Anthropogenic Salinization Research Articles

The influence of anthropogenic salinization on the soil mineralogy

The influence of anthropogenic salinization on the soil mineralogy

Spatial relationships between vegetation cover and irrigation-induced groundwater discharge on a semi-arid floodplain, Australia

Insight into spatial patterns of groundwater discharge through evapotranspiration is critical for understanding responses of groundwater dependent ecosystems. In the semi-arid floodplain environment of the lower River Murray, South Australia, patterns of steady state groundwater flux may indicate potential areas of anthropogenic salinisation due to adjacent irrigation and aid in management decisions for the protection of indigenous floodplain vegetation. This paper within the MODFLOW 2000 framework relationships for evapotranspiration response to groundwater depth and salt concentration, outlines the use of, to model spatial patterns of groundwater flux. This modelling approach is used to develop relationships between the steady state net rates evapotranspiration, seepage and baseflow, and floodplain properties including elevation, geometry, soil and vegetation distribution relevant to the field site. The model was applied to a key research site on the River Murray, South Australia, to facilitate understanding of the factors contributing to the development of spatial patterns of irrigation induced groundwater discharge. The inclusion of elevation and vegetation data in the methodology revealed the effects of microtopography and plant water use on groundwater discharge. Spatial distribution of vegetation had the highest correlation with patterns of groundwater evapotranspiration. Floodplain elevation, floodplain width and geometry, which related to vegetation cover, also affected both groundwater discharge and baseflow to the river.

Temporal and spatial dynamics of macroalgal communities along an anthropogenic salinity gradient in Biscayne Bay (Florida, USA)

The seasonal and spatial dynamics of two groups of macroalgae, drift algae and rhizophytes, commonly found in tropical seagrass meadows were studied. The aim of this study was to provide insight into how freshwater discharges may be altering seagrass-dominated nearshore tropical habitats. Species composition, biomass, and percent cover of macroalgae were collected at six Thalassia testudinum König dominated sites within Biscayne Bay, Florida, representing three salinity regimes: canal-influenced, natural sheet-flow, and oceanic conditions. Mean annual salinities in these three regimes correspond to 10, 25 and 35 psu, respectively, with much greater variability in the canal and sheet-flow regimes, than in the oceanic condition. There were distinct changes in the composition of the macroalgal community along this salinity gradient. Drift algae ( Chondria spp., Laurencia spp.) were most commonly found at canal-disturbed sites (10–85 g m −2), while rhizophytic calcareous green algae ( Halimeda spp., Penicillus spp.) were most abundant at the higher salinity oceanic sites (20–105 g m −2). Seasonal patterns exhibited by the two groups differed also, with drift algae being more abundant in the cooler dry-season months, while rhizophytic algae were more abundant during the warmer wet-season months. These periods of higher abundance correlated with higher growth rates (drift = 2.3% day −1, rhizophytes = 0.85% day −1) measured in representative species for each group. Grazing rates on drift algae were found to be low for tropical habitats and did not differ much between canal (0.44% h −1) and oceanic sites (0.42% h −1).

Soils, surficial geology, and geomicrobiology of saline-sodic wetlands, North Platte River Valley, Nebraska, USA

Saline-sodic wetlands along a 200-km stretch of the North Platte River Valley in western Nebraska, USA lie within an important agricultural region, but their processes, salt mineralogy, and geomicrobiology have not previously been investigated. Putative anthropogenic salinization has long been a concern, yet early historical accounts of widespread surface salts in the area have never been applied as comparative standards. Surface salts in the area originate from soil capillarity and surface evaporation. Thenardite (Na 2SO 4) and/or mirabilite (NaSO 4·10 H 2O) dominate, depending on ambient conditions. Bloedite (Na 2Mg[SO 4] 2·4[H 2O]), halite (NaCl), burkeite (Na 6CO 3[SO 4] 2), and calcite (CaCO 3) are minor constituents. Historical accounts indicate that salts accumulated naturally long before Euramerican settlement, apparently as a result of rock–water interaction in nearby volcaniclastic sediments of the Brule Formation. Ephemeral to permanent water-holding basins in the wetlands contain Na +-rich waters that vary widely in electrical conductivity (as high as 159 mS/cm) and in ionic composition, but local spring waters are extremely dilute. Basin floors exhibit a unique type of microrelief, which appears to form by the filling of microlows with water and the dispersal of soil material therein by Na +, followed by dewatering and collapse of the soil with drying. Illite dominates basin surface soils, but smectite dominates at depth; high soil pH, available K +, and frequent wetting–drying cycles in the wetlands suggest that in-situ illitization may have occurred. Soil crusts and vesicular surface horizons are common as are upward increases in electrical conductivity. The activity of sulfate-reducing microbes forms prominent near-surface horizons of sulfate reduction in saturated soils, which retract or disappear entirely during dry episodes. Saline-sodic wetland soils in the study area change on daily to seasonal scales. Cycles of surface salt development, microbial activity, and microrelief genesis are all controlled by regular wetting–drying cycles and the interaction of ponded surface waters and shallow groundwaters. Relatively unique aspects of microbial ecology and surface processes make the soils important as “geomicrobial reactors” wherein important parts of hydrological and geochemical cycles occur.

Relationship between anthropogenic salinity and temperature regime of permafrost, Central Yakutia

In Central Yakutia high-salinity soils are not limited to the active layer. Sometimes, cryopegs are formed that contain highly mineralized, negative-temperature groundwaters. There is a direct relationship between the ground temperature regime and soil salinity. Anthropogenic influences (i.e. urbanization) can cause intensive salt localization and the formation of taliks (cryopegs) to depths of 5–6 m or more. Copyright © 2000 John Wiley & Sons, Ltd. En Yakoutie centrale, des sols hautement sales n'existent pas seulement dans la couche active. Parfois des cryopegs apparaissent qui contiennent des eaux fortement mineralisees dont la temperature est negative. Il y a une relation directe entre le regime de temperature du sol et la salinite de celui-ci. Des influences anthropogeniques (par exemple l'urbanisation) peut entrainer la presence locale d'une quantite importante de sel dans le sol et la formation de taliks (cryopegs) jusqu'a une profondeur de 5 a 6 m ou meme plus. Copyright © 2000 John Wiley & Sons, Ltd.

Relationship between anthropogenic salinity and temperature regime of permafrost, Central Yakutia

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The relationship between anthropogenic salinization of permafrost and its temperature conditons, central yakutia1

Two Russian researchers examine the relationship between the temperature of permafrost underlying residential structures and soil chemical composition as affected by human activity (e.g., releases of wastewater in unheated basements). A particular focus is on the formation and dynamics of cryopegs in soils used for building foundations. The results are based on measurements from a network of boreholes at test sites for the measurement of ground temperature and salinity. Translated by Edward Torrey, Alexandria, VA from: Geografiya iprirodnyye resursy 2000, No. 2, pp. 80–84.