Isotopic evidence for mercury photoreduction and retention on particles in surface waters of Central California, USA.

Cache Creek (Coast Range, California) and the Yuba River (Sierra Nevada Foothills, California) are two river systems affected by extensive mercury (Hg) contamination due to legacy sources of Hg related to mining. Stable Hg isotope techniques have proven useful for elucidating the complex cycling of Hg within aquatic ecosystems, and we applied these techniques to improve understanding of Hg and methylmercury (MeHg) transformations in these watersheds. Total mercury (THg) concentrations and Hg stable isotope ratios were measured in filtered surface waters and suspended particulate matter collected from 14 sites within the Cache Cr. and Yuba R. watersheds. Filtered surface waters from both watersheds exhibited values of ∆199Hg (0.37‰ to 0.71‰), consistently elevated above those observed in sediments (∆199Hg average = 0.07‰). Associated suspended particulates from these surface water samples displayed a much greater range of values for ∆199Hg (-0.61‰ to 0.70‰), although suspended particulates from the Yuba R. exhibited mostly negative ∆199Hg values (-0.61‰ to 0.10‰). The relationship between ∆199Hg and ∆201Hg in the filtered surface waters and associated suspended particulates was calculated using a bivariate York regression, yielding a slope of 1.57 ±â€¯0.49 (±2SE) for the Yuba R. and 1.40 ±â€¯0.27 (±2SE) for Cache Cr., both within error of the previously reported experimentally-derived slopes for MeHg- and inorganic Hg(II)-photoreduction. This provides isotopic evidence that Hg photoreduction is occurring within these surface waters to a significant degree, and suspended particulate phases are retaining the reduced product of Hg photoreduction, particularly within the Yuba R. The isotopic compositions of filtered surface waters are consistent with the isotopic signatures recorded in biota at low trophic positions within these watersheds, suggesting that the reservoir of Hg incorporated within the biota of these systems is similar to the filter-passing Hg fraction in surface waters.

Hg isotopes reveal in-stream processing and legacy inputs in East Fork Poplar Creek, Oak Ridge, Tennessee, USA.

Natural abundance stable Hg isotope measurements were used to place new constraints on sources, transport, and transformations of Hg along the flow path of East Fork Poplar Creek (EFPC), a point-source contaminated headwater stream in Oak Ridge, Tennessee. Particulate-bound Hg in the water column of EFPC within the Y-12 National Security Complex, was isotopically similar to average metallic Hg(0) used in industry, having a mean δ202Hg value of -0.42 ± 0.09‰ (1SD) and near-zero Δ199Hg. On average, particulate fraction δ202Hg values increased downstream by 0.53‰, while Δ199Hg decreased by -0.10‰, converging with the Hg isotopic composition of the fine fraction of streambed sediment along the 26 km flow path. The dissolved fraction behaved differently. Although initial Δ199Hg values of the dissolved fraction were also near-zero, these values increased transiently along the flow path. Initial δ202Hg values of the dissolved fraction were more variable than in the particulate fraction, ranging from -0.44 to 0.18‰ among three seasonal sampling campaigns, but converged to an average δ202Hg value of 0.01 ± 0.10‰ (1SD) downstream. Dissolved Hg in the hyporheic and riparian pore water had higher and lower δ202Hg values, respectively, compared to dissolved Hg in stream water. Variations in Hg isotopic composition of the dissolved and suspended fractions along the flow path suggest that: (1) physical processes such as dilution and sedimentation do not fully explain decreases in total mercury concentrations along the flow path; (2) in-stream processes include photochemical reduction, but microbial reduction is likely more dominant; and (3) additional sources of dissolved mercury inputs to EFPC at baseflow during this study predominantly arise from the hyporheic zone.

Methylmercury degradation and exposure pathways in streams and wetlands impacted by historical mining.

Monomethyl mercury (MMHg) and total mercury (THg) concentrations and Hg stable isotope ratios (δ(202)Hg and Δ(199)Hg) were measured in sediment and aquatic organisms from Cache Creek (California Coast Range) and Yolo Bypass (Sacramento Valley). Cache Creek sediment had a large range in THg (87 to 3870ng/g) and δ(202)Hg (-1.69 to -0.20‰) reflecting the heterogeneity of Hg mining sources in sediment. The δ(202)Hg of Yolo Bypass wetland sediment suggests a mixture of high and low THg sediment sources. Relationships between %MMHg (the percent ratio of MMHg to THg) and Hg isotope values (δ(202)Hg and Δ(199)Hg) in fish and macroinvertebrates were used to identify and estimate the isotopic composition of MMHg. Deviation from linear relationships was found between %MMHg and Hg isotope values, which is indicative of the bioaccumulation of isotopically distinct pools of MMHg. The isotopic composition of pre-photodegraded MMHg (i.e., subtracting fractionation from photochemical reactions) was estimated and contrasting relationships were observed between the estimated δ(202)Hg of pre-photodegraded MMHg and sediment IHg. Cache Creek had mass dependent fractionation (MDF; δ(202)Hg) of at least -0.4‰ whereas Yolo Bypass had MDF of +0.2 to +0.5‰. This result supports the hypothesis that Hg isotope fractionation between IHg and MMHg observed in rivers (-MDF) is unique compared to +MDF observed in non-flowing water environments such as wetlands, lakes, and the coastal ocean.

Hydrologic indicators of hot spots and hot moments of mercury methylation potential along river corridors.

The biogeochemical cycling of metals and other contaminants in river-floodplain corridors is controlled by microbial activity responding to dynamic redox conditions. Riverine flooding thus has the potential to affect speciation of redox-sensitive metals such as mercury (Hg). Therefore, inundation history over a period of decades potentially holds information on past production of bioavailable Hg. We investigate this within a Northern California river system with a legacy of landscape-scale 19th century hydraulic gold mining. We combine hydraulic modeling, Hg measurements in sediment and biota, and first-order calculations of mercury transformation to assess the potential role of river floodplains in producing monomethylmercury (MMHg), a neurotoxin which accumulates in local and migratory food webs. We identify frequently inundated floodplain areas, as well as floodplain areas inundated for long periods. We quantify the probability of MMHg production potential (MPP) associated with hydrology in each sector of the river system as a function of the spatial patterns of overbank inundation and drainage, which affect long-term redox history of contaminated sediments. Our findings identify river floodplains as periodic, temporary, yet potentially important, loci of biogeochemical transformation in which contaminants may undergo change during limited periods of the hydrologic record. We suggest that inundation is an important driver of MPP in river corridors and that the entire flow history must be analyzed retrospectively in terms of inundation magnitude and frequency in order to accurately assess biogeochemical risks, rather than merely highlighting the largest floods or low-flow periods. MMHg bioaccumulation within the aquatic food web in this system may pose a major risk to humans and waterfowl that eat migratory salmonids, which are being encouraged to come up these rivers to spawn. There is a long-term pattern of MPP under the current flow regime that is likely to be accentuated by increasingly common large floods with extended duration.

Isotopic Composition of Inorganic Mercury and Methylmercury Downstream of a Historical Gold Mining Region.

We measured total mercury (THg) and monomethyl mercury (MMHg) concentrations and mercury (Hg) isotopic compositions in sediment and aquatic organisms from the Yuba River (California, USA) to identify Hg sources and biogeochemical transformations downstream of a historical gold mining region. Sediment THg concentrations and δ(202)Hg decreased from the upper Yuba Fan to the lower Yuba Fan and the Feather River. These results are consistent with the release of Hg during gold mining followed by downstream mixing and dilution. The Hg isotopic composition of Yuba Fan sediment (δ(202)Hg = -0.38 ± 0.17‰ and Δ(199)Hg = 0.04 ± 0.03‰; mean ± 1 SD, n = 7) provides a fingerprint of inorganic Hg (IHg) that could be methylated locally or after transport downstream. The isotopic composition of MMHg in the Yuba River food web was estimated using biota with a range of %MMHg (the percent of THg present as MMHg) and compared to IHg in sediment, algae, and the food web. The estimated δ(202)Hg of MMHg prior to photodegradation (-1.29 to -1.07‰) was lower than that of IHg and we suggest this is due to mass-dependent fractionation (MDF) of up to -0.9‰ between IHg and MMHg. This result is in contrast to net positive MDF (+0.4 to +0.8‰) previously observed in lakes, estuaries, coastal oceans, and forests. We hypothesize that this unique relationship could be due to differences in the extent or pathway of biotic MMHg degradation in stream environments.

Identification of multiple mercury sources to stream sediments near Oak Ridge, TN, USA.

Sediments were analyzed for total Hg concentration (THg) and isotopic composition from streams and rivers in the vicinity of the Y-12 National Security Complex (Y12) in Oak Ridge, TN (USA). In the stream directly draining Y12, where industrial releases of mercury (Hg) have been documented, high THg (3.26 to 60.1 µg/g) sediments had a distinct Hg isotopic composition (δ(202)Hg of 0.02 ± 0.15‰ and Δ(199)Hg of -0.07 ± 0.03‰; mean ± 1SD, n = 12) compared to sediments from relatively uncontaminated streams in the region (δ(202)Hg = -1.40 ± 0.06‰ and Δ(199)Hg of -0.26 ± 0.03‰; mean ± 1SD, n = 6). Additionally, several streams that are nearby but do not drain Y12 had sediments with intermediate THg (0.06 to 0.21 µg/g) and anomalous δ(202)Hg (as low as -5.07‰). We suggest that the low δ(202)Hg values in these sediments provide evidence for the contribution of an additional Hg source to sediments, possibly derived from atmospheric deposition. In sediments directly downstream of Y12 this third Hg source is not discernible, and the Hg isotopic composition can be largely explained by the mixing of low THg sediments with high THg sediments contaminated by Y12 discharges.

Basal cell adenocarcinoma of the supraglottic larynx: treatment of recurrent disease with tamoxifen.

At the age of 83, a woman presented with an extremely rare cancer, basal cell adenocarcinoma (BCAC) of the supraglottic larynx. Pathology revealed a stage IVA tumor, pathological stage T4N0M0. She was treated with surgery and did not receive any adjuvant chemotherapy or radiation therapy. At the age of 93, during a routine examination, the patient was found to have palpable adenopathy and underwent a fine needle aspiration in June 2010. Pathology revealed similar histologic characteristics of her 2001 BCAC diagnosis, and further IHC stains revealed positive estrogen receptor staining.

Diels-Alder reactivity of polycyclic aromatic hydrocarbon bay regions: implications for metal-free growth of single-chirality carbon nanotubes.

A soluble bisanthene derivative, 4,11-dimesitylbisanthene, has been synthesized in three steps from bianthrone. In hot toluene, this bisanthene undergoes a clean Diels-Alder reaction with diethyl acetylenedicarboxylate to give a rearomatized 1:1 cycloadduct and, more slowly, a rearomatized 2:1 cycloadduct. In a competition experiment with the shorter "periacene" perylene, only the bisanthene reacts, and the perylene remains unchanged. The experimental results stand in complete accord with density functional calculations (B3LYP/6-31G*), which predict that the activation energies for Diels-Alder cycloadditions in the bay regions of periacenes should diminish monotonically as the length of the molecule increases. This structure-activity relationship offers hope that single-chirality carbon nanotubes can be grown from suitable hydrocarbon templates, without metal catalysis, by a Diels-Alder cycloaddition/rearomatization strategy, using acetylene or a "masked acetylene" as the dienophile.

Is trivialisation of alcohol consumption a laughing matter? Alcohol incidence in a metropolitan daily newspaper's comic strips.

INTRODUCTION AND AIMS: A number of studies have looked at the incidence and nature of depictions of alcohol in various media, primarily in movies, television and magazines. However, there have been few studies of depictions of alcohol in comic strips in newspapers. DESIGN AND METHODS: This study analysed the content of the five comic strips in the 258 weekday editions of a metropolitan newspaper over a period of 1 year. Where alcohol was depicted, this was classified as either integral or incidental to the theme or story of that day's strip. As an indication of the nature of the depiction and in the absence of specific codes for the depiction of alcohol in comic strips, depictions were assessed against the Australian Alcoholic Beverages Advertising Code (ABAC). RESULTS: Of the 1 290 individual comic strips, 4% (n = 54) depicted alcohol. Depictions were equal in number incidental and integral to the 'story'. Over half of the strips depicting alcohol were deemed to breach the ABAC, with the most common breach related to trivialisation of alcohol consumption. One strip accounted for over 60% of all depictions with the majority breaching the ABAC. DISCUSSION AND CONCLUSIONS: These results suggest that newspaper publishers should consider a code for depictions of alcohol (and other unhealthy or risky products/behaviours) in comics. At the very least, comics that trivialise the abuse of alcohol should be excluded under such a code.

The synthesis of bivalent 2beta-carbomethoxy-3beta-(3,4-dichlorophenyl)-8-heterobicyclo[3.2.1]octanes as probes for proximal binding sites on the dopamine and serotonin transporters.

3-Aryltropanes have been widely explored for potential medications for remediation of cocaine abuse. Research has focused predominantly on 8-azatropanes and it is now well recognized that these compounds can be designed to manifest varied selectivity and potency for inhibition of the dopamine, serotonin, and norepinephrine uptake systems. We had reported that the 8-nitrogen atom present in the 3-aryltropanes is not essential for tropanes to bind to monoamine uptake systems. We demonstrated that compounds in which the amine had been exchanged for an ether or a thioether retained binding potency and selectivity. We have now designed bivalent compounds in which two tropane moieties are linked by an intervening chain. These 8-homo- and 8-heterotropane bivalent compounds allowed a search for adjacent tropane binding sites on the DAT as well as a further exploration of whether the binding sites for 8-azatropanes are the same as those for other 8-heterotropanes. A comparison of these compounds with their progenitor tropanes cast into doubt the existence of proximal binding sites on the DAT, and offered support for the existence of different binding sites for the 8-azatropanes compared with 8-oxa- and 8-thiatropanes. Indeed, 8-aza bivalent tropanes inhibited DAT with potency about 10-fold lower (DAT: IC50 = 31 nM) than their monovalent counterparts. Furthermore, bivalent ligands in which one or both of the tropanes was devoid of an amine suffered a further loss of inhibitory potency. We conclude that it is unlikely that there exist two tropane binding sites in close proximity to one another on either the DAT or SERT.

Reductive Bergman-type cyclizations of cross-conjugated enediynes to fulvene and fulvalene anions: the role of the substituent.

Various cross-conjugated enediynes undergo "Bergman-type" cycloaromatizations upon reduction with potassium metal, generating anions of fulvenes and fulvalene derivatives. This new anionic cyclization is considerably more facile than the classic Bergman cyclization with linear enediynes, creating highly reactive diradicals at -78 degrees C. Not all cross-conjugated enediynes yield cyclized dianions upon reduction; some give uncyclized, Y-shaped, cross-conjugated dianions, while others apparently yield radical-anions that either dimerize or persist as monomers. One system yields both a cyclized and an uncyclized dianion. The substituents are thus shown to be a critical factor in determining the outcome of the reduction. Cyclization occurs within a specific "window of opportunity" that is governed by the substituents.

Elaboration of diaryl ketones into naphthalenes fused on two or four sides: a naphthoannulation procedure.

Transition metal-catalyzed double ring closures of 1,1-diaryl-2,2-diethynylethylenes yield polycyclic aromatic hydrocarbons and heterocycles that contain a newly formed naphthalene ring system embedded in a larger polycyclic network. The diynes required for this procedure are readily synthesized from diaryl ketones by the Corey-Fuchs olefination and subsequent Sonogashira coupling with trimethylsilylacetylene followed by desilylation. This procedure provides easy access to new compounds such as 3,11-di-tert-butyl[4]helicene and 1,8,9-perinaphthothioxanthene. Double naphthoannulation of 9,10-anthraquinone by this procedure closes four new benzene rings in a single operation to give coronene, although the yield in this case is presently low.