Humic substances from sediments of Lobos Pond (Argentina). Isolation, characterization and limnological implications

Roberto G. Choconi,Victor H. Conzonno,Alberto A. Ghini,Alicia Fernández Cirelli

doi:10.1590/s0100-46702011000200007

Abstract

Humic substances (HS) were isolated from the sediments of Lobos Pond (Argentina) using mild conditions to preserve their native structure. The HS (humic and fulvic acids) were characterized by means of elemental analysis and FTIR spectroscopy. Also a by-product obtained during fulvic acids (FA) fractionation (an amorphous white solid residue) was analyzed. Results revealed possible interactions between FA and inorganic-organic substances that may have implications referring to bioavailability. Other limnological implications, such as autochtonous origin of HS linked with the hydrology, and change of pH during stormy weather that affects HS interactions, are discussed.

Highlights

Lobos Pond (35o 17 ́ S, 59o 07 ́ W) is a pampasic pond located in the Salado River drainage basin, Buenos Aires Province (Fig. 1 a, b, c), which is placed in the geomorphologic unit called “Pampa deprimida”
Paraffins were more abundant in the hexane extract, while esters of fatty acids; long chain alcohols and wax esters were predominant when more polar solvents were used
Humic substances extracted from the sample after extraction with organic solvents, rendered: humic acids (HA): 64 mg and fulvic acids (FA): 89 mg; representing more than 10% of sediments’ total organic matter (TOM)

Summary

Introduction

Lobos Pond (35o 17 ́ S, 59o 07 ́ W) is a pampasic pond located in the Salado River drainage basin, Buenos Aires Province (Fig. 1 a, b, c), which is placed in the geomorphologic unit called “Pampa deprimida”. This pond is a permanent shallow water body (mean depth: 1.07 m, surface area: 7.51 Km2) with a main tributary, Las Garzas Stream, and an outlet, Saladillo Stream, which is regulated by a dam, that drains to the wetland Cañada del Toro (Fig. 1 d). High pH and chlorophyll a concentration observed in the pond as a product of autotrophic activity, put on evidence the impact of the high concentrations of nutrients coming from Las Garzas Stream (Table 1)

Methods

Results

Conclusion