Isotopic mapping of groundwater perchlorate plumes.

Analyses of stable isotope ratios of chlorine and oxygen in perchlorate can, in some cases, be used for mapping and source identification of groundwater perchlorate plumes. This is demonstrated here for large, intersecting perchlorate plumes in groundwater from a region having extensive groundwater perchlorate contamination and a large population dependent on groundwater resources. The region contains both synthetic perchlorate derived from rocket fuel manufacturing and testing activities and agricultural perchlorate derived predominantly from imported Chilean (Atacama) nitrate fertilizer, along with a likely component of indigenous natural background perchlorate from local wet and dry atmospheric deposition.

Dip and anisotropy effects on flow using a vertically skewed model grid.

Darcy flow equations relating vertical and bedding-parallel flow to vertical and bedding-parallel gradient components are derived for a skewed Cartesian grid in a vertical plane, correcting for structural dip given the principal hydraulic conductivities in bedding-parallel and bedding-orthogonal directions. Incorrect-minus-correct flow error results are presented for ranges of structural dip (0 < or = theta < or = 90) and gradient directions (0 < or = phi < or = 360). The equations can be coded into ground water models (e.

Michigan basin regional ground water flow discharge to three Great Lakes.

Ground water discharge to the Great Lakes around the Lower Peninsula of Michigan is primarily from recharge in riparian basins and proximal upland areas that are especially important to the northern half of the Lake Michigan shoreline. A steady-state finite-difference model was developed to simulate ground water flow in four regional aquifers in Michigan's Lower Peninsula: the Glaciofluvial, Saginaw, Parma-Bayport, and Marshall aquifers interlayered with the Till/"red beds," Saginaw, and Michigan confining units, respectively. The model domain was laterally bound by a continuous specified-head boundary, formed from lakes Michigan, Huron, St.

Distribution of mono-, di, and tri-O-acetylated sialic acids in normal and neoplastic colon.

The purpose of this study was to compare the expression of O-acetylated sialic acids on normal colonic epithelial cells to that on primary and metastatic human adenocarcinoma of the colon and rectum. In 24 cases, the relative percentages of biosynthetically labeled non-, mono-, di-, and tri-O-acetylated sialic acids were measured after hydrolytic release, separation, and identification by paper chromatography. In one case, the presence of di- and tri-O-acetylated sialic acids was confirmed by fast atom bombardment-mass spectral analysis.