An assessment of the reported leakage of anthropogenic radionuclides from the underground nuclear test sites at Amchitka Island, Alaska, USA to the surface environment

Three underground nuclear tests representing approximately 15-16% of the total effective energy released during the United States underground nuclear testing program from 1951 to 1992 were conducted at Amchitka Island, Alaska. In 1996, Greenpeace reported that leakage of radionuclides, 241Am and 239+240Pu, from these underground tests to the terrestrial and freshwater environments had been detected. In response to this report, a federal, state, tribal and non-governmental team conducted a terrestrial and freshwater radiological sampling program in 1997. Additional radiological sampling was conducted in 1998. An assessment of the reported leakage to the freshwater environment was evaluated by assessing 3H values in surface waters and 240Pu/239Pu ratios in various sample media. Tritium values ranged from 0.41 Bq/l +/- 0.11 two sigma to 0.74 Bq/1 +/- 0.126 two sigma at the surface water sites sampled, including the reported leakage sites. Only at the Long Shot test site, where leakage of radioactive gases to the near-surface occurred in 1965. were higher 3H levels of 5.8 Bq/1 +/- 0.19 two sigma still observed in 1997, in mud pit #3. The mean 240Pu/239Pu for all of the Amchitka samples was 0.1991 +/- 0.0149 one standard deviation, with values ranging from 0.1824 +/- 1.43% one sigma to 0.2431 +/- 6.56% one sigma. The measured 3H levels and 240Pu/239Pu ratios in freshwater moss and sediments at Amchitka provide no evidence of leakage occurring at the sites reported by Buske and Miller (1998 Nuclear-Weapons-Free America and Alaska Community Action on Toxics, Anchorage, Ak, p.38) and Miller and Buske (1996 Nuclear Flashback: The Return to Anchitka, p.35). It was noted that the marine sample; 240Pu/239Pu ratios are statistically different than the global fallout ratios presented by Krey et al. (1976) and Kelley, Bond, and Beasley (1999). The additional non-fallout component 240Pu/239Pu ratio, assuming a single unique source, necessary to modify the global fallout 240Pu/239Pu ratio to that measured in the marine samples is on the order of 0.65 (Hameedi, Efurd, Harmon, Valette-Silver, & Robertson, 1999; Kelley et al., 1999). While this potentially suggests another plutonium source, such as high burn-up nuclear reactor fuel, rather than underground nuclear tests, the uncertainties in analyses and environmental processes need to be fully assessed before any conclusion can be reached. Further work is needed to evaluate these findings and to support any radiological assessment of the marine environment surrounding Amchitka. Based on geohydrological testing and modeling, leakage from the Amchitka Underground Nuclear Tests is projected to occur to the marine environment (Claassen, 1978; Fenske, 1972; Wheatcraft, 1995).     

Effect of phosphate and ammonium levels on photosynthetic and respiratory responses of the red alga Gracilaria verrucosa

Gracilaria verrucosa (Hudson) Papenfuss exposed to nutrient enriched media (0.1 mM PO₄; 1.0 mM NH ₄ ⁺ ) by pulse feeding 2 h every third day for a period of 5 wk at 20°C and 25–30 salinity showed significantly higher rates of photosynthesis regardless of photon flux density correlated with increased pigment levels. Algae in nonenriched media showed significantly higher levels of soluble carbohydrates and decreased levels of phycoerythrin and chlorophyll a. Photosynthetic and respiratory responses to temperature 15°, 25°, 30°C and salinity (15, 25, 30 S) combinations indicate broad tolerances by both nutrient enriched and non-nutrient enriched algae. Photosynthetic and respiratory rates were highest at the high temperatures. Pulse-fed algae had significantly higher photosynthetic rates than non-nutrient enriched plants at all temperature and salinity combinations. Non-nutrient enriched algae had significantly higher respiratory rates than nutrient enriched algae at only 30°C and 15. The respiratory rates of both nutrient enriched and non-nutrient algae decreased under combinations of higher temperatures and salinities. G. verrucosa, grown without nutrients, has lower tolerances to environmental stresses.     

Meta-analysis of time-series studies of air pollution and mortality: effects of gases and particles and the influence of cause of death,age, and season

A comprehensive, systematic synthesis was conducted of daily time-series studies of air pollution and mortality from around the world. Estimates of effect sizes were extracted from 109 studies, from single- and multipollutant models, and by cause of death, age, and season. Random effects pooled estimates of excess all-cause mortality (single-pollutant models) associated with a change in pollutant concentration equal to the mean value among a representative group of cities were 2.0% (95% CI 1.5-2.4%) per 31.3 microg/m3 particulate matter (PM) of median diameter < or = 10 microm (PM10); 1.7% (1.2-2.2%) per 1.1 ppm CO; 2.8% (2.1-3.5%) per 24.0 ppb NO2; 1.6% (1.1-2.0%) per 31.2 ppb O3; and 0.9% (0.7-1.2%) per 9.4 ppb SO2 (daily maximum concentration for O3, daily average for others). Effect sizes were generally reduced in multipollutant models, but remained significantly different from zero for PM10 and SO2. Larger effect sizes were observed for respiratory mortality for all pollutants except O3. Heterogeneity among studies was partially accounted for by differences in variability of pollutant concentrations, and results were robust to alternative approaches to selecting estimates from the pool of available candidates. This synthesis leaves little doubt that acute air pollution exposure is a significant contributor to mortality.     

Comparison of PM10 concentrations in high- and medium-volume samplers in a desert environment

The USEPA replaced TSP with PM₁₀ as the National Ambient Air Quality Standard for particulate matter. The commercially available PM₁₀ sampler is a high-volume model using quartz fiber filters. In certain investigations, such as source apportionment studies, chemical analysis of the filter is necessary, however, many analyses cannot be run on quartz filters. An alternate filter such as Teflon is amenable to XRF and ion chemical analyses but is not amenable to analysis for carbon. To overcome these problems DRI constructed a medium-volume PM₁₀ sampler that is capable of collecting particulates on both Teflon and quartz fiber filters simultaneously. This paper describes the design of the DRI medium-volume PM₁₀ sampler, discusses a method for determining equivalence of two samplers, the results of applying the method to test the equivalence of the medium-volume sampler and a commerical high-volume sampler, and examines differences between PM₁₀ and TSP measurements in a southwestern desert.     

Natal site and offshore swimming influence fitness and long-distance ocean transport in young sea turtles

Although long-distance transport of marine organisms is constrained by numerous oceanic and biological factors, some species have evolved life-histories reliant on such movements. We examine the factors that promote long-distance transport in a transoceanic migrant, young loggerhead sea turtles (Caretta caretta), from the southeastern U.S. Empirical data from near-surface buoys and simulations in two ocean circulation models indicated that passive drifters are often retained for long periods shoreward of oceanic fronts that delineate coastal and offshore waters. Further simulations revealed that offshore swimming aided newly hatched turtles in moving past fronts and increased turtles’ probability of survival, reaching distant foraging grounds, and encountering favorable temperatures. Swimming was most beneficial in regions that were more favorable under scenarios assuming passive drift. These results have broad implications for understanding the movement processes of many marine species, highlighting likely retention of more planktonic species and potential for dispersal in more nektonic species.     

Communal nesting in an ‘asocial’ mammal: social thermoregulation among spatially dispersed kin

Communal nesting can help defray the high cost of endothermic heat production in cold environments, but such social behavior is generally thought to be incompatible with the persistent defense of exclusive territories in typically ‘asocial’ animals. We examined the propensity for communal nesting in female red squirrels (Tamiasciurus hudsonicus), which maintain individual year-round territories, through intensive monitoring of litters over 22 years and by radio-tracking females during 3 years in late winter/early spring. Communal nesting was exceptionally rare during lactation: of 1,381 litters tracked to emergence, we observed a single instance in which two closely related (r?=?0.5) females pooled their litters into a single nest. In contrast, nest sharing between 2–3 females was relatively common in the late winter/early spring, prior to mating; at least 12 of 63 females (19 %) engaged in communal nesting during a year of systematic tracking of radio-collared females from late February to April. Communal nesting occurred more frequently when temperatures were colder, suggesting that such aggregations might function to reduce thermoregulatory costs. These social associations were typically, though not exclusively, between closely related individuals (r?≥?0.25 for seven of eight cases; mother–daughter dyads: four of eight), suggesting this cooperative behavior might evolve through kin selection and/or may reflect extended parental care. Our results demonstrate that female red squirrels engage in communal nesting, typically with closely related kin, despite a dispersed population structure that stems from the persistent defense of individual territories.