http://www.vliz.be/imisdocs/publications/242609.pdf

Seawater intrusion processes, investigation and management: Recent advances and future challenges

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1856&context=usdaarsfacpub

Beneath the surface of global change: Impacts of climate change on groundwater

The exchange of groundwater between land and sea is a major component of the hydrological cycle. This exchange, called submarine groundwater discharge (SGD), is comprised of terrestrial water mixed with sea water that has infiltrated coastal aquifers. The composition of SGD differs from that predicted by simple mixing because biogeochemical reactions in the aquifer modify its chemistry. To emphasize the importance of mixing and chemical reaction, these coastal aquifers are called subterranean estuaries. Geologists recognize this mixing zone as a site of carbonate diagenesis and dolomite formation. Biologists have recognized that terrestrial inputs of nutrients to the coastal ocean may occur through subterranean processes. Further evidence of SGD comes from the distribution of chemical tracers in the coastal ocean. These tracers originate within coastal aquifers and reach the ocean through SGD. Tracer studies reveal that SGD provides globally important fluxes of nutrients, carbon, and metals to coastal waters.

https://moritz.botany.ut.ee/~olli/eutrsem/Moore_2010.pdf

The Effect of Submarine Groundwater Discharge on the Ocean

Advective flows rapidly transport water, solutes, and particles into and out of permeable sand beds and significantly affects the biogeochemistry of coastal environments. In this paper, we reviewed the drivers of porewater and groundwater advection in permeable shelf sediments in an attempt to bridge gaps among different disciplines studying similar problems. We identified the following driving forces: (1) terrestrial hydraulic gradients, (2) seasonal changes in the aquifer level on land moving the location of the subterranean estuary, (3) wave setup and tidal pumping, (4) water level differences across permeable barriers, (5) flow- and topography-induced pressure gradients, (6) wave pumping; (7) ripple and other bed form migration, (8) fluid shear, (9) density-driven convection, (10) bioirrigation and bioturbation, (11) gas bubble upwelling, and (12) sediment compaction. While these drivers occur over spatial scales ranging from mm to km, and temporal scales ranging from seconds to years, their ultimate biogeochemical implications are very similar (i.e., they are often a source of new or recycled nutrients to seawater and transform organic carbon into inorganic carbon). Drivers 2–12 result in no net water input into the ocean. Taking all these mechanisms into account, we conservatively estimate that a volume equivalent to that of the entire ocean is filtered by permeable sediments at time scales of about 3000 years. Quantifying the relative contribution of these drivers is essential to understand the contribution of sediments to the global cycles of matter.

The driving forces of porewater and groundwater flow in permeable coastal sediments: a review

A majority of the global net primary production of mangroves is unaccounted for by current carbon budgets. It has been hypothesized that this ‘‘missing carbon’’ is exported as dissolved inorganic carbon (DIC) from subsurface respiration and groundwater (or pore-water) exchange driven by tidal pumping. We tested this hypothesis by measuring concentrations and d13C values of DIC, dissolved organic carbon (DOC), and particulate organic carbon (POC), along with radon (222Rn, a natural submarine groundwater discharge tracer), in a tidal creek in Moreton Bay, Australia. Concentrations and d13C values displayed consistent tidal variations, and mirrored the trend in 222Rn in summer and winter. DIC and DOC were exported from, and POC was imported to, the mangroves during all tidal cycles. The exported DOC had a similar d13C value in summer and winter (, 230%). The exported d13C-DIC showed no difference between summer and winter and had a d13C value slightly more enriched (, 222.5%) than the exported DOC. The imported POC had differing values in summer (, 216%) and winter (, 222%), reflecting a combination of seagrass and estuarine particulate organic matter (POM) in summer and most likely a dominance of estuarine POM in winter. A coupled 222Rn and carbon model showed that 93–99% of the DIC and 89–92% of the DOC exports were driven by groundwater advection. DIC export averaged 3 g C m22 d21 and was an order of magnitude higher than DOC export, and similar to global estimates of the mangrove missing carbon (i.e., , 1.9–2.7 g C m22 d21). The link between terrestrial and marine carbon cycles is an important yet poorly constrained component of the global carbon cycle. Most models of the global carbon cycle only include three reservoirs (terrestrial, marine, and atmosphere) with the link between terrestrial and marine components defined as an ‘‘unreactive pipe’’ (Cole et al. 2007). This unreactive pipe is defined as the flow of terrestrial-derived organic matter via surface waters (i.e., rivers) to the ocean. However, studies suggest that significant transformations of the organic matter pool

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2013.58.2.0475

Groundwater‐derived dissolved inorganic and organic carbon exports from a mangrove tidal creek: The missing mangrove carbon sink?

https://www.whoi.edu/science/MCG/groundwater/pubs/PDF/burnett%20et%20al..pdf

A. Loveless

Papers

Quantifying Submarine Groundwater Discharge in the Coastal Zone via Multiple Methods