2.3 In Vitro Bioassays Applied to Sediment Matrix in Aquatic
Environment Quality Monitoring
Since biological activity of dissolved phase samples may reflect only an intermittent
contamination of surface waters, in vitro bioassays were also applied to sediment
samples. Indeed, sediments act as a pollution storage tank concentrating many
persistent or pseudo-persistent compounds for long periods (e.g. PAHs, PCBs, sex
steroids, alkylphenols, plasticisers) as shown for French sediments [17–19]. In this
context, the oestrogenic potential was simultaneously measured on sediment and
water samples collected in the three pilot sites of the Seine axis during three
sampling periods in 2011–2012, using the MELN bioassay [20]. The spatial and
temporal oestrogenicity of sediment organic extracts are shown in Fig. 1a, b,
respectively.
The oestrogenicity dose–response curves showed a clear upstream–downstream
gradient for sediments collected during the low-flow period (June 2012) (Fig. 1a),
with EEQ values ranging from 1.95, 0.867 to 0.0005 ng E2-eq/g, for Triel, Bougival
and Marnay, respectively. These EEQ levels were in accordance with those observed
between small good-quality French rivers (Aisne, Vallon du Vivier and Lézarde
Rivers with oestrogenicity at 0.20–0.83 ng E2-eq/g sediment) and poor-quality
rivers (Rhonelle and Réveillon, with oestrogenicity at 1.69 and 6.43 ng E2-eq/g
sediment, respectively) according to French water agencies [18]. Triel-sur-Seine
sediments collected in the low-flow period showed a higher activity (EEQ, 1.95 ng
E2-eq/g in June 2012) than those sampled during other periods (EEQ, approximately
0.3 ng E2-eq/g for September 2011 and December 2012) (Fig. 1b). These spatial
and temporal variations in the oestrogenic potential of Seine River sediment were
in accordance with those evidenced for water samples (Fig. 1). Furthermore, the
sediments showed differences in oestrogenic activity in accordance with their
contamination levels in various hydrophobic and persistent organic pollutants
belonging to ED compound families (PAHs, PCBs, organochlorine pesticidesOCPs, PBDE) [20].
Contrary to the water column, today there are no trigger values for sediment
oestrogenicity regarding the environmental risks for benthic organisms [21]. Over
the two matrices studied, sediment appears, however, as the most suitable for
highlighting the ubiquitous oestrogenicity of the aquatic contamination and the
time–space variations of its biological activity. Compared to intermittently collected
water samples, the sediment extracts are more concentrated (while being noncytotoxic in the MELN bioassay) and integrate long-term contaminations. As a
result, the fold inductions of oestrogenic activity obtained with sediment extracts
(from Â4 to Â30 in comparison to blank samples; Fig. 1) were greater than those
obtained with dissolved phase extracts (from Â3 to Â12), ensuring quantifiable
transcriptional activities in each sediment sample, contrary to water samples.
248
M. Bonnard et al.
Environment Quality Monitoring
Since biological activity of dissolved phase samples may reflect only an intermittent
contamination of surface waters, in vitro bioassays were also applied to sediment
samples. Indeed, sediments act as a pollution storage tank concentrating many
persistent or pseudo-persistent compounds for long periods (e.g. PAHs, PCBs, sex
steroids, alkylphenols, plasticisers) as shown for French sediments [17–19]. In this
context, the oestrogenic potential was simultaneously measured on sediment and
water samples collected in the three pilot sites of the Seine axis during three
sampling periods in 2011–2012, using the MELN bioassay [20]. The spatial and
temporal oestrogenicity of sediment organic extracts are shown in Fig. 1a, b,
respectively.
The oestrogenicity dose–response curves showed a clear upstream–downstream
gradient for sediments collected during the low-flow period (June 2012) (Fig. 1a),
with EEQ values ranging from 1.95, 0.867 to 0.0005 ng E2-eq/g, for Triel, Bougival
and Marnay, respectively. These EEQ levels were in accordance with those observed
between small good-quality French rivers (Aisne, Vallon du Vivier and Lézarde
Rivers with oestrogenicity at 0.20–0.83 ng E2-eq/g sediment) and poor-quality
rivers (Rhonelle and Réveillon, with oestrogenicity at 1.69 and 6.43 ng E2-eq/g
sediment, respectively) according to French water agencies [18]. Triel-sur-Seine
sediments collected in the low-flow period showed a higher activity (EEQ, 1.95 ng
E2-eq/g in June 2012) than those sampled during other periods (EEQ, approximately
0.3 ng E2-eq/g for September 2011 and December 2012) (Fig. 1b). These spatial
and temporal variations in the oestrogenic potential of Seine River sediment were
in accordance with those evidenced for water samples (Fig. 1). Furthermore, the
sediments showed differences in oestrogenic activity in accordance with their
contamination levels in various hydrophobic and persistent organic pollutants
belonging to ED compound families (PAHs, PCBs, organochlorine pesticidesOCPs, PBDE) [20].
Contrary to the water column, today there are no trigger values for sediment
oestrogenicity regarding the environmental risks for benthic organisms [21]. Over
the two matrices studied, sediment appears, however, as the most suitable for
highlighting the ubiquitous oestrogenicity of the aquatic contamination and the
time–space variations of its biological activity. Compared to intermittently collected
water samples, the sediment extracts are more concentrated (while being noncytotoxic in the MELN bioassay) and integrate long-term contaminations. As a
result, the fold inductions of oestrogenic activity obtained with sediment extracts
(from Â4 to Â30 in comparison to blank samples; Fig. 1) were greater than those
obtained with dissolved phase extracts (from Â3 to Â12), ensuring quantifiable
transcriptional activities in each sediment sample, contrary to water samples.
248
M. Bonnard et al.