Midwestern Sites Research Articles

Herbicide movement and dissipation at four midwestern sites

This study was conducted to evaluate atrazine (2‐chloro‐4‐ethylamino‐6‐isopropyl‐1, 3, 5‐triazine) and alachlor (2‐chIoro‐N‐(methoxymethyl)acetamide) dissipation and movement to shallow aquifers across the Northern Sand Plains region of the United States. Sites were located at Minnesota on a Zimmerman fine sand, North Dakota on Hecla sandy loam, South Dakota on a Brandt silty clay loam, and Wisconsin on a Sparta sand. Herbicide concentrations were determined in soil samples taken to 90 cm four times during the growing season and water samples taken from the top one m of aquifer at least once every three months. Herbicides were detected to a depth of 30 cm in Sparta sand and 90 cm in all other soils. Some aquifer samples from each site contained atrazine with the highest concentration in the aquifer beneath the Sparta sand (1.28 μg L‐1). Alachlor was detected only once in the aquifer at the SD site. The time to 50% atrazine dissipation (DT50) in the top 15 cm of soil averaged about 21 d in Sparta and Zimmerman sands and more than 45 d for Brandt and Hecla soils. Atrazine DT50 was correlated positively with % clay and organic carbon (OC), and negatively with % fine sand. Alachlor DT50 ranged from 12 to 32 d for Zimmerman and Brandt soils, respectively, and was correlated negatively with % clay and OC and positively with % sand.

DNA Content and Chloroplast DNA Polymorphisms among Switchgrasses from Remnant Midwestern Prairies

Panicum virgatum L. (switchgrass) is perennial grass that is native to most of the USA. The principal use of switchgrass has been as a pasture and range grass for forage production during the warmer summer months. The objective of this research was to determine if DNA content and chloroplast DNA (cpDNA) polymorphisms existed among and within switchgrass accessions from Midwestern prairie sites. Twenty‐eight switchgrass accessions from remnant prairie sites were surveyed in 1994 for the upland cytotype (U) or lowland (L) cytotype in the cpDNA by means of restriction endonuclease BamHI and sorghum cpDNA probe pLD 5. These accessions were also surveyed in 1994 for DNA content differences ltow cytometry. One accession, IA 31, contained a mixture of cytotypes indicating that both cytotypes can occur at a single remnant prairie site. The other Midwestern remnant prairies that were represented in this study contained only the U cytotype. The flow cytometry results indicated that switchgrass populations found within the Midwestern sites can be a mixture of ploidy levels with either 3 (tetraploid) or 6 (octaploid) pg DNA per cell. These results indicated that germplasm from Midwestern prairies should be identified according to DNA content and cytotype before it is utilized in developmental programs by plant breeders.

Health Effects of Acid Aerosols on North American Children: Air Pollution Exposures

Air pollution measurements were conducted over a 1-year period in 24 North American communities participating in a respiratory health study. Ozone, particle strong acidity, sulfate, and mass (PM10 and PM2.1) were measured in all communities. In 20 of the communities, sulfur dioxide, ammonia, nitric acid, nitrous acid, and particulate nitrate were measured. The sampler was located centrally in the community whenever possible and samples were collected every other day. Concentrations of particle strong acidity, mass, sulfate, and ozone were highly correlated both in the region of the country defined as a high-sulfur source area and in the downwind transport regions. These regions of the eastern United States and southern Canada experienced the greatest particle strong acidity, sulfate, and particle mass concentrations during the spring and summer months (May-September). The particle strong acidity concentrations were highest in regions close to the high sulfur emission areas of the United States; that is, in the area immediately to the west of the Appalachian Plateau and west of the Allegheny Mountains (western Pennsylvania, eastern Ohio, and West Virginia) up through southern Ontario. The frequency of particle strong acidity events decreased with transport distance from the region of highest sulfur emissions. Low particle strong acidity and sulfates were found at the western and midwestern sites of both the United States and Canada. Substantial concentrations of nitric acid were found in two of the California sites as well as many sites in the northeastern portion of the United States. Sites selected for the epidemiologic study provide a range of annual mean particle strong acidity exposures from below the limit of detection to more than 50 nmol/m3.

Health effects of acid aerosols on North American children: air pollution exposures.

Air pollution measurements were conducted over a 1-year period in 24 North American communities participating in a respiratory health study. Ozone, particle strong acidity, sulfate, and mass (PM10 and PM2.1) were measured in all communities. In 20 of the communities, sulfur dioxide, ammonia, nitric acid, nitrous acid, and particulate nitrate were measured. The sampler was located centrally in the community whenever possible and samples were collected every other day. Concentrations of particle strong acidity, mass, sulfate, and ozone were highly correlated both in the region of the country defined as a high-sulfur source area and in the downwind transport regions. These regions of the eastern United States and southern Canada experienced the greatest particle strong acidity, sulfate, and particle mass concentrations during the spring and summer months (May-September). The particle strong acidity concentrations were highest in regions close to the high sulfur emission areas of the United States; that is, in the area immediately to the west of the Appalachian Plateau and west of the Allegheny Mountains (western Pennsylvania, eastern Ohio, and West Virginia) up through southern Ontario. The frequency of particle strong acidity events decreased with transport distance from the region of highest sulfur emissions. Low particle strong acidity and sulfates were found at the western and midwestern sites of both the United States and Canada. Substantial concentrations of nitric acid were found in two of the California sites as well as many sites in the northeastern portion of the United States. Sites selected for the epidemiologic study provide a range of annual mean particle strong acidity exposures from below the limit of detection to more than 50 nmol/m3.

Natural selection of PAH-degrading bacterial guilds at coal-tar disposal sites.

Microbial activity patterns at buried coal-tar disposal sites have been under investigation for several years to determine the response of naturally occurring microflora to polycyclic aromatic hydrocarbons (PAHs) at the sites. At one site in upstate New York, data have shown enrichment of PAH-degrading bacteria in subsurface contaminated zones but not in uncontaminated zones. Similar work at a midwestern site showed that the same trends existed in a heterogeneous disposal site except that a borehole outside the plume showed some PAH-mineralization activity. Polymerase chain reaction amplification of DNA extracted from sediment samples from the New York site indicated the presence of naphthalene metabolism genes nahAc and nahR, similar to those found on the NAH7 plasmid of Pseudomonas putida G7. Significant sequence polymorphism was observed in amplified nahAc products, indicating that divergent homologs of nahAc were present in the native community. Protozoan numbers were elevated in sediment samples displaying relatively high PAH-degrading activity, suggesting that a food chain was established based on PAH-degrading bacteria. Removal of the coal-tar source at the site occurred in 1991. In 1992, sampling of three key borehole stations revealed that mixing and backfilling operations had introduced soil microorganisms into the source area and introduced 14C-PAH-mineralization activity into the previously inactive pristine area. Thus removal of the source of the contaminants and restoration at the site have altered the microbial activity patterns outside the contaminant plume as well as in the source area.

Functional Organization of Stream Fish Assemblages in Relation to Hydrological Variability

Stream fish assmemblage data for 34 sites in Wisconsin and Minnesota were obtained from archived sources and were used in conjunction with long—term hydrological data to test the hypothesis that functional organization of fish communities is related to hydrological variability. For each of the 106 species present in the data set, six categories of species traits were derived to describe habitat, trophic, morphologica, and tolerance characteristics. A hierarchical clustering routine was used to identify two functionally similar groups of assemblages defined in terms of species presence/absence. Hydrological factors describing streamflow variability and predictability, as well as frequency and predictability of high flow and low flow extremes, were derived for each of the 34 sites and employed to explain differences among the functionally defined groups. Canonical discriminant analysis revealed that the hydrological data could clearly separate the two ecologically defined groups of assemblages, which were associated with either hydrologically variable streams (high coefficient of variation of daily flows, moderate frequency of spates) or hydrologically stable streams (high predictability of daily flows, stable baseflow conditions). Discriminant functions based on hydrological information classified the 34 fish assemblages into the correct ecological group with 85% accuracy. Assemblages from hydrologically variable sites had generalized feeding strategies, were associated with silt and general substrata, were characterized by slow—velocity species with headwater affinities, and were tolerant to silt. Proportions of species traits present at the 34 sites were regressed against an index of hydrological stability derived from a principal components analysis to test the hypothesis that functional organization of assemblages varied across a gradient of hydrological stability. Results were complementary with the discriminant analysis. Findings were in general agreement with theoretical predictions that variable should support resource generalists while stable habitats should be characterized by a higher proportion of specialist species. Several species of fish were identified as indicative of the variable—stable hydrological gradient among stream sites. A taxonomic analysis showed strong geographic patterns in species composition of the 34 assemblages. However, zoogeographic constraints did not explain the observed relationship between stream hydrology and functional organization of fish assemblages. The strong hydrological—assemblage relations found in the 34 midwestern sites suggest that hydrological factors are significant environmental variables influencing fish assemblage structure, and that hydrological alterations induced by climate change (or other anthropogenic disturbances) could modify stream fish assemblages structure in this region.

Alachlor and metolachlor movement during winter and early spring at three Midwestern sites

Abstract This study was undertaken to empirically assess alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide] and metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide] movement in soils during winter and early spring. Alachlor and metolachlor were applied to frozen soils in late November or early December at Rosemount, MN and Aurora and Beresford, SD. Soils were sampled in February, March, and April or May and dissected incrementally. Herbicides moved from the surface into the soil at each site. Herbicide redistribution was greatest at the last sampling date when alachlor was measured to 105 cm. Metolachlor was less mobile than alachlor with most remaining at or above the 15‐cm depth. These data indicate that most herbicide leaching occurred during the spring with water supplied by snowmelt, the melting frost lens, or spring rains.

Punctured Human Bones of the Laurel Culture from Smith Mound Four, Minnesota

Punctured human long bones have been reported at numerous midwestern sites, but none have as large a concentration as Smith Mound Four (21KC3). This northern Minnesota mound was built by the people of the Laurel culture and dates to A.D. 565. Analysis of the bones suggests that they were perforated on the basis of inherited group affiliation for purposes that did not involve marrow extraction and may have related to ideas of spirit release.

New Evidence Concerning the Chronology and Paleoethnobotany of Salts Cave, Kentucky

Recent research has resolved problems surrounding the chronology and archeobotanical record of the Salts Cave Vestibule. Formerly, widely disparate radiocarbon dates made assignment of the site to either the Late Archaic or Early Woodland period equally problematic. Eight new radiocarbon determinations from Vestibule charcoal indicate an occupation in the first millennium B.C., confirming an assignment to the Early Woodland period. Previous analyses of carbonized plant remains from stratified deposits in the Vestibule indicated that the domestication of two native plants, sumpweed and sunflower, preceded the introduction of cucurbits into this part of the Eastern Woodlands. Data from other Midwestern sites have contradicted this generalization. A recent analysis of a second series of archeobotanical samples indicates that cucurbits were present at Salts Cave as early as the domesticated native annuals. These new data render the archeobotanical record of Salts Cave less anomalous than previously, and support the currently accepted reconstructions of prehistoric subsistence change in the Eastern Woodlands.

Fog Chemistry at an Urban Midwestern Site

The Holcomb Research Institute is monitoring fog chemistry in Indianapolis, Indiana and at sites in and near the heavily industrialized Ohio River Valley. Results reported here indicate that fogs in this area can be strongly acidic, and that further studies are warranted. We report 1) the ionic composition of three fog events, samples collected in Indianapolis between December 1985 and February 1986, and 2) the pH of three additional events, samples collected between November 1985 and February 1986. (The volume of fog collected during the latter three events was insufficient for chemical analysis other than pH.) The pH of the fog samples ranged from 2.85 to 4.06; some of this fell within the range known to damage foliage and yield of some plant species. It has been demonstrated that even one exposure to highly acidic mists (pH par. delta 2.5) can damage certain crop species; hence, it is important to document the occurrence of any events having acidity near this level.

Variance Analysis of Wind Characteristics for Energy Conversion

Variance analysis of hourly wind data is utilized to assist in wind characteristic assessment for direct energy conversion systems. Feasibility of large-scale wind energy utilization, as well as sitting, sizing and operating policy, depend on the variability of the wind. Several Midwestern sites are used to illustrate a temporal study of variance sources that leads to the evaluation of equivalent independent hours. For the sites considered these vary from two to three per day. This information is utilized to determine duration of survey requirements for stated confidence levels and desired accuracy. Reasonably reliable and accurate estimates of the mean seasonal wind can be obtained in one or two years for the sites analyzed. Autocorrelation and cross-correlation analysis confirms the existence of significant correlation in the wind at a single site for a period of 8–12 h and between sites for similar time lags and separations up to 100 km or more. Meaningful prediction of variation from the mean appears possible in these cases. The diurnal cycle effect is seen to depend significantly on season and elevation.