Linking biogeochemistry to hydro-geometrical variability  in tidal estuaries: a generic modeling approach

Volta, Chiara; Laruelle, Goulven Gildas; Arndt, Sandra; Regnier, Pierre

doi:10.5194/hess-20-991-2016

Cited by 15 publications

(28 citation statements)

References 115 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The bulk of the remaining estimates falls in the 10%-50% range, which is consistent with our results where estuarine systems characterized by short residence times of several days like small deltas only denitrify a few percent of TN in , while systems such as fjords with residence times of several years denitrify up to 38% of TN in . Our results are also in line with the study of Volta, Laruelle, Arndt, and Regnier (2016) who used a generic, physically based estuarine modeling approach spanning a wide range of estuarine geometries; these authors report mean N losses via denitrification in the range 15%-25%.…”

Section: Nitrogen Input To Riverssupporting

confidence: 91%

Nitrous oxide emissions from inland waters: Are IPCC estimates too high?

Maavara

Lauerwald

Laruelle

et al. 2018

Global Change Biology

Self Cite

164

197

View full text Add to dashboard Cite

Nitrous oxide (N2O) emissions from inland waters remain a major source of uncertainty in global greenhouse gas budgets. N2O emissions are typically estimated using emission factors (EFs), defined as the proportion of the terrestrial nitrogen (N) load to a water body that is emitted as N2O to the atmosphere. The Intergovernmental Panel on Climate Change (IPCC) has proposed EFs of 0.25% and 0.75%, though studies have suggested that both these values are either too high or too low. In this work, we develop a mechanistic modeling approach to explicitly predict N2O production and emissions via nitrification and denitrification in rivers, reservoirs and estuaries. In particular, we introduce a water residence time dependence, which kinetically limits the extent of denitrification and nitrification in water bodies. We revise existing spatially explicit estimates of N loads to inland waters to predict both lumped watershed and half‐degree grid cell emissions and EFs worldwide, as well as the proportions of these emissions that originate from denitrification and nitrification. We estimate global inland water N2O emissions of 10.6–19.8 Gmol N year−1 (148–277 Gg N year−1), with reservoirs producing most N2O per unit area. Our results indicate that IPCC EFs are likely overestimated by up to an order of magnitude, and that achieving the magnitude of the IPCC's EFs is kinetically improbable in most river systems. Denitrification represents the major pathway of N2O production in river systems, whereas nitrification dominates production in reservoirs and estuaries.

show abstract

Section: Nitrogen Input To Riverssupporting

confidence: 91%

Nitrous oxide emissions from inland waters: Are IPCC estimates too high?

Maavara

Lauerwald

Laruelle

et al. 2018

Global Change Biology

Self Cite

164

197

View full text Add to dashboard Cite

show abstract

“…While many different studies consider flow-dependent river TA to anticorrelate with discharge (e.g., Wang et al, 2013;Evans et al, 2013), the strong Fraser River TA hysteresis demonstrated by our data links the strongest Fraser River TA fluctuations to rapid pulses in river discharge. A future shift to smaller freshets will thus likely reduce the already weak influence of flow-dependent freshwater TA in the model, supporting the use of fixed freshwater TA endmembers in large-scale acidification projection models (e.g., Volta et al, 2016). However, the present study highlights the importance of choosing a freshwater TA endmember carefully.…”

Section: Comparison To Other Rivers and Implications For Future Climatesupporting

confidence: 60%

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

2018

View full text Add to dashboard Cite

Abstract. Ocean acidification threatens to reduce pH and aragonite saturation state ( A ) in estuaries, potentially damaging their ecosystems. However, the impact of highly variable river total alkalinity (TA) and dissolved inorganic carbon (DIC) on pH and A in these estuaries is unknown. We assess the sensitivity of estuarine surface pH and A to river TA and DIC using a coupled biogeochemical model of the Strait of Georgia on the Canadian Pacific coast and place the results in the context of global rivers. The productive Strait of Georgia estuary has a large, seasonally variable freshwater input from the glacially fed, undammed Fraser River. Analyzing TA observations from this river plume and pH from the river mouth, we find that the Fraser is moderately alkaline (TA 500-1000 µmol kg −1 ) but relatively DICrich. Model results show that estuarine pH and A are sensitive to freshwater DIC and TA, but do not vary in synchrony except at high DIC : TA. The asynchrony occurs because increased freshwater TA is associated with increased DIC, which contributes to an increased estuarine DIC : TA and reduces pH, while the resulting higher carbonate ion concentration causes an increase in estuarine A . When freshwater DIC : TA increases (beyond ∼ 1.1), the shifting chemistry causes a paucity of the carbonate ion that overwhelms the simple dilution/enhancement effect. At this high DIC : TA ratio, estuarine sensitivity to river chemistry increases overall. Furthermore, this increased sensitivity extends to reduced flow regimes that are expected in future. Modulating these negative impacts is the seasonal productivity in the estuary which draws down DIC and reduces the sensitivity of estuarine pH to increasing DIC during the summer season.

show abstract

“…This explicit representation of the organic (OC) and inorganic carbon (IC) cycles allows simulating and quantifying the different processes controlling the OC/IC ratio and the emission of CO 2 into the atmosphere along the entire river network. Earlier modeling work in tidal estuaries using C-GEM alone evidenced the intense carbon processing taking place in the widest, marine part of estuaries (Regnier et al, 2013b;Volta et al, 2014Volta et al, , 2016a. The first integrated study presented here will allow further testing the hypothesis that the most downstream section of the river/estuarine system disproportionately contributes to the retention of carbon and CO 2 outgassing at the scale of an entire river network.…”

Section: Introductionmentioning

confidence: 71%

“…Our study relies on the off-line coupling of two transient, spatially discrete models: C-GEM and pyNuts-Riverstrahler. C-GEM is a recently developed generic estuarine model (Volta et al, 2014(Volta et al, , 2016a which has already been applied to several estuaries distributed along the coast of the North Atlantic Ocean (Volta et al, 2016b;Laruelle et al, 2017a) while the pyNuts-Riverstrahler platform is a well-established model coupling watersheds and river network (Billen et al, 1994;Garnier and Billen, 1994;Thieu et al, 2015). Simulations similar to those described in Marescaux (2018) are first performed with pyNuts-Riverstrahler for year 2010 over the entire Seine watershed.…”

Section: Modeling Strategymentioning

confidence: 99%

“…Spatially and temporally resolved numerical models are necessary to capture the CO 2 dynamics at the air-water interface, both in time and space (Regnier et al, 2013b). In this context, reactive transport models (RTM) allow reproducing the changes in chemical species concentrations due to both transport and biogeochemical transformations, thus providing a mechanistic insight into the fate of chemical species of interest in riverine and estuarine environments (Volta et al, 2014(Volta et al, , 2016aMarescaux, 2018;Romero et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation