This paper reports on concentrations and carbon isotopic results of dissolved inorganic carbon (DIC) in water samples collected at four locations and from several depths in Lake Biwa, central Japan, covering every season of the year, starting in the spring of 1995. Depth profiles of DIC concentration and DIC δ13C showed a strong seasonal pattern, as a result of vertical mixing of the lake water in winter and early spring, or lack of mixing in the other seasons. No seasonal change in DIC ∆14C depth profiles was recognizable, mainly owing to the wide scatter of DIC ∆14C. Values typically ranged from 0.47 to 0.65 mmol kg-1 for DIC concentration, and from -4 to -8‰ and from +10 to +80‰ for DIC ∆13C and DIC ∆14C, respectively, for the Lake Biwa water.

Radiocarbon activities and uranium isotopic disequilibria were measured in water samples from both the sandy Pleistocene coastal aquifer and within the upper Cretaceous Judea Group carbonate aquifer of northwestern Israel. The samples in both aquifers exhibit a decrease in 14C activity that is concomitant to the growth in 234U-excess. This suggests that under specific conditions, 234U-excess dating of groundwater can be used to corroborate 14C dates, while offering the possibility of extending the range of dating of groundwater beyond that of 14C.

There are many kinds of natural ice found on our planet. These include glacier ice, ice sheets, cave ice, massive ground ice, ice-wedge ice and permafrost ice. The problems associated with the recovery and dating of the CO2 and other gases contained in these kinds of ice is reviewed. New data are presented on various kinds of natural ice. How this kind of data can be used to help determine the origin and history of natural ice samples is discussed, along with the kind of paleoclimatic information that might be obtained from natural ice samples.

The excavation of the Cyclope cave, situated on the deserted island of Youra in the Northern Sporades (39°22'N, 24°10'E), revealed material of marine and terrestrial origin in undisturbed layers, suitable for radiocarbon dating. In some cases, material from different reservoirs was found together in the same archaeological layer. This research had two aims. The first was the dating of charcoal-seashell pairs in order to determine the marine reservoir effect in this region, based on samples with ages spanning from the end of the 8th millennium to the beginning of the 7th millennium bc. The second aim was dating the stratigraphy of this site, by using the calculated δR value in conjunction with the marine calibration curve. This enabled the accurate calibration of the 14C ages of marine samples found in layers without charcoal pieces. The results show that this is the oldest human settlement ever found on an island in the Aegean Sea.

We measured the 14C content of 36 living marine molluscs from Tairua Harbour and the rocky coast on the Coromandel Peninsula of New Zealand. We identified species suitable for radiocarbon dating and show that the open marine intertidal zone is enriched in 14C compared to the open marine subtidal zone or estuary. We also found a uniform 14C distribution in the Tairua Harbour, by analyzing samples of the estuarine bivalve Austrovenus stutchbwyi collected up to 5 km from the harbor entrance.

Organic matter in sediments and suspended matter is a complex mixture of constituents with different histories, sources and stabilities. To study these components in a suspended matter sample from the Ems-Dollard Estuary, we used combined molecular analysis with pyrolysis/gas chromatography/mass spectrometry and stable and radioactive carbon isotope analyses of the bulk and separated chemical fractions. Carbohydrates and proteins, ca. 50% of the total organic carbon (TOC), are much younger than the bulk sample and have a somewhat higher δ13C value. Lipids and the final residue are considerably older and have lower δ13C values. The final residue, ca. 17% of the total carbon, consists mainly of aliphatic macromolecules that could be derived from algae or terrestrial plants. The δ13C value points to a marine origin.

By comparing the radiocarbon age of the soils under burial mounds of known archaeological age with the surface-exposed (background) soils of the surrounding landscapes, we may evaluate the rates of humus renewal in these soils. In the cold climate of the mideastern areas of the Russian plains, the value of humus rejuvenation coefficient decreases. This shows that humus renewal is 5–10 times slower than in the warmer climate of the southern regions. Using the obtained data on the rejuvenation rate of humus substances, we can determine the age of paleosols and study the dynamics of the carbon exchange processes in the biosphere.

Three very different Canadian soils—clay soils of the St. Lawrence Lowlands, sandy forest soils of the Ottawa Valley, and organic-rich sediments from a wetland on the Canadian Shield—have been cored, sliced and separated into different density fractions, and the radiocarbon content of these soil fractions measured. In two of the areas sampled, cores were obtained close to operating nuclear reactors, as well as from beyond their region of influence. As a consequence, it has been possible to ascertain the depths of penetration of both the weapons-testing pulse (peaking in 1963), and a 25–50-yr chronic reactor input of 14C.

The percentage of carbon stored in different density fractions varied with soil type. Turnover times for bulk soil organic carbon, estimated from soil degassing rates, have been compared with those predicated on the residual “bomb” 14C in background cores, and/or on the ratio of reactor-emitted 14C retained in the soils to the total deposited during the lifetime of operation. Residence times for the heavy carbon fraction present at depths below the influence of anthropogenic inputs have also been estimated.

The accumulated data will be incorporated in a revised soil model, adjusted for the parameters deemed to be most important to carbon turnover rates under Canadian conditions.

This study, which was carried out in the southern Brazilian Amazon region (Rondônia state and Humaitá, Southern Amazon state), presents and discusses the significance of carbon isotope data measured in soil profiles collected across natural boundaries of forest to savanna vegetation. The main objective of this study was to evaluate the expansion-regression dynamics of these vegetation units in relation to climate changes during the Holocene. 14C data from charcoal, soil organic matter (SOM) and its component humin fraction indicate that the organic matter in the studied soils is essentially Holocene in origin. 13C data indicate that C3 type plants were the dominant vegetation at all study areas in the early Holocene, and during the entire Holocene, in the forest sites of Central Rondônia state and in the forest site 50 km from the city of Humaitá. 13C data also indicate that C4 plants have influenced significantly the vegetation at the transitional forest and the Cerrado (wooded savanna) sites of Southern Rondônia state and the forest ecosystem located 20 km from the Humaitá city. These typical C4 type isotopic signatures probably reflect a drier climate during the mid-Holocene. The 13C records representing probably the last 3000 yr show an expansion of the forest, due to a climatic improvement, in areas previously occupied by savanna vegetation. These results and other published data for the Amazon region indicate that the areas representing today's forest-savanna boundaries have been determined by significant vegetation changes during the Holocene. The boundary between forest and savanna vegetation seems to be quite sensitive to climatic change and should be the focus of more extensive research to correlate climate and past vegetation dynamics in the Amazon region.

In a study addressing composition and recovery of soil carbon following pasture installation on arable land, radiocarbon isotope ratios were measured in size- and density-separated soil organic matter (SOM) fractions in a pasture and maize plot. The average soil carbon age increased with depth from 444 yr in the 0–30-cm layer to 2456 yr in the 60–80-cm layer in the pasture soils, and from 42 to 1625 yr in the maize-cultivated soil. Weight fractionation of the macro-organic matter (size >150 μm) in a light (density <1.17 g cm-3) intermediate (1.17 g cm-3 < density < 1.37 g cm-3), and heavy fraction (density >1.37 g cm-3) resulted in markedly different ages for different fractions with ages increasing from 2 yr in the light fraction to >3000 yr in the heavy fractions. 13C and 14C (accelerator mass spectrometry (AMS)) isotope ratios in the <20 μm fraction in the 60–80-cm layer indicated that vertical displacement of colloidal organic material occurred during maize cropping. The physical fractionation method, in combination with natural level 13C and 14C analysis, resulted in a better insight in carbon dynamics that occur after the conversion of arable land to pasture.

The last scientific presentation at the conference was a special paper by Minze Stuiver, reviewing all radiocarbon calibration data available to date.