Global patterns of dissolved silica export to the coastal zone: Results from a spatially explicit global model

Beusen, Arthur; Bouwman, A. F.; Dürr, Hans H.; Dekkers, Arnold; Hartmann, Jens

doi:10.1029/2008gb003281

Cited by 121 publications

(161 citation statements)

References 66 publications

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“…A millennium of soil disturbance after deforestation has led to twofold to even threefold decreases in TSi flux from a watershed where the adjacent coastal zone has experienced significant eutrophication problems due to changed N:P:Si river deliveries in the last three decades 28,29 . Our results are the first to show that local factors controlling terrestrial Si mobilization can be separated from factors important at continental and global scales, where controlling factors largely include lithology, precipitation and slope 30,31 . We clearly show that land use should be included in watershed scale models for baseline Si mobilization.…”

Section: Discussionmentioning

confidence: 99%

Historical land use change has lowered terrestrial silica mobilization

et al. 2010

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Continental export of si to the coastal zone is closely linked to the ocean carbon sink and to the dynamics of phytoplankton blooms in coastal ecosystems. Presently, however, the impact of human cultivation of the landscape on terrestrial si fluxes remains unquantified and is not incorporated in models for terrestrial si mobilization. In this paper, we show that land use is the most important controlling factor of si mobilization in temperate European watersheds, with sustained cultivation ( > 250 years) of formerly forested areas leading to a twofold to threefold decrease in baseflow delivery of si. This is a breakthrough in our understanding of the biogeochemical si cycle: it shows that human cultivation of the landscape should be recognized as an important controlling factor of terrestrial si fluxes.

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Section: Discussionmentioning

confidence: 99%

Historical land use change has lowered terrestrial silica mobilization

et al. 2010

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“…Also shown in Table 4 are concentrations calculated from annual fluxes generated by the global Nutrient Export from Watersheds (NEWS 2) model, developed to estimate regional-and continental-scale nutrient fluxes to the ocean Harrison et al, 2005;Seitzinger et al, 2005;Beusen et al, 2009;Mayorga et al, 2010 Our time series sampling location drains only ~60% of the agricultural lands in the Fraser floodplain (Brisbin, 1994), and, importantly, lies entirely upstream of any inputs from the Vancouver metropolitan area. Our measurements may exclude significant inputs of N and P from fertilizer and manure runoff and sewage and stormwater overflow, sources which rival or dwarf natural fluxes in many other rivers (Howarth et al, 1996;Boyer et al, 2006;Shen and Liu, 2008;Alvarez-Cobelas et al, 2009)…”

Section: Global and Historical Context Of Current Resultsmentioning

confidence: 99%

Spatial and temporal dynamics of biogeochemical processes in the Fraser River, Canada : a coupled organic-inorganic perspective

Voß¹

2014

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The great geologic and climatic diversity of the Fraser River basin in southwestern Canada render it an excellent location for understanding biogeochemical cycling of sediments and terrigenous organic carbon in a relatively pristine, large, temperate watershed. Sediments delivered by all tributaries have the potential to reach the ocean due to a lack of main stem lakes or impoundments, a unique feature for a river of its size. This study documents the concentrations of a suite of dissolved and particulate organic and inorganic constituents, which elucidate spatial and temporal variations in chemical weathering (including carbonate weathering in certain areas) as well as organic carbon mobilization, export, and biogeochemical transformation. Radiogenic strontium isotopes are employed as a tracer of sediment provenance based on the wide variation in bedrock age and lithology in the Fraser basin. The influence of sediments derived from the headwaters is detectable at the river mouth, however more downstream sediment sources predominate, particularly during high discharge conditions. Bulk radiocarbon analyses are used to quantify terrestrial storage timescales of organic carbon and distinguish between petrogenic and biospheric organic carbon, which is critical to assessing the role of rivers in long-term atmospheric CO 2 consumption. The estimated terrestrial residence time of biospheric organic carbon in the Fraser basin is 650 years, which is relatively short compared to other larger rivers (Amazon, Ganges-Brahmaputra) in which this assessment has been performed, and is likely related to the limited floodplain storage capacity and non-steadystate post-glacial erosion state of the Fraser River. A large portion of the dissolved inorganic carbon load of the Fraser River (>80%) is estimated to derive from remineralization of dissolved organic carbon, particularly during the annual spring freshet when organic carbon concentrations increase rapidly. This thesis establishes a baseline for carbon cycling in a largely unperturbed modern mid-latitude river system and establishes a framework for future process studies on the mechanisms of organic carbon turnover and organic matter-mineral associations in river systems.

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“…Total N and P fluxes are calculated as the sum of the three constituent elemental forms as shown in Eqs. (4) and (5), whereas silica fluxes are derived from Beusen et al (2009):…”

Section: Basin Aggregationmentioning

confidence: 99%

Modeling sources of nutrients in rivers draining into the Bay of Bengal—a scenario analysis

et al. 2017

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We model future trends in river export of nutrients to the Bay of Bengal, and the sources of this pollution. We focus on total nitrogen (TN), total phosphorus (TP), and dissolved silica (DSi) inputs to the Bay of Bengal Large Marine Ecosystem (BOB LME) in the years 2000, 2030, and 2050. In 2000, rivers exported 7.1 Tg N and 1.5 Tg P to the BOB LME. Three rivers (Ganges, Godavari, Irrawaddy) account for 75-80% of the total river export of N and P. For 2050, we calculate an increase in river export of N to 8.6 Tg, while P export stabilizes at the 2000 level. Future trends are the net effect of increasing river export of dissolved N (by 40%) and P (by 80%), and decreasing river export of particulate N and P. The increases in dissolved N and P loads are associated primarily with increased N and P losses from agriculture and sewage systems. The decreasing export of particulate N and P is associated with damming of rivers and increased human water consumption. There are large differences in nutrient export among rivers. Rivers draining into the western BOB LME generally export more N and P than eastern BOB LME rivers. Most N and P in western BOB LME rivers are from anthropogenic sources. Future increases in dissolved inorganic N and P (DIN and DIP) export can be large for individual rivers: up to more than a factor of five for DIP and more than a doubling for DIN. The calculated nutrient export ratios (N and P relative to DSi) indicate an increasing risk for blooms of non-siliceous algal species, which can potentially produce toxins and otherwise disrupt coastal ecosystems. Our results indicate that basin-specific management may be the most effective approach towards reducing the risk of coastal eutrophication in the BOB LME.

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Global patterns of dissolved silica export to the coastal zone: Results from a spatially explicit global model

Cited by 121 publications

References 66 publications

Historical land use change has lowered terrestrial silica mobilization

Historical land use change has lowered terrestrial silica mobilization

Spatial and temporal dynamics of biogeochemical processes in the Fraser River, Canada : a coupled organic-inorganic perspective

Modeling sources of nutrients in rivers draining into the Bay of Bengal—a scenario analysis

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