Chemical and spectroscopic characterization of humic substances from sediments and riparian soil of a highly polluted urban river (Suquía River, Córdoba, Argentina)

CAROLINA MERLO; CAROLINA VÁSQUEZ; ANA G. IRIARTE; CARLOS M. ROMERO

INTERNATIONAL JOURNAL OF SEDIMENT RESEARCH

IRTCES

Año: 2020 vol. 35 p. 287 - 294

1001-6279

The Suquía River, the largest urban river in Córdoba (Argentina), has been severelypolluted for decades; actions must be taken to restore its environmental quality bymanaging riparian zones for increased water-self depuration. This study aimed tocharacterize organic matter (OM) dynamics and humic substances (HS) spectrochemicalproperties along the lower-middle basin of the Suquía River. Riparian soil (0-20 cm) andsediments (0-10 cm) samples were collected from a reference location (S1) and fourpolluted sites (S2-S5) during the low-flow period. The contents of soil and sedimentaryOM and HS fractions were analyzed by wet oxidation, as well as HS Fourier transforminfrared (FT-IR) and ultraviolet-visible (UV-Vis) spectroscopy properties. The OM and HSfractions from riparian soil were high upstream of Córdoba city (S1 and S2, 50.2-50.4 g kg -1OM) and within a 50 Km downstream location (S5, 30.9 g kg -1 OM) owing to a surplus offresh plant biomass-C inputs. Highly heterogeneous sediment samples did not show anysignificant differences among sites (P>0.05). The lowest values of E 4 /E 6 ratio (1.78) and ∆log K (0.15) coefficient (HS maturity degree) were obtained downstream of Córdoba city,for both riparian soil and sediments, indicating that HS were enriched by more condensedstructures within highly degraded portions of the river. All samples exhibited similar IRspectra, implying overlapping recalcitrant-C structures at the functional group level, butwith different absorbance intensity. Data from this study constitute a baseline forunderstanding the chemical nature of HS from sediments and riparian soil along the SuquíaRiver and could be used as a reference for future studies tracking OM compositionalchanges over time.