1. College of Land Science and Technology, China Agricultural University, Beijing 100193, China
2. Key Laboratory of Arable Land Conservation（North China）, Ministry of Agriculture, Beijing 100193, China
Abstract：Dissolved organic matter (DOM) is an important component of soil organic carbon pool, which plays a vital role in soil biochemical processes such as carbon and nitrogen cycle, nutrient conversion and pollutant migration. Exploring the adsorption behavior of DOM onto soil can provide a theoretical reference for the application of compost and the behavior of DOM in soil environmental. In this study, two different types of soils (black soil and fluvo-aquic soil), and quartz sand, were selected to carry out the adsorption experiment. UV-Visible spectroscopy and three-dimensional fluorescence spectroscopy combined with parallel factor method was applied to analysis the spectral characteristic of the DOM in the solution. The results showed that DOM was adsorbed by soil particles quickly. The adsorbed amount of DOM would gradually decrease with time. Due to the difference in properties of the three medium, the adsorbed amount of DOM is different. The adsorbed amount of DOM onto black soil, fluvo-aquic soil and quartz sand at 20 minutes，accounts for 61.94%, 67.43%, 61.57% of the adsorbed amount at 260 minutes. The adsorbed amount of DOM onto black soil, fluvo-aquic soil, and quartz sand up to 9.30, 9.18 and 8.90 mg·g-1 at 260 minutes. The UV-Vis spectroscopy showed that the absorbance of DOM in the solution decreased with adsorption time in the wavelength range of 200~600 nm, and the decrease degree of absorbance was larger in the first 5 minutes than that at 5~260 minutes. In addition, SUVA254 values increased firstly and then decreased with time. The results of PARAFAC analysis showed that there were three organic fluorescent components in the adsorption equilibrium solution. The C1 component (325/410 nm) was identified as UV humic-like, originating from terrestrially-derived organic matter, and the C2 component (two peaks are 260/435 nm, 350/435 nm) identified as humic-like, aromatic and derived primarily from terrestrial plant material, C3 component (two peaks are 280/500 nm, 375/500 nm) is a typical humus-like component of terrestrial origin, the poor contribution of macrophytes, allochthonous. The relative molecular weight of the C3 component is higher than that of the C1 and C2 components, but the degree of aromatization is lower than that of the C1 and C2 components. Black soil shows lower adsorption capacity for C1 and C2 components than fluvo-aquic soil and quartz sand, but for C3 component higher than fluvo-aquic soil and quartz sand. Fluvo-aquic soil has the largest adsorption capacity for C1 component, and quartz sand has the largest adsorption capacity for C2 component. In summary, the soil types and the structural characteristics of DOM was the main factor that affect the adsorption behavior of DOM onto the soil. Therefore, this study could provide a theoretical reference for the rational application of compost on different types of soil.
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