This study was undertaken in order to learn the relationships between clay minerals of stream sediments and the clay mineralogy of corresponding source materials. The York River tributary system was selected to conduct such a study because of its moderate size and its geographical and geological setting. The tributary basin spans the entire Piedmont and most of the Coastal Plain before reaching West Point, Virginia, and it covers 2242 square miles. River sediments and weathering products (source materials) of the basin were sampled in such a way that both were faithfully represented. Stream sediment samples were taken at closely spaced sites as cores, grab samples, and scoop samples from the channel bed. Source material samples were taken after reconnaissance of the area from road outs, cultivated fields and forests. Surface and subsurface source samples were collected. Five small tributaries of the system were similarly sampled in greater detail. X-ray analyses of more than 700 samples were made using powder diffraction techniques and a General Electric recording diffractometer. Filtered Cu-K radiation was used. Each sample was analyzed untreated as an oriented aggregate. Further X-ray analyses where necessary included glycolated and heat treated samples. Clay minerals of source materials and stream sediments of the York River tributary basin are naturally grouped into five categories on the basis of first-order basal spacings. Minerals identified are kaolinite, illite, expandable illite. typical vermiculite atypical vermiculite, montmorillonite and mixed-layer clay minerals involving 10 A and 14 A layers. Kaolinite is present in all source area samples Vermiculite is the next most frequent source mineral followed by illite. Montmorillonite is highly sporadic in occurrence and is a minor constituent in the source area. The stream sediments contain al1 the minerals found in the source area. No new minerals were observed in the stream environment. The frequency distribution of most minerals is different in sediments. Kaolinite and vermiculite occur in all stream sediments. Illite occurs in all sediment samples of the Mattaponi and Pamunkey tributaries and its reflections become more intense in the lower part of the system. Montmorillonite occurs in more than 86 per cent of the sediments of the Coastal Plain portion of the system. Mixed-layer clay minerals become less frequent in the streams of the basin in contrast to their frequency in the source materials and become more pronounced downstream. The intensity of X-ray reflections for source material clay minerals is typically 2-3 times as intense as those of stream sediments. Physical mechanisms are postulated to explain the decrease in mixed-layer structures, the increase in illite intensity downstream and the increase in the frequency of occurrence of montmorillonite in the sediments of the lower parts of the stream systems. Mixed-layer minerals become unmixed through a highly selective erosion and transportation process which results in removal of the clay in units of structure. This physical unmixing provides an explanation of the increase in illite reflections in sediments in the lower part of the stream. Montmorillonite is more frequent in the lower part of the stream because of its greater mobility than the other minerals. Results of this study may require that previous studies of modern sediments be re-evaluated in recognition of the appearance of atypical vermiculite in the source area and the process of unmixing of mixed-layer clay minerals. / Ph. D.

Entocytherid ostracods were collected on crayfishes inhabiting the James and York River basins of Virginia. Of the seventeen species encountered, only one (Donnaldsoncythere ardis) seems to be endemic. Ankylocythere ancyla, Dactylocythere banana, Dt. falcata, Dt. suteri, Donnaldsoncythere ardis, Dn. hiwasseensis, Dn. truncata, Entocythere sp. A, E. internotalus and Phymocythere phyma occur on the crayfishes Cambarus acuminatus, C. b. bartonii, C. longulus and Orconectes juvenilis in the streams of the Valley and Ridge Province. In the Coastal Plain where sluggish streams are encountered, Ankylocythere telmoecea and Ank. tiphophila are associated with Procambarus a. acutus. Cambarus acuminatus is also found in the Coastal Plain in moderately flowing streams and it is infested with Dactylocythere suteri and Donnaldsoncythere hiwasseensis. The primary burrowing crayfish of the Alleghany Mountains (Cambarus dubius) is host to Ascetocythere asceta and Dactylocythere chalaza whereas its ecological similar Cambarus d. diogenes of the Piedmont and Coastal Plain is the only host known with certainty for Dactylocythere jeanae, Okriocythere cheia and Ornithocythere waltonae. Ankylocythere tiphophila is associated with Fallicambarus uhleri, an inhabitant of swampy areas and marshes and may ocassionally construct simple burrows in the Coastal Plain. / Master of Science

This research examined effects of hypoxic environments on blue crabs, Callinectes sapidus in an estuarine environment. Hypoxic conditions were treated as a multiple stressor involving low dissolved oxygen (D.O.), increased carbon dioxide (hypercapnia), and low pH concurrently. The objectives were to: 1) identify hypoxiahypercapnia by monitoring D.O. and pH as an indicator of hypercapnia in shallow regions of the York River, 2) measure blue crab abundance, and 3) describe blue crab responses to hypoxiahypercapnia via field work at Taskinas Creek and lab measurements of respiration. Ambient D.O. and pH were positively correlated in the Taskinas Creek and York River sites (r= .73). Crab abundance (CPUE) was not significantly different among D.O. and pH ranges. It was concluded that hemolymph blood lactate concentration was not considered a good in situ biomarker for exposure to hypoxickypercapnic conditions. Oxygen uptake was not significantly different between normoxic and hypoxic conditions but was significantly affected by pH.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 150-155). Also available via the Internet.

This study investigated the effects of the detergent phosphorus ban implemented on January 1, 1988 in Virginia, on the treatment streams of the York River Wastewater Treatment Plant, a biological nutrient removal (BNR) system. Evaluation of the available historical data indicated that the influent phosphorus load entering the plant in the post-ban period had decreased 27% compared to the pre-ban period. The influent phosphorus concentration had decreased 29% from the pre- to the post-ban period. No definitive conclusion could be reached concerning the effects of the influent phosphorus decrease on the treatment efficiency due to operational changes which occurred at the time of the ban implementation. The combination of operational changes and the phosphorus ban resulted in 54% and 59% decreases in the effluent phosphorus load and concentration, respectively. Measurements and modelling of the anaerobic digester contents indicated that several minor changes had occurred in the digester which may be attributable to the phosphorus ban, but the equilibria of the digester regarding phosphorus compounds had not been dramatically altered. This was primarily due to improved operation of the clarifiers and sludge thickeners, which delivered Similar phosphorus loads to the digester in the pre- and post-ban periods. / Master of Science

This thesis details the literary and visual influences in my work, the definition of American Gothic, and its connection it to my work. Literary sources such as Edgar Allan Poe and Fanny Kemble help spark a vision of the landscape. Visual influences include Japanese woodblock prints, scenic wallpapers, vintage postcards and Victorian mourning pictures. My regional explorations span the James River, Tidewater swamps and architecture within the city of Richmond.My work depicts local history and ecology inspired by Richmond and the surrounding region. Subtle Gothic elements add anxiety to the otherwise pastoral scenes. Gothic foreboding in the work questions our ecological future and the permanence of our human presence in the landscape.