Recent Progress in River Biogeochemistry Research

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Water Quality and Contamination".

Deadline for manuscript submissions: closed (31 August 2019) | Viewed by 42527

Special Issue Editors

School of Freshwater Sciences, University of Wisconsin-Milwaukee, 600 East Greenfield Avenue, Milwaukee, WI 53204, USA
Interests: dissolved organic matter; nutrients; aquatic biogeochemistry
Special Issues, Collections and Topics in MDPI journals
Institut de Physique du Globe de Paris, Paris, France
Key Laboratory of Submarine Geosciences and Exploration Technology, Ocean University of China, Shandong, China
Interests: coastal sediment dynamics; land-sea interactions in context of global change; estuarine and coastal processes
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We invite you to submit your latest research findings showing progress in River Biogeochemistry to a special issue in Water (ISSN 2073-4441) – an open access journal (https://www.mdpi.com/journal/water). The world rivers discharge tremendous amounts of freshwater and dissolved and suspended solids to the sea, affecting physical, chemical, and biological domains of coastal and marine systems. The quantity and quality of the riverine outflows can be greatly affected by a number of factors in the drainage basins, including natural (e.g. climate fluctuation, earth surface, geochemical and terrestrial ecosystems processes), anthropogenic (e.g. land use change and river engineering) and the interactions with floodplains and wetlands. Over the past decades, many river basins have experienced significant climate, environmental and ecological changes. Concurrently, population growth and economic development have seen large areas of rural land converted for urban and industrial development. It is pertinent to quantify how these changes may have modified flow, sediment transport, and metal, nutrient and carbon fluxes from small and large rivers at a global scale. This special issue aims at bringing together the latest endeavors of research on material transport and biogeochemical processes along the aquatic continuum from river to estuary/coastal waters. We encourage submissions reporting the recent findings in the biogeochemistry of carbon, nutrients and trace elements from field observations, laboratory characterization, modeling, and synthetic studies of river systems, and we especially encourage papers that address the world’s large river systems and stimulate critical thinking pertinent to riverine biogeochemistry and its influence to the coastal and marine systems.

Prof. Dr. Y. Jun Xu
Prof. Dr. Laodong Guo
Prof. Dr. Jerome Gaillardet
Prof. Dr. Houjie Wang
Guest Editors

Manuscript Submission Information

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Keywords

  • River geochemistry
  • Biogeochemical processes of rivers
  • Riverine fluxes of carbon, nutrients, metals, and suspended sediment
  • Sediment and chemical constituents transport
  • Colloid chemistry in rivers
  • Biogeochemical connectivity of rivers, floodplains and wetlands
  • Climate and land use change effects on river biogeochemistry
  • Element transformation in freshwater-saltwater mixing
  • River data and modeling infrastructure

Published Papers (8 papers)

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Research

13 pages, 2260 KiB  
Article
The Po River Water Isotopes during the Drought Condition of the Year 2017
by Chiara Marchina, Claudio Natali and Gianluca Bianchini
Water 2019, 11(1), 150; https://doi.org/10.3390/w11010150 - 16 Jan 2019
Cited by 16 | Viewed by 5077
Abstract
The year 2017 was anomalously warm and dry across the whole Italian Peninsula, and the paucity of precipitation was emphasized during the extreme summer drought of the main Italian river, i.e., the Po river, which was characterized by a discharge persistently below 600 [...] Read more.
The year 2017 was anomalously warm and dry across the whole Italian Peninsula, and the paucity of precipitation was emphasized during the extreme summer drought of the main Italian river, i.e., the Po river, which was characterized by a discharge persistently below 600 m3/s (in spite of the average discharge of 1500 m3/s). During these extreme conditions, the Po river oxygen and hydrogen stable isotopes (δD, δ18O) displayed a relation (δD = 6.1*δ18O − 6.6) significantly different from that recorded in the previous investigation of the years 2012–2014 (δD = 7.5*δ18O + 6.5). The lowering of the slope and the negative intercept clearly reflect the transition toward arid conditions that characterized the investigated period. The difference is expressed by the derivative parameter Line-Conditioned excess (LC-exc), which better describes the compositional difference of Po river water in the year 2017 with respect to that of the period 2012–2014, when the system was less affected by warm or dry conditions and the river discharge was more similar to the historical trends. The isotopic anomaly observed in 2017 throughout the river is even greater in the terminal part of the river, where in the meanders of the deltaic branches, the river flow progressively slows down, suffering significant evaporation. The isotopic signature of the water appears, therefore, an appropriate tool to monitor the watershed response to evolving environmental conditions. These sensitive isotopic parameters could be interpreted as “essential climate variables” (ECV) that are physical, chemical, or biological geo-referenced parameters that critically contribute to the characterization of Earth’s climate. Future research needs to find relationships between ECV (including the water stable isotopes) and the evolution of ecosystems, which especially in the Mediterranean area, appear to be fragile and severely affected by natural and anthropogenic processes. Full article
(This article belongs to the Special Issue Recent Progress in River Biogeochemistry Research)
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15 pages, 2755 KiB  
Article
Diel Variability of pCO2 and CO2 Outgassing from the Lower Mississippi River: Implications for Riverine CO2 Outgassing Estimation
by Jeremy H. Reiman and Y. Jun Xu
Water 2019, 11(1), 43; https://doi.org/10.3390/w11010043 - 27 Dec 2018
Cited by 31 | Viewed by 5565
Abstract
Carbon dioxide (CO2) outgassing from river surface waters is an important component of the global carbon cycle currently not well constrained. To test the hypothesis that riverine partial pressure of CO2 (pCO2) and CO2 outgassing [...] Read more.
Carbon dioxide (CO2) outgassing from river surface waters is an important component of the global carbon cycle currently not well constrained. To test the hypothesis that riverine partial pressure of CO2 (pCO2) and CO2 outgassing rates differ between daylight and darkness, we conducted in-situ pCO2 and ambient water measurements over four 24-h periods in the spring and summer of 2018 in the Lower Mississippi River under varying flow regimes. We hypothesized that diel pCO2 variation will correlate inversely with solar radiation due to light-induced photosynthesis. Despite differing ambient conditions between seasons, we found a consistent diel cycle of riverine pCO2, with highest values before sunset and lowest values during peak daylight. Recorded pCO2 measurements varied by 206–607 µatm in spring and 344–377 µatm in summer, with significantly lower records during daylight in summer. CO2 outgassing was significantly lower during daylight in both seasons, with diel variation ranging between 1.5–4.4 mmol m−2 h−1 in spring and 1.9–2.1 mmol m−2 h−1 in summer. Daily outgassing rates calculated incorporating diel variation resulted in significantly greater rates (26.2 ± std. 12.7 mmol m−2 d−1) than calculations using a single daily pCO2 value. This study suggests a likely substantial underestimation of carbon outgassed from higher order rivers that make up a majority of the global river water surface. The findings highlight the need for high temporal resolution data and further research on diel CO2 outgassing in different climate regions to constrain uncertainties in riverine flux estimation. Full article
(This article belongs to the Special Issue Recent Progress in River Biogeochemistry Research)
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19 pages, 2312 KiB  
Article
Spatial Variations in the Abundance and Chemical Speciation of Phosphorus across the River–Sea Interface in the Northern Beibu Gulf
by Bin Yang, Zhen-Jun Kang, Dong-Liang Lu, Solomon Felix Dan, Zhi-Ming Ning, Wen-Lu Lan and Qiu-Ping Zhong
Water 2018, 10(8), 1103; https://doi.org/10.3390/w10081103 - 18 Aug 2018
Cited by 20 | Viewed by 7646
Abstract
Water samples were collected to measure dissolved and particulate phosphorus species in order to examine the dynamics of phosphorus in the water column across the river–sea interface from the lower Dafengjiang River to the open Beibu Gulf. Dissolved inorganic phosphorus concentrations were as [...] Read more.
Water samples were collected to measure dissolved and particulate phosphorus species in order to examine the dynamics of phosphorus in the water column across the river–sea interface from the lower Dafengjiang River to the open Beibu Gulf. Dissolved inorganic phosphorus concentrations were as high as 0.90 ± 0.42 μM in river water but decreased dramatically to as low as 0.02 ± 0.01 μM in open coastal waters. Total dissolved phosphorus was largely measured in the form of dissolved inorganic phosphorus in river waters (58% ± 18%), whereas dissolved organic phosphorus became the predominant species (>90% on average) in open coastal waters. Total dissolved phosphorus was the dominant species, comprising 76% ± 16% of the total phosphorus, while total particulate phosphorus only comprised 24% ± 16% of the total phosphorus pool. Riverine inputs, physical and biological processes, and particulate phosphorus regeneration were the dominant factors responsible for the dynamic variations of phosphorus species in the study area. Based on a two-end-member mixing model, the biological uptake resulted in a dissolved inorganic phosphorus depletion of 0.12 ± 0.08 μM in the coastal surface water, whereas the replenishment of dissolved inorganic phosphorus in the lower river from particle P regeneration and release resulted in an increase (0.19 ± 0.22 μM) of dissolved inorganic phosphorus in the estuarine mixing region. The molar ratios of dissolved inorganic nitrogen to dissolved inorganic phosphorus and dissolved silicate to dissolved inorganic phosphorus in the open surface waters were >22, suggesting that, although the lower Dafengjiang River contained elevated concentrations of dissolved inorganic phosphorus, the northern Beibu Gulf was an overall P-limited coastal ecosystem. Full article
(This article belongs to the Special Issue Recent Progress in River Biogeochemistry Research)
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18 pages, 7135 KiB  
Article
The Influences of a Clay Lens on the Hyporheic Exchange in a Sand Dune
by Chengpeng Lu, Congcong Yao, Xiaoru Su, Yong Jiang, Feifei Yuan and Maomei Wang
Water 2018, 10(7), 826; https://doi.org/10.3390/w10070826 - 22 Jun 2018
Cited by 3 | Viewed by 4970
Abstract
A laboratory flume simulating a riverbed sand dune containing a low-permeability clay lens was constructed to investigate its influence on the quality and quantity of hyporheic exchange. By varying the depths and spatial locations of the clay lens, 24 scenarios and one blank [...] Read more.
A laboratory flume simulating a riverbed sand dune containing a low-permeability clay lens was constructed to investigate its influence on the quality and quantity of hyporheic exchange. By varying the depths and spatial locations of the clay lens, 24 scenarios and one blank control experiment were created. Dye tracers were applied to visualize patterns of hyporheic exchange and the extent of the hyporheic zone, while NaCl tracers were used to calculate hyporheic fluxes. The results revealed that the clay lens reduces hyporheic exchange and that the reduction depends on its spatial location. In general, the effect was stronger when the lens was in the center of the sand dune. The effect weakened when the lens was moved near the boundary of the sand dune. A change in horizontal location had a stronger influence on the extent of the hyporheic zone compared with a change in depth. The size of the hyporheic zone changed with the depth and position of the clay lens. There was a maximum of hyporheic extent with the lens at a depth of 0.1 m caused by changes of water flow paths. Full article
(This article belongs to the Special Issue Recent Progress in River Biogeochemistry Research)
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24 pages, 5140 KiB  
Article
Phosphorus Fluxes from Three Coastal Watersheds under Varied Agriculture Intensities to the Northern Gulf of Mexico
by Songjie He and Y. Jun Xu
Water 2018, 10(6), 816; https://doi.org/10.3390/w10060816 - 20 Jun 2018
Cited by 1 | Viewed by 4201
Abstract
This study aims to evaluate recent total phosphorus (TP) and dissolved inorganic phosphorus (DIP) transport from three coastal rivers—the Calcasieu, Mermentau, and Vermilion Rivers—that drain watersheds with varied agriculture intensities (21%, 67%, and 61%, respectively) into the northern Gulf of Mexico, one of [...] Read more.
This study aims to evaluate recent total phosphorus (TP) and dissolved inorganic phosphorus (DIP) transport from three coastal rivers—the Calcasieu, Mermentau, and Vermilion Rivers—that drain watersheds with varied agriculture intensities (21%, 67%, and 61%, respectively) into the northern Gulf of Mexico, one of the world’s largest summer hypoxic zones. The study also examined the spatial trends of TP and DIP from freshwater to saltwater along an 88-km estuarine reach with salinity increasing from 0.02 to 29.50. The results showed that from 1990–2009 to 2010–2017, the TP fluxes for one of the agriculture-intensive rivers increased while no significant change was found for the other two rivers. Change in river discharge was the main reason for this TP flux trend. The two more agriculture-intensive river basins showed consistently higher TP and DIP concentrations and fluxes, as well as higher DIP:TP ratios than the river draining less agriculture-intensive land, confirming the strong effect of land uses on phosphorus input and speciation. Longitudinal profiles of DIP along the salinity gradient of the estuarine reach displayed characteristic input behavior. Desorption of DIP from suspended solids and river bed sediments, urban inputs, as well as stronger calcium carbonate and phosphorus co-precipitation at the marine endmember could be the reasons for such mixing dynamics. Full article
(This article belongs to the Special Issue Recent Progress in River Biogeochemistry Research)
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15 pages, 2148 KiB  
Article
Spatial and Seasonal Patterns of Nutrients and Heavy Metals in Twenty-Seven Rivers Draining into the South China Sea
by Amei Deng, Changdong Ye and Wenzhi Liu
Water 2018, 10(1), 50; https://doi.org/10.3390/w10010050 - 10 Jan 2018
Cited by 19 | Viewed by 4308
Abstract
Due to the acceleration of industrialization and urbanization in recent decades, the majority of coastal rivers and estuaries in China have been moderately or severely contaminated by a variety of pollutants. We investigated the spatial and seasonal variations of water nutrients (permanganate index, [...] Read more.
Due to the acceleration of industrialization and urbanization in recent decades, the majority of coastal rivers and estuaries in China have been moderately or severely contaminated by a variety of pollutants. We investigated the spatial and seasonal variations of water nutrients (permanganate index, chemical oxygen demand, biochemical oxygen demand, ammonium, nitrate, total nitrogen, and total phosphorus) and heavy metals (Hg, Pb, Cu, Zn, Se, As, Cd, Cr, Fe, and Mn) in 27 subtropical rivers draining into the South China Sea. Our results indicated that the average concentrations of all water quality parameters except ammonium, total nitrogen, and total phosphorus satisfied the requirements for grade III of the surface water quality standard of China. The concentrations of both nutrients and heavy metals showed a strong spatial variation. Cluster analysis classified the 27 rivers into three spatial clusters corresponding to low, moderate, and high pollution levels. In terms of seasonal variation, the values of chemical oxygen demand and biochemical oxygen demand in wet seasons were significantly lower than those in dry seasons. Multivariate statistical analyses demonstrated that river nutrients might mainly originate from domestic, industrial, and agricultural wastewaters, while heavy metals likely came from industrial activities and natural weathering processes. The findings of this study suggest that for reducing the pollution of subtropical rivers draining into the South China Sea, further efforts should be made to control nitrogen and phosphorus export from catchments. Full article
(This article belongs to the Special Issue Recent Progress in River Biogeochemistry Research)
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1659 KiB  
Article
Permafrost Boundary Shift in Western Siberia May Not Modify Dissolved Nutrient Concentrations in Rivers
by Sergey N. Vorobyev, Oleg S. Pokrovsky, Svetlana Serikova, Rinat M. Manasypov, Ivan V. Krickov, Liudmila S. Shirokova, Artem Lim, Larisa G. Kolesnichenko, Sergey N. Kirpotin and Jan Karlsson
Water 2017, 9(12), 985; https://doi.org/10.3390/w9120985 - 17 Dec 2017
Cited by 26 | Viewed by 5062
Abstract
Identifying the landscape and climate factors that control nutrient export by rivers in high latitude regions is one of the main challenges for understanding the Arctic Ocean response to ongoing climate change. This is especially true for Western Siberian rivers, which are responsible [...] Read more.
Identifying the landscape and climate factors that control nutrient export by rivers in high latitude regions is one of the main challenges for understanding the Arctic Ocean response to ongoing climate change. This is especially true for Western Siberian rivers, which are responsible for a significant part of freshwater and solutes delivery to the Arctic Ocean and are draining vast permafrost-affected areas most vulnerable to thaw. Forty-nine small- and medium-sized rivers (10–100,000 km2) were sampled along a 1700 km long N–S transect including both permafrost-affected and permafrost-free zones of the Western Siberian Lowland (WSL) in June and August 2015. The N, P, dissolved organic and inorganic carbon (DOC and DIC, respectively), particular organic carbon (POC), Si, Ca, K, Fe, and Mn were analyzed to assess the role of environmental parameters, such as temperature, runoff, latitude, permafrost, bogs, lake, and forest coverage on nutrient concentration. The size of the watershed had no influence on nutrient concentrations in the rivers. Bogs and lakes retained nutrients whereas forests supplied P, Si, K, Ca, DIC, and Mn to rivers. The river water temperature was negatively correlated with Si and positively correlated with Fe in permafrost-free rivers. In permafrost-bearing rivers, the decrease in T northward was coupled with significant increases in PO4, Ptot, NH4, pH, DIC, Si, Ca, and Mn. North of the permafrost boundary (61° N), there was no difference in nutrient concentrations among permafrost zones (isolated, sporadic, discontinuous, and continuous). The climate warming in Western Siberia may lead to a permafrost boundary shift northward. Using a substituting space for time scenario, this may decrease or maintain the current levels of N, P, Si, K, Ca, DIC, and DOC concentrations in rivers of continuous permafrost zones compared to the present state. As a result, the export flux of nutrients by the small- and medium-sized rivers of the Western Siberian subarctic to the Arctic Ocean coastal zone may remain constant, or even decrease. Full article
(This article belongs to the Special Issue Recent Progress in River Biogeochemistry Research)
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3196 KiB  
Article
Unravelling the Relative Contribution of Dissolved Carbon by the Red River to the Atchafalaya River
by Y. Jun Xu and Emily Marie DelDuco
Water 2017, 9(11), 871; https://doi.org/10.3390/w9110871 - 08 Nov 2017
Cited by 9 | Viewed by 4532
Abstract
The Atchafalaya River (AR), North America’s largest swamp river, annually discharges a large volume of freshwater (nearly 200 km3), delivering ~25% of the Mississippi River’s (MR) flow and the entire Red River’s (RR) flow into the Gulf of Mexico. Studies have reported higher [...] Read more.
The Atchafalaya River (AR), North America’s largest swamp river, annually discharges a large volume of freshwater (nearly 200 km3), delivering ~25% of the Mississippi River’s (MR) flow and the entire Red River’s (RR) flow into the Gulf of Mexico. Studies have reported higher levels of organic carbon in the AR’s outlets compared to the MR’s outlet, raising questions about local carbon sources. In this study, we investigated dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) inputs into the AR from the RR and MR using DOC and DIC concentrations, mass loading, and isotopic signature (δ13C) analyses. Monthly river water sampling was conducted in the MR and RR near their confluence where the AR is formed from May 2015–May 2016. DIC concentrations in the RR were found to be only half of those found in the MR, while the RR’s DOC concentrations were on average 1.8 times higher than those found in the MR. Based on the models developed for this study period, the RR’s contribution to DIC mass loading in the AR represented 1.41 teragrams (Tg) (or, 29.7%) of the total 4.76 Tg DIC transported by both tributaries, while its contribution to DOC mass loading was disproportionately high, accounting for 1.74 Tg of the 2.75 Tg DOC (or, 63.2% of total DOC) entering the AR. Both δ13CDIC and δ13CDOC showed significantly more negative values in the RR than those found in the MR. Significant correlation between δ13CDIC and δ13CDOC isotope values in the RR indicated interrelation of dissolved carbon processing, which was not observable in the MR. These results strongly suggest that the RR is an extremely significant source of DOC to the AR, and thus the Gulf of Mexico, and additionally plays an important role in diluting the anthropogenically enhanced DIC fluxes of the MR. Full article
(This article belongs to the Special Issue Recent Progress in River Biogeochemistry Research)
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