Properties of zeolitized tuff/organic matter aggregates relevant for their use in pedotechnique. III: organic matter stability and exchange properties

A study was performed to evaluate the suitability of zeolitized tuffs to restore degraded soils. Ca-saturated Neapolitan yellow tuff or clinoptilolite-rich tuff from Turkey were mixed with organic matter either as humic matter (tannic acid, humic acids) or non-humic matter (polygalacturonic acid). Organic matter was strongly stabilized in clinoptilolite-rich tuff aggregates based on humic matter, whereas it was more easily oxidized in models with nonhumic matter. Cation exchange capacity (CEC) was determined according to Ba/Mg-TEA method and by ammonium acetate procedure. The former method underestimated the CEC of the zeolitized tuffs, but was able to detect the contribution of organic matter to the CEC of aggregates. The latter method provided consistent CEC values for the zeolitized tuffs, but underestimated the exchange activity of the organic components of aggregates. CEC of aggregates including tannic acid was practically nil. Binding tannic acid to zeolite via Cabridges, results evidently in occlusion of zeolite pores. © 2007 Elsevier B.V. All rights reserved.A study was performed to evaluate the suitability of zeolitized tuffs to restore degraded soils. Ca-saturated Neapolitan yellow tuff or clinoptilolite-rich tuff from Turkey were mixed with organic matter either as humic matter (tannic acid, humic acids) or non-humic matter (polygalacturonic acid). Organic matter was strongly stabilized in clinoptilolite-rich tuff aggregates based on humic matter, whereas it was more easily oxidized in models with non-humic matter. Cation exchange capacity (CEC) was determined according to Ba/Mg-TEA method and by ammonium acetate procedure. The former method underestimated the CEC of the zeolitized tuffs, but was able to detect the contribution of organic matter to the CEC of aggregates. The latter method provided consistent CEC values for the zeolitized tuffs, but underestimated the exchange activity of the organic components of aggregates. CEC of aggregates including tannic acid was practically nil. Binding tannic acid to zeolite via Ca-bridges, results evidently in occlusion of zeolite pores