Abstract The chlorine isotopic ratio and elemental composition of two granite cores collected in a deep underground tunnel has been measured; neutrons were detected using a helium-3-filled proportional counter placed in a borehole. The thermal neutron flux determined from the chlorine isotopic ratio from accelerator mass spectrometry is (3.8 ± 0.2) × 10−5 and that determined from the granite's elemental composition is (4.4 ± 0.3) × 10−5(cm−2 s−1). The results of in-situ measurements using the proportional counter yielded a thermal neutron flux value of (3.3 ± 0.1) × 10−5(cm−2 s−1). This good agreement among the results shows the validity of the neutron flux evaluation obtained from the elemental composition and/or the isotopic ratio of 36Cl/Cl. Further, it reveals that the neutron flux in the underground environment remains stable for at least one million years, i.e., the period over which chlorine-36 attains equilibrium.

To verify groundwater dating using 36Cl, we confirmed the precision of 36Cl measurements by comparing three laboratories that have routinely measured 36Cl. This comparison was conducted using the same 15 sample units consisting of a water sample and AgCl precipitation sample. The 36Cl/Cl ratio of the sample ranged from <10−15 to 4 × 10−13. There was minor uncertainty in measurement of the 36Cl/Cl ratio among the three laboratories when samples had relatively high ratios of more than 10−14. On the other hand, differences in the chemical separation processes are one of major factors in the high degree of uncertainty in measurement when the ratio of 36Cl/Cl is lower than 10−14.

An artificial single dose contaminant was released at Nagasaki, Japan on August 9, 1945 detonating plutonium (10-15 kg) atomic bomb. A portion, 1.2 kg of 239Pu was fissioned releasing 21 kt TNT energy along with various fission products. The rest of the unexpended fissile material, 239+240Pu; 13.8 kg (3.49 x 1013 Bq), was dispersed into the atmosphere along with a fission product, 137Cs, 23.4 g (7.44 x 1013 Bq). The fate of 239+240Pu and 137Cs was investigated by analysing both local and global fallout. The highest concentration of 239+240Pu was 64.5 mBq/g (181 mBq/cm2) while it was 188 mBq/g (526 mBq/cm2) for 137Cs both at 2.8 km east from the hypocentre. The total amount of deposition in the local fallout region of 264 km2 was 37.5 g (9.48 xl010Bq) for 239+240Pu and 3.14 mg (5.88 x 1010Bq) for 137Cs. The ratio of the local fallout against the total amount of the radionuclides released was 0.27 % for 239+240Pu and 0.134 % for 137Cs. Recent advancements in analytical technology made it possible for artificial radionuclides released from the Nagasaki explosion to be detected in the Arctic ice core layer of 1945. The 239+240Pu and the 137Cs, were measured by collecting 10 ice cores on the Agassiz ice cap, Ellesmere Island, Canada. The deposition was 0.16 juBq/cm2 for 239+240Pu and 20 μBq/cm2 for 137Cs. During the atmospheric testing, the deposition of 239+240Pu and 137Cs varied more than 100 times with the highest peaks of over 50 μBq/cm2 for 239+240Pu and over 800 μBq/cm2 for 137Cs both occurred in 1962. Analyzing Arctic data, there are many new information for long global transport, the history of nuclear weapons development etc.

A historic event, the release of man-made global pollutants, was observed at Nagasaki, Japan on August 9, 1945 with the detonation of a plutonium (10-15 kg) atomic bomb. A portion, 1.2 kg of Pu-239, was fissioned releasing 21 kt TNT energy along with various fission products. The rest of the unexpended fissile material, 13.8 kg (3.49 x 10(13) Bq) of Pu239+240, was discharged into the atmosphere along with the fission product, Cs-137. 23.4g (7.44 x 10(13) Bq). The fate of the Pu239+240 and Cs-137 was investigated by analysing both local and globat fallout. The highest concentration of Pu239+240 was 64.5 mBq/g (181 mBq/cm(2)) while it was 188 mBq/g (526 mBq/cm(2)) for Cs-137, both at 2.8 km east of the hypocentre. The total amount of deposition in the local fallout region of 264 km(2) was 37.5 g (9.48 x 10(10) Bq) for Pu239+240 and 3.14 mg (5.88 x 10(10) Bq) for Cs-137. The ratio of the local fallout against the total amount of the radionuclides released was 0.27% for Pu239+240 and 0.134% for Cs-137. Recent advances in analytical technology have made it possible for artificial radionuclides released from the Nagasaki explosion to be detected in the Arctic ice core layer of 1945. The unexpended fissile material, Pu239+240, and the fission product, Cs-137, originating from the Nagasaki A-bomb, were measured by collecting 10 ice cores on the Agassiz ice cap, Ellesmere Island, Canada. The deposition was 0.16 mu Bq/cm(2) for Pu239+240 and 20 mu Bq/cm(2) for Cs-137 originating from Nagasaki. During atmospheric testing, the deposition of Pu239+240 and Cs-137 varied by more than 100 times with the highest peaks of over 50 mu Bq/cm(2) for Pu239+240 and over 8 mBq/cm(2) for Cs-137 both occurring in 1962. Deposition from the first French nuclear test in 1960 was also clearly shown in the ice cores. Assuming there is consistency in climate for the next 10 000 years, the chronological anthropogenic deposits, mainly of Pu239+240, should be detectable in the ice layer between 97-98 m from the snow surface on the Agassiz ice cap in 11 999 AD. Even if there were no improvements in the radioanalytical method used, the ice layers for the 1945-1980 periods could still be easily identified with the present analytical technology. Hopefully this study may establish a way to use our generation's artifacts for the benefit of our future descendants.

The sorption of Pu to the anaerobic bacteria activated under specific conditions of temperature, pH and depleted nutrients after long dormant period was investigated. After 4 h at neutral pH, the distribution coefficient (Kd) between bacteria and aqueous phase at 308 and 278 K had around 103 to 104. After over 5 days, however, the Kd at only 308 K had increased to over 105. Sterilized (dead) and dormant anaerobic bacteria adsorbed Pu to the same extent.

Mobile plutonium was found in waterlogged soil and reservoir sediment from the Nishiyama district of Nagasaki, accumulating from the local fallout released in the explosion of the A-bomb in 1945. Less than 10% of the total deposited plutonium had turned into a mobile form in the bottom sediment of the reservoir. The environmental conditions in the soil and sediment are expected to be rich in organic materials and to have high bacterial activities under anaerobic conditions. During growth, anaerobic bacteria have a strong ability to tahr up and retain plutonium. The K-d of plutonium for living bacteria is 20 times higher than for dead bacteria under anaerobic conditions. The results of field observations combined with empirical laboratory tests indicate that mobile plutonium in soil and sediment may be affected not only by the binding to natural organic materials but also by activities of living bacteria. Furthermore, the intensity of the reducing environment dominates the degree of mobility of plutonium in the soil and sedimentary environments.

While considering the geological disposal of radioactive wastes, the behavior of radionuclides such as plutonium was investigated in the presence of bacteria with bentonite which was used as a backfill to simulate conditions at geologic repositories. The interaction between radionuclides and bacteria was evaluated using the solid/liquid distribution coefficient (K(d)) with bacteria and/or bentonite as the solid phase and radionuclides in the aqueous phase. The radionuclides were added with the liquid phase. Two types of anaerobic bacteria were used. The first type, non-sterilized active anaerobic bacteria, originally used for the treatment of pulp and paper wastewater, accumulated considerable amounts of plutonium at a neutral pH. This neutral pH condition was more suitable for the accumulation of plutonium when compared with acidic or alkaline conditions. When the anaerobic bacteria were sterilized, the Kd values for neutral pH decreased to nearly those for acidic and alkaline pH. Thr K(d) values for neptunium and protactinium were compared with plutonium, Adsorption of neptunium was very little influenced by sterilization, whereas protactinium behaved like plutonium. The second type, Desulfovibrio desulfuricans, showed a markedly different behavior from the mixed anaerobic bacteria. This was due to differences in the bacteria themselves and to the chemical environment such as E(h).

Trace amounts of heavy metals in the ice cores from Canadian Arctic were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). A custom made plastic device and ceramic knives were used to remove the contamination on the ice core surface. Ice cores could be broken into small sections (2–3 cm thick) after decontamination with the plastic device and ceramic knives. High-resolution depth profiles of various elements, i.e. As, Cd, Co, Cu, Ni, Pb, Zn and U, were thus attained. Concentrations in 518 ice core samples range from 0.1 (U) to 673.3 (Zn) pg g−1.

While considering the geological disposal of radioactive wastes, the behaviour of the radionuclide Np and its daughter element Pa was investigated in the presence of a mixture of anaerobic bacteria (MAB). Originally, MAB were used for the treatment of pulp and paper wastewater. The interaction between radionuclides and bacteria was evaluated by determining distribution coefficients (Kd) over 10 days and at 5°C and 35°C. Kd for Np at 35°C after 5 days had a low value around 10−2. After 10 days, however, Kd was >100-fold higher. On the other hand, Kd at 5°C was low (10−2) throughout, without any significant increase over time. The interaction between Pa and MAB was found to be stronger than that for Np, with Kd for Pa about 100 times higher. The Kd was controlled by some basic factors; the activity of MAB, the complexing capacity of MAB, and the chemical conditions in the solution such as pH and Eh.

A historical man-made global pollution of hazardous materials occurred at Nagasaki, Japan on August 9, 1945 detonation of a plutonium (10–15 kg) atomic bomb. Recent advancements in analytical technology made it possible for artificial radionuclides released from the nuclear explosion to be detected in the Arctic ice core layer of 1945. The fission product, 137Cs (23.4 g or 7.44×1013 Bq), and unexpended fission material, 239+240Pu (8.8–13.8 kg or 2.22–3.49×1013 Bq), originating from the Nagasaki A-bomb were measured by collecting 10 ice cores on the Agassiz ice cap, Ellesmere Island, Canada. The deposition rates were 20 mBq/cm2 for 137Cs and 0.16 mBq/cm2 for 239+240Pu, originating from Nagasaki. Assuming the radionuclides, excluding the amount deposited as local fallout, are deposited evenly throughout the northern hemisphere, a rate of 67% of the expected amount of 137Cs arrived at the Arctic while 1.1% of 239+240Pu reached the Arctic. The results suggest that different transport mechanisms exist for these two hazardous contaminants in the global transport system. A non-reactive rare gas, such as neon and argon, can spread evenly throughout northern hemisphere, including Ellesmere island at the Canadian Arctic, while a reactive gas, sulfur dioxide (SO2) will not reach the ice cap. The measured global transport rates of 137Cs and 239+240Pu were 67% and 1.1%, respectively. These measured rates were for the historical man-made hazardous materials and probably obtained for the longest distance of global transport over 10,000 km. Assuming there was a consistency in climate for the next 10,000 years, the chronological anthropogenic deposits, mainly of 239+240Pu, could be detected in the ice layer between 97–98 m from the snow surface at 11,999 AD on the Agassiz ice cap. Even if there were no improvements in the radioactive analytical method used, the ice layers for the 1945–1980 period could still be easily identified with the present analytical technology. Hopefully this study will find a way to use our generation's artefacts for the benefit of our future descendants.

Mercury concentrations were measured in sediment cores collected from the Yatsushiro Sea to clarify physical transport of mercury from Minamata, the site of major methylmercury pollution in Japan, to the surrounding sea. The results suggested that the mercury pollution in the Yatsushiro Sea sediment was caused by a slow migration of mercury-bearing sediment particles from Minamata Bay. The deposition rate of mercury observed at the Yatsushiro Sea was correlated with cumulative loss of mercury from an acetaldehyde facility in Chisso Minamata, with a certain time-lag.

To investigate the formation of mobile organic plutonium, we analyzed the plutonium contents of the fulvic (FA) and humic (HA) acids from the soil samples obtained at Nishiyama, Nagasaki, Japan. The percentages of the plutonium bound strongly to HA and to FA vs. the total plutonium in the soil were 5–10% and 1%, respectively, at the depth of 0–0.1 m, much higher values than those of137Cs and uranium. After being weathered for 51 years under a temperate climate, the initial highfired oxides of fallout plutonium have become as chemically reactive plutonium from nuclear fuel reprocessing plants.

Studies on ice cores drilled in Antarctic, Greenland and Canadian Arctic ice caps provide the environmental composition and the climate in the past. This information and further study will help in the understanding of the basic natural processes and the extent of human impact on the environment and climate. This will eventually enable us to predict the future of the environment. This review summarizes the state of the art methodologies used in ice core studies, with highlights on the recent studies in this group.

One of the most visible tragedies by industrial water pollution is Minamata disease, methylmercury poisoning caused by eating contaminated fish, which has killed more than 100 people and paralyzed several thousand people around Minamata Bay, Japan and the adjacent Yatsushiro Sea since 1956. The cause of Minamata disease was confirmed, not by analyzing environmental samples such as sediments (containing more than 600 ppm of Hg) or fish (at least 20 ppm) at the bay, but by symptoms of Minamata disease patients that resembled previous mercury poisoning reported in a European medical journal. Mercury dispersion was traced for 22 years to collect mercury concentration measurements in Yatsushiro Sea surface sediments at 24 fixed stations. The analytical results of mercury revealed four trends of mercury movement from the bay: 1) a rapid increase in Hg concentrations up to 1984; 2) a dramatic decrease in mercury concentrations after an artificial mercury decontamination project began in 1984; 3) a strange drop in mercury contents due to an historical rainfall in the region in 1982 and; 4) natural decontamination, which has been underway since 1985. The tragedy at Minamata has provided many lessons which have shaped the scientific field in environmental research, especially in the area of water quality.

Recent advancements in analytical technology make it possible for artificial radionuclides released from nuclear explosions to be detected in Arctic ice core layers. The fission product, 137Cs, and the unexpended fission material, 239+240Pu, originating from the Nagasaki A-bomb of August 1945, were measured by collecting 10 ice cores on the Agassiz ice cap, Ellesmere Island, Canada. The deposition rates were 0·020mBqcm-2 for 137Cs and 0·0016mBqcm-2 for 239+240Pu, originating from Nagasaki. Assuming the radionuclides, excluding the amount fissioned from the explosion and deposi-ted as local fallout, are deposited evenly throughout the Northern Hemisphere, 67% of the expected amount of 137Cs reached the Arctic while 1·1% of 239+240Pu reached the Arctic. The results suggest that different transport mechanisms exist for various contaminants in the global transport system.

Mobile plutonium was found in the bottom sediment in the Nishiyama reservoir in Nagasaki after more than 40 years from deposition of local fallout released in the explosion of the ABomb in 1945. Less than 10% of total deposited plutonium had turned into a mobile form in the bottom environment of the reservoir. The environmental conditions at bottom sediment is expected to be rich organic materials and high bacterial population under anaerobic conditions. Anaerobic bacteria have a high ability to uptake plutonium into cell during their growth. The Kd of plutonium to living bacteria is 20 times greater than the dead bacteria under anaerobic conditions. The results of field observations combined with empirical laboratory tests indicate that mobile plutonium in soil and sediment may be affected not only by binding with dissolved natural organic materials but also by the number of living anaerobic bacteria.

The solid DC electrical conductivity (ECM – Electrical Conductivity Method) of polar ice cores has become an important tool in identifying and quantifying volcanic acid layers, and this paper addresses the question of how much signal and noise there is in single ECM series. A number of high-resolution (10 samples/year) ice-core ECM records from the Agassiz Ice Cap are correlated over the last 900 years. Corre lations decrease with distance apart due to local drift and melt layer noise, but correlations are probably reduced also by differences in methodology and core storage. It is found that only peak sizes in the uppermost two percentiles retain their ranking and recognizability from core to core. With continuous sampling, however, the smaller peaks can be cross-identified between cores, even though they lose their size rank. Averaging or stacking several ECM records reduces the noise. Five-year averages of ECM for the Holocene are presented for the Agassiz cores and their correlations interpreted as functions of distance apart and differences in method. The large-scale melting in the early Holocene (8ka to 10ka) almost completely de-acidifies the ice in all the Agas siz cores.

Abstract Pit-wall samples were collected from two sites about 2 km apart on Agassiz Ice Cap, Ellesmere Island, Northwest Territories, Canada, in 1992, 1993 and 1994, and from a site a further 1 km distant, in order to study spatial and seasonal variations in snow chemistry. Two of the pits were dug in wind-scoured zones and one in an unscoured zone. Although a large part of the winter snow is removed from the scoured zones (which do not show very negative δ 18O values) the winter/spring anion peaks are still evident; this may be due to the predominance of dry deposition in mid-winter. The Cl− and SO4 2– ions peak in late winter/early spring, while NO3 − peaks both in late winter/early spring and in summer. Vertical concentration profiles of all anions did not significantly alter over a 2 year period, indicating that there are no serious post-depositional changes due to evaporation, snow melting or photochemical reactions. However, comparisons between stake/board snow-accumulation measurements and those derived from the least scoured pit indicate that a single pit will represent annual accumulation rates for a local area only.