The medium-term effect of natural compost on the spectroscopic properties of humic acids of Czech soils

Abstract

In the current work, humic acids (HAs) isolated from natural compost and unamended and amended soils in a medium-time field experiment were characterized to evaluate the effects of the amendment at rates of 124, 239 and 478 t/ha on their chemical, compositional and structural features. The impact of the application of compost on their properties was observed over 3 years. Humic acids were characterized using spectral methods and elemental analysis. Humic acid isolated from compost was predominantly aliphatic, with a larger content of nitrogen and low degree of aromaticity and humification. The typical maximum (280/345 nm) of HA obtained from compost lies within the T (tryptophan-like) region, which can be ascribed to proteinaceous organic materials. On the other hand, the HAs obtained from amended soil were mainly aromatic in character, with a larger distribution of oxygen-containing functional groups, molecular weight and greater aromaticity. Fluorophores of HAs obtained from amended soil lie within the C (humic-like) region with typical maxima centred in the range 430–450/500–540 nm, occurring usually in HAs isolated from soil, peat and lignite. According to ultra-violet/visible and Fourier-transform infrared (FTIR) spectroscopy, the larger oxygen contents of these HAs are associated with the substitution of aromatic rings by oxygen-containing functional groups such as carboxylic, hydroxyls and ethers. On the basis of FTIR spectra, it was shown that HAs obtained from amended soil 2 and 3 years after compost application were enriched by peptid, aromatic and polysaccharide compounds absorbing at 1540, 1515 and 1040/cm, respectively.

Significantly Accelerated Photosensitized Formation of Atmospheric Sulfate at the Air–Water Interface of Microdroplets

“…Our Fourier transform infrared (FTIR) spectroscopy analysis indicates that the HULIS proxy exhibits similar characteristic bands to those of authentic HULIS samples that were isolated and purified from rainwater and atmospheric aerosols (Figure a). − According to the assignment of the vibrational bands of HULIS summarized in previous studies (Table S1), − a battery of functional groups can be readily identified. In detail, the vibrational bands around 1034 cm –1 correspond to C–O groups in lactones and anhydrides, while the peak at 1385 cm –1 is attributed to aliphatic C–H, with that at ∼ 1584 cm –1 attributed to stretching vibrations of aromatic rings and CC double bonds ,, and ∼1710 cm –1 attributed to CO stretching vibrations of carboxyl groups, carbonyl groups, and aldehydes . The peaks at ∼2930 and ∼2850 cm –1 belong to aliphatic C–H stretching .…”

“…61−63 According to the assignment of the vibrational bands of HULIS summarized in previous studies (Table S1), 64−70 a battery of functional groups can be readily identified. In detail, the vibrational bands around 1034 cm −1 correspond to C−O groups in lactones and anhydrides, 69 while the peak at 1385 cm −1 is attributed to aliphatic C−H, 70 with that at ∼ 1584 cm −1 attributed to stretching vibrations of aromatic rings and C�C double bonds 67,72,73 and ∼1710 cm −1 attributed to C� O stretching vibrations of carboxyl groups, carbonyl groups, and aldehydes. 70 The peaks at ∼2930 and ∼2850 cm −1 belong to aliphatic C−H stretching.…”