Effects of Land Use on the Amount and Composition of Dissolved Organic Matter in a Chinese Headwater Stream Watershed

Abstract

The source and composition of dissolved organic matter (DOM) are important drivers of its biogeochemical role in aquatic environments. Different land use types may alter DOM amount and composition in freshwaters. Here, water samples were collected from the outlets of 16 subcatchments within mixed land use patterns in the South Tiaoxi River in Eastern China. Dissolved organic carbon (DOC), DOM absorption coefficient (α 350 ), and fluorescence spectrum were measured. These 16 subcatchments were grouped into four clusters with different land use features: natural forest land, planted forest land (Phyllostachys praecox, a bamboo species), cropland, and residential land. Two humic-like and two protein-like fluorescent components were identified using parallel factor analysis (PARAFAC). DOC concentrations were the lowest in natural forest land dominated subcatchments as compared to other land uses with intensive anthropogenic activities, so did α 350 and fluorescent intensities of different components. Protein-like fluorescence was more pronounced for the subcatchments dominated by residential land, while terrestrial humic-like fluorescence was the most abundant component for the subcatchments dominated by the other three land use types. The relationships between the percentage of cropland and that of fluorescence fraction appear to be a threshold response, indicating that effects on DOM composition varied with agricultural activity patterns. The reservoir would have a positive effect on DOM amount and the percentage of protein-like fluorescence associated with autochthonous activities. This study in general shows the impact of anthropogenic land use patterns on the amount and composition of DOM in headwater streams, which may affect ecosystem function and health of aquatic environments.

Anthropogenic Influences of Paved Runoff and Sanitary Sewage on the Dissolved Organic Matter Quality of Wet Weather Overflows: An Excitation–Emission Matrix Parallel Factor Analysis Assessment

“…As the DOM has a complex assemblage of chemical structures, many analytical approaches provide only limited proxy information on the quality of DOM . However, excitation–emission matrix parallel factor analysis (EEM–PARAFAC) is a powerful tool with which to assess the natural DOM dynamics − that can resolve the complex mixtures of EEM data sets into several typical components. , Many published works had utilized the EEM–PARAFAC method to identify the sources of DOM in natural streams or lake ecosystems, such as terrestrial runoff, agricultural runoff, forest soil, and aquatic production. − In terms of the research matrix of municipal water supply, wastewater treatment, and groundwater monitoring, this method had also been commonly applied. − Furthermore, an increasing number of studies had characterized and traced the sources of DOM within urban stormwaters or streams using EEM–PARAFAC to explore the influences of urban landscapes, environmental factors, and urbanization gradients on the urban waterbodies. ,, More recently, EEM–PARAFAC had been successfully applied to DOM real-time monitoring of point source contaminations, such as fecal matter in drinking water, , which highlighted the capacity and prospect of this technique for online pollutant source identification. Therefore, the EEM–PARAFAC method has the potential ability to explain the anthropogenic influences of paved runoff and sanitary sewage on the quality of WWF DOM.…”