Effect of zinc on the growth and development of larvae of bay scallopArgopecten Irradians

The 48-h straight-hinge larvae ofArgopecten irradians were exposed for 9 days to various concentrations of zinc in seawater. The growth rate of larvae in the 50 ppb Zn mediums was 77% that of the controls, and nearly zero in the 200 ppb Zn mediums. A progressive decrease in growth and increase in larval deformity and mortality was observed with increasing zinc concentrations from 50 to 200 ppb. 50 and 100 ppb Zn resulted in delayed development of eye spot and metamorphosis and reduced numbers of larvae at both stages. All larvae subjected to higher zinc concentrations died before attaining the eye-spot stage. The zinc concentrations which caused 50% reduction in growth (G C₅₀) and 50% mortality (LC₅₀) were 109 and 120 ppb respectively. Growing in the medium with 100 ppb Zn, the larvae fed withIsochrysis galbana cultured in a medium with 100 ppb Zn showed more suppressed growth and development than those fed with normal food. It is suggested that zinc contaminated food has strong influence on the bay scallop larvae. Contribution No. 1616 from the Institute of Oceanology, Academia Sinica.     

A New Geochemical Classification of Elements

The geochemical classification proposed by Goldschmidt was based on meteoritic analysis and elemental partition in blast furnace. There are many surprises when applied to the discussion of natural occurrences. A modified classification of elements based on basic chemical properties and their occurrences. A modified classification of elements based on basic chemical properties and their occurrences in nature is, therefore, proposed for students learning geochemistry and geologists working in the field. Elements are classified into six groups including lithophile, oxyphile, siderophile, chalcophile, biophile, and atmophile elements. Five terms are taken from Goldshcmidt's original classification. Oxyphile is a new term.     

Historical Sediment Record of ~(137)Cs, δ-HCH,and δ~(13)C Reflects the Impact of Land Use on Soil Erosion

This paper reports the concentrations of 137 Cs, hexachlorocyclohexane(HCH), dichlorodiphenyltrichloroethanes(DDT) and its main degradation products, δ13C, and organic carbon in pond sediments(0-210 cm, sectioned by 2-20 cm interval) and surface soils(the 0-3 cm horizon) collected in 2010 from Chenjia catchment, which is located in Yanting county in the hilly central Sichuan of China. α-, δ-, and γ-HCH, DDT, and DDD were not detected throughout the sediment profile. Trace concentrations of δ-HCH(0.89-29.31 ng g-1) and p,p′-DDE(1.85-6.02 ng g-1) were detected only in top 40 cm sediment. The 137 Cs fallout peak in 1963(corresponding to the 55-60 cm depth), the sedimentary signature left by the last year of HCH use in 1989(an additional indicator at 20-25 cm), and the obvious original channel bed prior to the construction of the pond in 1956 were used as temporal markers to estimate changes in average sedimentation rate between different periods due to changes in land use. Continuous, marked decrease in average sedimentation rate(i.e., 3.79, 1.35 and 1.07 cm year-1 in 1956-1963, 1963-1989, and 1989-2010, respectively)over time was observed, probably due to the reforestation, abandoning of steep sloping farmland for afforestation and natural re-vegetation(implementation of the Grain for Green Program), and the conversion of part of gently sloping farmland terraces to orchard land since the 1980 s, especially since the 1990 s. This was corroborated by the observed decrease(more negative) in δ13C of sediment towards the surface, which indicates increased relative contribution of eroded soil particles coming from slopes with increased tree cover in sediment source area. Combined use of 137 Cs, δ-HCH, and δ13C record in sediments has been demonstrated to be a powerful approach to reconstruction of response in sedimentation rate to historical land use changes.