Cinética e variação molecular de substâncias húmicas formadas da lixiviação de macrófitas aquáticas
Abstract
The humic substances (HS) are important to aquatic ecosystems. In this study we
investigated the kinetics and molecular variations of dissolved fulvic acids (FA) and
humic acids (HA) formed from aquatic macrophytes decomposition under aerobic and
anaerobic conditions. The results supported the proposition and validation of kinetic
models that treated the formation, transformation and mineralization of dissolved SH.
Although mineralization and humification are concurrent events, the aerobic condition
favored these two processes contributed primarily to HA formation. The detritus
showed different mineralization and HS formation potentials. Larger amounts of HS
were related to higher carbon content in the detritus and lower mineralization of
dissolved organic carbon (DOC). The SH mass loss rates were lower than the refractory
fraction of particulate detritus, showing the recalcitrance of dissolved HS. The DOC
with higher C/N proportions presented higher coefficient rates. The HS presented
similar characteristics regardless of detritus source. However, aerobic conditions
favored variation of polysaccharides content in HS, indicating transformation of these
compounds. Aerobic conditions favored dissolved HS mineralization and its
assimilation by microorganisms. The AH presented higher reactive fraction than FA,
and was an important precursor of FA. The FA presented refractory characteristics and
formed less HA, indicating that the liginocellulosic compounds of the detritus are the
main precursors of HA.