Dissolved organic matter in surface runoff in the Loess Plateau of China: The role of rainfall events and land‐use

Abstract

Exploring the chemical characterization of dissolved organic matter (DOM) is important for understanding the fate of laterally transported organic matter in watersheds. We hypothesized that differences in water‐extractable organic matter (WEOM) in soils of varying land uses and rainfall events may significantly affect the quality and the quantity of stream DOM. To test our hypotheses, characteristics of rainfall‐runoff DOM and WEOM of source materials (topsoil from different land uses and gullies, as well as typical vegetation) were investigated at two adjacent catchments in the Loess Plateau of China, using ultraviolet–visible absorbance and excitation emission matrix fluorescence with parallel factor analysis (PARAFAC). Results indicated that land‐use types may significantly affect the chemical composition of soil WEOM, including its aromaticity, molecular weight, and degree of humification. The PARAFAC analysis demonstrated that the soils and stream water were dominated by terrestrial/allochthonous humic‐like substances and microbial transformable humic‐like fluorophores. Shifts in the fluorescence properties of stream DOM suggested a pronounced change in the relative proportion of allochthonous versus autochthonous material under different rainfall patterns and land uses. For example, high proportions of forestland could provide more allochthonous DOM input. This study highlights the relevance of soils and hydrological dynamics on the composition and fluxes of DOM issuing from watersheds. The composition of DOM in soils was influenced by land‐use type. Precipitation patterns influenced the proportion of terrestrial versus microbial origins of DOM in surface runoff. Contributions of allochthonous, terrestrially derived DOM inputs were highest from forested landscapes.

Effects of cornstalk mulching and rainfall intensity on the quantity and quality of dissolved organic carbon in runoff: A field rainfall simulation at the plot scale

“…The soil DOC leaching further influences riverine DOC and thus greenhouse gas outgassing (Ni & Li, 2023; Tang et al, 2023; Zhang et al, 2023). Although DOC represents only a very small part of the global carbon budget (Doetterl et al, 2016; Mchunu et al, 2011), its dynamic change is a key process that intensively impacts the global carbon cycle (Lal, 2003; Li et al, 2020). Generally, the quantity and quality of DOC jointly determine the abovementioned DOC biogeochemical processes (Hosen et al, 2014; Mao et al, 2017; Williams et al, 2016).…”

Spectral Characteristic Of The Waters With Different Sizes Of Particles: Impact Of Hydrochemical Property And Land Use Type

“…For a speci c watershed, the land-use types especially impacted the composition and fate of NCs in water. The land-use types could change the physicochemical properties of the soils in the watershed, which would further impact the counterparts of the rainfall and water within the watershed (Li et al, 2020). For example, NCs in aquatic environments were mainly terrestrial sources, and NCs from the cultivated land had more terrestrial humic substances than those from forestland.…”

Maximum Entropy Distribution of Rainfall Intensity and Duration – MEDRID: a method for precipitation temporal downscaling for sediment delivery assessment

“…This is why soil erosion turned into a key challenge for the Sustainable Development Goals of the UN (Keesstra et al, 2016;Borrelli et al, 2017). Soil erosion also imposes a threat to water supply, as pollutants and heavy metals are transported along with sediment, augmenting toxicity, turbidity and eutrophication in aquatic environments (Coelho et al, 2017;Li et al, 2020).…”

“…This is why soil erosion turned into a key challenge for the Sustainable Development Goals of the UN (Keesstra et al, 2016;Borrelli et al, 2017). Soil erosion also imposes a threat to water supply, as pollutants and heavy metals are transported along with sediment, augmenting toxicity, turbidity and eutrophication in aquatic environments (Coelho et al, 2017;Li et al, 2020).In addition, 30% of all land on Earth has arid or semiarid climate (Sivakumar et al, 2005), which causes places to be especially vulnerable to climate change and soil erosion (Huang et al…”