Adsorption of pesticides onto quartz, calcite, kaolinite, and α-alumina

Liselotte Clausen, Ida Lykke Fabricius, L. Madsen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The fate of pesticides in aquifers is influenced by the small but not insignificant adsorption of pesticides to mineral surfaces. Batch experiments with five pesticides and four minerals were conducted to quantify the contributions to adsorption from different mineral surfaces and compare adsorption characteristics of selected pesticides. Investigated mineral phases included quartz, calcite, kaolinite, and alpha -alumina. Selected pesticides comprised atrazine (6-chloro-N-2-ethyl-N-4-isopropyl-1,3,5-triazine-2,4-diamine isoproturon [3-(4-isopropyl-phenyl)-1,1-dimethylurea)], mecoprop [(RS)-2-(4-chloro-2-methyl phenoxy)propionic acid], 2,4-D (2,4-dichlorophenoxyacetic acid), and bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4-(3H)-one 2,2-dioxide]. Specific surface area and mineral surface charge proved to be important for the adsorption of these pesticides. Detectable adsorption of the anionic pesticides (mecoprop, 2,4-D, and bentazone) was only measured when positive sites were present on the mineral surface. However, when CaCl2 was added as an electrolyte, a detect able adsorption of mecoprop and 2,4-D was also measured on kaolinite (which exhibits a negative surface charge), probably due to formation of Ca-pesticide-surface complexes. Adsorption of the uncharged pesticides (atrazine and isoproturon) was detected only on kaolinite. The lack of adsorption on alpha -alumina indicates that the uncharged pesticides have a greater affinity for the silanol surface sites (= SiOH) than for the aluminol surface sites (= AIOH) in kaolinite. No measurable effect of ionic strength was found for the uncharged pesticides. The results indicate that quartz and calcite play a smaller role than clay minerals.
Original languageEnglish
JournalJournal of Environmental Quality
Volume30
Pages (from-to)846-857
ISSN0047-2425
Publication statusPublished - 2001

Keywords

  • SOLUBILITIES
  • BENZOIC-ACID
  • SURFACE COMPLEXATION
  • WATER
  • ORGANIC-COMPOUNDS
  • COMPONENTS
  • MINERAL SURFACES
  • 2,4-DICHLOROPHENOXYACETIC ACID
  • SORPTION
  • SOIL

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