Detection of Coronal Mass Ejections in V471 Tauri with the Hubble Space Telescope

V471 Tauri, an eclipsing system consisting of a hot DA white dwarf (WD) and a dK2 companion in a 12.5-hour orbit, is the prototype of the pre-cataclysmic binaries. The late-type component is magnetically active, due to its being constrained to rotate synchronously with the short orbital period. During a program of UV spectroscopy of V471 Tau, carried out with the Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope, we serendipitously detected two episodes in which transient absorptions in the Si III 1206 A resonance line appeared suddenly, on a timescale of <2 min. The observations were taken in a narrow spectral region around Ly-alpha, and were all obtained near the two quadratures of the binary orbit, i.e., at maximum projected separation (~3.3 Rsun) of the WD and K star. We suggest that these transient features arise when coronal mass ejections (CME's) from the K2 dwarf pass across the line of sight to the WD. Estimates of the velocities, densities, and masses of the events in V471 Tau are generally consistent with the properties of solar CME's. Given our detection of 2 events during 6.8 hr of GHRS observing, along with a consideration of the restricted range of latitudes and longitudes on the K star's surface that can give rise to trajectories passing in front of the WD as seen from Earth, we estimate that the active V471 Tau dK star emits some 100-500 CME's per day, as compared to 1-3 per day for the Sun. The K dwarf's mass-loss rate associated with CME's is at least (5-25) x 10^{-14} Msun/yr, but it may well be orders of magnitude higher if most of the silicon is in ionization states other than Si III.Comment: 24 pages AASTeX, 4 figures. Accepted by Astrophysical Journa

Correlations in metal release profiles following sorption by Lemna minor

ABSTRACT: Following the rapid uptake of contaminants in the first few hours of exposure, plants typically attempt to cope with the toxic burden by releasing part of the sorbed material back into the environment. The present study investigates the general trends in the release profiles of different metal(loid)s in the aquatic macrophyte Lemna minor and details the correlations that exist between the release of metal(loid) species. Water samples with distinct contamination profiles were taken from Nilüfer River (Bursa, Turkey), Yeniçağa Lake (Bolu, Turkey), and Beyşehir Lake (Konya, Turkey) and used for release studies; 36 samples were tested in total. Accumulation and release profiles were monitored over five days for 11 metals and a metalloid (208Pb, 111Cd, 52Cr,53Cr,60Ni,63Cu,65Cu,75As,55Mn, 137Ba, 27Al, 57Fe, 66Zn,68Zn) and correlation, cluster and principal component analyses were employed to determine the factors that affect the release of these elements. Release profiles of the tested metal(loid)s were largely observed to be distinct; however, strong correlations have been observed between certain metal pairs (Cr/Ni, Cr/Cu, Zn/Ni) and principal component analysis was able to separate the metal(loid)s into three well-resolved groups based on their release. © 2016 Taylor & Francis Group, LLC

Interactions between metals accumulated in the narrow-clawed crayfish Astacus leptodactylus (Eschscholtz, 1823) in Dikilitaş Lake, Turkey

The accumulations of Al, Cd, Cr, Cu, Fe, Ni, Pb and Zn in the exoskeleton, gills, hepatopancreas and abdominal muscles of crayfish Astacus leptodactylus (Eschscholtz, 1823) were determined. The strongest correlation observed was between Cr and Ni in the gills (r = 0.904); moderate to strong correlations between Al, Cr, Fe, Ni and Cu were also observed in gill tissue. Disregarding the gills, the strongest correlation was found between Cu and Zn in the hepatopancreas (r = 0.808); the correlation between these two metals might have been a result of metallothionein activity. The accumulation of Pb was found to correlate with that of Cd in the exoskeleton, Cd and Zn in the gills, Zn and Cu in the hepatopancreas and Cu in the abdominal muscle. None of these correlations were present in lakewater and sediment samples, suggesting that the crayfish metabolism may be responsible for the co-accumulation of metal–metal pairs. As all correlations in non-gill tissues are observed between divalent metals, a shared transporter such as divalent metal transporter 1 might be involved in the accumulation of these metals. © 2015 Taylor & Francis

Effects of laser ablated silver nanoparticles on Lemna minor

Cataloged from PDF version of article.The present study investigates and models the effect of laser ablated silver nanoparticles (AgNPs) on the development of the aquatic macrophyte Lemna minor. Toxic effects of five different AgNP concentrations (8, 16, 32, 96 and 128μgL-1) on L. minor were recorded over seven days under simulated natural conditions. Biosorption of AgNPs by L. minor was modeled using four sorption isotherms, and the sorption behavior was found to agree most closely with the Langmuir-Freundlich model (R2=0.997). While toxic effects of AgNPs could be observed in all models and concentrations, the greatest increase in toxicity was in the 8-32μgL-1 range. Dry weight- and frond number-based inhibition experiments suggest that growth inhibition does not necessarily scale with AgNP concentration, and that slight fluctuations in inhibition rates exist over certain concentration ranges. Very close fits (R2=0.999) were obtained for all removal models, suggesting that the fluctuations are not caused by experimental variation. In addition, L. minor was found to be a successful bioremediation agent for AgNPs, and displayed higher removal rates for increasing AgNP doses. FT-IR spectroscopy suggests that carbonyl groups are involved in AgNP remediation. © 2014 Elsevier Ltd

Phytoremediation of Cu, Cr and Pb mixtures by lemna minor

The present study reports the capacity of the aquatic macrophyte Lemna minor to remediate combinations of Cu(II), Pb(II) and Cr(III) from a simulated natural environment. The effect of these metal mixtures on the growth of L. minor was also investigated using growth rate and biomass inhibition calculations. L. minor was successful in removing Cr and Pb from the water, and it remained an effective remediation agent when both metals were present in the environment. However, a relatively low absorption capacity was observed for Cu, increasing concentrations of which were associated with significant decreases in growth rate. No statistically significant difference was found between the 24 h and 7 days absorption rates of Cu, Pb and Cr, suggesting that, at the concentrations tested, equilibrium occurs within 24 h of metal exposure. © 2013 Springer Science+Business Media New York

Tissue distribution and correlation profiles of heavy-metal accumulation in the freshwater crayfish astacus leptodactylus

The present work details the analysis of heavy-metal and metalloid concentrations in exoskeleton, gill, hepatopancreas, and abdominal muscle tissues of 60 crayfish (Astacus leptodactylus) specimens collected from Lake HirfanlI, a dam lake located in KIrşehir (Turkey) with a low metal-contamination profile. Concentrations of 11 metals (aluminum [Al], chromium [Cd], manganese [Mn], cobalt [Co], nickel [Ni], copper [Cu], molybdenum [Mo], silver [Ag], cadmium [Cd], mercury [Hg], and lead [Pb]) and a metalloid (arsenic [As]) were measured by inductively coupled plasma-mass spectrometry, and the relative frequencies of the most abundant isotopes of Cr, Cu, Ag, Cd, Hg, and Pb were evaluated. Three correlation trends were evaluated between the following: (1) different elements in the each individual tissue, (2) individual elements in different tissues, and (3) different elements in different tissues. In addition, correlation rates of growth parameters (weight, cephalothorax length, and total length) with heavy-metal and metalloid concentrations in each tissue were investigated. Our results suggest that substantial differences in metal and metalloid-accumulation levels exist between male and female specimens, with stronger correlations between the heavy-metal concentrations observed in the male cohort. It is notable that correlation trends of Co, Cu, 52As, Cr, and Ni in exoskeleton of the male specimens display strong similarities. Likewise, a very strong correlation is present in Ni-Cd and Ni-Pb accumulations in abdominal muscle of the male specimens; a similar trend is present between Cd and Pb concentrations in the same tissue of female specimens. For correlation rates of different heavy metals and metalloid in different tissues, the strongest positive association observed was between 63Cu in gill and As in hepatopancreas, whereas the strongest negative correlation was between accumulated Ni in abdominal muscle and As in exoskeleton. Strong correlations between metals and metalloid accumulations were observed between exoskeleton and gill. In many cases, metal and metalloid accumulation was negatively correlated with growth parameters. Preferential accumulation of Cr and Cu isotopes was observed in different tissues, suggesting that significant amounts of isotope fractionation occur during heavy-metal accumulation. Relatively low correlation rates were observed between 52Cr/ 53Cr and 63Cu/65Cu concentrations in several tissue types in both male and female cohorts, whereas no such trend was observed between Cd and Pb isotopes. © 2013 Springer Science+Business Media New York

Differences in the accumulation and distribution profile of heavy metals and metalloid between male and female crayfish (Astacus leptodactylus)

Concentrations of selected heavy metals and a metalloid were measured by ICP-MS in crayfish (Astacus leptodactylus) collected from Lake Hirfanli, Turkey. Aluminum (Al), chromium (52Cr, 53Cr), copper ( 63Cu, 65Cu), manganese (Mn), nickel (Ni) and arsenic (As) were measured in the exoskeleton, gills, hepatopancreas and abdominal muscle tissues of 60 crayfish of both genders. With the exception of Al, differences were determined between male and female cohorts for the accumulation trends of the above-mentioned elements in the four tissues. It was also noted that the accumulation rates of Ni and As were significantly lower in gill tissue of females compared to males and no significant difference was observed for Cu isotopes in female crayfish. Cluster Analysis (CA) recovered similar results for both genders, with links between accumulations of Ni and As being notable. Accumulation models were described separately for male and female crayfish using regression analysis, and are presented for models where R2 &gt; 0.85. © 2013 Springer Science+Business Media New York

Chromium(VI) Biosorption and Bioaccumulation by Live and Acid-Modified Biomass of a Novel Morganella morganii Isolate

Conventional methods of chromium removal are often insufficient for the remediation of chromium-contaminated natural environments, necessitating the development of alternative strategies. In this paper, we report the isolation of a novel Morganella morganii strain capable of reducing hexavalent chromium to its less-toxic and less-soluble trivalent form. Cr(VI) reduction by this strain was evaluated in both acidic environments and conditions reflecting natural freshwater sources. The isolate achieved equilibrium within 3 h and displayed a specific uptake rate of 24.30 ± 1.67 mg Cr(VI)/g biomass following HCl treatment. Without acid treatment, a reduction of over 90% was recorded within 72 h for an initial Cr(VI) concentration 20 mg/L, corresponding to a Cr(VI) removal capacity of 19.36 ± 1.89 mg/g. Absorption data of acid-treated STB5 biomass most closely followed the Toth and Langmuir models. FTIR results indicate that hydroxyl groups and extracellular or cell membrane polysaccharides may be potential adsorption sites for hexavalent chromium. Our results suggest that the isolate may be used in situ for treatment of polluted freshwater environments. Copyright © Taylor & Francis Group, LLC

Oxidative stress in Arthrospira platensis by two organophosphate pesticides

Abstract Although it is known that organophosphate insecticides are harmfull to aquatic ecosystems, oxidative damages caused by Dimethoate and Chlorpyrifos are not studied on Arthrospira platensis Gomont. In this study, various Chlorpyrifos (0-150 µg mL-1) and Dimethoate (0-250 µg mL-1) concentrations were added to the culture medium in laboratory to evaulate growth rate, chlorophyll-a content and antioxidant parameters of A. platensis. Optical Density (OD560) and chlorophyll-a decreased compared to the control for seven days in both pesticide applications. Superoxide dismutase (SOD) activity increased at 50 µg mL-1 Chlorpyrifos concentration but it decreased at all concentrations. Although Ascorbate peroxidase (APX) and glutathione reductase (GR) activities increased with Chlorpyrifos application, they did not change with Dimethoate application. Malondialdehyde (MDA) amount decreased at 150 µg mL-1 Chlorpyrifos concentration but it increased in Dimethoate application. The H2O2 content were increased in both applications. Proline decreased in 50 and 75 µg mL-1 Chlorpyrifos concentrations and increased at 150 µg mL-1 concentration, while it increased at 25 µg mL-1 Dimethoate concentration. The results were tested at 0.05 significance level. These pesticides inhibit A. platensis growth and chlorophyll-a production and cause oxidative stress. The excessive use may affect the phytoplankton and have negative consequences in the aquatic ecosystem