D10: Impact of Contaminants - Hydromod

Integrated Water Resource Management for Important Deep European Lakes and their Catchment Areas
EUROLAKES
D10: Impact of Contaminants
FP5_Contract No.: EVK1-CT1999-00004
Version: 4.0
Date: 25/07/01
File: D10-vers.4.0.doc
Page 49 of 136
the soil atrazine is predominantly metabolised microbial but also abiotically e. g. by sunlight
and hydrolysis [FEDERAL ENVIRONMENT AGENCY, AUSTRIA]. The hydrolysis
is fast in acidic or basic environments and rather slower in a neutral pH range. The average
half-life period is 45 days. In soils with a low part of loam or low content of organic
substances atrazine is moderate to highly volatile [EXTOXNET]. Under moist and
warm conditions, the half-life period of atrazine in the topsoil is about 60 days. In subsurface
soil or in water the half-life period is generally longer [COMFORT and ROETH
1996]. Under dry or cold conditions atrazine can persist more than a year. Because it
does not adsorb strongly at soil particles atrazine has a high potential to contaminate
the ground water despite its moderate water solubility [EXTOXNET]. The biodegradation
in water and ground water is slower because here atrazine and its metabolites are
very persistent [FEDERAL ENVIRONMENT AGENCY, AUSTRIA]. By the feeders the
herbicide attains the epilimnion where it is subject to the different processes of water
mixing. Between April and November (stratified lake) atrazine is spread in the epilimnion
within some days. A continuos elimination takes place by the lake outflow. The
vertical water mixing is significantly slower and transports a small amount into the
metalimnion and the hypolimnion. During the winter circulation between December and
March the residual amount of atrazine is spread in the whole lake [FENT 1998]. He also
points out, that some by-products have also a small herbicide effect. Due to the low vapour
pressure and a small henry-constant the volatility into the atmosphere is negligible.
The relatively high water solubility of atrazine and the small distribution coefficient
causing a relative high mobility from the soil into surface and ground water. Therefore
atrazine sorbs hardly at sediment and soil particles. The microbial degradability is low.
Atrazine is relatively persistent but there is no important bio-accumulation in organisms.
Because the photochemical and biological degradation is also low, the disposition of
atrazine in the lake is caused by the disposition and transport processes.
Concentration in the Environment: During the application period highest values are
measured. In the 1980's atrazine was measured in concentrations of more than 0.1 µg/l
in many drinking water reservoirs. In the period of three weeks 0.5 - 9.1 µg/l and maximum
values of 23 µg/l are measured in American rivers. Here the medium atrazine
concentrations lie between 0.3 - 4.7 µg/l. In small lakes the values are specifically high.
Surface runoff from agricultural fields continue approximately one month after the use
and have values up to 250 µg/l. In May/June up to 0.15 µg/l are measured in the rain in
Switzerland [FENT 1998].
Ecotoxicological Effects: For birds, beneficial animals (e. g. bees) and soil-dwelling
organisms atrazine is extensively harmless. Atrazine does not accumulate itself in the
food chain. The acute toxicity of atrazine for humans is low. Sporadically irritations of
skin, eyes and the respiratory tract are recognised. Human toxicologically it is almost
harmless. It is not safe to say that atrazine has a mutagenic res. teratogenic effect. In
long-term studies an increased rate of breast cancer has been recognised. The EPA
classified atrazine to be a "Possible Human Carcinogen". It is suspected to have an
unwanted estrogene effect [FEDERAL ENVIRONMENT AGENCY, AUSTRIA].
Atrazine represses the photosynthesis and is an environmental chemical with a herbicide
effect. In the water it mainly impairs algae and water plants but between related
groups of organisms high species differences occur [FENT 1998]. For fishes atrazine is