Melanie A. Barnes

Effect of titanium dioxide nanomaterials and ultraviolet light coexposure on African clawed frogs (Xenopus laevis)

Titanium dioxide nanomaterials (nano-TiO(2) ) exhibit stronger photochemical oxidation/reduction capacity compared with their bulk counterparts, but the effectiveness of nano-TiO(2) interaction with ultraviolet (UV) light strongly depends on particle size. In this study, the dependence of nano-TiO(2) toxicity on particle size and interaction with UV light were investigated. Toxicity tests with Xenopus laevis included eight concentrations of nano-TiO(2) in the presence of either white light or UVA (315-400 nm). We quantified viability and growth of Xenopus laevis. Results showed that, regardless of UV light exposure, increasing TiO(2) concentration decreased X. laevis survival (p < 0.05). Coexposure to 5-nm TiO(2) and UVA caused near-significant decreases in X. laevis survival (p = 0.08). Coexposure to 10-nm TiO(2) and UVA significantly decreased X. laevis survival (p = 0.005). However, coexposure to 32-nm TiO(2) and UVA had no statistical effect on X. laevis survival (p = 0.8). For all three particle sizes, whether alone or with UV light, the nano-TiO(2) concentrations significantly affected growth of tadpoles as determined by total body length, snout-vent length, and developmental stage. High-concentration TiO(2) solutions suppressed tadpole body length and delayed developmental stages. Further research to explore reasons for the growth and mortality in tadpoles is still underway in our laboratory. Given the widespread application of nano-TiO(2) , our results may be useful in the management of nano-TiO(2) released from industrial, municipal, and nonpoint sources.

Architecture of a 1.38-1.34 Ga granite-rhyolite complex as revealed by geochronology and isotopic and elemental geochemistry of subsurface samples from west Texas, USA

Abstract During the evolution of Laurentia, a Mesoproterozoic felsic igneous belt extended from Fennoscandia through Canada to the southwestern United States. This belt, referred to as the granite–rhyolite province in North America, forms much of the west Texas and eastern New Mexico basement. We present data from 41 closely spaced wells in west Texas that penetrated several hundred meters into the southern granite–rhyolite province and provide the first opportunity to develop a three-dimensional view of the basement from subsurface samples. The felsic rock types include hornblende-bearing quartz monzonite, ignimbritic rhyolite, and comagmatic granite with eutectic textures. These rocks plot in the high-K to ultra-high-K field. Quartz syenite, which plots exclusively in the ultra-high-K field, is the final felsic phase of magmatism. All of the felsic magmas were variably oxidizing based on biotite compositions. UPb chronology supports the intrusive relations established by petrography: the quartz monzonite is oldest (∼1380 Ma) and is followed by the granite–rhyolite sequence (∼1360 Ma) and the quartz syenite (∼1340 Ma). Nd model ages range from 1520 to 1740 Ma, indicating involvement of older Proterozoic crust. In many wells, thick mafic sills intrude the granite–rhyolite sequence. Nd model ages for the mafic rocks range from 1560 to 1440 Ma, implying that they are Mesoproterozoic in age. The mafic rocks include an alkaline, OIB-like suite, which is not supportive of a subduction origin. UPb ages are also reported for the Mescalero Well #1 in eastern New Mexico. In this well, metasedimentary and metavolcanic rocks of the Debaca sequence unconformably overlie a quartz syenite similar to the quartz syenite from the west Texas wells. Detrital zircons from the basal meta-arkose of the sequence are ∼1690 and ∼1320 Ma, indicating a maximum age of ∼1300 Ma for this sequence.

Batch-wise assembly and zoning of a tilted calc-alkaline batholith: Field relations, timing, and compositional variation

The Wooley Creek batholith is a tilted, zoned, calc-alkaline plutonic complex in the Klamath Mountains, northern California, USA. It consists of three main compositional-temporal zones. The lower zone consists of gabbro through tonalite. Textural heterogeneities on the scale of tens to hundreds of meters combined with bulk-rock data suggest that it was assembled from numerous magma batches that did not interact extensively with one another despite the lack of sharp contacts and identical ages of two lower zone samples (U-Pb [zircon] chemical abrasion–isotope dilution–thermal ionization mass spectrometry ages of 158.99 ± 0.17 and 159.22 ± 0.10 Ma). The upper zone is slightly younger, with 3 samples yielding ages from 158.25 ± 0.46 to 158.21 ± 0.17 Ma, and is upwardly zoned from tonalite to granite. This zoning can be explained by crystal-liquid separation and is related to upward increases in the proportions of interstitial K-feldspar and quartz. Porphyritic dacitic to rhyodacitic roof dikes have compositions coincident with evolved samples of the upper zone. These data indicate that the upper zone was an eruptible mush that crystallized from a nearly homogeneous parental magma that evolved primarily by upward percolation of interstitial melt. The central zone is a recharge area with variably disrupted synplutonic dikes and swarms of mafic enclaves. Central zone ages (159.01 ± 0.20 to 158.30 ± 0.16 Ma) are similar to both lower and upper zones crystallization ages. In the main part of the Wooley Creek batholith, age data constrain magmatism to a short period of time (

Isotopic and elemental chemistry of subsurface Precambrian igneous rocks, west Texas and eastern New Mexico

We present major element, trace element, and Nd isotopic analyses from cuttings and core samples for three subsurface terranes in west Texas and eastern New Mexico. The most northerly is the Panhandle volcanic terrane, which represents a large part of the Mesoproterozoic southern granite-rhyolite province. This terrane is comprised of undeformed rhyolite, ignimbritic tuff, granite, and diabase. The Panhandle terrane is split by the Debaca terrane, which consists of intercalated metasedimentary and metavolcanic rocks intruded by olivine gabbro, ferrogabbro, and diabase. Mildly to strongly deformed intermediate and felsic intrusive rocks of unknown affinity make up the third terrane, called here the crystalline terrane; it is located south and southeast of the Panhandle and Debaca terranes. Intermediate-to-felsic rocks of the terranes can be subdivided on the basis of their geochemistry into those with: (1) K 2 O/Na 2 O > 1 and A-type trace element characteristics; and (2) K 2 O/Na 2 O 1.7-Ga crust. The southern edge of Laurentia, therefore, is farther south than previously inferred. A diabase from the Panhandle terrane has a T DM of 1.44 Ga. If this model age is close to the crystallization age, then diabase in the Panhandle terrane is approximately coeval with the granite and rhyolite. The model age for the gabbro from the Debaca terrane is distinctly younger at 1.26 Ga, and is the same as crystallization ages of felsic tuffs associated with shelf carbonates in the Franklin Mountains and Van Horn area. In the crystalline terrane, both A- and I-type granites are present. Model ages for the I-type granites are 1.40–1.47 Ga. These are distinctly younger than the model age for the Panhandle terrane, and an A-type granite has a T DM of 1.35 Ga. These data indicate that granites in the crystalline terrane are not part of the granite-rhyolite province; rather, they constitute a separate group.

Measurement of soil/dust arsenic by gas phase chemiluminescence

A gas phase chemiluminescence (GPCL)-based method for trace measurement of arsenic has been recently described for the measurement of arsenic in water. The principle is based on the reduction of inorganic As to AsH(3) at a controlled pH (the choice of pH governs whether only As(III) or all inorganic As is converted) and the reaction of AsH(3) with O(3) to produce chemiluminescence (Idowu et al., Anal. Chem. 78 (2006) 7088-7097). The same general principle has also been used in postcolumn reaction detection of As, where As species are separated chromatographically, then converted into inorganic As by passing through a UV photochemical reactor followed by AsH(3) generation and CL reaction with ozone (Idowu and Dasgupta, Anal. Chem. 79 (2007) 9197-9204). In the present paper we describe the measurement of As in different soil and dust samples by serial extraction with water, citric acid, sulfuric acid and nitric acid. We also compare parallel measurements for total As by induction coupled plasma mass spectrometry (ICP-MS). As(V) was the only species found in our samples. Because of chloride interference of isobaric ArCl(+) ICP-MS analyses could only be carried out by standard addition; these results were highly correlated with direct GPCL and LC-GPCL results (r(2)=0.9935 and 1.0000, respectively). The limit of detection (LOD) in the extracts was 0.36 microg/L by direct GPCL compared to 0.1 microg/L by ICP-MS. In sulfuric acid-based extracts, the LC-GPCL method provided LODs inferior to those previously observed for water-based standards and were 2.6, 1.3, 6.7, and 6.4 microg/L for As(III), As(V), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA), respectively.

Use of trace element abundances in augite and hornblende to determine the size, connectivity, timing, and evolution of magma batches in a tilted batholith

The tilted Wooley Creek batholith (Klamath Mountains, California, USA) consists of three main zones. Field and textural relationships in the older lower zone suggest batchwise emplacement. However, compositions of augite from individual samples plot along individually distinct fractionation trends, confi rming emplacement as magma batches that did not interact extensively. The younger upper zone is upwardly zoned from tonalite to granite. Major and trace element compositions of hornblende show similar variations from sample to sample, indicating growth from a single magma batch that was homogenized by convection and then evolved via upward percolation of interstitial melt. Highly porphyritic dacitic roof dikes, the hornblende compositions of which match those of upper zone rocks, demonstrate that the upper zone mush was eruptible. The central zone contains rocks of both lower and upper zone age, although in most samples hornblende compositions match those of the upper zone. The zone is rich in synplutonic dikes and mafi c magmatic enclaves. These features indicate that the central zone was a broad transition zone between upper and lower parts of the batholith and preserves part of the feeder system to the upper zone. Homogenization of the upper zone was probably triggered by the arrival of mafi c magma in the central zone. Continued emplacement of mafi c magmas may have provided heat that permitted differentiation of the upper zone magma by upward melt percolation. This study illustrates the potential for use of trace element compositions and variation in rock-forming minerals to identify individual magma batches, assess interactions between them, and characterize magmatic processes.

INORGANIC ELEMENTS IN GREEN SEA TURTLES (CHELONIA MYDAS): RELATIONSHIPS AMONG EXTERNAL AND INTERNAL TISSUES

Inorganic elements from anthropogenic sources have entered marine environments worldwide and are detectable in marine organisms, including sea turtles. Threatened and endangered classifications of sea turtles have heretofore made assessments of contaminant concentrations difficult because of regulatory restrictions on obtaining samples using nonlethal techniques. In the present study, claw and skin biopsy samples were examined as potential indicators of internal tissue burdens in green sea turtles (Chelonia mydas). Significant relationships were observed between claw and liver, and claw and muscle concentrations of mercury, nickel, arsenic, and selenium (p < 0.05). Similarly, significant relationships were observed between skin biopsy concentrations and those in liver, kidney, and muscle tissues for mercury, arsenic, selenium, and vanadium (p < 0.05). Concentrations of arsenic, barium, chromium, nickel, strontium, vanadium, and zinc in claws and skin biopsies were substantially elevated when compared with all other tissues, indicating that these highly keratinized tissues may represent sequestration or excretion pathways. Correlations between standard carapace length and cobalt, lead, and manganese concentrations were observed (p < 0.05), indicating that tissue concentrations of these elements may be related to age and size. Results suggest that claws may indeed be useful indicators of mercury and nickel concentrations in liver and muscle tissues, whereas skin biopsy inorganic element concentrations may be better suited as indicators of mercury, selenium, and vanadium concentrations in liver, kidney, and muscle tissues of green sea turtles.

Petrology of Late Eocene basaltic lavas at Cascade Head, Oregon Coast Range

Abstract Cascade Head is one of three prominent Middle to Late Eocene volcanic centers in the Oregon Coast Range that erupted alkalic basalt. At Cascade Head, 300–600 m of submarine to subaerial volcanic rocks are interbedded with thin-bedded, tuffaceous, brackish-water marine siltstone of the Nestucca Formation. The intercalated basalts in the Nestucca Formation are informally named Yachats Basalt of Cascade Head. This volcanic sequence consists of basal submarine basaltic breccia and lapilli tuff, ankaramitic basalt, aphyric submarine to subaerial alkali basalt lavas (which account for 75% of the volcanic pile), hornblende trachyandesite lavas and dikes, and an uppermost basaltic sandstone unit. The Nestucca Formation also contains andesitic and more silicic ash deposits. Major- and trace-element trends and mass-balance modeling of the Cascade Head lavas are compatible with fractional crystallization of the observed phenocryst phases: olivine, clinopyroxene, plagioclase + apatite ± ilmenite. The suite is characterized by enrichments in high field strength elements (HFSE) and by steeply negatively sloping rare earth element (REE) patterns ((La/Lu) n = 15–20). Transition metal contents are low (Ni, 5–36 ppm; Cr, 3–87 ppm; Sc, 1–22 ppm), indicating that none of the lavas are primitive. Elemental abundance diagrams are typical of continental alkalic basalt in that they show K depletion, and Nb and Ta enrichment. Element abundance diagrams of interbedded andesitic ash are distinct from those of the basalts, are depleted in Nb, Ta, and Ti, and indicate an arc source. The geochemical signature of the Yachats Basalt of Cascade Head is consistent with a fore-arc tectonic setting that was undergoing extension during late Eocene time. The basalts may be related to nearby hot spot activity but they could also have erupted through a “slab window” formed during plate reorganization during a decrease in the rate of convergence between the Farallon and North American plates.

Characterization and Age of the Mesoproterozoic Debaca Sequence in the Tucumcari Basin, New Mexico

Petrographic, geochronologic, and well log data from two deep oil wells (Mescalero 1 and State Mr. Jones 1) in the Tucumcari Basin, New Mexico are used to characterize a thick vertical section of the Mesoproterozoic Debaca sequence and portions of the underlying crystalline basement. This information is coupled with industry seismic data to constrain the geometry of the northernmost extent of the Mesoproterozoic Debaca basin. The Debaca sequence, a weakly metamorphosed sedimentary-volcanic package, is composed of volcaniclastic sandstone, tuffaceous sandstone, rhyolite, quartz-rich dolostone, dolomitic quartzite, sandstone, and arkose. The sequence rests disconformably on deeply weathered quartz syenite of the underlying Mesoproterozoic Panhandle Igneous Complex. Numerous sills and dikes of gabbro cut the Debaca sequence, imparting contact metamorphism to the adjacent rock units. U-Pb SHRIMP and 40 Ar/ 39 Ar ages for samples from the Mescalero 1 well indicate that Debaca sequence was formed ca. 1105-1332 Ma. Zircon from a quartz diorite (gradationally below the syenite) that is part of the crystalline basement beneath the Debaca sequence yields a SHRIMP U-Pb age of 1332 ± 18 Ma. Eight detrital grains of zircon from the arkose, the basal unit of the Debaca sequence, yield SHRIMP U-Pb zircon ages ranging from 1308 ± 52 to 1708 ± 14 Ma. 40 Ar/ 39 Ar ages on hornblende and biotite indicate a mean emplacement age of 1105±3 Ma for the gabbro. Three pulses of magmatism, one bimodal episode at 1.33 Ga, one felsic episode at ∼ 1.26 Ga, and one mafic episode at 1.09 Ga, have been identified in Mescalero 1.

The S.M.A.R.T. (small mass, affordable, rapid, transfer-less) digestion method for heavy metal determinations

ABSTRACT The S.M.A.R.T. (small mass, affordable, rapid, transfer-less) digestion method was developed to determine heavy metal concentrations in small sample masses. The S.M.A.R.T. digestion method is a hot water bath digestion where sample digestion and dilution are performed in the original sample tube. This method is faster than the typical methods used and reduces potential sources of error. Masses as small as 0.01 g have been digested and analysed using this method. The preparation and digestion time is reduced from 10 h to less than 4 h. Acid volumes are reduced from millilitres to microlitres and the only disposable supplies needed are sample tubes and pipette tips. Method accuracy was determined by digesting seven replicates of two standard reference materials using the S.M.A.R.T. method and analysing samples by inductively coupled plasma mass spectrometry. The S.M.A.R.T. digestion method was found to provide excellent recoveries for Al (76 ± 2.7%), Mn (99 ± 11%), Co (92 ± 17%), Ni (93 ± 28%), Cu (109 ± 33%), Zn (97 ± 7.1%), As (108 ± 20%), Sr (90 ± 12%), Mo (84 ± 23%), Ag (91 ± 1.8%), Cd (95 ± 6.2%), Sn (139 ± 52%) and Pb (95 ± 22%). This study has successfully developed an efficient and reproducible digestion method for heavy metal determination in limited biomass samples.