Effect of the nature of exogenous organic matter on pesticide sorption by the soil

A study was carried out on the sorption of two sparingly water-soluble pesticides (diazinon and linuron) by a sandy loam soil modified with different exogenous organic materials (EOMs) containing humic like substances: city refuse compost (CRC), peat (P), commercial humic acid (HA), liquid humic acid (LHA) extracted from leonardite and two (non humic) model compounds (surfactants): tetradecyltrimethylammonium bromide (TDTMA) and sodium dodecyl sulphate (SDS) before and after 2 and 8 months incubation periods with the soil. In all cases, the isotherms fitted the Freundlich sorption equation (x/m=KCen), generally with r2 values greater than 0.99. The value of the sorption constant K for the natural soil was 8.81 for diazinon and 2.29 for linuron. These values increased significantly for EOM modified soils with respect to natural soil, with the exception of the samples modified with SDS and LHA, in which cases they decreased, possibly due to the micellar properties of these compounds. Incubation of EOMs with soil increased their sorption capacity: the Koc values were increased proportionally to the incubation time for both pesticides and for all treatments carried out. Accordingly, the sorption capacity of hydrophobic pesticides increases with the degree of evolution in the soil of EOMs with humic type compounds, possibly due, among other causes, to the increase in the EOMs colloidal properties and the modifications occurring in the hydrophobic- hydrophilic characteristics of the soil surfaces. The main conclusion is that application to the soil of solid carbon rich wastes, especially those with a high degree of maturity, may offer an important strategy for reducing pesticide leaching, and for eliminating pesticide residues from soil with the use of liquid humic acids.Peer reviewe

Effect of the nature of exogenous organic matter on pesticide sorption by the soil

A study was carried out on the sorption of two sparingly water-soluble pesticides (diazinon and linuron) by a sandy loam soil modified with different exogenous organic materials (EOMs) containing humic like substances: city refuse compost (CRC), peat (P), commercial humic acid (HA), liquid humic acid (LHA) extracted from leonardite and two (non humic) model compounds (surfactants): tetradecyltrimethylammonium bromide (TDTMA) and sodium dodecyl sulphate (SDS) before and after 2 and 8 months incubation periods with the soil. In all cases, the isotherms fitted the Freundlich sorption equation (x/m=KCen), generally with r2 values greater than 0.99. The value of the sorption constant K for the natural soil was 8.81 for diazinon and 2.29 for linuron. These values increased significantly for EOM modified soils with respect to natural soil, with the exception of the samples modified with SDS and LHA, in which cases they decreased, possibly due to the micellar properties of these compounds. Incubation of EOMs with soil increased their sorption capacity: the Koc values were increased proportionally to the incubation time for both pesticides and for all treatments carried out. Accordingly, the sorption capacity of hydrophobic pesticides increases with the degree of evolution in the soil of EOMs with humic type compounds, possibly due, among other causes, to the increase in the EOMs colloidal properties and the modifications occurring in the hydrophobic- hydrophilic characteristics of the soil surfaces. The main conclusion is that application to the soil of solid carbon rich wastes, especially those with a high degree of maturity, may offer an important strategy for reducing pesticide leaching, and for eliminating pesticide residues from soil with the use of liquid humic acids.Peer reviewe

Estudio mineralógico de arcillas cerámicas de la provincia de Zamora III. Yacimientos en el basamento paleozoico

[ES] Se ha realizado el estudio mineralógico de 15 muestras de arcilla, procedentes de 8 yacimiento de la provincia de Zamora situados en el basamento paleozoico. Las técnicas empleadas han sido las siguientes: capacidad de cambio de cationes, anáilisis químico, análisis térmico diferencial, análisis termogravimétrico y difracción de rayos X. Se concluye que las arcillas de las yacimientos XX y XXII están comipuestas fundamentalmente por ilita (60-80 %) y caolin (20-40 %). En el resto de las muestras hay ilita (2040 %), caolín (10-40 %) y montmorillonita (15-50 %).[EN] The mineralogical propiertes of 15 samples from 8 ceramic deposits of the province of Zamora have been studied. The deposit are localed in the Paleozoic. The tecniques used were: cation-exchange capacity, chemical analysis, differential thermal analysis, therrnogravimetric analysis and X-ray diffraction. It is concluded that the samples from deposits XX and XXII are composed, mainly, by illite (60-80 %) and kaolinite (20-40 %). The other samples contain illite (20-60 %), kaolinite (10-40 %) and montmorillonite (15-50 %).Peer reviewe

Presencia, distribución y evolución de paligorskita en suelos sobre sedimentos terciarios de la Cuenca del Duero.

8 p.[ENG]Palygorskite distribution and evolution in the clay fraction of nine soil profiles developed from Tertiary sediments of the Duero Basin, have been studied. The mineral encountered in clay fraction, studied adopting XRD, DTA and TEM techniques, are illite as predominant component, low quantities of kaolinite, me dium or low amounts of smectite and palygorskite. Palygorskite contents were observed to be higher in the subsoil than the top soil and, in Ap horizonts, it lacks or is observed only in very small quantities. The amount of smectite increases when palygorskite content decreases, but in some of the Ap horizonts, the amount of smectite also decreases by destruction process and or washing of it to accumulation horizonts.[ESP]Se estudia la distribución y evolución de paligorskita en la fracción arciIla de nueve perfiles de suelos desarrollados sobre sedimentos y rocas sedimentarias en el terciario de la cuenca del Duero. La fracción arcilla estudiada empleando las técnicas de difracción de rayos X, ATD y MET, esta compuesta de ilita como mineral dominante, acompañada de pequeñas proporciones de caolinita y medias o bajas de esmectita. La paligorskita. más abundante en los horizontes subsuperficiales, disminuye al ascender en los perfiles, disminuci6n que suele ir acompañada por un aumento en la proporción de esmectita. En los horizontes antrópicos desaparece o sufre una fuerte disminución el contenido en paligorskita y en algunos disminuye notablemente el contenido en esmectita debido a un proceso de destrucción y/o lavado de la misma hacia horizontes de acumulación

City refuse compost and sodium dodecyl sulphate as modifiers of diazinon leaching in soil

Spanish "Comisi6n Interminterial de Ciencia y Tecnologia" (Projet AMB94-0688). Consejo Superior de Investigaciones Científicas (CSIC.Peer reviewe