The impact of rainfall events, catchment characteristics and estuarine processes on the export of dissolved organic matter from two lowland rivers and their shared estuary

Panton, Anouska; Couceiro, Fay; Fones, Gary R.; Purdie, Duncan A.

doi:10.1016/j.scitotenv.2020.139481

Cited by 32 publications

(24 citation statements)

References 58 publications

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“…The nitrate N is 46.7% of that in the reach of the Yellow River that spans the irrigation area, exceeding the WHO drinking water standard values for NO 3 − N [7]. Although the rains coincide with the main period of nitrogen transport, little work has focused on nitrate dynamics before and after rainfall events in the low plain estuarine delta [28].…”

Section: Introductionmentioning

confidence: 99%

Strong Precipitation and Human Activity Spur Rapid Nitrate Deposition in Estuarine Delta: Multi-Isotope and Auxiliary Data Evidence

Xie

Huang

et al. 2021

IJERPH

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The intensive development of the Yellow River Delta has caused huge transportation of non-point pollutants into the Bohai Sea through source river estuaries and thus poses a considerable threat to eco-environmental security in the region. Long-term irrigation in the Yellow River basin, with occasional heavy rainfall and the related effects of ensuring hydrological processes and human activities in terms of nitrate N transport via surface water systems, is unclear. Using stable isotope (δ2H-H2O and δ18O-H2O, δ15N-NO3− and δ18O- NO3−) and auxiliary geographic data, the ISO source model was run to quantitatively analyze the supply relationship of river systems and the rapid change in the spatial pattern of nitrate N due to heavy rainfall in the estuarine delta. This analysis made clear the dominant contribution of agricultural activities and urbanization to NO3−-N emission, on which basis refined management measures were proposed to deal with NO3− in surface water from the “source-process”. The results of the study show that: (1) The relationship of surface water replenishment in the Yellow River Delta was affected not only by rainfall, irrigation, and other water conservancy measures but also the proportion of water from Yellow River flow declined from the source to estuary; (2) To a certain extent, rainfall diluted the concentration of nitrate N in the river and increased instantaneous flux of nitrate N into the sea, where nitrate N flux continuously increased from upstream to downstream; (3) The rapid deposition of nitrate in the estuary delta was driven by heavy rainfall and human activities such as excessive use of nitrogen fertilizers, rapid urbanization, and livestock waste discharge, and; (4) Scientific measures were needed to realize the interactive effect of the output of non-point source pollutants and the carrying and absorption capacity of coastal fragile ecosystems of the exogenous inputs.

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Section: Introductionmentioning

confidence: 99%

Strong Precipitation and Human Activity Spur Rapid Nitrate Deposition in Estuarine Delta: Multi-Isotope and Auxiliary Data Evidence

Xie

Huang

et al. 2021

IJERPH

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“…This monitoring programme detected summer low oxygen saturations and high chlorophyll concentrations in the upper estuary. The observational data sets obtained from both a discrete sampling programme (Panton et al 2018;Panton et al 2020) and automated continuous monitoring (Beaton et al 2017) conducted during the project (between 2012 and 2017) will be most beneficial for use in model calibration, validation and parameterisation. Of particular interest is the interaction between tidal and fluvial dominance in small shallow estuaries and as such is something we look into in this system.…”

Section: Introductionmentioning

confidence: 99%

Modelling the Influence of Riverine Inputs on the Circulation and Flushing Times of Small Shallow Estuaries

Huggett

Purdie

Haigh

2020

Estuaries and Coasts

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Simple flushing time calculations for estuarine systems can be used as proxies for eutrophication susceptibility. However, more complex methods are required to better understand entire systems. Understanding of the hydrodynamics driving circulation and flushing times in small, eutrophic, temperate estuaries is less advanced than larger counterparts due to lack of data and difficulties in accurately modelling small-scale systems. This paper uses the microtidal Christchurch Harbour estuary in Southern UK as a case study to elucidate the physical controls on eutrophication susceptibility in small shallow basins. A depth-averaged hydrodynamic model has been configured of the estuary to investigate the physical processes driving circulation with particular emphasis on understanding the impact of riverine inputs to this system. Results indicate circulation control changes from tidally to fluvially driven as riverine inputs increase. Flushing times, calculated using a particle tracking method, indicate that the system can take as long as 132 h to flush when river flow is low, or as short as 12 h when riverine input is exceptionally high. When total river flow into the estuary is less than 30 m 3 s −1 , tidal flux is the dominant hydrodynamic control, which results in high flushing times during neap tides. Conversely, when riverine input is greater than 30 m 3 s −1 , the dominant hydrodynamic control is fluvial flux, and flushing times during spring tides are longer than at neaps. The methodology presented here shows that modelling at small spatial scales is possible but highlights the importance of particle tracking methods to determine flushing time variability across a system.

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“…Lake water will thus become darker and more carbon rich, the first effect being more immediately evident and lending its name to the phenomenon (water browning or brownification ). 33 , 34 Strong precipitation events also enhance export of nutrients from the basin to the water bodies, 16 , 17 which can favor algal growth.…”

Section: Summer Stratification and Water Browningmentioning

confidence: 99%

Foreseen Effects of Climate-Impacted Scenarios on the Photochemical Fate of Selected Cyanotoxins in Surface Freshwaters

Vione

Rosario‐Ortiz

2021

Environ. Sci. Technol.

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Cyanobacteria populate most water environments, and their ability to effectively exploit light and nutrients provide them with a competitive advantage over other life forms. In particular conditions, cyanobacteria may experience considerable growth and give rise to the so-called harmful algal blooms (HABs). HABs are often characterized by the production of cyanotoxins, which cause adverse effects to both aquatic organisms and humans and even threaten drinking water supplies. The concentration of cyanotoxins in surface waters results from the budget between production by cyanobacteria and transformation, including photodegradation under sunlight exposure. Climate change will likely provide favorable conditions for HABs, which are expected to increase in frequency over both space and time. Moreover, climate change could modify the ability of some surface waters to induce phototransformation reactions. Photochemical modeling is here carried out for two cyanotoxins of known photoreaction kinetics (microcystin-LR and cylindrospermopsin), which follow different phototransformation pathways and for particular freshwater scenarios (summertime stratification in lakes, water browning, and evaporative water concentration). On this basis, it is possible to quantitatively predict that the expected changes in water-column conditions under a changing climate would enhance photodegradation of those cyanotoxins that are significantly transformed by reaction with the triplet states of chromophoric dissolved organic matter ( 3 CDOM*). This is known to be the case for microcystin-LR, for which faster photodegradation in some environments would at least partially offset enhanced occurrence. Unfortunately, very few data are currently available for the role of 3 CDOM* in the degradation of other cyanotoxins, which is a major knowledge gap in understanding the link between cyanotoxin photodegradation and changing climate.

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The impact of rainfall events, catchment characteristics and estuarine processes on the export of dissolved organic matter from two lowland rivers and their shared estuary

Cited by 32 publications

References 58 publications

Strong Precipitation and Human Activity Spur Rapid Nitrate Deposition in Estuarine Delta: Multi-Isotope and Auxiliary Data Evidence

Strong Precipitation and Human Activity Spur Rapid Nitrate Deposition in Estuarine Delta: Multi-Isotope and Auxiliary Data Evidence

Modelling the Influence of Riverine Inputs on the Circulation and Flushing Times of Small Shallow Estuaries

Foreseen Effects of Climate-Impacted Scenarios on the Photochemical Fate of Selected Cyanotoxins in Surface Freshwaters

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