Preliminary study on the effect of cascade dams on organic matter sources of sediments in the middle Lancang–Mekong River

Zhao, Chen; Dong, Shikui; An, Nannan; Sylvie, Isange; Zhao, Haidi; Liu, Qi; Wu, Xiaoyu

doi:10.1007/s11368-017-1790-5

Cited by 10 publications

(6 citation statements)

References 49 publications

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“…The mean monthly air temperature and precipitation increase downstream and are both higher in the wet than dry season ( p < 0.05; Supporting Information Figure S1). The lower Lancang basin has a subtropical climate with two distinct seasons, that is, a dry season (from December to next April) and a wet season (from May to November) …”

Section: Materials and Methodsmentioning

confidence: 99%

“…The lower Lancang basin has a subtropical climate with two distinct seasons, that is, a dry season (from December to next April) and a wet season (from May to November). 29 River Water Sampling. Surface water was collected from the middle of the river at eight locations on the mainstem of the Lancang River and one relatively large tributary (AQ) near the upstream of CD in July 2016 (wet season) and April 2017 (dry season; Figure 1a), according to the seasonality of the lower Lancang basin.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

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Evolution of the Dissolved Organic Matter Composition along the Upper Mekong (Lancang) River

Liu

Wang

et al. 2021

ACS Earth Space Chem.

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The Mekong River is the tenth largest river in the world in terms of water discharge, representing a substantial source of organic matter to the South China Sea. However, the composition and variation of dissolved organic matter (DOM) remain poorly studied in this international river flowing through contrasting climates and severely affected by cascade reservoirs. Herein, using biomarkers, optical spectroscopy, and ultrahigh-resolution mass spectrometry analyses, we present a benchmark investigation of DOM evolution in the upper Mekong (Lancang) River. We show that terrestrial plantderived DOM accumulates in the wet season but degrades downstream in the dry season in the upper natural reach of Lancang. In contrast, terrestrial DOM decreases consistently in both wet and dry seasons along the lower reach affected by reservoirs, accompanied by decreases (instead of increases) in lignin oxidation indices (i.e., acid-to-aldehyde ratios) and high-oxygen highly unsaturated compounds. While photo-and microbial oxidation is considered to partly contribute to terrestrial DOM removal, we employ a series of batch sorption experiments to further show that sorption to finesized mineral particles may explain the decreasing lignin acid-to-aldehyde ratios in DOM. Given the high abundance of fine-sized suspended particles and long residence time in the Lancang reservoirs, removal via sorption (and possibly flocculation) is a potential important pathway for terrestrial DOM in the Lancang River. Cascade reservoirs hence are a hot spot of DOM processing, and an in situ quantitative assessment of sorptive removal of DOM therein warrants closer attention.

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Section: Materials and Methodsmentioning

confidence: 99%

Section: ■ Materials and Methodsmentioning

confidence: 99%

Evolution of the Dissolved Organic Matter Composition along the Upper Mekong (Lancang) River

Liu

Wang

et al. 2021

ACS Earth Space Chem.

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“…When the local water level drops, most of the water in the pores will penetrate downwards under the action of gravity. In soil science, this is defined as the gravitational water [18], which is adsorbed on the pore wall or in the capillary, and does not permeate downwards with gravity as adsorbed water.…”

Section: Discussionmentioning

confidence: 99%

Micro‐element statistics and their application in the study of soil model electrical conductivity

Cao

Wang

et al. 2021

IET Generation Trans & Dist

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The design of a grounding system is influenced by the soil conductivity. The cost of a ground grid in areas with different soil resistivities varies from tens to hundreds of times to achieve the same ground resistance. Existing studies have found that the electrical performance of soil changes suddenly with the change in water contents. However, it can only be assumed macroscopically that this change is caused by the connectivity of water distribution. Neither this assumption can be confirmed nor any critical conditions can be defined. This paper presents a mathematical study of soil conductivity from a microscopic point of view, known as the micro‐element statistical method. The method uses scientific statistical analysis to study the apparent conductivity of water elements in soil and is used to conclude that the apparent conductivity at the micro level is exponentially distributed. Based on the relationship between the mean of apparent conductivity distribution and water contents, the critical condition of soil resistivity mutation is defined, and the mechanism of soil resistivity change is explained. The method presented in this work can be used to study the influence of temperature, ion type concentration, solid particle type and pore structure on soil conductivity by changing the corresponding conditions and material type.

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“…The sources of TOC in sediments are both endogenous and exogenous. According to the C/N value analysis, the TOC in surface sediments of the Nuozhadu and Jinghong Reservoirs is derived mainly from algae and plankton, but when Zhao et al [31] studied the source of organic matter in the sediments of Manwan and Dachaoshan Reservoirs of the Lancang River, results indicated that the organic matter consisted mainly of terrestrial sources, including plant, soil and granular organic matter. Based on the research under taken by Zhang et al [32], TOC derives mainly from endogenous sources with C/N less than 10, while its exogenous sources measure more than 10.…”

Section: Discussionmentioning

confidence: 99%

Spatial Distribution of Carbon, Nitrogen and Phosphorus within Surface Sediments in the Lower Lancang River: Pollution Assessment Related to Dams

Hong-jun¹,

Fu²,

Peng³

et al. 2018

JEP

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Surface sediment is one of the main sources of nutrients in overlying water environments, and these can also indirectly reflect the degree of eutrophication. In this paper, the spatial distribution characteristics of total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) in the surface sediments of 11 sections in the lower Lancang River during flood season are analyzed, as well as the distribution of phosphorus in different forms. The main sources of TOC and its correlation with TN and TP are discussed and, finally, the pollution levels of the surface sediments are evaluated. The results show that the average content of TOC in the surface sediments of the lower Lancang River is 9003.75 mg/kg. The average TN content is 893.79 mg/kg, while the average TP content is 521.35 mg/kg. The TOC in the surface sediments of the lower Lancang River is derived mainly from algae and plankton in the river, and the TN and TP have similar sources. The total phosphorus in the surface sediments of the lower Lancang River is composed mainly of calcium-bound phosphorus (Ca-P). The evaluations of the organic pollution index and comprehensive pollution index show that the surface sediment pollution degree at the upper sections of the Nuozhadu and Jinghong Dams are more serious than those below the dams. Furthermore, the tributary sections are all slightly polluted, with the exception of the Mengyang River, which is considered moderately polluted.

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Preliminary study on the effect of cascade dams on organic matter sources of sediments in the middle Lancang–Mekong River

Cited by 10 publications

References 49 publications

Evolution of the Dissolved Organic Matter Composition along the Upper Mekong (Lancang) River

Evolution of the Dissolved Organic Matter Composition along the Upper Mekong (Lancang) River

Micro‐element statistics and their application in the study of soil model electrical conductivity

Spatial Distribution of Carbon, Nitrogen and Phosphorus within Surface Sediments in the Lower Lancang River: Pollution Assessment Related to Dams

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