Colonization of the northwest Atlantic by the blue mussel, <Emphasis Type="Italic">Mytilus trossulus</Emphasis> postdates the last glacial maximum

Blue mussels in the genus Mytilus first arrived in the Atlantic Ocean from the Pacific during the Pliocene, following the opening of the Bering Strait. Repeated periods of glaciation throughout the Pleistocene led to re-isolation of the two ocean basins and the allopatric divergence of Mytilus edulis in the Atlantic and M. trossulus in the Pacific. Mytilus trossulus has subsequently colonized the northwest Atlantic (NW Atlantic) so that the two species are presently sympatric and hybridize throughout much of the Canadian Maritimes and the Gulf of Maine. To estimate when M. trossulus arrived in the NW Atlantic, we have examined sequence variation within a portion of the female mtDNA lineage large untranslated region (F-LUR) for 156 mussels sampled from three Pacific and eleven Atlantic populations of M. trossulus. Although we found no evidence of reciprocal monophyly for Pacific and NW Atlantic M. trossulus, limited gene flow between ocean basins has led to the divergence of unique sequence clades within each ocean basin. In contrast, relative genetic homogeneity indicates high levels of gene flow within each basin. Coalescence-based analysis of the F-LUR sequences suggests that M. trossulus recolonized the NW Atlantic from the northeast Pacific subsequent to a demographic expansion in the Pacific that occurred ~96,000 years before present (ybp). Estimates of timing of divergence for Pacific and NW Atlantic populations and the time since expansion among NW Atlantic sequence clades indicate that M. trossulus arrived in the NW Atlantic more recently, between 20,000 and 46,000 ybp. Given that these estimates overlap with the dates of peak ice in the NW Atlantic during the last glacial maximum (LGM, ~18,000–21,000 ybp), we suggest that colonization of the NW Atlantic by M. trossulus occurred during, but more likely just subsequent to, the LGM and was followed by rapid temporal and spatial expansion in the region.     

Comparison of white-footed mice and rice rats as biomonitors of polychlorinated biphenyl and metal contamination

A study was conducted to assess differences in contaminant assimilation among co-occurring white-footed mice (Peromyscus leucopus) and rice rats (Oryomys palustris) captured at a contaminated site. Rodents were collected from five areas at the Paducah Gaseous Diffusion Plant (PGDP), a uranium enrichment facility. Relatively few white-footed mice (8.7%) had quantifiable concentrations of PCBs compared to 42% of rice rats (chi2 = 6.49, d.f. = 1, P < 0.025), and seven of the 11 rice rats (64%) over 50 g body mass had quantifiable concentrations of PCBs in their livers. White-footed mice had higher mean concentrations of barium (P < 0.0001), chromium (P = 0.0010), copper (P = 0.0011), lead (P = 0.0335), and aluminum (P = 0.0006) than rice rats at all five sampling areas. Species-specific differences in accumulation of PCBs and metals were observed and attributed to differences in habitat use and foraging strategies.     

The use of thermal desorption in monitoring for the chemical weapons demilitarization program

Under international treaty, the United States and Russia are disposing of their aging stockpile of chemical weapons. Incineration and chemical neutralization are options for sites in the United States, although Russia prefers the latter. The storage and disposal of bulk and chemical agents and weapons involve unique hazards of handling extremely toxic materials. There are three major areas of concern--the storage stockpile, the disposal area, and the discovery and destruction of "found" material not considered part of the stockpile. Methods have been developed to detect the presence of chemical agents in the air, and these are used to help assure worker protection and the safety of the local population. Exposure limits for all chemical agents are low, sometimes nanograms per cubic meter for worker control limits and picograms per cubic meter for general population limits. There are three types of monitoring used in the USA: alarm, confirmation, and historical. Alarm monitors are required to give relatively immediate real-time responses to agent leaks. They are simple to operate and rugged, and provide an alarm in near real-time (generally a few minutes). Alarm monitors for the demilitarization program are based on sorbent pre-concentration followed by thermal desorption and simple gas chromatography. Alarms may need to be confirmed by another method, such as sample tubes collocated with the alarm monitor and analyzed in a laboratory by more sophisticated chromatography. Sample tubes are also used for historical perimeter monitoring, with sample periods typically of 12 h. The most common detector is the flame photometric detector, in sulfur or phosphorous mode, although others, such as mass-selective detectors, also have been used. All agents have specific problems with collection, chromatography and detection. Monitoring is not made easier by interferences from pesticide spraying, busy roadways or military firing ranges. Exposure limits drive the requirements for analytical sensitivity. Lowering limits adds additional difficulties to the monitoring efforts. The various monitoring methods and the role they play in ensuring worker and general population safety are discussed.     

Ammonia volatilization from surface-applied poultry litter under conservation tillage management practices

Land application of poultry litter can provide essential plant nutrients for crop production, but ammonia (NH(3)) volatilization from the litter can be detrimental to the environment. A multiseason study was conducted to quantify NH(3) volatilization rates from surface-applied poultry litter under no-till and paraplowed conservation tillage managements. Litter was applied to supply 90 to 140 kg N ha(-1). Evaluation of NH(3) volatilization was determined using gas concentrations and the flux-gradient gas transport technique using the momentum balance transport coefficient. Ammonia fluxes ranged from 3.3 to 24% of the total N applied during the winter and summer, respectively. Ammonia volatilization was rapid immediately after litter application and stopped within 7 to 8 d. Precipitation of 17 mm essentially halted volatilization, probably by transporting litter N into the soil matrix. Application of poultry to conservation-tilled cropland immediately before rainfall events would reduce N losses to the atmosphere but could also increase NO(3) leaching and runoff to streams and rivers.     

Comparison of discharge silver concentrations from electrolytic plating and metallic replacement silver recovery units

Silver-based photographic X-ray film is made of solid crystals of silver chloride or silver bromide suspended in a gelatin and then coated on a film. During the X-ray developing process, the image is processed and the nonimage areas containing solid silver chloride or silver bromide crystals are removed in a solution called the fixer. There may be local environmental regulations that regulate the amount of silver discharged from a facility. To meet these regulations, many facilities have added silver recovery units to their processes. Two different types of recovery processes are in use in a large hospital and three clinics under study. All of the units were claimed by their respective manufacturers to be able to recover silver down to concentrations of 5 mg/L. This concentration would ensure that the building that houses each unit would meet the local county limit of 0.5 mg/L silver for total building silver discharge. The hypothesis for this research is that one system, newer and more expensive, consisting of so-called electrolytic plating units (EPUs) (which are followed by so-called metallic replacement units [MRUs] as a backup), will have better silver recovery than MRUs alone. A total of six units were sampled, three EPUs (in combination with MRUs) and three MRUs. The units were sampled once or twice a day for 10 days for a total of 17 samples from each. The samples then were analyzed by inductively coupled plasma spectroscopy, and an analysis of variance was performed on the results. The range for the electrolytic plating unit/metallic replacement unit combinations was 0.20-99.9 mg/L (mean of 35.15 mg/L; median of 33.8 mg/L). The range for the MRUs alone was 7.2-1112 mg/L (mean of 565.5 mg/L; median of 720 mg/L). Many individual results exceeded 5 mg/L, such that extensive dilution would be required to ensure the building effluent did not exceed 0.5 mg/L. It is suggested that the metallic replacement units be changed to EPUs (with metallic replacement backup units) because they had better silver recovery. Also, the EPU combinations need to be sampled regularly to ensure that their silver concentrations are at acceptable levels.     

Prenatal diagnosis of hunter syndrome

Sixteen pregnancies at risk for Hunter syndrome have been monitored by amniocentesis. Iduronate 2-sulphate sulphatase levels were measured in amniotic fluid, cultured amniotic fluid cells and cord blood. Thirteen of the pregnancies resulted in normal livebirths, two are continuing and one affected pregnancy was terminated. Reduced enzyme levels were observed in either amniotic fluid, cells or cord blood for four female fetuses. Such fetuses are likely to be carriers expressing reduced enzyme levels. The affected male fetus had reduced enzyme activity in amniotic fluid; insufficient cells were cultured for enzyme estimation, however no enzyme activity was detected in fetal liver after termination. Eight cord blood enzyme estimations have been performed, five confirming normal male infants.     

Economic use value of the Belize marine ecosystem: Potential risks and benefits from offshore oil exploration

The announcement of plans for exploratory oil drilling at a number of offshore sites in Belize raised concerns about the risks associated with drilling, particularly given the socio‐economic importance of the marine ecosystem. The current economic value of fisheries and marine ecotourism is estimated, along with the potential revenue from offshore oil and potential economic losses stemming from oil pollution, under various assumptions on risk and uncertainty. Marine fisheries and ecotourism are estimated to generate around US$ 183 million per year. Single‐year estimated maximum revenue is higher for oil extraction initially but quickly declines; during a 50 year (two generation) period, total discounted benefits from marine fisheries and ecotourism are estimated at US$ 5.1 billion, compared to US$ 3.2 billion from offshore oil revenue. Following a hypothetical oil spill, discounted losses in marine fisheries and ecotourism due to perception and ecological impacts are estimated at US$ 912 million, with clean‐up costs and capital losses of US$ 6.1‐10.4 billion. Considering the short extraction life of oil resources compared to fisheries and ecotourism, the difference in benefits increases substantially in favour of the latter with a longer time horizon. A recent public referendum resulted in a 98% vote against oil exploration and a subsequent annulment of oil concessions pending environmental impact assessments.     

Development of a field enhanced photocatalytic device for biocide of coliform bacteria

A field enhanced flow reactor using bias assisted photocatalysis was developed for bacterial disinfection in lab-synthesized and natural waters. The reactor provided complete inactivation of contaminated waters with flow rates of 50 m L/min. The device consisted of titanium dioxide nanotube arrays, with an externally applied bias of up to 6 V. Light intensity, applied voltage, background electrolytes and bacteria concentration were all found to impact the device performance. Complete inactivation of Escherichia coli W3110(~ 8 × 10~3CFU/m L) occurred in 15 sec in the reactor irradiated at 25 m W/cm~2 with an applied voltage of 4 V in a 100 ppm NaCl solution. Real world testing was conducted using source water from Emigration Creek in Salt Lake City, Utah. Disinfection of natural creek water proved more challenging, providing complete bacterial inactivation after 25 sec at 6 V. A reduction in bactericidal efficacy was attributed to the presence of inorganic and organic species, as well as the increase in robustness of natural bacteria.     

EFFECTWENESS OF INTEGRATED STORMWATER MANAGEMENT IN A PORTLAND,OREGON, WATERSHED1

ABSTRACT: The City of Portland's stormwater management program, winner of EPA's Environmental Excellence Award for 1996, is committed to partnership-based, cost-effective, “green” approaches to healthy neighborhoods and water quality. The stormwater program encourages innovative, non-structural pollution reduction techniques like native landscaping, stormwater pollution reduction bioswales and ponds, and public involvement and education. Effectiveness of stormwater best management practices (BMPs) has been difficult to determine on a citywide basis. Recognizing this problem, the City of Portland launched the Parkrose Pilot Project in 1994 to test the effectiveness of a wide range of BMPs in a small watershed in north Portland, the Parkrose catchment, and monitor the results prior to citywide implementation. This catchment was selected because of its small size (144 acres), its representative mix of land uses, and an extensive record of water quality monitoring data. This paper examines the City's strategy in selecting the Parkrose study area as a pilot watershed, the BMPs chosen for use in the watershed, and the results of the program to date. Final success of the Parkrose project will be gauged by the attainment of measurable pollution reduction within the catchment while providing opportunities for meaningful participation by the local community in achieving water quality. Involvement by private citizens in the community is crucial to the success of the project and to ensure compliance with the federal mandate to reduce pollutants to the maximum extent practicable.     

Integrating density functional theory into reductive dechlorination research

Chlorinated organics have been frequently detected in groundwaters, threatening the quality of drinking water supplies worldwide. A promising method for groundwater remediation involves reductive dechlorination (RD), in which chlorine atoms are sequentially removed and substituted by hydrogen, producing less harmful byproducts. In this paper, for the first time, RD research is reviewed in light of the growing incorporation of density functional theory (DFT) as a research tool. DFT has been used to uncover a variety of reaction properties for a range of relevant groundwater pollutants, including 1,2,3-trichloropropane, hexachlorobenzene, and various dioxins. DFT models have revealed the role of surface interactions in driving the kinetics of catalytically driven RD. Mechanisms involved with biologically mediated RD have also been elucidated with insights gleaned from DFT. Issues and challenges for future research are also discussed.