Effects of the duration of exposure to mercuric chloride on the embryogenesis of the estuarine teleost, Fundulus heteroclitus

Embryos of Fundulus heteroclitus in the 4–8 cell stage were exposed nine Hg⁺⁺ (as mercuric chloride) concentrations from 0 to 100 μg/litre (ppb) for 32 days, 5 days, 2 days and 1 day. All but the chronically (32-day) exposed embryos were allowed to continue development in mercury-free water (20% S) after the exposure period to determine the effect of duration of exposure on three parameters of development. Ninety-six hour survival, total hatching success and per cent incidence of lateral spinal curvature were measured. Only embryos exposed to mercury for a single day showed a significant increase in survival in comparison with embryos exposed for a longer period of time after four days of development. Under all conditions of exposure, survival was reduced at concentrations greater than 40 ppb Hg⁺⁺. Hatching success of chronically exposed embryos was significantly reduced at concentrations greater than 10 ppb Hg⁺⁺. Significant increases in total hatchability were effected by reducing the duration of exposure to five days and one day. Of eleutheroembryos emerging following chronic exposure to mercury, increases in the incidence of lateral spinal curvature were noted at all concentrations above 20 ppb Hg⁺⁺. Significant reductions of this disorder were observed among eleutheroembryos exposed to mercury for 5 days, 2 days or 1 day. Of the three parameters measured, the incidence of lateral spinal curvature and the resulting VH₅₀ value gave a more sensitive evaluation of the embryotoxic effects of Hg⁺⁺ as mercuric chloride on the estuarine teleost, Fundulus heteroclitus.     

Bioavailability of chromium from a used chrome lignosulphonate drilling mud to five species of marine invertebrates

The bioavailability of chromium from a used seawater chrome lignosulphonate drilling mud to three marine crustaceans, Portunus spinicarpus, Penaeus aztecus and Palaemonetes pugio, a polychaete worm, Neanthes virens, and a bivalve mollusc, Rangia cuneata, was evaluated. All five species showed an apparent accumulation of chromium during exposure to different types of mud-seawater mixtures. When the crustaceans were returned to mud-free seawater they rapidly released the accumulated chromium. Clams R. cuneata accumulated significant amounts of chromium when exposed to a substrate containing a layer of drilling mud. However, most of the chromium was released within 24 h when the clams were returned to a clean natural substrate, indicating that much of the chromium accumulated was in the form of unassimilated mud components in the digestive tract or on the gills. When the clams were exposed for 16 days to the mud aqueous fraction they accumulated up to 19 ppm chromium in their tissues. When returned to clean seawater, they released approximately half the chromium in 11 days. When exposed to the mud aqueous fraction, polychaetes Neanthes virerns accumulated less chromium than the other species studied, but retained nearly all the chromium during a 96 h depuration period. Bioavailability of chromium from a used chrome lignosulphonate drilling mud during short-term exposure is relatively low and is species dependent. Chromium associated with the soluble or fine particulate phase of the mud appears to be more bioavailable than that associated with the dense, rapidly sedimenting particles.     

Compositional analysis of Yayoi‐Heian period ceramics from Okinawa: Examining the potential for provenance study

In Okinawa, locally produced pottery dates back to the Initial Jomon period (˜6500 ¹⁴C yr B.P.). Later in time, especially during the Early Yayoi‐Heian period (˜300 B.C.–A.D. 300), ceramic assemblages appear to contain mainland (Japan) Yayoi pottery. A greater number of these sherds present in Okinawa over time coincide with an increasing amount of interaction with mainland Japan, as evidenced by other exchange items. In this preliminary study, the authors analyzed sherds from several Early Yayoi‐Heian period deposits from sites in Okinawa using thin‐section petrography and laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS). The objective was to examine the applicability of these techniques for Okinawan ceramic provenance studies, assess intra‐ and intersite variation in mineralogical and chemical composition, and determine whether some sites exhibited a higher frequency of pottery from one locale versus another that might suggest the importation of pottery from mainland Japan. Results are equivocal, suggesting that the region's geological complexity may inhibit successful provenance study of ceramics using these and possibly other compositional techniques. © 2006 Wiley Periodicals, Inc.     

Absolute spectrophotometry of Comet Kohoutek 1973f: I. Column densities of cyanogen

Absolute spectrophotometry of the coma of Comet Kohoutek 1973f is discussed for the nights of January 24 and 26, 1974. Specific intensities are measured for spectral features and a continuum band in the wavelength region λλ3460–6062Å. The (0, 0) band of the Δν = 0 sequence of the violet system of the cyanogen molecule is analyzed and column densities of 1.7 × 10¹⁵m^?2 and 3.4 × 10¹⁴m^?2 are found for January 24 and 26, 1974, respectively. The analysis of the bands of C₂ will be reported in a second paper of this series.     

Differentiation of clay resources on a limestone plain: The analysis of clay utilization during the Maya Formative at K'axob Belize

Differentiating clay resources in a uniform limestone plain, such as occurs in northern Belize, offers special challenges for the archaeologist. Combining data from soil mapping with petrographic and neutron activation analysis provides a mechanism for distinguishing possible resource areas. This study employed each of these differing avenues of analysis to determine possible clay resource areas used during the Maya Formative in northern Belize Central America. The results indicate that clay usage changed significantly from the Middle Formative period to the end of Late Formative period. These changes suggest a move to increased localized production and resource exploitation by the end of the period. © 2000 John Wiley & Sons, Inc.