1,721,022 research outputs found
Pig Slurry Amendment and Herbicide Coapplication Effects on s‐Triazine Mobility in Soil: An Adsorption‐Desorption Study
No full textAmendments with pig slurry containing dissolved organic matter (PSDOM) and herbicide coapplication are agronomical practices that can influence the mobility of herbicides through the soil profile, thus enhancing the risk of groundwater pollution. Batch equilibrium experiments were conducted on a clay loam soil to quantify the influence of these practices on the sorption and desorption of three s-triazine herbicides:atrazine oro-4-ethylamino-6-isopropylamino-1,3,5-triazine), prometryn(2,4-bis (isopropylamino)-6-methylthio-1,3,5-triazine), and terbuthylazine -butylamino-4-chloro-6-ethylamino-1,3,5-triazine). Soil adsorption and desorption capability for atrazine was reduced when it was applied with the other two s-triazines in the batch experiment solution. The PSDOM treatment immediately after atrazine application had a greater enhancing effect on its desorption than treatment with a 0.01 M CaCl2 solution alone. No enhanced desorption effect was observed on any ofthe three s-triazines when PSDOM treatment was carried out after repeated 0.01 M CaCl2 treatments. Soil treatment with PSDOM before atrazine application enhanced soil adsorption capability for the herbicide. On calculating the balance between the adsorbed and desorbed atrazine in the PSDOM-treated soil, a fourfold increase of the atrazine retainedwas observed. Therefore, to reduce the risk of groundwater s-triazinepollution, pig slurry should be applied to the soil before herbicide treatment
Speciazione dei metalli pesanti in un terreno antropogenico di copertura di una discarica controllata.
No full textAdsorbimento e desorbimento del Ni(II) in un terreno calcareo mediante la tecnica del flusso continuo (stir-flow) - XXIII Convegno Nazionale della Società Italiana di Chimica Agraria
No full textFactors involved in the retention and release of lead by a Central Italy soil: a stirred-flow approach
No full textTo improve the prediction and management of problems associated with toxicity in lead (Pb)-contaminated soils, a better understanding of their sorptive and desorptive behaviors is required. In this research, the sorptive and desorptive behaviors of Pb for a clay loam soil (Fluventic Xerochrept), typical of central Italy, were measured using a stirred-flow reactor, where the products of desorption are continuously removed from solution. In addition, we investigated the effects of the presence of calcium carbonate, organic matter (OM), and clay on Pb sorption and desorption behaviors by successively extracting calcium carbonate, OM, and oxides from the soil sample before the experiments. For all four substrates, Pb sorption was characterized by a fast initial reaction in which all the Pb added to the stirred-flow chamber was sorbed. After this, the sorption continued and appeared to be pH dependent. The presence of calcium carbonate led to a pH in the soil that caused the Pb to be insoluble, this being the main cause of the Pb sorption. When the pH of the original soil was lowered, depriving the soil of calcium carbonate, its Pb-sorptive capacity was significantly reduced and the percentage of Pb desorption increased. The elimination of OM from the soil sample previously deprived of calcium carbonate further increased the percentage of Pb desorption. The Pb sorption characteristics of the clay fraction were fast and nonhysteretic
Sorption Mechanisms Determining Ni(II) Retention by a Calcareous Soil
No full textThe objective of the study was to determine the mechanisms of Ni retention in a calcareous soil by comparing the sorption kinetics and adsorption-desorption isotherms of the whole soil and of some of its fractions. The study was performed using diffiractometric, microscopic, and thermogravimetric techniques to corroborate the mechanisms hypothesized from the equilibrium and kinetic studies. The sorption kinetics and the adsorption-desorption isotherms show that in a calcareous soil, Ni(II) is also retained by carbonates. In addition to the well known insolubilization process as a hydroxide caused by the high pH value induced by the presence of carbonates, calcium carbonate also contributes to Ni retention through the formation of a strong complex probably ascribable to a co-precipitation process that involves Ni/Ca carbonate double salt or mixed Ni/Al hydroxides and carbonates formation. The study also demonstrates that montmorillonite and illite clays may contribute to the adsorption of Ni with a nonspecific ion exchange mechanism, but as the Ni retention in the calcareous soil is totally specific, it can be presumed that this clay sorption mechanism is totally overshadowed by the double effect (Ni precipitation and complexation) caused by CaCO3
Evaluation of Pb and Ni Mobility to Groundwater in Calcareous Urban Soils of Ancona, Italy
No full textThis study was performed on 21 soils with the aim of establishing whether Pb and Ni adsorption/desorption parameters could be considered as good indicators of the risk of groundwater pollution. Results showed that high pH values in soil caused a totally irreversible Pb adsorption, thus excluding any risk of Pb groundwater pollution. Sorption/desorption studies, quantified by the desorption index (DI), showed that Ni retention was only partly affected by the basic pH values but it was also due to the electrostatic attraction processes occurring on soil surfaces, as demonstrated by the partial reversibility of the Ni sorbed. This justifies possible risks of Ni groundwater pollution. The results of a monitoring research confirmed these findings. Results suggested that the adsorption/desorption parameters, namely DI, are promising indicators to predict the risk of groundwater pollution from metals in calcareous soils
Composition changes of soil humus after massive application of urban waste compost: a comparison between FT-IR spectroscopy and humification parameters
No full textA laboratory trial and a six-year field experiment were carried out to evaluate the changes in the composition of humic substances in a soil amended for six years with urban waste compost (UWC), and to compare the results obtained by FT-IR spectroscopy with empirical humification parameters. The fulvic acid FT-IR spectra showed that amended soils contain a higher concentration of carboxylic and aliphatic groups compared to unamended soil (UNAS). The six-year amended soil (SYAS) also showed a higher content of polysaccharides on FT-IR spectra of both humic and fulvic acids. The polysaccharide increase in the six-year amended soil is attributable to the humification process since polysaccharides were not present in a high quantity in the UWC or laboratory amended soil (LAAS). The humification index and the degree of humification values indicate that the urban waste compost and soils studied can be classified in decreasing order of humification as follows: UNAS > SYAS > LAAS > UWC. This behaviour is the consequence of an increasing presence of the non humified fraction in NaOH extracted organic matter. The carboxylic and aliphatic groups content from FT-IR spectra confirmed this behaviour, thus indicating the validity of the humification parameters used to evaluate the status of the organic matter from refuse and soil
Effetto di alcuni componenti della frazione colloidale del suolo sulla ritenzione del piombo- Volume dei Riassunti dei Contributi Scientifici del XX Convegno Nazionale della Società Italiana di Chimica Agraria, Padova, 24-27 settembre, p. 116
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