Spectroscopic and Molecular-Level Characteristics of Dissolved Organic Matter in a Highly Polluted Urban River in South China

Abstract

China is undergoing unprecedented rapid urbanization, which is accompanied by the formation of more than 2000 black and odorous urban rivers. Dissolved organic matter (DOM) is an essential component in aquatic ecosystems and regulates the carbon and nutrient cycle, but its characteristics in highly polluted urban rivers are still not well understood. Here, water samples from the mainstream, tributaries, ponds, and reservoirs within the highly urbanized Maozhou River watershed (Shenzhen, China) were analyzed using absorption and fluorescence spectroscopy, stable carbon isotope analysis, and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to explore the impact of urbanization on DOM characteristics. The results showed elevated dissolved organic carbon concentrations in the disturbed waters (mainstream, tributary, and pond) compared to those in the reservoir water. Results of the spectroscopic, isotopic, and FT-ICR MS analyses suggest that disturbed water DOM had lower aromaticity, average molecular weight, and plant-and soil-derived terrestrial (e.g., lignin-like) contributions but greater contributions from microbial-derived protein-like and anthropogenic sulfur-containing compounds (e.g., synthetic surfactants) than those of reservoir DOM. These characteristics were strengthened from the upper to the lower mainstream, which implies greater anthropogenic impact on downstream waters. Point-source wastewater effluent input caused increases in DOM level in the mainstream water and abrupt changes in DOM characteristics with very strong anthropogenic characteristics. The distinct chemistry of urban DOM from natural organic matter highlights a potentially strong impact of rapid urbanization on carbon and nutrient cycle in aquatic ecosystems.

Characterization of Fluorescent Dissolved Organic Matter in an Affected Pollution Raw Water Source using an Excitation-Emission Matrix and PARAFAC

“…The observed results were within the range of FI values for polluted water body such as Han River (1.54-2.07) (Hur et al, 2014), and above the FI values for a natural water body such as Epulu-Congo River during the dry season (1.45) (Spencer et al, 2010). These suggest that the high values of FI in water body was most likely due to the contribution of wastewater discharges as reported by Ye et al (2019).…”

“…These BIX values are comparable with those reported by (Hur et al, 2014) for a polluted river (0.58-1.04). Ye et al (2019) have found that the more polluted the water body, the higher the BIX value. Therefore, the observed BIX during the dry season may indicate an increase in tryptophan compound which had possibly been the result of microorganisms decomposition activity in the cattle waste (Parlanti et al, 2000).…”

“…These occurred possibly due to the presence of DOM in the raw water, particularly in tropical countries when the intensity of precipitation may affect the characteristics of DOM in water bodies (Vasyukova et al, 2012). However, the presence of DOM, particularly in polluted raw water bodies and its changes along the water treatment plant (WTP) are not well understood (Ye et al, 2019). Moreover, the majority of drinking water treatment in Indonesia use chlorine-based disinfection because of their low cost and availability (Sururi et al, 2017).…”

Anthropogenic landcover impacts fluvial dissolved organic matter composition in the Upper Mississippi River Basin

“…algae and bacteria) and microbial processing (Williams et al 2010;Kellerman et al 2018) within agricultural and urban streams, as well as possible wastewater inputs to urban streams (e.g. Ye et al 2019). The association of these compounds with agriculture and urban landcovers is further supported by the more negative scores for these landcovers along PC1 (Fig.…”

Dissolved Metal(loid) Concentrations and Their Relations with Chromophoric and Fluorescent Dissolved Organic Matter in an Urban River in Shenzhen, South China

“…While many studies have been performed on DOM-metal(loid) interactions in natural water [10,27], the understanding of DOM-metal(loid) interactions in black and odorous rivers is relatively limited. In particular, the DOM from urban regions often has complex sources and characteristics and is distinct from that in natural water [28,29]. Because the metal-binding constant of DOM depends on the DOM origin [22], the observed relationships between DOM and metals in natural water could not be generalized for water subjected to intensive human disturbance.…”