Pesticide Sorption by Low Organic Carbon Sediments: A Screening for Seven Herbicides

Abstract

The sorption of seven pesticides in 10 Danish aquifer sediments has been studied. These sediments all have a total organic carbon (TOC) content below 1 g kg−1, and include carbonate‐bearing and carbonate‐free Quatenary sand deposits and a Cretaceous chalk aquifer. Batch experiments were carried out with metamitron, atrazine, isoproturon, mecoprop, 2,4‐D, bentazone, and metsulfuron‐methyl at an initial pesticide concentration of 0.25 mg L−1 in ground water. Generally, the sorption decreases in the order: metamitron, atrazine, isoproturon, mecoprop, 2,4‐D, metsulfuron‐methyl. The bentazone sorption was found to be insignificant. For a specific pesticide the sorption covers a range of Kd values (L kg−1) reflecting the different sediment characteristics. Multivariate regression analyses demonstrate that: (i) metamitron sorption is enhanced by increasing content of iron silicates; by contrast the oxalate extractable iron oxides have no influence on the metamitron sorption; (ii) sorption of atrazine, mecoprop, and 2,4‐D depends primarily on pH; the sorption is high at low pH (<6.7) compared with sorption at higher pH (>7.4); (iii) metsulfuron‐methyl only sorbs at pH below 5; and (iv) isoproturon sorption is primarily influenced by the specific surface area (SSA) and TOC. The present results illustrate the importance of choosing sediments of different geological origin in order to describe the influence of sediment properties on pesticide sorption.

Vertical small scale variations of sorption and mineralization of three herbicides in subsurface limestone and sandy aquifer

“…Stock solutions of 131 14 C-labeled pesticide was prepared with 14 C-labelled pesticides in sterile filtered MilliQ water 132 ). The sediment samples were crushed (only limestone), freeze-dried and 133 sieved (<2 mm) (Madsen et al, 2000). The investigations were carried out in glass tubes (10 134 mL) with Teflon caps at 10°C in the dark and previous tests excluded adsorption on those 135 materials (Madsen et al, 2000).…”

“…The sediment samples were crushed (only limestone), freeze-dried and 133 sieved (<2 mm) (Madsen et al, 2000). The investigations were carried out in glass tubes (10 134 mL) with Teflon caps at 10°C in the dark and previous tests excluded adsorption on those 135 materials (Madsen et al, 2000). The water from the Brévilles Spring in the catchment was 136 used as equilibrium liquid in the investigations as representative for the groundwater after 137 treatment with activated carbon to remove pesticides and sterile filtering.…”

A field study to assess the degradation and transport of diuron and its metabolites in a calcareous soil

“…The carbon content of both the soil and the soil solution is expected to have a significant effect on diuron transport since sorption is considered a key process in attenuation (Madsen et al, 2000). The relative proportions of solid phase organic matter and dissolved organic matter effectively compete for hydrophobic organic molecules.…”

Water and Atrazine Movement in a Calcareous Compost Applied Soil During Simulated Multiple Storms Events

“…Soil organic matter plays a critical role in atrazine adsorption (Shea, 1989). Sorption of atrazine is high at pH ≤ 6.7 when compared with sorption at higher pH levels greater than 7.4 (Madsen et al, 2000). Clay et al (1995) reported that a combination of ammonia fertilizer and higher soil pH level increased atrazine movement through the soil.…”