The Adsorption and Mobility of Paraquat on Different Soils and Soil Constituents*

Abstract

Summary. The adsorption capacity for paraquat of the following materials was examined: three peat soils; two peaty layers below a turf; a commercial sphagnum peat; grass; Begbroke soil; Fullers’ earth; humic acids isolated from a peat soil; lignin isolated from hardwood sawdust; cellulose powder. The Strong Adsorption Capacity (SAC) of these adsorbents was examined first using a chemical method of analysis and then with the more sensitive Lemna bioassay. Peat soils had an appreciable SAC for paraquat even when measured with the bioassay (88–165 kg/ha 2–5 cm depth, 750–1000 ppm), > 10 times that of Begbroke soil (14 kg/ha, 50 ppm). Humic acids had a higher adsorption capacity (k = 42, 000) than lignin (k = 2600), while cellulose adsorbed very little paraquat (k = 64). The adsorption of paraquat decreased as the ratio of soil to water increased. Temperature appeared to have very small effects on adsorption in organic soils. Results were consistent with calcium competing for adsorption sites. Paraquat sprayed on the surface of a peat soil up to 36 kg/ha remained in the top 7 mm after leaching with 305 mm of natural rainfall over a period of 4 months. Paraquat adsorbed on commercial sphagnum peat could transfer to clays after incorporation and be inactivated. Adsorption et mobilité du paraquat sur diffétrents sols et constituents du sol Résumé , La capacityé d'adsorption du paraquat par les milieux suivants a étéétudiée: 3 sols tourbeux, 2 assises tourbeuses sous un gazon, une tourbe commerciale de sphagnum, une tourbe, un sol de Begbroke, une terre à foulon, un acide humique extrait d'un sol tourbeux, une lignine extraite d'une sciure de bois dur, de la poudre de cellulose. La capacityé brute d'adsorption (CBA) de ces adsorbants a été examinée, au moyen d'une méthode chimique d'analyse puis avec la méthode biologique plus sensible utilisant Lemna. Les sols tourbeux montrèrent une CBA appréciable pour le paraquat même lorsqu'elle fut mesurée par la voie biologique (88/165 kg/ha 2,5 cm de profondeur, 750–1000 ppm), plus de 10 fois celle du sol de Begbroke (14 kg/ha 50 ppm). Pour les acides humiques, la capacityé d'adsorption fut plus éievée (k = 42 000) que pour la lignine (k = 2600) alors que la cellulose n'adsorba que très peu de paraquat (k = 64). L'adsorption du paraquat diminua à mesure que le rapport sol/eau augmentait. La temperature n'eut que de très faibles effets sur l'adsorption dans les sols organiques. Les résultats furent en accord avec la concurrence du calcium pour les lieux d'adsorption. Le paraquat appliquéà la surfaee d'un sol tourbeux jusquà la dose de 36 kg/ha resta dans les 7 premiers millimètres après lessivage par 305 mm de pluie natureile péndant une période de 4 mois. Le paraquat adsorbé sur une tourbe commerciale de sphagnum put être transféréè des argiles aprtè avoir été incorporé et inactiveée. Adsorption und Beweglichkeit von Paraquat in verschiedenen Böden und Bodenbestandteilen Zusammenfassung. Die Adsorptionskapazität von Paraquat wurde für folgende Materialien untersucht: 3 Torfböde...

Humic substances reactions involving bipyridylium herbicides in soil and aquatic environments

“…However, DAMANAKIS et al (1970) observed that 48-hour shaking was required for adsorption of paraquat on HA to reach equilibrium. The speed of adsorption of the bipyridylium herbicide by HA relative to organic and mineral soils is slower (CALDERBANK 1968).…”

“…The adsorption of paraquat from the solution phase by the organic matter was demonstrated by the reduction in its phytotoxicity to plants grown in media containing the organic soils (SCOTT and WEBER 1967, COFFEY and W AHREN 1969, DAMANAKIS et al 1970. SCOTT and WEBER (1967) suggested that the bipyridylium cation is adsorbed in exchange for other inorganic cations on the soil organic matter.…”

“…Bipyridylium herbicides are known to become inactivated in highly organic soils (HARRIS and W AHREN 1964, O'TOOLE 1966, CALDERBANK 1968, CALDERBANK and TOMLINSON 1969, DAMANAKIS et al 1970). However, due to a slow approach to the adsorption equilibria the inactivation process in the field has been occaSionally either very slow or incomplete (CALDERBANK and TOMLINSON 1969).…”

“…c) Adsorption on to some other organic surfaces DAMANAKIS et al (1970) determined the adsorption capacity for paraquat of grass, lignin isolated from hardwood sawdust, and cellulose powder. The relative adsorption of paraquat by cellulose as compared with lignin and grass was significantly small.…”

“…The latter are widely distributed in nature, occurring in soils (SCHNITZER and KHAN 1972), lakes (ISHIWATARI 1969), rivers (LAMAR 1968), and in the sea (RASHID and KING 1969). The bipyridylium herbicides are widely used as aquatic and contact herbicides (CALDERBANK 1968, AKHAVEIN andLINSCOTI 1968) and are known to be readily absorbed by organic surfaces, such as humic substances (DAMANAKIS et al 1970;BEST et al 1972;BURNS et al 1973 a, b, and c;KHAN 1973 a and c), organo-clay complex (KHAN 1973 b), activated carbon (COFFEY and WARREN 1969, WEBBER et al 1965, FAUST and ZARINS 1969, cellulose and lignin (DAMANAKIS et al 1970), and peat, muck, and organic soils (HARRIS and WARREN 1964, O'TOOLE 1966, SCOTI and WEBER 1967, TUCKER et al 1969, COFFEY and WARREN 1969, CALDERBANK and TOMLINSON 1969, DAMANAKIS et al 1970, WATKIN and SAGAR 1971, FRANK 1972. In view of the ubiquitous occurrence of humic substances and the wide use of bipyridylium herbicides in soil and aquatic environments, it appears appropriate to present a brief account of the information available at present on the interaction of humic materials with bipyridylium compounds.…”