Photodegradation, chemical and biologic oxidations from mineralization
of Utricularia breviscapa leachate
SANTOS1, M.G.; CUNHA-SANTINO1,2, M.B. & BIANCHINI 1,2 JR., I.
1,2 Departamento de Hidrobiologia, e Programa de Pós-Graduação em Ecologia e Recursos Naturais, Universidade Federal de São Carlos. Via Washington Luiz, km 235. Cx. Postal 676. 13565-905. São Carlos, SP, Brasil.
marigonzaga@walla.com, irineu@power.ufscar.br e pmbc@iris.ufscar.br
ABSTRACT: The aquatic macrophytes are important source of organic matter. During the decomposition, this plants release large quantities of dissolved and particulate organic matter that are channeled to the trophic chains. This research aimed at determining the oxidation coefficients of leachate extracted from one aquatic macrophyte species (Utricularia breviscapa), collected in the Óleo Lagoon (21o 36‘ S and 47o 49‘ W; Luiz Antonio, SP). The leachate was submitted to photodegradation, chemical oxidation and bacterial activity; for which eight chambers with leachate and lagoon water were used. The incubations were maintained under aerobic conditions, with four kept under solar radiation (two with azide and two without azide) and four kept in the dark (two with azide and two without azide). During 130 days the dissolved oxygen concentrations were measured periodically in the chambers. The results were fitted to first-order kinetics model. The deoxygenation coefficient (kd) was approximately seven times higher in the incubations without azide and not exposed to solar radiation (biological oxidation) than in the incubations without azide and exposed to solar radiation (photodegradation). It was also approximately four times more elevated than for incubations where only chemical oxidation occurred. Based on the experimental results we concluded that although the chemical oxidation and photodegradation are important processes on mineralization of U. breviscapa leachate; the biological oxidation is more effective process in the cycling of dissolved organic matter of this macrophyte in the Óleo Lagoon.
Key-words: aquatic macrophyte, dissolved organic carbon, decay rates, microbial activity, solar radiation.