Heavy metals in sediments_'problems concerning determination of the anthropogenic influence. Study in the Krka River estuary, eastern Adriatic coast, Yugoslavia, 1989, Prohi'_ Esad, Jura' I'_,

Evaluation of terra rossa geochemical baselines from Croatian karst regions, 1999, Miko S. , Durn G. , Prohic E. ,

In karst regions of Croatia, regolith is the only favourable medium for geochemical mapping. Mediterranean climate and good drainage due to hard, fissured, permeable limestones and dolomites result in a spacious distribution of terra rossa (FAO-luvisols and cambisols) - a polygenetic type of soil. Samples of terra rossa from coastal and inland Croatian Dinaric karst terrains were collected during the initial studies for the Geochemical Map of Croatia at a density of 1 site/25 km(2). A total of 87 terra rossa soil samples taken from a depth of 5-25 cm together with 27 samples from deeper profiles (down to 850 cm) were analysed for total Al, Ba, Ca, Co, Cr, Cu, Fe, Ga, La, Mg, Mn, Ni, Pb, Na, Sr, Ti, V and Zn concentrations. A stoichiometric approach was applied by modeling of terra rossa baselines on the basis of Linear regressions of metals on Al and the calculation of enrichment factors (EF and CEFs) on the basis of soil standards. A noticeable enrichment of Pb was found in surface samples compared to the terra rossa deeper in the soil profile. Using these baseline relationships, an attempt is made to partition terra rossa metal concentrations into natural and anthropogenic fractions. Also, the models from both polluted and less polluted (uninhabited) karstic terrains improve the comparability of element contents through correction of variable background concentrations. A comparison of elemental concentrations revealed that due to contributions of bauxite debris, a number of studied samples is enriched in Cr and Ni (also with variable amounts of boehmite). The corrections will serve to reduce data variability and to increase the detection of spatial and temporal differences presented on the geochemical maps. (C) 1999 Elsevier Science B.V. All rights reserved

Toward a coastal ground-water typology, 2001, Bokuniewicz H,

Although submarine ground-water discharge is recognised as being of physical and ecological significance, direct measurements are rare, and calculations are hampered by a lack of offshore data. Classification of the world's coast with respect to its potential, submarine ground-water contribution would help to focus attention on the most important areas and to extrapolate existing data. A classification may be based on relevant physical/climatological parameters (e.g. precipitation, soil type etc.), or geologic/geomorphic classes (e.g. karst, coastal plain, etc.), or on a collection of state parameters. State parameters for a coastal ground-water typology may include aquifer thickness, onshore hydraulic gradient, anisotropy and fractal dimension of the shoreline. Topographic gradient can serve as a surrogate for the hydraulic gradient. A fourth type of classification may be based on the distribution of salinity in the subterranean estuary but adequate subsurface data are not yet available. (C) 2001 Elsevier Science B.V. All rights reserved

The hydrogeochemistry of the karst aquifer system of the northern Yucatan Peninsula, Mexico, 2002, Perry E. , Velazquezoliman G. , Marin L. ,

Based on groundwater geochemistry, stratigraphy, and surficial and tectonic characteristics, the northern Yucatan Peninsula, Mexico, a possible analog for ancient carbonate platforms, is divided into six hydrogeochemical/physiographic regions: (1) Chicxulub Sedimentary Basin, a Tertiary basin within the Chicxulub impact crater; (2) Cenote Ring, a semicircular region of sinkholes; (3) Pockmarked Terrain, a region of mature karst; (4) Ticul fault zone; (5) Holbox Fracture Zone-Xel-Ha Zone; and (6) Evaporite Region. Regional characteristics result from tectonics, rock type, and patterns of sedimentation, erosion, and rainfall. The Cenote Ring, characterized by high groundwater flow, outlines the Chicxulub Basin. Most groundwater approaches saturation in calcite and dolomite but is undersaturated in gypsum. Important groundwater parameters are: SO4/Cl ratios related to seawater mixing and sulfate dissolution; Sr correlation with SO4, and saturation of Lake Chichancanab water with celestite. indicating celestite as a major source of Sr; high Sr in deep water of cenotes, indicating deep circulation and contact of groundwater with evaporite; and correlation of Ca, Mg, and SO4, probably related to gypsum dissolution and dedolomitization. Based on geochemistry we propose: (1) a fault between Lake Chichancanab and Cenote Azul; (2) deep seaward movement of groundwater near Cenote Azul; and (3) contribution of evaporite dissolution to karst development in the Pockmarked Terrain. Chemical erosion by mixing-zone dissolution is important in formation of Estuario Celestun and other estuaries, but is perhaps inhibited at Lake Bacalar where groundwater dissolves gypsum, is high in Ca, low in CO3, and does not become undersaturated in calcite when mixed with seawater

An inexpensive, automatic, submersible water sampler, 2004, Martin J. B. , Thomas R. G. , Hartl K. M. ,

Currently available water samplers are manually actuated, can only be deployed onshore, limiting their use to small or developed water bodies, or are designed for deployment in the deep sea, making them large and expensive. The automatic submersible water sampler described here is small, lightweight, actuated by a microprocessor, and inexpensively and easily constructed. The sampler consists of a pressure case, sample containers constructed of 10 spring-loaded 60 mL syringes connected to solenoid valves, and electronics to control opening and closing of the solenoid valves. Vacuum in the syringes keeps the springs compressed while the solenoid valves are closed. When a valve opens, the spring expands and draws water past a screen and/or filter into the syringe. Once the syringe is filled, the solenoid valve closes, storing the sample. More than one syringe can be opened simultaneously if more than 60 mL are required. Preservatives can be added to the syringe prior to deployment. Some environments where it could be used include karst aquifers, lakes, large rivers, and estuaries

The transition of a freshwater karst aquifer to an anoxic marine system, 2005, Garman Km, Garey Jr,

Jewfish Sink is located in the shallow seagrass flats of the Gulf of Mexico in west central Florida. Jewfish Sink was a submarine spring until the drought of 1961-1962 when it ceased flowing. Today, the sink is an anaerobic marine basin and provides the opportunity to study the implications of saltwater intrusion in coastal karstic areas. The biogeochemistry of Jewfish Sink was studied from summer 2001 through spring 2004. A distinct feature of the sink is the uniform cold temperature (16-17 degrees C) of the deeper anoxic water that does not match groundwater found nearshore or onshore (22-24 degrees C). There are four zones within the sink: oxic zone, transition zone, upper anoxic zone, and anoxic bottom water. The anoxic bottom water does not mix with water from above but may be linked to deep Gulf shelf water through ancient aquifer conduits. The other three zones vary seasonally in oxygen, salinity, and temperature because of limited mixing in the winter due to cooling and sinking of surface water. The walls of the anoxic zones have characteristic microbial mats that are found in other sulfidic karstic features in the area. Bacterial activity appears to be carbon limited in the anoxic zones where sulfate reduction appears to be the major metabolic process. The reduction of sulfate to sulfide appears to be driven by irregular influxes of organic matter including macroalgae, horseshoe crabs, and stingrays that become entrapped within the sink. Bacterial activity in the oxic zones appears to be phosphate limited. Although the system is partially isolated from the overlying marine ecosystem, organic input from above drives the bacterial anaerobic ecosystem, resulting in a sulfide pump. In this model, sulfide percolates up through the karst and removes oxygen from the overlying sediment, which has likely caused changes in the shallow benthic ecosystem. Jewfish Sink appears to be part of an extensive anoxic subterranean estuary that extends under parts of at least three coastal counties in Florida and can serve as a model for the effects of rising sea levels or aquifer mining