SIR, In-situ measurements of electrical conductivity and pH in core samples from a glacier in Spitsbergen. Svalbard
The Japanese Arctic Research Project in the Svalbard region, in the Arctic, began in the early summer of 1987. The object was to clarify fluctuations in past and present sedimentary environments which would help us to forecast future features of the Earth’s environmental system. An ice core gives us various information on the past. The precise details of this project together with information on the coring site have already been reported by Reference Watanabe and FujiiWatanabe and Fujii (1988).
Methods And Materials
By coring at the top of a glacier, the whole core from the surface to the bottom was obtained with individual core lengths of c. 60 cm. Each sample was examined visually to determine the stratigraphy, and contained bubble and dust features. Some of the core samples were prepared so that they could be carried back to the home laboratory in a frozen condition. Some of the others were used for the determination of density and crystal structure. The remainder were converted into the liquid phase as follows.
The surface of each sample was scraped carefully with a knife after being cut with a band saw into suitable shapes. The decontaminated samples were put into pre-cleaned 1 litre bottles, which were immersed in warm water so the contents could become liquid. The melted samples were then put into other pre-cleaned 100 ml bottles; these were then used for the determination of both EC and pH.
The measurement of EC was done at 0°C with an electrical conductivity meter (CM-1K, TOA Electronics Ltd), to which was attached a sensor for low conductivity (CV-1001SC, TOA Electronics Ltd), and pH by a pH meter (HM-30S, TOA Electronics Ltd). In the laboratory at home, major ion and micro-particle concentrations were determined on some samples.
Here, we show the continuous vertical distributions of the EC and pH values in the core, measured in situ, which will be useful for the later re-arrangement and reconstruction the various continuous information from the core data.
Results and Discussion
The sampling interval was about 10—20 cm and there were as many as 500 samples. The vertical profiles for EC and pH are shown in Figure 1. Two high values of EC were observed adjacent to each other just below a 30 m depth; this corresponds to the respective lowest and highest values throughout the core. For these samples, we repeated both the sampling and the measuring procedures twice independently, which proved that the remarkable variation had not been due to contamination during the sampling and measuring procedures. The pH value gradually increases with depth, a tendency which is a little more marked above a 20 m depth. These data reflect the recent increase in acidity of the precipitation in the region.
The core records represented by the EC and pH values were divided into three fractions: upper, middle, and lower. The upper fraction is from the surface to c. 20 m depth, the middle from c. 20 m to c. 50 m depth, and the lower from c. 50 m depth to the base of the glacier.
The characteristics of each fraction are as follows: in the upper fraction, the pH value increases with depth and the increase in the EC value causes the decrease in pH; in the middle fraction, both EC and pH values fluctuate anomalously and here the lowest and the highest values occur in both EC and pH; in the lowest fraction, variations in both EC and pH with depth are small and the EC and pH values remain comparatively low and high, respectively.
Such fractions possibly correspond to those decades of similar past sedimentary environments. The chemical compositions of the ice-core samples will give us more refined information about past environments. Here, we have shown only the vertical distributions of the EC and pH values obtained in situ and these will be further discussed later, together with other information such as chemical composition, etc.
Fig.1. Vertical profiles of electrical conductivity and pH in the liquid phase of core samples.
