Major Water Constituents Research Articles

Geology and geochemistry of the Atacama Desert

The Atacama Desert, the driest of its kind on Earth, hosts a number of unique geological and geochemical features that make it unlike any other environment on the planet. Considering its location on the western border of South America, between 17 and 28°S, its climate has been characterized as arid to hyperarid for at least the past 10 million years. Notably dry climatic conditions of the Atacama Desert have been related to uplift of the Andes and are believed to have played an important role in the development of the most distinctive features of this desert, including: (i) nitrates and iodine deposits in the Central Depression, (ii) secondary enrichment in porphyry copper deposits in the Precordillera, (iii) Li enrichment in salt flats of the Altiplano, and (iv) life in extreme habitats. The geology and physiography of the Atacama Desert have been largely shaped by the convergent margin present since the Mesozoic era. The geochemistry of surface materials is related to rock geochemistry (Co, Cr, Fe, Mn, V, and Zn), salt flats, and evaporite compositions in endorheic basins (As, B, and Li), in addition to anthropogenic activities (Cu, Mo, and Pb). The composition of surface water is highly variable, nonetheless in general it presents a circumneutral pH with higher conductivity and total dissolved solids in brines. Major water constituents, with the exception of HCO3-, are generally related to the increase of salinity, and despite the fact that trace elements are not well-documented, surface waters of the Atacama Desert are enriched in As, B, and Li when compared to the average respective concentrations in rivers worldwide.

Remote sensing reflectance and inherent optical properties in the mid Chesapeake Bay

We used an extensive set of bio-optical data to examine the relationships between inherent optical properties and remotely sensed quantities in an optically complex and biologically productive region of the Chesapeake Bay. Field observations showed that the chlorophyll algorithms used by the MODIS (MODerate resolution Imaging Spectroradiometer) ocean color sensor (i.e. Chlor_a, chlor_MODIS, chlor_a_3 products) do not perform accurately in these Case 2 waters. This is because, at high concentrations of chlorophyll, all MODIS algorithms are based on empirical relationships between chlorophyll concentration and blue:green wavelength remote sensing reflectance ( R rs) ratios that do not account for the typically strong blue-wavelength absorption by non-covarying, dissolved and non-algal particulate components. We found stronger correlation between chlorophyll concentration and red:green R rs ratios (i.e. R rs(677)/ R rs(554)). Regionally-specific algorithms that are based on the phytoplankton optical properties in the red wavelength region provide a better basis for satellite monitoring of phytoplankton blooms in these Case 2 waters. Our estimates of f/ Q (proportionality factor in the relationship between R rs and the ratio of water backscattering, b b, and absorption, a, coefficients, b b/( a + b b)) were not considerably different from f/ Q previously estimated for same measurement geometry but Case 1 waters. Variation in surface b b significantly affected R rs magnitude across the visible spectrum and was most strongly correlated ( R 2 = 0.88) with observed variability in R rs at 670 nm. Surface values of particulate backscattering were strongly correlated with non-algal particulate absorption, a nap ( R 2 = 0.83). These results, along with the measured backscattering fraction and non-algal particulate absorption spectral slope, indicate that suspended non-algal particles with high inorganic content are the major water constituents regulating b b variability in the studied region of the Chesapeake Bay. Remote retrieval of surface a nap from R rs(670) could be used in conjunction with inversion of UV-blue wavelengths to separate contribution by non-algal particles and colored dissolved organic matter to total light absorption, and monitor non-algal suspended particle concentration and distribution in these Case 2 waters.

Trace analysis of anionic surfactants in mineral waters and soft drinks by spectrophotometry

The applicability of the extractive spectrophotometric method using Ethyl Violet as the chromogenic reagent for identification and quantification of anionic surfactants in different types of mineralized drinking waters, as well as in some non-alcoholic beverages, was investigated. The matrix-analyte interactions of major water constituents and soft-drink ingredients in the combinations and concentration ranges met in practice were studied individually. The method was evaluated by performing recovery tests on commercial and natural samples, with sodium dodecyl sulphate added as a model surfactant. The recoveries at the 57.6 and 86.4 μg/l levels ranged from 98% to 104%.

The Ocean Color Experiment (OCE) on the Second Orbital Flight Test of the Space Shuttle (OSTA-I)

The Ocean Color Experiment was one of the six remote-sensing experiments which for the first time were launched and success fully operated on board of the second flight of the Space Shuttle during November 1981. The experiment consists of a multispectral image scanner dedicated to the measurement of water color and its interpretation in terms of major water constituents and circulation patterns. The objectives of the experiment, the test site selection, and associated activities are described. The actual mission and results of an initial data analysis is discussed.

Répartition des éléments traces dans les eaux thermominérales

This paper is an approach to define the origin and mineralization of thermal waters, based on new data on spring waters from southern France (Massif Central and Alps) and from Iran (eastern Azerbaijan). The behaviour of some minor elements, such as B, F −, Br −, I −, Sr 2+, Rb +, Li +, and the significance of characteristic ratios between minor and major water constituents enable us to distinguish between mineral and thermal waters associated with granitic, metamorphic or volcanic rocks and those originating from sedimentary evaporites. Trace-element distribution seems to be controlled by magmatic influences, the chemical composition of the wallrock, the presence of large distended fractures as well as by the effect of temperature on groundwaters. Ratios such as Br − I − and Sr 2+ Rb + enable us to determine the eroded-rock type. In some mineral waters the occurrence of chloride being relatively independent of other halogens seems to indicate a different origin for chlorine compared to other elements.