhagen, Denmark (Figure 1). For the purpose of this study, sewage effluents and
water abstraction could be disregarded since only one sewage treatment plant was present
and the water abstraction areas were located on third and fourth-order stream segments, respectively.
Ecological indicators investigated were benthic macroinvertebrates. Stressor parameters investigated from early spring until late summer include presence of pesticides from storm
events (diffuse run-off), assessment of physical stream properties (habitat survey), general
water chemistry, as well as presence of xenobiotics originating from both diffuse and point
sources. The water sampling was conducted by grab sampling and storm flow samplers
(Figure 2).
Figure 1 Left: Hove catchment on Sealand. Right: A sub area (within the green line) where the investigation was conducted. The investigations were made primarily on 1. order streams green. The study
area is characterised by a significant groundwater abstraction by local water works and well fields
managed by Copenhagen Energy.
A total of 13 sampling locations were broken into three categories of sites: 6 contaminated
sites, 4 urban discharges and 3 diffuse agricultural sites. Additionally, 6 undisturbed firstorder streams were included as reference conditions. GIS tools are applied for source identification and multivariate statistics approach is applied to rank-order the impact of each examined stressor on benthic macroinvertebrates.
Figure 2 Photos from field sampling and characterisation of physical, chemical and ecological parameters and properties of streams in the Hove Catchment.
RESULTS
The results for diffuse run-off after a storm event (sampling occurred 4 times between midmay and mid-august) revealed that the sampling campaign successfully captured the early
spring application of metamitron, a pesticide sprayed typically only during early spring (Figure 3, May 16).
Figure 3 Sum of pesticides at two sampling dates in 2010. The May, 16 sampling represents sampling
by stormwater samplers (Figure 2) immediately after a rain event. The sampling in August, 10 represents grab samples at low flow in streams, where base flow is expected to dominate. Metamitron is
only found in the spring sampling.
2-methyl-4-chlorophenoxyacetic acid (MCPA), trichloroacetic acid, 2,6-dichlorbenzamide
(BAM) and 4,6-Dinitro-o-cresol (DNOC) were found to dominate the pesticide results for all
four sampling campaigns (Figure 3. These pesticides are not related to immediate spraying,
but originate from groundwater inflow to the streams. In at least two cases, the presence of
xenobiotics/pesticides in the stream could be linked to the contaminated sites.
FINAL REMARKS
The assessment of the large amount of data collected during this comprehensive field campaign is on-going. Preliminary conclusions on the stressors impact on the stream water quality will be presented at the ATV Vingsted meeting 2011.
ACKNOWLEDGEMENT
We wish to acknowledge the help from Capital Region of Denmark, Environmental Centre,
Roskilde, the municipalities and site owners in the Hove Catchment. Technicians from the
Technical University of Denmark and National Research Institution, Århus University contributed to a significant part of the field and laboratory work. The project was conducted as part
of the Risk point, which is supported by the Technical University of Denmark and Danish
Council for Strategic Research.
REFERENCES
McKnight, U.S., Funder, S.G., Rasmussen, J.J., Finkel, M., Binning, P.J., Bjerg, P.L. (2010):
An integrated model for assessing the risk of TCE groundwater contamination to human receptors and surface water ecosystems. Ecological Engineering, 36, 1126-1137.
Bacey, J., Spurlock, F. (2007): Biological Assessment of Urban and Agricultural Streams in
the California Central Valley. Environ Monit Assess, 130, 483–493.