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151.
Ben?Harp Jeremy?Hogue Logan?Peck Drew?SpainEmail author 《Natural Resources Research》2005,14(2):101-107
An earlier investigation by the Kansas Geological Survey in central Kansas studied the movement of nitrate from fertilizer through soil into the groundwater. Nitrate concentrations in soil water were measured on samples collected at three locations during a three-year span, from sets of lysimeters buried at different depths. Although patterns seemed apparent in the resulting measurements, no statistical analyses were performed to test their significance; this re-study of the data uses analyses of variance to test for differences in nitrate concentration attributable to time and to depth in the soil. The mean nitrate concentration of samples collected in the first year of the experiment was significantly higher than the means of second and third year samples at all three locations, perhaps reflecting the confounding influence of a previous flooding experiment. ANOVAs of depth across years determined few significant differences in nitrate concentration with depth. The wintertime gap in measurements and unequal sampling through time precludes formal time-series analyses, but graphs of concentration versus time show that peak concentration occurs at later times with increasing depth, and that maximum concentration decreases with depth. These statistical analyses support the conclusions from the original investigation. 相似文献
152.
153.
Spatial distribution of the probability of occurrence and the value of petroleum: Kansas, an example
L. J. Drew 《Mathematical Geology》1972,4(2):155-171
This paper suggests a new formulation for exploration-decision models useful in predicting the economics of exploring for petroleum in the United States. The methods used to date have been based on the premise of exploring for entire deposits. This approach may be unrealistic if exploring for petroleum in the United States because land ownership has so fragmented the surface that there is only a small probability that an entire deposit will be contained in any land tract held by a single exploration interest. As a result, it is suggested here that petroleum exploration-decision models intended for use by a single exploration interest should be based on frequency distributions of the probability of occurrence and value of petroleum occurring within land tracts. To achieve this goal, these distributions have been investigated in a 69,120-sq mi area in Kansas. 相似文献
154.
Rochelle Plutchak Kelly Major Just Cebrian C. Drew Foster Mary-Elizabeth C. Miller Andrea Anton Kate L. Sheehan Kenneth L. HeckJr. Sean P. Powers 《Estuaries and Coasts》2010,33(6):1355-1364
The ability of oysters to remove large quantities of particulates from the water column, thereby potentially improving water
quality, has been cited as one of the reasons for oyster reef restoration. However, this ability has not yet been effectively
demonstrated in the field. As part of the Alabama Oyster Reef Restoration Project, this study was designed to assess impacts
of restored eastern oyster (Crassostrea virginica) reefs on primary production, nutrient dynamics, and water quality in shallow tidal creeks. Using a Before–After-Control–Impact
(BACI) design, we monitored tidal creeks around Dauphin Island, AL, for changes induced by the introduction of oyster reefs.
Reef placement resulted in increased ammonium (NH4+) in two of the three experimental creeks. Interestingly, oyster reefs did not seem to reduce water column particulates or
have an impact on phytoplankton or microphytobenthic biomass or productivity. We do not believe that our data discount the
importance and/or usefulness of oysters in modifying the water column. Rather, we acknowledge that it is difficult to detect
these impacts/environmental services in this type of system (i.e., a tidal creek system), because they seem to be very localized
and short-lived (i.e., not ecologically relevant on a creek-wide scale). This study highlights the need to consider location
and habitat in planning oyster restoration projects. Also, it demonstrates that the types, magnitudes, and spatial extent
of changes in ecosystem services that should be expected after reef restoration might need to be re-evaluated. 相似文献
155.