Spectral characteristics of dissolved organic matter in various agricultural soils throughout China

Abstract

Dissolved organic matter (DOM) plays an essential role in many environmental processes, particularly in soil ecosystems. In the present study, ultraviolet-visible (UV-Vis) spectroscopy and parallel factor analysis (PARAFAC) of three-dimensional fluorescence excitation-emission matrices (3D-EEMs) were used to characterize DOM extracted from various agricultural soils across four climate regions of China. The maximum (86.01 mg L) and minimum (17.39 mg L) dissolved organic carbon (DOC) concentrations were found in soils from Jiangsu and Yunnan, respectively. Specific UV-Vis absorption at 254 nm (SUVA) for soil DOM from the temperate continental climate (TCC) region was higher than that of soil DOM in other climate regions. Three fluorescence components including UVC humic-like substances (excitation peak at 400 nm, emission peak at 525 nm), UVA humic-like substances (250(330)/430 nm), and tyrosine-like materials (220(275)/320 nm) were identified in soil DOM using PARAFAC analysis. However, there were no significant differences in the distributions of these three components for soil DOM from different climate regions. Positive correlations were found among the humification index (HIX), fluorescence index (FI), and autochthonous index (BIX). Our results demonstrate that EEMs-PARAFAC could be a feasible approach for characterizing DOM in agricultural soils from different crop systems and can be used to further study complex DOM in agricultural environments.

Compositional and chemical characteristics of dissolved organic matter in various types of cropped and natural Chinese soils

“…The extraction of soil DOM was performed referring to a simply modified method described by Gao et al [1]. In brief, 4 g of freeze-dried soil was mixed with deionized water with a soil/water ratio of 1:10 in a 50-ml centrifuge tube.…”

“…As shown in Fig. 1, five fluorescence components (C1-C5) were identified by the PARAFAC of all the DOM samples and assigned to be: UVA fulvic-like substances (C1, Ex/Em = 265/460 nm) [27,28], UVC fulvic-like substances (C2, Ex/Em = 230/400 nm) [34], humic-like substances (C3, Ex/Em = 320 (250)/400 nm) [35,36], tryptophan-like substances (C4, Ex/Em = 230 (275)/330 nm) [37] and peptide-like compounds (C5, Ex/Em = 220/330 nm) [1,4,38]. C1 (16.2%-47.9%) and C2 (15.4%-40.5%) were the prevailing fluorescence components in the DOM (Fig.…”

“…Soil dissolved organic matter (DOM) is a mixture of various soluble organic compounds, which are mainly derived from terrestrial and autochthonous sources [1], including soluble substances in decaying root and leaf, root exudates, leaching or decomposition of older soil organic matter (SOM) and microbial metabolism [2]. Despite its small content in soil, DOM is the most reactive fraction of organic matter in soils and plays a significant role in the terrestrial biogeochemical cycles [3][4][5].…”

“…Some studies also observed varied chemical properties and compositions of DOM under different land-uses, especially when comparing the natural and cropped lands [19,20]. Additionally, Gao et al [1] found that the DOM in chestnut and red soils had higher aromaticity than in other soils such as chernozem and cinnamon soils. Wang et al [21] also reported that DOM of a clayey soil showed a remarkably higher aromaticity and hydrophobicity than the DOM of a sandy soil.…”

Supplementary material to "The evolutionary behavior of chromophoric brown carbon during ozone aging of fine particles from biomass burning"

“…extracts(Chen et al, 2016a), urban, forest and marine aerosols WSOM(Chen et al, 2016b), crop straw combustion emitted HULIS(Huo et al, 2018), compost-derived DOM(Huang et al, 2018), agricultural soil DOM(Gao et al, 2017), biochar DOM(Jamieson et alextracts (Chen et al, 2016a), urban, forest and marine Aerosols WSOM(Chen et al, 2016b), compost-derived DOM(Huang et al, 2018)extracts(Chen et al, 2016a), urban, forest and marine Aerosols WSOM(Chen et al, 2016b), crop straw combustion emitted HULIS(Huo et al, 2018), rice-straw-derived DOM(Huang et al, …”