Natural and anthropogenic lead in sediments of the Rotorua lakes, New Zealand

Global atmospheric sources of lead have increased more than 100-fold over the past century as a result of deforestation, coal combustion, ore smelting and leaded petroleum. Lead compounds generally accumulate in depositional areas across the globe where, due to low solubility and relative freedom from microbial degradation, the history of their inputs is preserved. In lakes there is rapid deposition and often little bioturbation of lead, resulting in an excellent depositional history of changes in both natural and anthropogenic sources. The objective of this study was to use sediments from a regionally bounded set of lakes to provide an indication of the rates of environmental inputs of lead whilst taking into account differences of trophic state and lead exposure between lakes. Intact sediment gravity cores were collected from 13 Rotorua lakes in North Island of New Zealand between March 2006 and January 2007. Cores penetrated sediments to a depth of 16–30 cm and contained volcanic tephra from the 1886 AD Tarawera eruption. The upper depth of the Tarawera tephra enabled prescription of a date for the associated depth in the core (120 years). Each core showed a sub-surface peak in lead concentration above the Tarawera tephra which was contemporaneous with the peak use of lead alkyl as a petroleum additive in New Zealand. An 8 m piston core was taken in the largest of the lakes, Lake Rotorua, in March 2007. The lake is antipodal to the pre-industrial sources of atmospheric lead but still shows increasing lead concentrations from <2 up to 3.5 μg g−1 between the Whakatane eruption (5530 ± 60 cal. yr BP) and the Tarawera eruption. Peaks in lead concentration in Lake Rotorua are associated with volcanic tephras, but are small compared with those arising from recent anthropogenic-derived lead deposition. Our results show that diagenetic processes associated with iron, manganese and sulfate oxidation-reduction, and sulfide precipitation, act to smooth distributions of lead from anthropogenic sources in the lake sediments. The extent of this smoothing can be related to changes in sulfate availability and reduction in sulfide driven by differences in trophic status amongst the lakes. Greatest lead mobilisation occurs in mesotrophic lakes during seasonal anoxia as iron and manganese are released to the porewater, allowing upward migration of lead towards the sediment–water interface. This lead mobilisation can only occur if sulfides are not present. The sub-surface peak in lead concentrations in lake sediments ascribed to lead alkyl in petroleum persists despite the diagenetic processes acting to disperse lead within the sediments and into the overlying water

Pb0.4Bi1.6Sr2Ca1Cu2O8+xPb_{0.4}Bi_{1.6}Sr_{2}Ca_{1}Cu_{2}O_{8+x} and Oxygen Stoichiometry: Structure, Resistivity, Fermi Surface Topology and Normal State Properties

$Pb_{0.4}Bi_{1.6}Sr_2CaCu_2O_{8+x}$ ($Bi(Pb)-$2212) single crystal samples were studied using transmission electron microscopy (TEM), $ab-$plane ($\rho_{ab}$) and $c-$axis ($\rho_c$) resistivity, and high resolution angle-resolved ultraviolet photoemission spectroscopy (ARUPS). TEM reveals that the modulation in the $b-$axis for $Pb(0.4)-$doped $Bi(Pb)-$2212 is dominantly of $Pb-$type that is not sensitive to the oxygen content of the system, and the system clearly shows a structure of orthorhombic symmetry. Oxygen annealed samples exhibit a much lower $c-$axis resistivity and a resistivity minimum at $80-130$K. He-annealed samples exhibit a much higher $c-$axis resistivity and $d\rho_c/dT<0$ behavior below 300K. The Fermi surface (FS) of oxygen annealed $Bi(Pb)-$2212 mapped out by ARUPS has a pocket in the FS around the $\bar{M}$ point and exhibits orthorhombic symmetry. There are flat, parallel sections of the FS, about 60\% of the maximum possible along $k_x = k_y$, and about 30\% along $k_x = - k_y$. The wavevectors connecting the flat sections are about $0.72(\pi, \pi)$ along $k_x = k_y$, and about $0.80(\pi, \pi)$ along $k_x = - k_y$, rather than $(\pi,\pi)$. The symmetry of the near-Fermi-energy dispersing states in the normal state changes between oxygen-annealed and He-annealed samples.Comment: APS_REVTEX 3.0, 49 pages, including 11 figures, available upon request. Submitted to Phys. Rev. B

Description of the male of Psyllaephagus euphyllurae (Masi) (Hymenoptera, Encyrtidae), a parasitoid of the olive psylla, Euphyllura olivina (Costa) (Hemiptera, Liviidae), with notes on its reproductive traits and hyperparasitoids

A colony of the encyrtid wasp <em>Psyllaephagus</em> <em>euphyllurae</em> (Masi) (Hymenoptera, Encyrtidae) has been established in the quarantine laboratory at the University of California, Riverside, California, USA as part of a classical biological control program against its invasive host, the olive psylla, <em>Euphyllura</em> <em>olivina</em> (Costa) (Hemiptera, Psylloidea, Liviidae), an important pest of olives in some parts of the world. The colony originators were reared from the same host found on abandoned, commercial olives in Catalonia, Spain; additional collections were made in Murcia. The parasitoid reproduces primarily by thelytoky; however, a few occasional males have been found in the field in Spain, but not in colonies reared under quarantine or laboratory conditions. Here, the female of <em>P</em>. <em>euphyllurae</em> is redescribed and its male is described and illustrated for the first time; the only previous mention of male <em>P</em>. <em>euphyllurae</em> was from Tunisia, reared from the same psyllid host but without any details on its morphology. A lectotype is designated for <em>Encyrtus</em> <em>euphyllurae</em> Masi. Information is given on the results of genetic matching between the two sexes of the parasitoid and also on the presence of the bacterial <em>Wolbachia</em> symbiont that apparently is affecting reproduction of this species, including its sex ratio in the field. Two species of hyperparasitoids have also emerged from the parasitized olive psylla nymphs from Catalonia: numerous specimens of <em>Apocharips</em> <em>trapezoidea</em> (Hartig) (Hymenoptera, Figitidae) and one specimen of a <em>Pachyneuron</em> sp. (Hymenoptera, Pteromalidae)