THE NATURAL C ¹⁴ CONTENTS OF MATERIALS FROM HARD-WATER LAKES

Abstract

16 M. Stem, unpublished data, Corrosion Laboratory, M.I.T.17 G. Gemmell found that the corrosion rate for mild steel (0.06 per cent C) in deaerated 4 per cent NaCl of pH 5.6 was zero within the experimental variations of such measurements, whereas at pH 3.8 the rate averaged 24 mg/dm2/day (mdd), in agreement with Stern's value for iron. This means that the rate at pH 5.6 must be less than perhaps the order of 0.5 mdd. Pryor and Cohen, J. Electrochem. Soc., 100, 206 (1953), report a value of 0.3 mdd for the corrosion rate of mild steel in deaerated water. . 21 Based on atomic percentages and atomic radii of Cd and Hg, the fraction of surface composed of Cd atoms for 10-13 per cent Cd amalgam is equal to about 0.2. However, in measurements of anodic polarization, this fraction remains constant up to fairly high current densities because the potential for formation of Hg2++ is not approached so long as the surface concentration of Cd is appreciable. Therefore, measured values of b are for an anodic area similar to that which applies to the corrosion process, and, hence, the apparent value of A in eq. (2) under these conditions is equal to unity. Data by Wagner and Traud, op. cit., for zinc amalgam confirm this conclusion. For iron, on the other hand, the anodic surface becomes larger, the higher the value of current density externally applied for anodic polarization, and, hence, A is usually less than unity.

The freshwater reservoir effect in radiocarbon dating

“…These results disagree with previous studies where emergent plants and floating leaves of N. lutea were found to have 14 C contents in equilibrium with the atmosphere [5,26]. The specimen of N. lutea analysed by Olsson and Kaup [26], however, originated from a softwater lake.…”

“…The effect was considered by Godwin in 1951 [4] when discussing radiocarbon dates from the British Isles, and measured for the first time in 1954 on aquatic plants [5]. The marine reservoir effect was observed and discussed slightly later in the 1950s [6][7][8].…”

A lack of freshwater reservoir effects in human radiocarbon dates in the Eneolithic to Iron Age in the Minusinsk Basin

“…One source of Bold^carbon in freshwater is dissolved inorganic carbon from 14 C-free carbonate minerals in groundwater (e.g. Godwin 1951;Deevey et al 1954;Sveinbjörnsdóttir et al 1995;Culleton, 2006). In the process of underwater photosynthesis, this carbon becomes incorporated into aquatic plants and algae, and is then transferred further up the food chain to aquatic fauna and terrestrial animals (including humans) that rely on aquatic sources.…”

Climatic imprint of the mid-latitude Westerlies in the Central Tian Shan of Kyrgyzstan and teleconnections to North Atlantic climate variability during the last 6000 years

“…As such material is commonly regarded to give too old radiocarbon ages because of the incorporation of dissolved, 14 C-depleted carbon, for example, from catchment rocks (Deevey et al, 1954;Olsson, 1986), a living deepwater algae (Poz-47591) from coring site D was dated to assess the recent hardwater effect and its possible impact on 14 C dates obtained from lacustrine materials. The obtained conventional radiocarbon age of 155 ± 30 14 C yr BP (Table 1) shows that the recent hardwater effect is rather small, but as this might have changed through time, several cross-datings on terrestrial and aquatic samples from the same stratigraphic level in the composite profile were carried out.…”