low-pH Zone Research Articles

Continuous on-line concentration based on dynamic pH junction for trimethoprim and sulfamethoxazole by microfluidic capillary electrophoresis combined with flow injection analysis system

A novel, rapid and continuous on-line concentration approach based on dynamic pH junction for the analysis of trimethoprim (TMP) and sulfamethoxazole (SMZ) by microfluidic capillary electrophoresis (CE) combined with flow injection analysis is developed in this paper. Stacking is due to decreases in the velocity of analytes when migrating from the low-pH sample zone (sample was dissolved in 50 mM HCl) to a relatively high-pH buffer (30 mM phosphate buffer, pH 8.5) filled in the capillary. This results in 2.9-4.7-fold improvement in concentration sensitivity relative to conventional capillary electrophoresis methods. The separation could be achieved within 2 min and sample throughput rate can reach up to 38 h(-1).

Use of light and inorganic carbon acquisition by two morphotypes of Zostera noltii Hornem

The affinity for dissolved inorganic carbon (DIC) and the mechanisms to use HCO 3 − as a source of DIC for photosynthesis were investigated in two morphotypes of Zostera noltii Hornem. Both morphotypes were collected at Ria Formosa lagoon (Southern Portugal) at two different levels in the intertidal. Affinity for DIC at saturating photon fluence rate (PFR), estimated as photosynthetic conductance for CO 2 ( g p(CO 2) ), was reduced by 75% in the Z. noltii plants adapted to shade conditions (lower intertidal) in comparison to the sun morphotype (45×10 −6 and 182×10 −6 m s −1, respectively), indicating that the plants acclimated to sun conditions (higher intertidal) had a higher capacity to use HCO 3 − as DIC source for photosynthesis. Since external carbonic anhydrase activity was negligible and a large inhibitory effect was produced by Tris buffer addition, this HCO 3 − use was attributed to the operation of H + ATPases creating low pH zones in periplasmic space. The photosynthetic CO 2-flux supported for this mechanism was calculated to be 53 μmol O 2 m −2 s −1 in sun morphotype, about 80% out of maximum photosynthesis rate. In order to determine the possible photosynthetic energy cost of the HCO 3 − use, the effect of decreasing light on photosynthetic rates and g p(CO 2) was estimated. Photosynthetic conductance decreased in both morphotypes at non-saturating PFR. This dependence of g p(CO 2) on PFR indicated the existence of a positive interactive effect between DIC and PFR which was more pronounced in the shade morphotype since the ascending slope of O 2 evolution vs. PFR curves at limiting PFRs was reduced from 7.2 to 2.3 mmol O 2 mol photon −1 at 4 and 0.5 mol m −3 of DIC, respectively.

Contents of Volume

The affinity for dissolved inorganic carbon (DIC) and the mechanisms to use HCO3− as a source of DIC for photosynthesis were investigated in two morphotypes of Zostera noltii Hornem. Both morphotypes were collected at Ria Formosa lagoon (Southern Portugal) at two different levels in the intertidal. Affinity for DIC at saturating photon fluence rate (PFR), estimated as photosynthetic conductance for CO2 (gp(CO2)), was reduced by 75% in the Z. noltii plants adapted to shade conditions (lower intertidal) in comparison to the sun morphotype (45×10−6 and 182×10−6 m s−1, respectively), indicating that the plants acclimated to sun conditions (higher intertidal) had a higher capacity to use HCO3− as DIC source for photosynthesis. Since external carbonic anhydrase activity was negligible and a large inhibitory effect was produced by Tris buffer addition, this HCO3− use was attributed to the operation of H+ ATPases creating low pH zones in periplasmic space. The photosynthetic CO2-flux supported for this mechanism was calculated to be 53 μmol O2 m−2 s−1 in sun morphotype, about 80% out of maximum photosynthesis rate. In order to determine the possible photosynthetic energy cost of the HCO3− use, the effect of decreasing light on photosynthetic rates and gp(CO2) was estimated. Photosynthetic conductance decreased in both morphotypes at non-saturating PFR. This dependence of gp(CO2) on PFR indicated the existence of a positive interactive effect between DIC and PFR which was more pronounced in the shade morphotype since the ascending slope of O2 evolution vs. PFR curves at limiting PFRs was reduced from 7.2 to 2.3 mmol O2 mol photon−1 at 4 and 0.5 mol m−3 of DIC, respectively.

Supergene mineralization in mining residues of the Matchless cupreous pyrite deposit (Namibia)—a clue to the origin of modern and fossil duricrusts in semiarid climates

Mineralogical, geochemical, sedimentological and microbiological investigations of the evolution of supergene mineralization of mining residues at Matchless chalcopyrite–pyrite deposit (Namibia) have delineated what may be called “the minero-stratigraphy of tailings”. The encrustations of the supergene or secondary mineralization have originated from alteration of sulfides and carbonates of the primary mineralization and from chemical agents (e.g. lime, phosphate) added during processing of ore. The variation in tailings discharge and the early diagenetic alteration led to a pronounced bedding and the development of distinct layers within the tailings impoundment: (1) gypsum–carbonate (e.g. huntite), (2) gypsum–sulfate (e.g. melanterite), (3) gypsum–phosphate (e.g. brushite), (4) gypsum–chloride (e.g. halite), (5) sulfate–gypsum efflorescence (e.g. copiapite). Deposition and early diagenesis of tailings may be described as follows: During deposition of tailings, oxidation began because of relocations of the discharge point. Phyllosilicate-rich layers form local aquatards and minimize solution homogenization in the succeeding cycles of deposition. The whole impoundment is a series of paleo-oxidation zones on which the current oxidation in the vadose zone is being superimposed. Low-pH zones, even though some are now in the saturated part of the impoundment, owe their low pH to low dolomite content, reflecting variations in the input of primary minerals. Excess pyrite and Fe hydrolysis is still generating acidity and the formation of a typical “gossan-type” profile is in progress. The modern hardpans in the tailings may, during late diagenesis, eventually evolve to duricrusts analogous to those duricrusts that have largely been studied in geological series prevalently of Cenozoic age.

Particulate metals contamination in the Kishon River estuary, Israel

Suspended particulate matter (SPM) collected along the axis of the Kishon River, its estuary and Haifa Bay were analysed for trace metal concentrations together with measurements of water density, pH and dissolved oxygen. The concentrations of particulate Cd, Zn and Cu generally increased from the upper Kishon system (upstream from Tzipori-Kishon Junction) downstream and decreased from the Kishon Harbour seaward, while particulate Al concentrations decreased downstream and towards the open sea. Enrichment of Cd, Zn and Cu was found at Haifa Bay compared to the upper Kishon system. The axial profile of Mn concentrations indicated reduction of Mn at the anoxic and low pH zone of the lower river system and precipitation of Mnoxides at the estuary in response to the increase in pH and dissolved oxygen concentrations. Although Fe concentrations showed similar behavior to that of Al, the higher Fe Al ratios at the estuary are probably due to precipitation of Fe-oxides onto pre-existing particles. This spatial non-conservative behavior of metals is presumably due to the: 1. mixing between polluted river-borne particles and material of drainage basin and coastal origin; 2. changes of the distribution coefficient of metals between the particulate and solution phases (K d) with variations of salinity, pH and SPM concentrations; and 3. physical settling and currents. Short-term, tidal cycle measurements undertaken at the lower Kishon system (Julius Simon Bridge) indicated a high contribution of resuspended sediments to the SPM amounts due to the high tidal energy. It is hypothesized that the latter is the main mechanism by which SPM, which settles in the estuary, is transported landward creating a turbidity maximum zone between the Julius Simon and Histadrut bridges, i.e. about 3 km upstream from the estuary. It is proposed that the upper estuary zone acts as a purging system through which a low flux of SPM, enriched by organic and trace metal content, is transported seaward and from which a high flux of SPM is returned landward due to tidal stress.

Aqueous geochemistry and analysis of pyrite surfaces in sulfide-rich mine tailings

Aqueous geochemical techniques and analysis of pyrite surfaces have been used to study element partitioning between the aqueous and solid phase and to infer mechanisms that limit the concentrations of elements in porewater in a sulfide-rich mine tailings impoundment. Porewater samples and pyrite grains for surface analysis were collected from oxidized and unoxidized zones within the tailings. Surface analyses were conducted using a Time-of-Flight Laser-Ionization Mass Spectrometer (TOFLIMS). The porewater pH at the different sample locations varies from 3.85 to 6.98. High relative abundances of Na, K, Ca, Mg, Al, and Ni occur at the surfaces of the pyrite grains from all of the sample locations. The porewater concentrations of these elements in the low-pH zone may be controlled by precipitation or coprecipitation in secondary mineral coatings on the pyrite surface. Surface abundances of the metals Cu, Ag, Pb, Zn, and Cd are lowest, and porewater concentrations are highest, in the low-pH oxidized tailings. Surface abundances of As are greatest, and porewater concentrations are lowest, in the low-pH sulfide-oxidation zone. These trends vs. pH are consistent with an adsorption model for attenuation of Cu, Ag, Pb, Zn, Cd, and As from the porewater. The porewater Cu and Ag concentrations may be limited by replacement reactions that form secondary Cu and Ag sulfides at the pyrite surface. The highest abundance of C on the surface of the pyrite grains is in the shallow sulfide-oxidation zone; this interval coincides with large abundances of chemolithotrophic bacteria and may reflect populations of iron- and sulfur-oxidizing bacteria such as Thiobacilli.

Fundamental Studies on Utilization of Micro Green Algae at Treatments of Iudustrial Wastes or Polluted Waters. II. : Resistance of Living Micro Algae against Toxicity of Industrial Wastes

In the cultivation of green algae Chlorella with hard polluted river water in Nagoya City cell numbers became 105-6/ml. This cultivated water is called asalgae waterby the author. This Chlorella inalgae waterwas able to live until pH 3 in a low pH zone, and until 0.5 ppm of Cu2+, until 1.0 ppm of Pb2+, Zn2+, Ni2+ and Cr6+ for more than two days without any influence. These metals are contained in a plating waste. Limits of added waste volume to thealgae waterfor living of green algae was 1/10 volume at the gas work, 1/20 volume at the plating factory, and 1/5 volume at the milling factory. These Facts show a part of information about the resistance of micro planktonic green algae against wastewaters.