Modeling biogeochemical processes in subterranean estuaries: Effect of flow dynamics and redox conditions on submarine groundwater discharge of nutrients

A two-dimensional density-dependent reactive transport model, which couples groundwater flow and biogeochemical reactions, is used to investigate the fate of nutrients (NO3 −, NH4 +, and PO4) in idealized subterranean estuaries representing four end-members of oxic/anoxic aquifer and seawater redox conditions. Results from the simplified model representations show that the prevalent flow characteristics and redox conditions in the freshwater-seawater mixing zone determine the extent of nutrient removal and the input of nitrogen and phosphorus to coastal waters. At low to moderate groundwater velocities, simultaneous nitrification and denitrification can lead to a reversal in the depth of freshwater NO3 − and NH4 +-PO4 plumes, compared to their original positions at the landward source. Model results suggest that autotrophic denitrification pathways with Fe2+ or FeS2 may provide an important, often overlooked link between nitrogen and phosphorus biogeochemistry through the precipitation of iron oxides and subsequent binding of phosphorus. Simulations also highlight that deviations of nutrient data from conservative mixing curves do not necessarily indicate nutrient removal.

[1]  R. Gillham,et al.  Denitrification and Organic Carbon Availability in Two Aquifers , 1993 .

[2]  W. Moore,et al.  Submarine groundwater discharge : A large, previously unrecognized source of dissolved iron to the South Atlantic Ocean , 2006 .

[3]  P. Régnier,et al.  Modelling the geochemical fate and transport of wastewater-derived phosphorus in contrasting groundwater systems. , 2007, Journal of contaminant hydrology.

[4]  B. L. Howes,et al.  Denitrification and Nitrogen Transport in a Coastal Aquifer Receiving Wastewater Discharge , 1996 .

[5]  Michael Rode,et al.  Modelling nitrate transport and turnover in a lowland catchment system , 2006 .

[6]  B. Nowicki,et al.  The discharge of nitrate‐contaminated groundwater from developed shoreline to marsh‐fringed estuary , 1998 .

[7]  M. Charette,et al.  Trace element cycling in a subterranean estuary: Part 2. Geochemistry of the pore water , 2006 .

[8]  S. Korom.  Natural denitrification in the saturated zone: a review , 1992 .

[9]  R. Johannes.  The Ecological Significance of the Submarine Discharge of Groundwater , 1980 .

[10]  A. Shiller.  The effect of recycling traps and upwelling on estuarine chemical flux estimates , 1996 .

[11]  C. Appelo,et al.  Geochemistry, groundwater and pollution , 1993 .

[12]  Hans W. Paerl,et al.  Coastal eutrophication and harmful algal blooms: Importance of atmospheric deposition and groundwater as “new” nitrogen and other nutrient sources , 1997 .

[13]  Brian L. Howes,et al.  Transport of groundwater-borne nutrients from watersheds and their effects on coastal waters , 1990 .

[14]  William C. Burnett,et al.  Estimating groundwater discharge into the northeastern Gulf of Mexico using radon-222 , 1996 .

[15]  R. Howarth.  Nutrient Limitation of Net Primary Production in Marine Ecosystems , 1988 .

[16]  C. Officer.  Discussion of the behaviour of nonconservative dissolved constituents in estuaries , 1979 .

[17]  D. Capone,et al.  Denitrification in Aquifer Soil and Nearshore Marine Sediments Influenced by Groundwater Nitrate , 1987 .

[18]  F. Comín,et al.  Nutrient water quality in a tropical coastal zone with groundwater discharge, northwest Yucatán, Mexico , 2006 .

[19]  P. Weiskel,et al.  Quantifying Dissolved Nitrogen Flux Through a Coastal Watershed , 1991 .

[20]  Robert Axelrod,et al.  The Global Environment , 1999 .

[21]  W. Moore,et al.  Submarine groundwater discharge: An important source of new inorganic nitrogen to coral reef ecosystems , 2006 .

[22]  W. Burnett,et al.  Patterns of groundwater discharge into Florida Bay , 1999 .

[23]  M. Brossard,et al.  Reactions controlling the cycling of P in soils , 1995 .

[24]  M. Charette,et al.  Oxidative precipitation of groundwater‐derived ferrous iron in the subterranean estuary of a coastal bay , 2002 .

[25]  D. Postma.  Kinetics of nitrate reduction by detrital Fe(II)-silicates , 1990 .

[26]  Douglas C. Miller,et al.  Groundwater mixing, nutrient diagenesis, and discharges across a sandy beachface, Cape Henlopen, Delaware (USA) , 2003 .

[27]  G. Kameia,et al.  The kinetics of reactions between pyrite and O2-bearing water revealed from in situ monitoring of DO, Eh and pH in a closed system , 2000 .

[28]  W. Moore,et al.  Marsh nutrient export supplied by groundwater discharge: Evidence from radium measurements , 2000 .

[29]  Wang Yifeng,et al.  Metal cycling in surface sediments; modeling the interplay of transport and reaction , 1995 .

[30]  D. Lynch,et al.  Dynamics of mixing in estuaries , 1981 .

[31]  M. Charette,et al.  Trace element cycling in a subterranean estuary: Part 1. Geochemistry of the permeable sediments , 2005 .

[32]  W. Moore.  The subterranean estuary: a reaction zone of ground water and sea water , 1999 .

[33]  T. Church.  An underground route for the water cycle , 1996, Nature.

[34]  P. Kitanidis,et al.  Experimental determination of transverse dispersivity in a helix and a cochlea , 2006 .

[35]  A. Giblin,et al.  Nitrogen inputs to a marine embayment: the importance of groundwater , 1990 .

[36]  L. N. Plummer,et al.  Mixing of carbonate waters , 1976 .

[37]  Brad Seely,et al.  NITROGEN LOADING FROM COASTAL WATERSHEDS TO RECEIVING ESTUARIES: NEW METHOD AND APPLICATION , 1997 .

[38]  A. Scheidegger.  General Theory of Dispersion in Porous Media , 1961 .

[39]  J. Catalán,et al.  Temporal changes of microbial assemblages in the ice and snow cover of a high mountain lake , 1999 .

[40]  J. Bratton,et al.  Submarine groundwater discharge to a small estuary estimated from radon and salinity measurements and a box model , 2005 .

[41]  C. Slomp,et al.  Nutrient inputs to the coastal ocean through submarine groundwater discharge: controls and potential impact , 2004 .

[42]  A. Paytan,et al.  Composition and flux of groundwater from a California beach aquifer: Implications for nutrient supply to the surf zone , 2006 .

[43]  D. Capone,et al.  A groundwater source of nitrate in nearshore marine sediments , 1985, Nature.

[44]  W. Burnett,et al.  Groundwater-derived nutrient inputs to the Upper Gulf of Thailand , 2007 .

[45]  Emil O. Frind,et al.  Modeling of multicomponent transport with microbial transformation in groundwater: The Fuhrberg Case , 1990 .

[46]  D. Postma,et al.  Nitrate Reduction in an Unconfined Sandy Aquifer: Water Chemistry, Reduction Processes, and Geochemical Modeling , 1991 .

[47]  P. Falkowski,et al.  Brown Tide blooms in Long Island’s coastal waters linked to interannual variability in groundwater flow , 1997 .

[48]  J. Oberdorfer,et al.  Groundwater contribution to the nutrient budget of Tomales Bay, California , 1990 .

[49]  M. Krom,et al.  Adsorption of phosphate in anoxic marine sediments1 , 1980 .

[50]  Other.  Submarine groundwater discharge: management implications, measurements and effects , 2004 .

[51]  F. Widdel,et al.  Anaerobic, nitrate-dependent microbial oxidation of ferrous iron , 1996, Applied and environmental microbiology.

[52]  P. Sewell.  Urban groundwater as a possible nutrient source for an estuarine benthic algal bloom , 1982 .

[53]  B. Lapointe,et al.  Nutrient couplings between on-site sewage disposal systems, groundwaters, and nearshore surface waters of the Florida Keys , 1990 .

[54]  Jeffrey C. Silvertooth,et al.  Kinetics of hydroxyapatite precipitation at pH 7.4 to 8.4 , 1988 .

[55]  Submarine groundwater discharge into the sea and associated nutrient transport in a Sandy Beach , 2000 .

[56]  M. Baskaran,et al.  Biogeochemical transport in the Loxahatchee River estuary, Florida: The role of submarine groundwater discharge , 2005 .

[57]  B. Nowicki,et al.  The role of sediment denitrification in reducing groundwater-derived nitrate inputs to Nauset Marsh estuary, Cape Cod, Massachusetts , 1999 .

[58]  Kagan Tuncay,et al.  Scale dependence of reaction rates in porous media , 2006 .

[59]  M. Charette,et al.  Nitrogen flux and speciation through the subterranean estuary of Waquoit Bay, Massachusetts. , 2003, The Biological bulletin.

[60]  G. Garrison,et al.  Measurement of submarine groundwater discharge in Kahana Bay, O'ahu, Hawai'i , 2003 .

[61]  W. Burnett,et al.  Investigation of submarine groundwater discharge , 2002 .

[62]  D. Capone,et al.  Interannual patterns of water table height and groundwater derived nitrate in nearshore sediments , 1990 .

[63]  R. Johannes,et al.  The effect of submarine groundwater discharge on nutrient and salinity regimes in a coastal lagoon o , 1985 .

[64]  M. Charette,et al.  Utility of radium isotopes for evaluating the input and transport of groundwater‐derived nitrogen to a Cape Cod estuary , 2001 .

[65]  S. Ueda,et al.  Denitrification in a seashore sandy deposit influenced by groundwater discharge , 2003 .

[66]  M. Sivapalan,et al.  Nitrate attenuation in agricultural catchments: Shifting balances between transport and reaction , 2006 .

[67]  S. Ueda,et al.  Control of Phosphate Concentration through Adsorption and Desorption Processes in Groundwater and Seawater Mixing at Sandy Beaches in Tokyo Bay, Japan , 2000 .

[68]  William C. Burnett,et al.  The importance of groundwater discharge to the methane budgets of nearshore and continental shelf waters of the northeastern Gulf of Mexico , 1996 .

[69]  J. Reddy.  An introduction to the finite element method , 1989 .

[70]  D. R. Kester,et al.  Determination of the Apparent Dissociation Constants of Phosphoric Acid in SEAWATER1 , 1967 .

[71]  B. L. Howes,et al.  Differential transport of sewage-derived nitrogen and phosphorus through a coastal watershed , 1992 .

[72]  J. Bear.  Dynamics of Fluids in Porous Media , 1975 .

[73]  T. Stieglitz,et al.  Quantifying submarine groundwater discharge in the coastal zone via multiple methods. , 2006, The Science of the total environment.

[74]  K. Lajtha,et al.  Couplings of watersheds and coastal waters: Sources and consequences of nutrient enrichment in Waquoit Bay, Massachusetts , 1992 .

[75]  M. Charette,et al.  pH-Dependent iron oxide precipitation in a subterranean estuary , 2006 .

[76]  S. Stadler,et al.  Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations. , 2006, Journal of contaminant hydrology.