The effect of pH, dissolved humic substances, and ionic composition on the transfer of iron and phosphate to particulate size fractions in epilimnetic lake water

Abstract

Transformations of dissolved iron and phosphate to particulate material (>0.2 µm) were investigated by adding 55FeCl3 and 32PO43 to pH adjusted epilimnetic lake water samples of contrasting ionic strengths and dissolved humic substances (DHS) concentrations. The distributions of these tracers between particulate size fractions in samples without appreciable DHS after 24 h of dark incubation varied markedly over the pH range 4–8. The effect of pH on the movement of 55Fe and 32P to particulate size fractions in clear‐water samples depended on the ionic strength. Over the same pH range, the presence of DHS suppressed the movement of 55Fe and 32P to particulate size fractions. There was little difference between low and high ionic strength DHS‐rich samples. The capability of DHS to maintain added 55Fe and 32P in solution (<0.2 µm) was confirmed by simultaneous measurements of precipitation losses.

Analytical electron microscopy as a tool for accessing colloid formation process in natural waters

“…Although they present a high heterogeneity, they have properties in common: their propensity to aggregate (Ghosh & Schnitzer, 1980; Leppard et al ., 1986); and their complexation properties towards cations (Stumm & Morgan, 1996). Amongst others, they are known to stabilize iron cations (HA‐Fe 2+ , HA‐Fe 3+ ) in solution (Luther et al ., 1992; Shaw, 1994). In our study, analytical electron microscopy shows that humic substances also act as nucleation sites for the formation of iron oxy(hydr)oxide.…”

Phosphorus and nitrogen allocation in Allium ursinum on an alluvial floodplain (Eastern France). Is there an effect of flooding history?

“…So, in flooded forests, the control of nutrient bioavailability is rather complex. The water saturation of soils causes a decrease of redox potential that favours the P bioavailability (Fardeau and Dorioz 2000;Patrick et al 1985;Shaw 1994), but leads to the removal of nitrate nitrogen by denitrification (Haycock and Pinay 1993;Lowrance et al 1984;Lowrance et al 1995;Pinay et al 1993).…”

Treatment of humic acids with ferric, aluminum, and chromium ions in water

“…Humic acids are the mixture of polyelectrolytes covering a wide range of molecular weight and containing carboxyl and hydroxyl functional groups [5,6]. They bind many inorganic ions such as aluminum [7,8] and iron [9]. Investigation of copper ion adsorption on biowaste containing humic acids showed [10,11] that the concentration of copper ions bound by humic acid decreases when the pH of the mixture increases.…”