CHAPTER 5
Estuarine Sediments
5.1
Metals
5.1.1
Iron
Lucotte and D' Anglejan [327] compared five different methods for the extraction and
determination of iron hydroxides and / or associated phosphorus in estuarine particulate matter from the St. Lawrence and Eastmain Rivers estuaries. The extraction
reagents examined were citrate-dithionite-bicarbonate, ammonium oxalate-oxalic
acid, hydroxylamine hydrochloride, calcium nitrilotriacetic acid, and acetate-tartrate.
The procedure using the citrate-dithionite bicarbonate extraction reagent was generally more specific and reproducible than the others. This extraction procedure was
included in an extraction sequence which differentiated the exchangeable phosphorus
and iron fraction, the iron hydroxides and associated phosphorus, and the organic
phosphorus and lithogenous iron.
5.1.2
Mercury
Fresnet-Robin and Ottmann [328] studied the distrubition of mercury between water
and sediment in samples taken from the Loire estuary between 1972 and 1975, and
observed a decrease in mercury pollution during this period. The ratio of mercury in
sediment / mercury in water increased with increasing salinity of the estuary water.
Mercury fixes most on suspensions in the surface water, as these suspensions comprise smaller particles.
Bothner et al. [329] have studied mercury loss from contaminated estuarine sediments. A systematic decrease of mercury with an apparent half-life of about 1.3 years
was observed in oxidising sediments sampled. Insitu measurements of the mercury
flux from sediments could not account for this decrease. It is suggested that removal is
associated with sediment particles transport. The decrease was modelled using a
steady-state mixing model. Mercury concentration in anoxic interstitial waters was
126 times higher than that in overlying sea water.
Estuarine Sediments
5.1
Metals
5.1.1
Iron
Lucotte and D' Anglejan [327] compared five different methods for the extraction and
determination of iron hydroxides and / or associated phosphorus in estuarine particulate matter from the St. Lawrence and Eastmain Rivers estuaries. The extraction
reagents examined were citrate-dithionite-bicarbonate, ammonium oxalate-oxalic
acid, hydroxylamine hydrochloride, calcium nitrilotriacetic acid, and acetate-tartrate.
The procedure using the citrate-dithionite bicarbonate extraction reagent was generally more specific and reproducible than the others. This extraction procedure was
included in an extraction sequence which differentiated the exchangeable phosphorus
and iron fraction, the iron hydroxides and associated phosphorus, and the organic
phosphorus and lithogenous iron.
5.1.2
Mercury
Fresnet-Robin and Ottmann [328] studied the distrubition of mercury between water
and sediment in samples taken from the Loire estuary between 1972 and 1975, and
observed a decrease in mercury pollution during this period. The ratio of mercury in
sediment / mercury in water increased with increasing salinity of the estuary water.
Mercury fixes most on suspensions in the surface water, as these suspensions comprise smaller particles.
Bothner et al. [329] have studied mercury loss from contaminated estuarine sediments. A systematic decrease of mercury with an apparent half-life of about 1.3 years
was observed in oxidising sediments sampled. Insitu measurements of the mercury
flux from sediments could not account for this decrease. It is suggested that removal is
associated with sediment particles transport. The decrease was modelled using a
steady-state mixing model. Mercury concentration in anoxic interstitial waters was
126 times higher than that in overlying sea water.