Environmental Engineering Reference
In-Depth Information
Isoproturon (IPU)
Short-Term Effects
Gustavson et al. (
2003
) measured periphyton photosynthesis following exposure
durations of 1 and 24 h, and found no effect concentration (NEC) values of 1 mg/L
and 0.019 mg/L IPU, respectively. IPU was more toxic than the three other herbicides
they tested (i.e., metribuzin, hexazinone, and pendimethalin).
Chronic Effects, PICT Assessment and Recovery Processes
Schmitt-Jansen and Altenburger (
2005a, b, 2008
) performed a series of investigations
using 20 L glass aquaria to evaluate the effects on periphytic communities of a 14- or
28-day exposure to IPU (2.4-312 mg/L). Periphyton chl
a
luorescence was inhibited at
IPU concentrations above 20 mg/L, while algal populations shifted from diatoms to
chlorophytes at concentrations in the range 20-312 mg/L. At the highest test concen-
trations,
Navicula halophila
was predominant in the diatom community (89%), but
microscopy revealed abnormally shaped cells among these organisms. The replacement
of diatom species was associated with an increase in tolerance, as was observed in
short-term inhibition tests on photosynthesis (using pulse-amplitude-modulated (PAM)
luorometry or
14
C-carbonate incorporation). The authors also addressed their dificulty
in comparing their observed effects with SSD predictions, because the database used for
IPU toxicity on algae was very poor (Schmitt-Jansen and Altenburger
2005a
).
In other studies, it was showed that diatom density and composition in periphyton
were impacted by IPU at concentrations ranging from 5 to 30 mg/L; in addition, IPU
treatments seemed to favor facultative heterotroph diatoms, which are able to switch
trophic mode from autotrophy to heterotrophy (Pérès et al.
1996
; Debenest et al.
2009
). However, Laviale et al. (
2010
) observed that light, which can be considered
as a direct physical stressor, slightly modulated the acute toxic effects of IPU on the
photosynthesis of natural periphytic communities.
Knauert et al. (
2009
) also reported an impact of IPU on density and diversity of phy-
toplankton communities that were exposed for 5 weeks to a constant nominal IPU con-
centration of 14 mg/L. The observed effects followed similar patterns to those of diuron
in the same study (see Sect. 2.1.2.1), and were followed by a recovery period as IPU dis-
sipated from the water (
t
1/2
= 35 days). In contrast to the results described above,
Traunspurger et al. (
1996
) did not ind any effects of IPU on phytoplankton cell abun-
dance or community composition at nominal concentrations up to 90 mg/L, following an
8-week exposure. However, it is important to note that real IPU concentrations in the
microcosms were not monitored, and microcosms were not replicated during this study.
Linuron
Chronic Direct Effects
The chronic effects of linuron on phytoplankton and periphtyon have been investi-
gated using microcosms at concentrations ranging from 0.5 mg/L (Van Geest et al.
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