No abstract

In Chesapeake Bay, Maryland, USA, some of the most contaminated sediments are found in the highly industrialized Baltimore Harbor-Patapsco River area. As part of a comprehensive assessment of sediment quality in this system, sediment toxicity was assessed in 10-d acute tests with the estuarine amphipod Leptocheirus plumulosus. Mean amphipod survival was significantly reduced in 7 of the 25 samples tested despite the occurrence of minor experimental artifacts. The most toxic sediments were collected from Bear Creek; other areas exhibiting toxicity included the Inner Harbor and Colgate Creek. Marginal toxicity was observed in samples from Curtis Creek, Lazeretto Point, and Back River. Negative relationships were detected between survival and concentrations of select sediment-associated contaminants, whereas a very strong positive association existed between survival in laboratory exposures and density of L. plumulosus at the test sites. A weight of evidence approach, including correlation analyses, a model of polycyclic aromatic hydrocarbon bioavailability, and comparisons to benchmark sediment levels, was used to tentatively identify classes of contaminants that contributed to the observed toxicity. Analysis of results suggested that toxicity at stations in Bear Creek and Colgate Creek may have been driven by sediment-associated metals, whereas toxicity at stations in the Inner Harbor was likely due to both metal and organic contaminants. The observed relationships among toxicity test results, concentrations of sediment-associated contaminants, and abundance of L. plumulosus at the test sites suggests that acute toxicity tests with this species are indicative of adverse biological effects in the field.

[1] We report on the climatology of equatorial thermospheric winds and temperatures based on Fabry-Perot interferometer measurements of Doppler shifts and Doppler broadenings of the 630.0 nm spectral emission from the Cajazeiras observatory located in the northeastern part of Brazil (6.89°S, 38.56°W). These results apply to the lower thermosphere region near 240 km and were obtained during a period of weak solar activity with the solar flux typically within the range of 72 and 82 solar flux units. Examination of the monthly averaged meridional thermospheric winds for 1 year of measurement from October 2009 to September 2010 found the wind direction to be equatorward during summer months throughout the early evening hours with maximum speeds reaching ∼65 ms −1 . During winter months, the early evening meridional wind direction reversed to poleward with similar speeds. This result is attributed to the cross-hemispheric flow from the summer to winter hemisphere. Superimposed upon this wintertime meridional wind flow was an equatorward surge shortly before midnight. This surge shifted to earlier local times in the transition from the vernal equinox to summer and to later local times between the summer solstice and the autumnal equinox; this flow feature is attributed to tidal wave forcing. The temperature observations exhibited the expected behavior, with the midnight temperature maximum showing a greater amplitude, ∼120 K, in the vernal equinox with somewhat weaker amplitudes, ∼75 K, seen at earlier local times during the summer. Also observed was a phase lag of 60 to 90 min between the appearance of the equatorward meridional wind flow and occurrence of the midnight temperature maximum peak.

We present a climatology of quiet time thermospheric winds and temperatures estimated from high‐resolution Fabry‐Perot interferometer measurements of the 630.0 nm airglow emission spectral line shape. Three locations are examined in this long‐term study: northeastern Brazil (August 2009 to August 2014), a midlatitude site in North Carolina, USA (June 2011 to December 2014), and a midlatitude site in Morocco (November 2013 to December 2014). We discuss the day‐to‐day, seasonal, and solar cycle trends and variations of thermospheric meridional winds, zonal winds, neutral temperatures, and for the first time vertical winds. Observations made from solar minimum to solar maximum (with F10.7 values ranging from ∼70 to ∼159 solar flux units) confirm that neutral temperatures have a strong solar cycle dependence. However, this data set shows that the neutral winds are more closely tied to the seasonal variation, rather than the solar cycle. We also present comparisons between the two midlatitude sites and include neutral wind comparisons to the updated Horizontal Wind Model 14.