Application of VLEACH to Vadose Zone Transport of VOCs at an Arizona Superfund Site

Cleanup standards for volatile organic compounds in thick vadose zones can be based on indirect risk (transport to ground water) when contamination is below depths of significant direct risk. At one Arizona Superfund site, a one-dimensional vadose zone transport model (VLE-ACH) was used to estimate the continued transport of VOCs from the vadose zone to ground water. VLEACH is a relatively simple and readily available model that proved useful for estimating indirect risk from VOCs in the vadose zone at this site. The estimates of total soil concentrations used as initial conditions for VLF.ACH incorporated a variety of data from the site. Soil gas concentrations were found to be more useful than soil matrix data for estimating total soil concentrations at this arid-zone site. A simple mixing cell model was used with the VLEACH-derived mass loading estimates from the vadose zone over time to estimate the resulting changes in ground water concentrations. For this site, the results of the linked VLEACH/mixing cell simulations indicate it is likely that the federal MCI. for TCE will be exceeded in underlying ground water if remedial action on I he vadose zone is not pursued.     

A re-evaluation and spatial analysis of evidence for a Younger Dryas climatic reversal in Beringia

An objective classification of paleoclimatic proxies from 75 lake and peat records is used to re-evaluate data quality and inferred climatic patterns in Beringia during the Younger Dryas. Mapped data reveal coherent but spatially-complex regional patterns, suggesting the Younger Dryas was characterized by: (1) cooling in Southern Alaska, Eastern Siberia, and portions of Northeastern Siberia; and (2) uniform to warmer-than-present conditions through most of Central Alaska, Northeastern Siberia, and possibly the Russian Far East and Northern Alaska. The Beringian patterns correspond to distinctive large-scale climatic forcings, although in some locations further modified by more local influences, such as topography. General circulation models and modern synoptic climatology provide a conceptual framework for exploring possible mechanisms responsible for the observed changes. Forcings and associated climatic responses consistent with the proxy data include: (1) lowered sea-surface temperatures in the North Atlantic and Pacific reducing temperature and precipitation in Eastern Siberia; (2) intensified Aleutian low and lowered sea-surface temperatures causing cooler summers and higher winter precipitation in Southern Alaska; (3) stronger Pacific Subtropical High and an eastward shift of the East Asian Trough reducing summer temperatures in Southern Alaska and causing relative warmth in Northeastern Siberia; and (4) strong high pressure system producing warm, dry conditions in interior Alaska.     

Avalanche Climatology of the Western United States,with an Emphasis on Alta,Utah*

Climate and snowpack characteristics of avalanches vary spatially across the western United States, distinguishing three regions. The coastal mountain renges have warmer, denser snow; interior (continental) ranges have colder, less-dense snow; and intermountain ranges have intermediate characteristics. Avalanche character of Alta, Utah, is related to eastern Pacific 700-mb height anomalies for December, January, and March, but not for February. Avalanche conditions around Alta do not always relate to localized pressure gradient winds for December and February.     

AVALANCHE CLIMATOLOGY OF THE CONTINENTAL ZONE IN THE SOUTHERN ROCKY MOUNTAINS

The avalanche hazard in the United States is most severe in the continental zone of Colorado, where property damage and deaths exceed those in any other state. The continental zone is normally characterized by a shallow snowpack, faceted crystal growth, and relatively fewer avalanches as compared to the coastal and intermountain zones farther west. This study illustrates that variations in the avalanche character in the continental zone may, at times, resemble some less continental characteristics that are found farther west as a result of anomalous atmospheric circulation patterns. Results from cluster analyses show that some sites in the southern portion of the continental zone generally represent a less continental character. Anomalies of 500-mb heights explain the variability of avalanche climates for selected sites, particularly for Berthoud Pass, within the continental zone. Negative heights over the southwestern United States during early winter correspond with less continental conditions, but the zone of negative heights tends to shift westward over the eastern Pacific Ocean during February and March. However, generalizations of how synoptic patterns govern avalanche climate variations also vary between different locations as a result of smaller-scale climatic controls that operate over the region. [Key words: avalanche climatology, continental zone, 500-mb heights, Rocky Mountains.]     

What can we learn from genomics approaches in marine ecology? From sequences to eco‐systems biology!

The application of genomic approaches to marine biota has profoundly altered our understanding of life in the oceans, especially regarding concepts of adaptation, speciation and evolution. The avalanche of genomic data has provided an unbiased view of marine biology that has never been seen before. In particular, comparative and metagenomic approaches with microbes from different biogeochemical marine provinces provided the first insights into how they acquire and discard genes as needed, even across kingdom boundaries, in response to their environment. These data clearly reveal that marine microbes have remarkable abilities to change their genomes according to both environmental stresses and biotic interactions. Thus, it is most likely that the flux of energy and matter in the marine system is reflected by the presence or absence of genes and proteins in marine organisms, which could provide novel tools to understand biogeochemical processes of global significance. However, the challenge is to put the reductionistic knowledge gained by genomics and metagenomics into the larger contexts of cellular systems and ecosystems to identify emergent properties that could not have been predicted by breaking down the whole into its individual parts.     

The Major Snow Avalanche Cycle of February 1986 in the Western United States

Snow avalanches are a significant hazard in mountainous environments around the world. This paper investigates the major February 1986 avalanche cycle that occurred in the western United States, and broadly analyzes the avalanche, snowpack, and weather conditions at twenty sites. These analyses suggest that the avalanche cycle resulted from the interaction of a relatively `normal' snowpack with an exceptional storm event, which was particularly noteworthy for the amount of precipitation it produced. Composited 500-hPa anomaly maps show the event resulted from an uncommonly persistent blocking pattern that resulted in a strong zonal flow and copious moisture being funneled over the western United States. Understanding severe and widespread avalanche cycles may improve our long-term forecasting of these events, and help mitigate theresulting avalanche activity.     

Rainfall in the Garden of the United States Great Plains, 1870–1889

The recent accumulation of all published precipitation records from 1870–1889 in the central and northern Great Plains of the United States provides a renewed potential in analyzing climatic reality during early settlement, corresponding to a time when some written histories documented that the Rain followed the Plow. Growing season precipitation in the central and northern Great Plains from 1870–1889 were examined relative to modern climatic normals (1961–1990). Growing season totals mostly exhibit little changes in precipitation in the region as compared to today. Some wetter springs and summers occurred in the Dakotas during the late 1870s and early 1880s, subsequent to the drier early-mid 1870s and corresponding to the Great Dakota Boom. Wetter summers occurred over the central Plains in the mid-1880s, corresponding to increased migration in Nebraska and Kansas. Drier summers occurred during the early 1870s and inactive settlement in the early 1880s. Although increased rainfall may have been conducive for early settlement, in general the Rain did not follow the Plow, with extreme seasonal and monthly heavy precipitation events at the subregional scale perhaps playing important roles on settlers' climatic perceptions. The results of this study provide a framework in order to conduct historical climate impact analyses as well as information that can be applied towards understanding spatial climatic variations further back into time.