Park, H., & Schlesinger, W. (2002). Global biochemical cycle of boron. Global Biogeochemical Cycles, 16, 1072.
Abstract: The global Boron (B) cycle is primarily driven by a large flux (1.44 Tg B/yr) through the atmosphere derived from seasalt aerosols. Other significant sources of atmospheric boron include emissions during the combustion of biomass (0.26-0.43 Tg B/yr) and coal, which adds 0.20 Tg B/yr as an anthropogenic contribution. These known inputs to the atmosphere cannot account for the boron removed from the atmosphere during rainfall (3.0 Tg B/yr) and estimated dry deposition (1.3-2.7 Tg B/yr). In addition to atmospheric deposition, rock weathering is a source of boron (0.19 Tg B/yr) for terrestrial ecosystems, and humans mine about 0.31 Tg B/yr from the Earth's crust. More than 4.8 Tg B/yr circulates in the biogeochemical cycle of land plants, and about 0.53-0.63 Tg B/yr is carried from land to sea by rivers. The biogeochemical cycle of boron in the sea includes 4.4 Tg B/yr circulating in the marine biosphere, and an annual loss of 0.47 Tg B/yr to the oceanic crust via a variety of sedimentary processes that collectively remove only a small fraction of the total annual inputs to the oceans. Thus with our current understanding of the global biogeochemistry of B, the atmospheric budget shows outputs > inputs, while the marine compartments show inputs > outputs. Despite these uncertainties, it is clear that the human perturbation of the global B cycle has more than doubled the mobilization of B from the crust and contributes significantly to the B transport in rivers.
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Han, D., Post, V. E. A., & Song, X. (2015). Groundwater salinization processes and reversibility of seawater intrusion in coastal carbonate aquifers. Journal of Hydrology, 531, 1067–1080.
Abstract: Seawater intrusion (SWI) has led to salinization of fresh groundwater reserves in coastal areas worldwide and has forced the closure of water supply wells. There is a paucity of well-documented studies that report on the reversal of SWI after the closure of a well field. This study presents data from the coastal carbonate aquifer in northeast China, where large-scale extraction has ceased since 2001 after salinization of the main well field. The physical flow and concomitant hydrogeochemical processes were investigated by analyzing water level and geochemical data, including major ion chemistry and stable water isotope data. Seasonal water table and salinity fluctuations, as well as changes of δ2H–δ18O values of groundwater between the wet and dry season, suggest local meteoric recharge with a pronounced seasonal regime. Historical monitoring testifies of the reversibility of SWI in the carbonate aquifer, as evidenced by a decrease of the Cl− concentrations in groundwater following restrictions on groundwater abstraction. This is attributed to the rapid flushing in this system where flow occurs preferentially along karst conduits, fractures and fault zones. The partially positive correlation between δ18O values and TDS concentrations of groundwater, as well as high NO3− concentrations (\textgreater39mg/L), suggest that irrigation return flow is a significant recharge component. Therefore, the present-day elevated salinities are more likely due to agricultural activities rather than SWI. Nevertheless, seawater mixing with fresh groundwater cannot be ruled out in particular where formerly intruded seawater may still reside in immobile zones of the carbonate aquifer. The massive expansion of fish farming in seawater ponds in the coastal zone poses a new risk of salinization. Cation exchange, carbonate dissolution, and fertilizer application are the dominant processes further modifying the groundwater composition, which is investigated quantitatively using hydrogeochemical models.
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Panagopoulos, G. (2009). Application of major and trace elements as well as boron isotopes for tracing hydrochemical processes: the case of Trifilia coastal karst aquifer, Greece. Environmental Geology, 58(5), 1067–1082.
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Pulido-Leboeuf, P., Pulido-Bosch, A., Calvache, M. L., Vallejos, Á., & Andreu, J. M. (2003). Strontium, SO42-/Cl- and Mg2+/Ca2+ ratios as tracers for the evolution of seawater into coastal aquifers: the example of Castell de Ferro aquifer (SE Spain). Comptes Rendus Geoscience, 335(14), 1039–1048.
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Wigley, T. M. L., & Plummer, L. N. (1976). Mixing of carbonate waters. Geochimica et Cosmochimica Acta, 40(9), 989–995.
Abstract: When mineral solutions of different compositions are mixed, the molalities and activities of individual ions in the mixture are often non-linear functions of their end-member values. This non-linearity is particularly significant in determining mineral saturation levels. Mixtures of saturated solutions may be either undersaturated or supersaturated depending on the end-member compositions and the physical conditions in which end-members and their mixtures exist. In carbonate solutions important non-linear effects occur due to redistribution of carbonate species. In extreme cases this causes mixture pH to be below both the end-member pH values. A simple but precise computer program (WATMIX) has been developed for calculating mixture composition for closed and open system mixing of arbitrary end-members. A number of mixing examples are considered which allow one to isolate three important processes leading to non-linear behaviour: the algebraic effect, the δPCO2 effect, and the ionic strength effect.
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