Development of an equation to relate electrical conductivity to soil and water salinity in a Mediterranean agricultural environment

A linear equation to relate total ionic concentration to electrical conductivity (EC) in natural aqueous systems from low to medium level salt content was derived from the theory of EC in aqueous solutions. Some of the empirical equations used in soil science to characterise the salinity of soil and water based on the EC can be reduced to that equation. Also, it can be seen that aqueous systems with different relative ionic compositions have different values for the regression coefficient that relates EC to total ionic concentration. The equation was validated on the basis of the Faraday constant with some soil saturation extracts and irrigation waters sampled in different places along the Valencian Community (eastern Spain, western Mediterranean basin), and with data from the literature. The validation was performed using the chemical speciation program SOILSOLN. The results of the validation improved when activities were considered instead of concentrations, and in more dilute aqueous systems. Finally, the validation showed that the formation of ion pairs in the aqueous systems analysed was negligible due to the relatively low concentrations of sulfate, magnesium, and calcium.

Ostracodes as Hydrologic Indicators in Springs, Streams and Wetlands: A Tool for Environmental and Paleoenvironmental Assessment

Although the majority of publications on extant nonmarine ostracode species in North America are concerned with lacustrine settings, many species that are potentially valuable as indicators of water quality changes live in non-lacustrine settings. Ostracode distributions in 157 springs, wetlands and streams in the United States are examined here in order to assess 1) species richness, 2) association with physical and chemical parameters of their habitats and 3) the presence of potentially useful biomonitors and environmental sentinels. The 157 non-lacustrine sites are a subset of a large database (North American Non-marine Ostracode Database: NANODe version 1) consisting of 611 mostly lacustrine sites with ostracode species, presence-absence data, hydrochemistry and climate data (Forester et al., in review). Of the 89 species represented in NANODe version 1, 51 species are found in springs, 59 species are found in wetlands and only 15 species are found in streams. Many species are found in at least two of these habitats and some in all three. Principal Components Analysis of these 157 sites indicates that 71% of the variance is explained by salinity (total ionic concentration), alkalinity and temperature, a result consistent with previously published analyses of natural water. Cluster analysis shows that spring species are most strongly tied to temperature, whereas wetlands and streams are most strongly tied to ionic composition. Three species are found to be potentially valuable biomonitors: Cavernocypris wardi in springs, Fabaeformiscandona rawsoni in wetlands and Physocypria globula in streams.

The Ionic Composition of Lakes Fed by Ground Water and Precipitation in the Upper Romerike District

In the Upper Romerike District the lakes possess widely different chemical characteristics depending on their hydrological conditions. The most dilute lakes are fed only by precipitation, and the more concentrated ones by ground water. In the precipitation fed lakes the total ionic concentration was similar to that of the average precipitation, but the ionic ratio was different. Ionic sorption and exchange affected mostly calcium which decreased in concentration while the monovalent ions increased. The ground water fed lakes were dominated by bicarbonate, and their ionic proportions were constant regardless of total concentrations. The percentage composition was: Ca: 82%, Mg: 10.1%, Na: 6.5%, K: 1.4%, HCO3: 78.3%, S04: 17.1%, Cl: 4.6%.

Effect of nutrient potassium: calcium: magnesium ration in the production of flue-cured tobacco

In an outdoor trial with tobacco in sand culture, four potassium: magnesium ratios were combined with three calcium levels in the nutrient solution while the pH and total ionic concentration were maintained constant. By reduction of the concentration during ripening, the nitrogen regime was manipulated so as to produce plants closely resembling those in a held grown crop. Optimum leaf quality was found to result from the use of a nutrient solution containing 20-40 per cent of the cations as calcium on an equivalent basis. When calcium exceeded 40 per cent of the total cations, no good quality leaf was obtained ; when it formed only 20 per cent, the potassium : magnesium ratio had a less marked effect on quality. The concentrations of the three elements in the leaf of optimum quality are given for several leaf positions. At each leaf position the calcium content of the leaf was negatively correlated with quality. A potassium : magnesium ratio of 3:l in the nutrient led to quicker ripening of the leaf, and leaf thickness was dependent on the potassium : magnesium ratio of the nutrient.

The Composition of the Blood of the Shore Crab, Carcinus Moenas (Pennant), in Relation to Sex and Body Size

1. The influence of sex and body weight on the concentration of the non-protein nitrogen (N.P.N.) in the blood of Carcinus moenas was investigated. 2. Blood N.P.N. decreased with body size in both sexes until a minimum was reached at a body weight of about 35 g. Thereafter it increased with increasing body weight. 3. For body weights less than 35 g. males had higher N.P.N. values than females; above this weight male values were lower. Statistically these differences were highly significant. 4. Frequency distribution of reproductive activity with body size showed peaks which correspond with those for total ionic concentration (Gilbert, 1959a, b) and with the troughs for N.P.N. 5. Results of the present work have been discussed in relation to those reported earlier for conductivity, total O.P., chloride and sulphate (Gilbert, 1959a, b).