Sorption of Napropamide on Clay and Soil in the Presence of Dissolved Organic Matter

Abstract

Dissolved organic matter (DOM) can affect the distribution of solutes between solution and sorbed phases and the availability and environmental fate of the solutes. Batch sorption isotherm techniques were used to evaluate solute-solute and solute-sorbent interactions that control the effects of DOM on the sorption of a nonionic, moderately polar organic solute by solid sorbents. The sorption of napropamide (2-(a-naphthoxy-7V,A'-diethyl propionamide) by NaS Cu 2 *-, and Al^-montmorillonite decreased when dissolved humic acid derived from peat (peat-DHA) was present in the slurry. For Na-montmorillonite, the effect of DOM on sorption was reduced when a dialysis membrane prevented contact between the DOM and the clay. This suggests that competition for sorption sites on the clay between DOM and the pesticide contributed to decreased napropamide sorption. The extent of the DOM effect was also dependent on the concentration and the source of DOM added. In contrast to the montmorillonite system, the effect of DOM on napropamide sorption by soil was observed only when the dialysis membrane was present or when the dissolution of native organic matter from the sorbate surface itself was enhanced by increasing the pH of the slurry system. These results demonstrate that the effect of DOM on the sorption of nonionic pesticides by soils and sediments can be a function of the association of DOM with pesticides in the solution phase, interactive forces of both DOM and the pesticide with the sorbent surface and the nature of the sorbent surface.

Impact of exotic and inherent dissolved organic matter on sorption of phenanthrene by soils

“…The association of DOM with NOCs such as nonionic pesticides in solution phase is well documented, and has been proposed as an important process that results in solubility enhancement and reduced the sorption of these compounds by soil sorbents [13,14,17,24,25]. There is also much evidence of the interaction of DOM with PAHs in aqueous solution.…”

“…Some studies revealed that the presence of DOM promoted sorption of NOCs such as nonionic pesticides [21,24]. By contrast, in other cases the sorption of NOCs was obviously inhibited in the presence of DOM [4,5,17,25]. Cox et al [18] reported that DOM reduced sorption of herbicide due to DOM-herbicide interactions and/or competition for sorption sites on soil particles.…”

Effect of liquid sewage sludge addition on atrazine sorption and desorption by soil

“…This can be explained by interactions between the soil and the organic matter of LSS that could result in some blockage of sorption sites for atrazine on both soil and LSS. Moreover, the presence of DOM fi'om LSS (LSSDOM) could also reduce atrazine sorption on soil through stable interactions in solution or by processes taking place at the soil/solution interface, such as competition for sorption sites on the soil surface [13,23]. In fact, DOC measured in the supematant of the soil-LSS mixtures before atrazine addition (Table 1) were only 25-50% of the initially added DOC, indicating that much of the LSSDOM is sorbed by the soil.…”

“…3 between the experimental and calculated Kf values for the soil-LSS mixtures. The association of DOM with organic compounds in the solution phase has been proposed as the principal process which can reduce the sorption of organic compounds by solid sorbents [23][24][25];…”

“…however, DOM can also reduce pesticide sorption by processes taking place at the soil/solution interface, such as competition for sorption sites on the soil surface [10,13,23]. Sorption of DOM on soil may also modify the charge characteristics or the hydrophobic/hydrophilie character of the soil surface, thus changing its affinity for a given pesticide.…”