Beata Szymczycha

Nutrient fluxes via submarine groundwater discharge to the Bay of Puck, southern Baltic Sea

Submarine groundwater discharge (SGD) has been recognized as an important exchange pathway between hydrologic reservoirs due to its impact on biogeochemical cycles of the coastal ocean. This study reports nutrient concentrations and loads delivered by SGD into the Bay of Puck, the southern Baltic Sea. Measurements were carried out between September, 2009 and October, 2010 at groundwater seepage sites identified by low salinity of pore water. Groundwater fluxes, measured using seepage meters, ranged from 3 to 22 L m(-2)day(-1). Average concentrations of nutrients in groundwater samples collected were as follows: 0.4 μmol L(-1) nitrate (NO(3)), 0.8 μmol L(-1) nitrite (NO(2)), 18.2 μmol L(-1) ammonium (NH(4)) and 60.6 μmol L(-1) orthophosphate (PO(4)). Levels of NH(4) and PO(4) were significantly higher in samples from SGD sites than in seawater. Seawater and SGD samples showed similar NO(2) concentrations but SGD samples exhibited lower NO(3) levels than those observed in seawater samples. Measured seepage water fluxes and nutrient concentrations were used to calculate nutrient loads discharged into the study area while the literature groundwater flux and the measured nutrient concentrations were used to estimate nutrient loads discharged into the Bay of Puck. The estimates suggest that SGD delivers a dissolved inorganic nitrogen (DIN) load of 49.9 ± 18.0 t yr(-1) and a PO(4)(-) load of 56.3 ± 5.5tyr(-1) into the Bay of Puck. The projected estimates are significant in comparison with loads delivered to the bay from other, well-recognized sources (705 ty r(-1) and 105 ty r(-1) respectively for DIN and PO(4)). Nutrient discharge input loads were projected to the entire Baltic Sea The extrapolated values indicate SGD contributes a significant proportion of phosphate load but only an insignificant proportion of DIN load. Further studies are necessary to better understand SGD contributions to the nutrient budget in the Baltic Sea.

Significance of groundwater discharge along the coast of Poland as a source of dissolved metals to the southern Baltic Sea

Fluxes of dissolved trace metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) via groundwater discharge along the southern Baltic Sea have been assessed for the first time. Dissolved metal concentrations in groundwater samples were less variable than in seawater and were generally one or two orders of magnitude higher: Cd (2.1-2.8nmolL(-1)), Co (8.70-8.76nmolL(-1)), Cr (18.1-18.5nmolL(-1)), Mn (2.4-2.8μmolL(-1)), Pb (1.2-1.5nmolL(-1)), Zn (33.1-34.0nmolL(-1)). Concentrations of Cu (0.5-0.8nmolL(-1)) and Ni (4.9-5.8nmolL(-1)) were, respectively, 32 and 4 times lower, than in seawater. Groundwater-derived trace metal fluxes constitute 93% for Cd, 80% for Co, 91% for Cr, 6% for Cu, 66% for Mn, 4% for Ni, 70% for Pb and 93% for Zn of the total freshwater trace metal flux to the Bay of Puck. Groundwater-seawater mixing, redox conditions and Mn-cycling are the main processes responsible for trace metal distribution in groundwater discharge sites.

Depth of the vadose zone controls aquifer biogeochemical conditions and extent of anthropogenic nitrogen removal

We investigated biogeochemical conditions and watershed features controlling the extent of nitrate removal through microbial dinitrogen (N2) production within the surficial glacial aquifer located on the north and south shores of Long Island, NY, USA. The extent of N2 production differs within portions of the aquifer, with greatest N2 production observed at the south shore of Long Island where the vadose zone is thinnest, while limited N2 production occurred under the thick vadose zones on the north shore. In areas with a shallow water table and thin vadose zone, low oxygen concentrations and sufficient DOC concentrations are conducive to N2 production. Results support the hypothesis that in aquifers without a significant supply of sediment-bound reducing potential, vadose zone thickness exerts an important control of the extent of N2 production. Since quantification of excess N2 relies on knowledge of equilibrium N2 concentration at recharge, calculated based on temperature at recharge, we further identify several features, such as land use and cover, seasonality of recharge, and climate change that should be considered to refine estimation of recharge temperature, its deviation from mean annual air temperature, and resulting deviation from expected equilibrium gas concentrations.

Research on Submarine Groundwater Discharge in the Baltic Sea

SGD has been recognized as an important pathway of material transport from land to the marine environment. Despite numerous studies as regards hydraulic fluxes and chemical composition of groundwater seeping to the coastal ocean much remains to be done to characterize SGD impact on the coastal marine environment. The Baltic Sea is an example of a region highly influenced by a variety of human activities that affect the ecosystem. SGD is a source introducing dissolved substances into the Baltic Sea that has not been quantified so far. Little is known regarding the concentrations and fluxes of chemical substances in groundwater discharged to the Baltic Sea and chemical reactions that control their flux into the coastal ecosystem.

Sorption of Cr, Pb, Cu, Zn, Cd, Ni, and Co to nano-TiO2 in seawater

In this study, the role of nanoparticles in complex aqueous matrices such as the Baltic Sea was investigated in batch-mode experiments in which titanium dioxide nanoparticles (nano-TiO2) were tested for their ability to remove heavy metals (Cr, Pb, Cu, Zn, Cd, Ni, Co) from multicomponent spiked and non-spiked Baltic Sea water. The experimental data were analyzed using different isotherms (Langmuir, Freundlich, Dubinin-Kaganer-Radushkevich (DKR)) and models (pseudo-first-order and pseudo-second-order models, the double-exponential model, and the Weber-Morris model). The equilibria and kinetic investigations showed that metal sorption to nano-TiO2 occurs in a two-step, multilayer process and that there is strong competition for sorption sites. The results of the DKR isotherm and dilution experiment indicated weak electrostatic bonds, except for Pb. The distribution coefficient values (1.8 × 103 to 2.8 × 105 ml g-1) were consistent with the good sorbent properties of nano-TiO2 and supported the use of the particles in seawater purification technologies. However, metal-enriched nano-TiO2 may also act as an effective carriers of metals to marine sediments, which could increase their availability to benthic organisms.

State of Art and Theory of Submarine Groundwater Discharge (SGD)

The water discharge is the most important pathway connecting land and ocean. Surface water inputs (e.g., rivers and streams) are usually easily visible and are typically large point material sources to the coastal ocean (Mulligan and Charette 2009). Hence, the contribution of surface water discharge to the ocean geochemical budgets has been well studied. The hydrodynamics and impact of terrestrial water on geochemical cycles of elements and its influence on the ocean ecosystem has been well recognised.

Characteristic of the Baltic Sea

The Baltic Sea is a land locked sea located in the Northern Europe. To this south the Baltic Sea border with the European mainland (Russia, Estonia, Latvia, Lithuania, Poland, Germany, Denmark), while to the north—the Scandinavian Peninsula (Finland and Sweden). The only connection to the North Sea is through the shallow and nerrow Danish Straits and further through the Kattegat and the Skagerrak. The Belt Sea, including the Danish Straits, is the transition zone between the Baltic Sea with the North Sea.

Submarine Groundwater Discharge to the Bay of Puck, Southern Baltic Sea and Its Possible Changes with Regard to Predicted Climate Changes

The climate change is an ongoing phenomenon causing numerous environmental problems, including modifications of the already seriously influenced by anthropogenic activity hydrological cycle. Estimating the climate change influence on groundwater is challenging because climate change can modify hydrological processes and groundwater resources directly and indirectly. Under the climate scenarios for the southern Baltic, precipitation is projected to increase in the entire Baltic Sea watershed in winter, while in summer increase of precipitation is mainly projected in the northern part of the basin. Thus, the precipitation will impact the groundwater discharge to the sea (SGD). Consequently, the already substantial SGD to the Bay of Puck, southern Baltic Sea can increase. Not only the additional amount of water will enter the marine environment by means of SGD but also significant load of chemical substances.