wAbstract
@We experimentally determined the adsorption characteristics of
natural, freshly precipitated Al(OH)3 for
SO4 and PO4. The fresh
Al precipitate occurred in stream sediment of Jachymov Stream
(Czech Republic). The Al-rich sediment strongly adsorbed added
PO4 prior to acidification experiment; this
sorbed PO4 was released only after substantial
dissolution of the sediment, at pH3.67. sorption of P by Al(OH)3 appears to be an important control on dissolved
PO4 concentration in surface waters, unless
there is a large excess of PO4. Acidification
of the sediment-solution system caused protonation of the sediment
surface, thereby increasing the adsorption capacity for SO4. Maximum SO4 adsorption
occurred at pH 4.2, below which dissolution of the sediment offset
the increasing anion adsorption capacity, and formation of AlSO4+ inhibited the increasing SO4 adsorption capacity. This research demonstrates
that there are important pH thresholds for anion adsorption in
freshwaters below which dissolution of the Al(OH)3
substrate reduces total capacity for anion adsorption. In freshwaters,
with sufficient concentrations of suspended Al(OH)3,
or in Al(OH)3-rich sediment, PO4
mobility will be severely restricted. Suspended Al(OH)3
in acidified surface waters cannot strongly influence SO4 concentrations because of the considerably higher
total SO4 concentrations compared to the
available surface area.
Keywords: Adsorption; Anions; A;l precipitates; Acidification;
Alkalization; Oligotrophyx
1. Introduction
2. Site description, materials, and methods
3. Results
@3.1. Stream water
@3.2. Sediment
@3.3. Experimental acidification and alkalization
@3.4. SO4 adsorption
4. Discussion
@4.1. Inferences from experimental results for processes in
lake sediments
5. Conclusions
Acknowledgments
References