TY - JOUR
T1 - Application of stable isotopes of water to study coupled submarine groundwater discharge and nutrient delivery
AU - Duque, Carlos
AU - Jessen, Søren
AU - Tirado-Conde, Joel
AU - Karan, Sachin
AU - Engesgaard, Peter
N1 - Funding Information:
We thank Iris Tobelaim, Christian Hansen and students in the Hydrogeological field course (2016) for field and laboratory assistance. The research leading to these results has received funding from the European Union Seventh Framework Programme FP7/2007-2013 under grant agreement number 624496, the European Union's Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement number 722028 and the HOBE project (Hobe.dk) funded by the Villum Fundation. This work was carried out as part of the activities of the Aarhus University Centre for Water Technology, WATEC.
Publisher Copyright:
© 2019 by the authors.
PY - 2019/9
Y1 - 2019/9
N2 - Submarine groundwater discharge (SGD)-including terrestrial freshwater, density-driven flow at the saltwater-freshwater interface, and benthic exchange-can deliver nutrients to coastal areas, generating a negative effect in the quality of marine water bodies. It is recognized that water stable isotopes (18O and 2H) can be helpful tracers to identify different flow paths and origins of water. Here, we show that they can be also applied when assessing sources of nutrients to coastal areas. A field site near a lagoon (Ringkøbing Fjord, Denmark) has been monitored at a metric scale to test if stable isotopes of water can be used to achieve a better understanding of the hydrochemical processes taking place in coastal aquifers, where there is a transition from freshwater to saltwater. Results show that 18O and 2H differentiate the coastal aquifer into three zones: Freshwater, shallow, and deep saline zones, which corresponded well with zones having distinct concentrations of inorganic phosphorous. The explanation is associated with three mechanisms: (1) Differences in sediment composition, (2) chemical reactions triggered by mixing of different type of fluxes, and (3) biochemical and diffusive processes in the lagoon bed. The different behaviors of nutrients in Ringkøbing Fjord need to be considered in water quality management. PO4 underneath the lagoon exceeds the groundwater concentration inland, thus demonstrating an intra-lagoon origin, while NO3, higher inland due to anthropogenic activity, is denitrified in the study area before reaching the lagoon.
AB - Submarine groundwater discharge (SGD)-including terrestrial freshwater, density-driven flow at the saltwater-freshwater interface, and benthic exchange-can deliver nutrients to coastal areas, generating a negative effect in the quality of marine water bodies. It is recognized that water stable isotopes (18O and 2H) can be helpful tracers to identify different flow paths and origins of water. Here, we show that they can be also applied when assessing sources of nutrients to coastal areas. A field site near a lagoon (Ringkøbing Fjord, Denmark) has been monitored at a metric scale to test if stable isotopes of water can be used to achieve a better understanding of the hydrochemical processes taking place in coastal aquifers, where there is a transition from freshwater to saltwater. Results show that 18O and 2H differentiate the coastal aquifer into three zones: Freshwater, shallow, and deep saline zones, which corresponded well with zones having distinct concentrations of inorganic phosphorous. The explanation is associated with three mechanisms: (1) Differences in sediment composition, (2) chemical reactions triggered by mixing of different type of fluxes, and (3) biochemical and diffusive processes in the lagoon bed. The different behaviors of nutrients in Ringkøbing Fjord need to be considered in water quality management. PO4 underneath the lagoon exceeds the groundwater concentration inland, thus demonstrating an intra-lagoon origin, while NO3, higher inland due to anthropogenic activity, is denitrified in the study area before reaching the lagoon.
KW - Freshwater- saltwater interface
KW - Nutrients
KW - Ringkøbing Fjord
KW - Stable isotopes of water
KW - Submarine groundwater discharge
UR - http://www.scopus.com/inward/record.url?scp=85072215834&partnerID=8YFLogxK
U2 - 10.3390/w11091842
DO - 10.3390/w11091842
M3 - Article
AN - SCOPUS:85072215834
SN - 2073-4441
VL - 11
JO - Water (Switzerland)
JF - Water (Switzerland)
IS - 9
M1 - 1842
ER -