Despite the numerous papers on the statistical analyses of pH, there is no explicit opinion on the use of arithmetic mean as a measure of the central tendency for pH and H+ activity. The problem arises because the transformation of the arithmetic mean for one does not give the arithmetic mean for the other. The paper presents 1) the theoretical considerations on the distribution of pH and H+ activity and relation between them, properties of these distributions, the choice of distributions which should be consistent with the distribution of pH and the distribution of H+ activity and measures of central tendency for features of such distributions and 2) examples of calculations of measures of central tendency for pH and H+ activity based on the literature data on soil and lake water pH. These data analyses included distributions of pH and H+ activities, properties of distribution, descriptive statistics for pH and for the H+ activity and comparison of arithmetic mean with the geometric mean. From the results, it could be concluded that a uniform approach to the choice of measure for the central tendency of pH and H+ activity requires the determination of the type of measure (mean) for one of them and then consistent transformation of this measure. The choice of measure of the central tendency for the variable should be preceded by determination of its distribution. Normal probability distribution of pH and thus lognormal distribution of H+ activity indicate that the arithmetic mean, and its corresponding geometric mean should be used as proper measures of the central tendency for pH and for H+ activity. Besides, the position statistic that is a median can be used for each of those variables, irrespective of their probability distributions.
Sediments of two dam reservoirs in SE Poland, Zalew Zemborzycki (ZZ) and Brody Iłżeckie (BI) were studied. The sediments from both reservoirs were sampled in the transects perpendicular to the shoreline, at the river inflow and the frontal dam. The total concentration of Mn, Zn, Pb, Cd, Cu, Cr and Ni was determined by ICP-EAS method after the sample digestion in the mixture of concentrated HNO3 and HClO4 acids. The statistical analyses: value intervals, mean values, variation coefficient, the median and the skewed distribution were performed. To estimate differences between the means for transects, Tukey’s test was applied with least significant difference (LSD) determination. The maps of the metal spatial distribution were drawn and sediment quality according to the geochemical and ecotoxicological criteria evaluated. Differences between the reservoirs in terms of heavy metals concentration in bottom sediments, and regularities in their spatial distribution were found. In the ZZ sediments the concentration was at the level of geochemical background (Zn, Cr), slightly (Cd, Cu, Ni) or moderately (Pb) contaminated sediments. The metal concentration in the sediments of the BI was up to eight times higher as compared to the ZZ. Moreover, sediments from the BI reservoir showed a greater variability of metal concentration than those from ZZ, which resulted from the dredging operation performed in the part of the reservoir. Metal concentration in sediments of the dredged part was ca. 2–5 times lower than in the undredged one, which indicates that after the dredging operation, accumulation of these metals was slight. The concentrations of Zn, Pb and Cd from the undredged part of BI were at the level of contaminated sediments and exceeded the probable effects level (PEL). In the ZZ, the greatest accumulation of metals occurred in the upper part of the reservoir and at the frontal dam, and the lowest in the middle part of the reservoir. In BI, the lower outflow of water in this reservoir caused a lower metal concentration in the sediments at the frontal dam, as compared with the other sediments in the undredged part of the reservoir. The results indicate that in small and shallow reservoirs, areas of accumulation of heavy metals depend on such factors as a parent river current, reservoir depth, water waving, reservoir shape (narrowing, coves/bays), and type of water outflow.
The purpose of the present study was to analyse the contents of calcium, magnesium, potassium, and sodium in bottom sediments of two water reservoirs. The chemical composition of the bottom sediments and the ratios between the studied macronutrients were assessed, taking into account the nutritional requirements of plants, to determine whether the sediments were suitable for use in natural/agricultural settings.
The study was conducted at two water reservoirs: the Brody Iłżeckie reservoir built on the Kamienna River in the Świętokrzyskie Province, and Zalew Zemborzycki, lake on the Bystrzyca River in the Lublin Province. Both bodies of water serve as flood water diversion and leisure facilities, and are also used, to a small extent, by the industry. They have a similar age and surface area. Bottom sediments were collected from the reservoirs a single time: 14 samples from Zalew Zemborzycki and 17 from Brody Iłżeckie. Samples were tested for total contents of Ca, Mg, K, and Na. The bottom sediments from Zalew Zemborzycki contained higher amounts of calcium, magnesium, and potassium than the material from Brody Iłżeckie. The values of ratios between K:Mg and K:(Ca + Mg) were similar for both reservoirs, and Ca:Mg and Ca:K were slightly more favourable for the sediments taken from Brody Iłżeckie.