Comparison of marine and river water humic substances in a Patagonian environment (Argentina)

Abstract

Structural aspects of humic substances (HSs) in marine waters of Engaño Bay (Atlantic Ocean) and water from the Chubut River (Patagonia, Argentina) were compared. The HSs were isolated, purified, and analyzed using a multiple-method approach for structural characterization: elemental analysis, nuclear magnetic resonance ( 13 C and 1 H NMR), infrared spectroscopy (FTIR), UV-visible absorption and fluorescence. Similarities between the marine and freshwater components were evaluated on the basis of N and O contents, H/C and C/N atomic ratios, infrared bands from nitrogen-containing and carboxylic groups, percentage of functional groups obtained from NMR spectra, spectral slope coefficient of absorption spectra, absorbance ratios at 250 and 365 nm (E 2 /E 3 ), aromaticity, excitation-emission matrices and fluorescence quantum yield. Both the Engaño Bay and Chubut River waters have HSs that are mainly composed of fulvic acids (FAs); although they are very similar, they may be distinguished from one another. Similarities include the predominance of aliphatic carbon content (low aromatic content); however, the water bodies differed in their content of proteins and carboxylic acids. The Engaño Bay FAs have mainly an aquatic origin; although the Chubut River FAs suggest a similar aquagenic origin, there is also evidence of contributions from pedogenic FAs.

UV–vis spectral modifications of water samples under irradiation: Lake vs. subterranean water

“…Figure 3b shows the time trend upon irradiation of the spectral slope S, compared with the trend in the dark. Interestingly, a significant decrease of S could be detected in the irradiated vs. dark samples, which would imply an increase of CDOM molecular weight and/or aromaticity [9,21,30].…”

“…The absorption spectra of CDOM in surface waters usually show an almost featureless exponential decrease with wavelength, which accounts for the widespread use of the spectral slope S for a qualitative or semi-quantitative description of CDOM characteristics such as molecular weight and aromaticity [8,9]. Note that S values are obtained by fitting the absorbance (A λ ) spectra of natural waters with the equation .…”

Solar radiation effect on the complexation capacity of aquatic humic substances with metals

“…[27][28][29] The fluorescence has advantages over others, such as nuclear magnetic resonance (NMR) which is also widely used in AHS studies. [30][31][32] Using fluorescence is possible to work with liquid samples and thus eliminating physical and chemical treatments which could alter AHS structure, and also enables the use of small samples, as well as having good sensitivity, robustness and its low cost. The fluorescence analysis of humic substances generate information about the structure, conformation and heterogeneity.…”

Seasonally Variation of Nitrate Level Before and After Fertilizers Application in Ground Water of Sikar District (India)

“…The physical, chemical and bacterial characteristics of ground water determine its usefulness for domestic, industrial, municipal and agricultural applications 1,4,17,19 . The changes in modern agricultural practice have allowed an increased production using fertilizers, herbicides and other pesticides.…”

“…The changes in modern agricultural practice have allowed an increased production using fertilizers, herbicides and other pesticides. The traditional organic fertilizers are less toxic than inorganic or synthetic fertilizers 5,6,17,20 . The effect of modern farming on biodiversity is a considerable threat to many organisms, including plants, insects and birds 3,13,14,18 .…”