Analysis of effluents and associated sediments and tissue for toxic organic compounds, 1987-1988 : final report to Virginia State Water Control Board

Effluent and sediment samples were collected from 30 point source discharge sites within tributaries to the Chesapeake Bay, and analyzed for the presence of toxic organic compounds. The facilities selected included: municipal treatment plants, oil refining and storage operations, shipyards, military bases, paper companies, electrical power generators and various other manufacturing enterprises. In addition to sediment, shellfish were collected from the receiving streams. Unfortunately, environmental conditions in the vicinity of many of the facilities were unsatisfactory for the long-term survival of shellfish. As a consequence their availability was limited. ...

Resolving environmental drivers of microbial community structure in Antarctic soils

Antarctic soils are extremely cold, dry, and oligotrophic, yet harbour surprisingly high bacterial diversity. The severity of environmental conditions has constrained the development of multi-trophic communities, and species richness and distribution is thought to be driven primarily by abiotic factors. Sites in northern and southern Victoria Land were sampled for bacterial community structure and soil physicochemical properties in conjunction with the US and New Zealand Latitudinal Gradient Project. Bacterial community structure was determined using a high-resolution molecular fingerprinting method for 80 soil samples from Taylor Valley and Cape Hallett sites which are separated by five degrees of latitude and have distinct soil chemistry. Taylor Valley is part of the McMurdo Dry Valleys, while Cape Hallett is the site of a penguin rookery and contains ornithogenic soils. The influence of soil moisture, pH, conductivity, ammonia, nitrate, total nitrogen and organic carbon on community structure was revealed using Spearman rank correlation, Mantel test, and principal components analysis. High spatial variability was detected in bacterial communities and community structure was correlated with soil moisture and pH. Both unique and shared bacterial community members were detected at Taylor Valley and Cape Hallett despite the considerable distance between the sites

Prototype for a Regional Online Toxics Database

An interactive online computerized database for retrieval of chemical analytical information on volatile and extractable organic compounds, and the priority pollutant metals has been developed. Current information about samples from the Chesapeake Bay region in Virginia and Maryland are available. This database stores information on organic compounds in effluent, water, tissue, and sediment in a format which does place restrictions on the number of compounds per sample. It includes various QA/QC items as well as the analyst\u27s assessment of the validity of the data. A variety of keyed retrieval options permits selection of reporting format, and flagging of items exceeding selected limits of concentration. Application includes retrievals for use by managers, and by researchers in planning and interpreting environmental studies related to toxic chemicals.https://scholarworks.wm.edu/vimsbooks/1178/thumbnail.jp

Acidosis slows electrical conduction through the atrio-ventricular node

Acidosis affects the mechanical and electrical activity of mammalian hearts but comparatively little is known about its effects on the function of the atrio-ventricular node (AVN). In this study, the electrical activity of the epicardial surface of the left ventricle of isolated Langendorff-perfused rabbit hearts was examined using optical methods. Perfusion with hypercapnic Tyrode's solution (20% CO2, pH 6.7) increased the time of earliest activation (Tact) from 100.5 ± 7.9 to 166.1 ± 7.2 ms (n = 8) at a pacing cycle length (PCL) of 300 ms (37°C). Tact increased at shorter PCL, and the hypercapnic solution prolonged Tact further: at 150 ms PCL, Tact was prolonged from 131.0 ± 5.2 to 174.9 ± 16.3 ms. 2:1 AVN block was common at shorter cycle lengths. Atrial and ventricular conduction times were not significantly affected by the hypercapnic solution suggesting that the increased delay originated in the AVN. Isolated right atrial preparations were superfused with Tyrode's solutions at pH 7.4 (control), 6.8 and 6.3. Low pH prolonged the atrial-Hisian (AH) interval, the AVN effective and functional refractory periods and Wenckebach cycle length significantly. Complete AVN block occurred in 6 out of 9 preparations. Optical imaging of conduction at the AV junction revealed increased conduction delay in the region of the AVN, with less marked effects in atrial and ventricular tissue. Thus acidosis can dramatically prolong the AVN delay, and in combination with short cycle lengths, this can cause partial or complete AVN block and is therefore implicated in the development of brady-arrhythmias in conditions of local or systemic acidosis

A particle introduction experiment in Santa Catalina Basin sediments: Testing the age-dependent mixing hypothesis

The occurrence of age-dependent mixing, a process by which recently deposited, food-rich particles undergo more intense bioturbation than older, food-poor particles, could dramatically alter patterns of organic-matter diagenesis in deep-sea sediments. To explicitly test for age-dependent mixing, an in-situ particle introduction experiment was conducted on the bathyal Santa Catalina Basin floor. Mixtures of radioisotope-tagged particles representing a food quality gradient were dispersed in small amounts on the seafloor and sampled over periods of 0 to 594 days. Introduced particle types were all similar in size and included fresh diatoms ( young particles), surface sediments ( intermediate-age particles), and particles from 30-cm deep in the sediment column ( old particles). This approach permitted evaluation of particle mixing intensity for several particle ages and provided an independent check on mixing coefficients determined from naturally occurring radioisotopes (234Thxs and 210Pbxs). All particles experienced rapid (\u3c6 h) transport into the upper 2 cm of the seabed resulting from passive deposition down burrows or extremely rapid bioturbation. Intense bioturbation on 4-d time scales included both biodiffusive and nondiffusive (bioadvective and nonlocal) transport. Bioturbation of tracers exhibited time (or age ) dependence in two ways: (1) Diffusive mixing intensity for all tracer types decreased with time (4-d Db = 293 cm2 y-1, Db at 520 d = 2.6 cm2 y-1), and (2) The nature of bioturbation changed over this period with more efficient bioadvection and nonlocal exchange giving way to slower diffusive mixing. Both changes are consistent with the age-dependent-mixing hypothesis. Biodiffusive mixing was not measurably selective, with no significant preference for a single particle type. In contrast, nondiffusive transport, likely caused by deposit-feeding cirratulid polychaetes, exhibited distinct particle selectivity, especially over 4-d time scales, with the diatom tracer transported most rapidly to depth. Degradation of the labile organic carbon in diatoms most likely led to decreasing selection of diatoms by deposit feeders until diatoms and old sediment particles experienced comparable mixing intensities