116
T. Gremm et al.
3.2 Toxicity Tests
To assess the toxicity of the water samples from the mouth region, a luminescent
bacteria test and a seed growth test was used. The seed test (ST) proved to be
more sensitive compared to the luminescent bacteria test (LBT). With the LBT, no
significant toxicological effects were determined in the tested water samples. In
contrast, all water samples from the Moskva River and from the Oka River
downstream of the confluence area showed a significant inhibition of the growth
of Lepidium sativum (Fig. 8). The high sensitivity of L. sativum to different
pollutants was also reported by Bendt (1987) and Helma et al. (1998). A
correlation of the root length with different water chemical parameters showed a
significant correlation between the inhibition effect and the concentrations of
nitrate, phosphate, chloride, and AOX. Bendt (1987) studied the effect of nitrate,
sulfate, and chloride on the growth of L. sativum and found no inhibition effect up
to a concentration of 1000 mgri. The concentrations of these anions in the tested
water samples were much lower compared to the concentrations tested by Bendt
(1987) and could therefore not be responsible for the toxicological effects. The
same author also determined the no-effect concentrations (NOEC) for heavy
metals. The NOEC ranged between 40 f!gr i for Cu and 500 f!gr i for Zn. Copper
showed the highest toxicity. The concentrations of Cu as well as the other heavy
metals in the Moskva River and Oka River were generally lower than their NOEC
concentrations. The results of the toxicity studies indicate that the toxic effects on
L. sativum are caused by the AOX substances and probably the P AH present in the
water samples. However, in this context it also has to be considered that
synergetic effects can significantly increase the toxicity of a pollutant. Although
this topic needs to be studied further, the results of the seed growth test show that
there are negative ecological effects connected with the critical water quality in
the Moskva River and deteriorated water quality in the Oka River.
T. Gremm et al.
3.2 Toxicity Tests
To assess the toxicity of the water samples from the mouth region, a luminescent
bacteria test and a seed growth test was used. The seed test (ST) proved to be
more sensitive compared to the luminescent bacteria test (LBT). With the LBT, no
significant toxicological effects were determined in the tested water samples. In
contrast, all water samples from the Moskva River and from the Oka River
downstream of the confluence area showed a significant inhibition of the growth
of Lepidium sativum (Fig. 8). The high sensitivity of L. sativum to different
pollutants was also reported by Bendt (1987) and Helma et al. (1998). A
correlation of the root length with different water chemical parameters showed a
significant correlation between the inhibition effect and the concentrations of
nitrate, phosphate, chloride, and AOX. Bendt (1987) studied the effect of nitrate,
sulfate, and chloride on the growth of L. sativum and found no inhibition effect up
to a concentration of 1000 mgri. The concentrations of these anions in the tested
water samples were much lower compared to the concentrations tested by Bendt
(1987) and could therefore not be responsible for the toxicological effects. The
same author also determined the no-effect concentrations (NOEC) for heavy
metals. The NOEC ranged between 40 f!gr i for Cu and 500 f!gr i for Zn. Copper
showed the highest toxicity. The concentrations of Cu as well as the other heavy
metals in the Moskva River and Oka River were generally lower than their NOEC
concentrations. The results of the toxicity studies indicate that the toxic effects on
L. sativum are caused by the AOX substances and probably the P AH present in the
water samples. However, in this context it also has to be considered that
synergetic effects can significantly increase the toxicity of a pollutant. Although
this topic needs to be studied further, the results of the seed growth test show that
there are negative ecological effects connected with the critical water quality in
the Moskva River and deteriorated water quality in the Oka River.