About the Role of Quinones in the Action of Some Polyphenols on the Streaming of Protoplasm in Nitella sp. Cells

The concentration of phenols and quinones which stopped the protoplasmic movement in the Nitella cells after 15 min was determined. The quinones (β-naphthoquinone, α-naphthoquinone, p-benzoquinone, o-toluquinone, o-bromanil) stopped the protoplasmic movement in the concentration of (1 3) 10^?4 M, phenols (m-cresol, p-cresol, hydroquinone, guaiacol, phenol, gallic acid, pyrogallic acid, resorcinol) in the concentration of (0.2 5) 10^?2 M, except catechol – 2 10^?3 M. Very high toxicity of catechol and in the prolonged experiments (3 hours) also of hydroquinone is connected with the action of quinonoid productions of its oxidation. This suggestion is confirmed by the experiments:

• – by adding the phenol solutions to Nitella shoots (catechol, hydroquinone, resorcinol) we observed the greatest increase of oxygen absorption in case of catechol (86%), less in case of hydroquinone (38%), and for resorcinol oxygen absorption practically remained on the control level;
• – the action of catechol, hydroquinone and p-benzoquinone did not take place in the presence of glutathione and cysteine (but not cystine and oxidated glutathione);
• – diethyldithiocarbamate as an inhibitor of o-diphenoloxidase reduced the ability of catechol solutions to stop the protoplasmic movement;
• – the low concentrations of benzoquinones were able to stop the protoplasmic movement;
• – for stopping the protoplasmic movement under the prolonged time of incubation from 15 min to 3 hours there was necessary a lower concentration of solutions of hydroquinone and catechol in comparison with resorcinol.

     

Bioavailability and toxicity of aluminium in a model planktonic food chain (Chlamydomonas-Daphnia) at neutral pH

Dissolved aluminium (Al) is generally at low concentrations in neutral freshwater due to its insolubility. However, a fall in pH resulting from acid deposition and mining alters the mobility of Al and so entry to adjacent neutral waters. The present study examines the environmental behaviour, cell-associated surface adsorption/absorption and toxicity of Al at neutral pH to the alga Chlamydomonas gigantea in the presence and absence of the key Al-binding ligand silica. We then examined transfer of Al from C. gigantea to the planktonic crustacean Daphnia pulex. Finally, the effect of Al on the elemental composition (and hence nutritional value) of the two organisms was compared to unexposed controls. C. gigantea increased the amount of Al in the algal culture medium. Binding of Al to extracellular glycoprotein is probably the reason why only one-third of the biosorbed Al was absorbed (accumulated) by C. gigantea. Aluminium concentrations between 50 and 500 μg l⁻¹ reduced growth of C. gigantea at 16 days exposure to the metal. Silica reduced biosorption, accumulation and toxicity of Al by C. gigantea. The concentration of Al in D. pulex fed Al-contaminated C. gigantea for 16 days did not differ from those fed alga grown in the absence of added Al. C. gigantea contaminated with Al contained less sulphur, magnesium, potassium and sodium although only sulphur fell in D. pulex subsequently fed the contaminated alga. Chloride, calcium, iron and silicon were significantly higher in D. pulex.     

Projected climate change impacts on spatial distribution of bioclimatic zones and ecoregions within the Kailash Sacred Landscape of China,India, Nepal

Rapidly accelerating climate change in the Himalaya is projected to have major implications for montane species, ecosystems, and mountain farming and pastoral systems. A geospatial modeling approach based on a global environmental stratification is used to explore potential impacts of projected climate change on the spatial distribution of bioclimatic strata and ecoregions within the transboundary Kailash Sacred Landscape (KSL) of China, India and Nepal. Twenty-eight strata, comprising seven bioclimatic zones, were aggregated to develop an ecoregional classification of 12 ecoregions (generally defined by their potential dominant vegetation type), based upon vegetation and landcover characteristics. Projected climate change impacts were modeled by reconstructing the stratification based upon an ensemble of 19 Earth System Models (CIMP5) across four Representative Concentration Pathways (RCP) emission scenarios (i.e. 63 impact simulations), and identifying the change in spatial distribution of bioclimatic zones and ecoregions. Large and substantial shifts in bioclimatic conditions can be expected throughout the KSL area by the year 2050, within all bioclimatic zones and ecoregions. Over 76 % of the total area may shift to a different stratum, 55 % to a different bioclimatic zone, and 36.6 % to a different ecoregion. Potential impacts include upward shift in mean elevation of bioclimatic zones (357 m) and ecoregions (371 m), decreases in area of the highest elevation zones and ecoregions, large expansion of the lower tropical and sub-tropical zones and ecoregions, and the disappearance of several strata representing unique bioclimatic conditions within the KSL, with potentially high levels of biotic perturbance by 2050, and a high likelihood of major consequences for biodiversity, ecosystems, ecosystem services, conservation efforts and sustainable development policies in the region.     

Optical growth of highly viscous organic/sulfate particles

Light extinction by atmospheric particles is strongly dependent on their chemical composition and water content. Since light extinction directly impacts climate, optical measurements of atmospherically relevant aerosols at varying relative humidities (RH) are needed. Recent studies have highlighted the possibility that some atmospheric aerosols are glassy under ambient conditions. Here, the particle optical growth factor, fRH_ext, was measured for liquid and glassy particles using cavity ring-down aerosol extinction spectroscopy. The particles were composed of ammonium sulfate (AS), 1,2,6-hexanetriol, sucrose, raffinose, and mixed particles containing AS and either sucrose or raffinose. Both sucrose and raffinose can be glassy at room temperature. For the pure organics, the highly viscous sucrose and raffinose particles have similar optical growth curves to the liquid 1,2,6 hexanetriol particles. However, for particles composed of sucrose or raffinose mixed with AS, optical growth depends on the AS weight-percent, which in turn controls the phase state of the AS and ultimately the water uptake.     

A Study of DMS Oxidation in the Tropics: Comparison of Christmas Island Field Observations of DMS, SO2, and DMSO with Model Simulations

This study reports comparisonsbetween model simulations, based on current sulfurmechanisms, with the DMS, SO₂ and DMSOobservational data reported by Bandy et al.(1996) in their 1994 Christmas Island field study. For both DMS and SO₂, the model results werefound to be in excellent agreement with theobservations when the observations were filtered so asto establish a common meteorological environment. Thisfiltered DMS and SO₂ data encompassedapproximately half of the total sampled days. Basedon these composite profiles, it was shown thatoxidation of DMS via OH was the dominant pathway withno more than 5 to 15% proceeding through Cl atoms andless than 3% through NO₃. This analysis wasbased on an estimated DMS sea-to-air flux of 3.4 ×10⁹ molecs cm^-2 s^-1. The dominant sourceof BL SO₂ was oxidation of DMS, the overallconversion efficiency being evaluated at 0.65 ± 0.15. The major loss of SO₂ was deposition to theocean's surface and scavenging by aerosol. Theresulting combined first order k value was estimated at 1.6 × 10^-5 s^-1. In contrast to the DMSand SO₂ simulations, the model under-predictedthe observed DMSO levels by nearly a factor of 50. Although DMSO instrument measurement problems can notbe totally ruled out, the possibility of DMSO sourcesother than gas phase oxidation of DMS must beseriously considered and should be explored in futurestudies.     

Use of a watershed hydrologic model to estimate interbasin groundwater flow in a Costa Rican rainforest

The watershed hydrologic model TOPMODEL was used to estimate interbasin groundwater flow (IGF) into a small lowland rainforest watershed in Costa Rica. IGF is a common hydrological process but often difficult to quantify. Four‐year simulations (2006–2009) using three different model approaches gave estimates of IGF that were very similar to each other (10.1, 10.2, and 9.8 m/year) and to an earlier estimate (10.0 m/year) based on 1998–2002 data from a budget study that did not use a hydrologic simulation model, providing confidence in the new estimates and suggesting each of the three model approaches is viable. Results show no significant temporal variation in IGF during 2006–2009 (or between this period and the earlier study from 1998–2002). Simulations of the 16 consecutive 3‐month periods in 2006–2009 gave 16 values of IGF rate with a mean (10.1 m/year, standard deviation = 0.6 m/year) very similar to the estimates above from the 4‐year simulations. This suggests the modified version of TOPMODEL can be used to model stream discharge and estimate IGF for sub‐annual time periods during which change in water storage is not necessarily equal to zero. Thus, simple watershed models may be used to estimate IGF based on even relatively short calibration periods, making such models useful tools in the study of this widespread hydrological process that affects water and chemical fluxes and budgets but is often difficult and costly to quantify. Copyright © 2013 John Wiley & Sons, Ltd.