Te. Murray, THE CORRELATION BETWEEN IRON SULFIDE PRECIPITATION AND HYPOLIMNETIC PHOSPHORUS ACCUMULATION DURING ONE SUMMER IN A SOFTWATER LAKE, Canadian journal of fisheries and aquatic sciences, 52(6), 1995, pp. 1190-1194
During late summer, 1992, the water immediately overlying the sediment
in the anoxic hypolimnion of Crystal Lake, Conn., was saturated with
ferrous sulfide (FeS). The average solubility product (pK(sp)) at the
bottom of the hypolimnion was 3.25, which is consistent with other lak
e and laboratory studies and is in the range of both amorphous FeS and
mackinawite. The precipitation of iron sulfide removed Fe2+ and HS- f
rom the water column, and acid volatile sulfide (AVS) accumulated in t
he top 6-8 cm of the sediment. Pyrite was formed at deeper depths and
did not increase during the study. The accumulation of AVS in the sedi
ment was correlated with an increased accumulation of phosphorus in th
e water column. The rate of accumulation of phosphorus in the hypolimn
ion was greatest when iron was lost to the sediment as AVS. The statis
tically significant link between iron storage in the sediment and phos
phorus accumulation in the overlying water suggests that reoxidation o
f ferrous iron to ferric (hydr)oxides is decreased, and therefore prec
ipitation of ferric phosphate is limited.