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Iron chemistry in seawater has been extensively studied in the laboratory, mostly in small-volume sample bottles. However, little has been reported about iron wall sorption in these bottles. In this paper, radio-iron 55Fe was used to assess iron wall adsorption, both in terms of capacity, affinity and kinetics. Various bottle materials were tested. Iron sorption increased from polyethylene/polycarbonate to polymethylmetacrylate (PMMA)/high-density polyethylene/polytetrafluoroethylene to glass/quartz, reaching equilibrium in a 25–70 h period. PMMA was studied in more detail: ferric iron (Fe(III)) adsorbed on the walls of the bottles, whereas ferrous iron (Fe(II)) did not. Considering that in seawater the inorganic iron pool mostly consists of ferric iron, the wall will be a factor that needs to be considered in bottle experiments.The present data indicate that for PMMA with specific surface (S)-to-volume (V) ratio S/V, both iron capacity (42 ± 16 × 10− 9 mol/m2 or 1.7 × 10− 9 mol/L recalculated for the S/V-specific PMMA bottles used) and affinity (log KFe'W = 11.0 ± 0.3 m2/mol or 12.4 ± 0.3 L/mol, recalculated for the S/V-specific PMMA bottles used) are of similar magnitude as the iron capacity and -affinity of the natural ligands in the presently used seawater and thus cannot be ignored.Calculation of rate constants for association and dissociation of both Fe'L (iron bound to natural occurring organic ligands) and Fe'W (iron adsorbed on the wall of vessels) suggests that the two iron complexes are also of rather similar kinetics, with rate constants for dissociation in the order of 10 −4–10− 5 L/s and rate constants for association in the order of 108 L/(mol s). This makes that iron wall sorption should be seriously considered in small-volume experiments, both in assessments of shorter-term dynamics and in end-point observations in equilibrium conditions. Therefore, the present data strongly advocate making use of iron mass balances throughout in experiments in smaller volume set-ups on marine iron (bio) chemistry.  相似文献   
2.
The present work evaluates the stress effects in two epiphytic lichen species with different thallus morphology, the foliose Parmelia caperata and the fruticose Evernia prunastri, as resulting from transplanting from an unpolluted to an air-polluted area. Lichen samples were collected in Portugal in a clean area, during the spring 2003, and transplanted (1) to the same zone nearby and (2) to a polluted area as affected by an industrial complex. Transplant samples were taken periodically during four months in both places. At the same time lichen samples from the clean-air site native (in-situ) populations were also collected. For each sample were measured the chlorophyll content, the chlorophyll degradation and the cell membrane damage, the latter represented by leacheate conductivity. During the experiment the meteorological conditions were registered. The results indicate the absence of stress effects of transplanting as such, and suggest that leachate conductivity may be the more sensitive indicator of general lichen vitality.  相似文献   
3.
Preface     
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4.
The International Atomic Energy Agency (IAEA) organized a co-ordinated research project (CRP) on Validation and application of plants as biomonitors of trace element atmospheric pollution analysed by nuclear and related techniques involving 14 participating countries. The CRPs objective was to identify appropriate bioindicators for local and/or regional application and validate them for general air pollution monitoring. Activities included quantification studies, research into spatial and time resolution for particular organisms, and physiological studies. A number of suitable bioindicators were identified in different parts of the globe and tested during the CRP. Sampling strategies were reviewed and the recommended approach adopted by the group. Appropriate sample preparation procedures were assessed and harmonised to the degree allowed by different geographic and climatic conditions in the participating countries. Two interlaboratory comparison exercises were carried out on lichen and moss materials. Results confirmed definite improvement in analytical performance of the participating laboratories, but also revealed possible inconsistencies due to different sample processing procedures. Several monitoring surveys were carried out and consequently pollution maps drawn for extended areas or countries. Overall results confirmed applicability of lower plants for assessing the degree of atmospheric pollution and provided several countries with effective monitoring tools not used before.  相似文献   
5.
A three-step sequential extraction procedure with Milli-Q, CaCl2 and H3PO4 was applied for extraction of arsenic species in lichen transplants and airborne particulate matter (fine and coarse fractions). The samples used in this work were collected in 1994–1995 near coal-fired power plants. Both transplant lichens and airborne particulate matter were submitted to the same environment simultaneously. Arsenic species identification and quantification was performed by HPLC–UV–HG–AFS. Inorganic forms of arsenic (arsenite and arsenate) were present in significant amounts in most of the samples. Only in lichens also organic forms of arsenic (monomethyl arsonic acid and dimethyl arsinic acid) were identified which may indicate biotransformation of inorganic arsenic.  相似文献   
6.
It is generally challenging to predict the post-abandonment behaviour and integrity of wellbores. Leakage is, moreover, difficult to mitigate, particularly between the steel casing and outer cement sheath. Radially expanding the casing with some form of internal plug, thereby closing annular voids and fractures around it, offers a possible solution to both issues. However, such expansion requires development of substantial internal stresses. Chemical reactions that involve a solid volume increase and produce a force of crystallisation (FoC), such as CaO hydration, offer obvious potential. However, while thermodynamically capable of producing stresses in the GPa range, the maximum stress obtainable by CaO hydration has not been validated or determined experimentally. Here, we report uniaxial compaction/expansion experiments performed in an oedometer-type apparatus on precompacted CaO powder, at 65 °C and at atmospheric pore fluid pressure. Using this set-up, the FoC generated during CaO hydration could be measured directly. Our results show FoC-induced stresses reaching up to 153 MPa, with reaction stopping or slowing down before completion. Failure to achieve the GPa stresses predicted by theory is attributed to competition between FoC development and its inhibiting effect on reaction progress. Microstructural observations indicate that reaction-induced stresses shut down pathways for water into the sample, hampering ongoing reaction and limiting the magnitude of stress build-up to the values observed. The results nonetheless point the way to understanding the behaviour of such systems and to finding engineering solutions that may allow large controlled stresses and strains to be achieved in wellbore sealing operations in future.  相似文献   
7.
An iron enrichment experiment, EisenEx, was performed in the Atlantic sector of the Southern Ocean during the Antarctic spring of 2000. Deck incubations of open ocean water were performed to investigate the influence of ultraviolet B (UVB: 280–315 nm) and ultraviolet A (UVA: 315–400 nm) on the speciation of iron in seawater, using an addition of the radioisotopes 59Fe(III) (1.25 nM) or 55Fe(III) (0.5 nM). Seawater was sampled inside and outside the iron-enriched region. The radioisotopic Fe(II) concentration was monitored during daylight under three different light conditions: the full solar spectrum (total), total minus UVB, and total minus UVB+UVA. A distinct diel cycle was observed with a clear distinction between the three different light regimes. A clear linear relationship was found for the concentration of radioisotopic Fe(II) versus irradiance. UVB produced most of the Fe(II) followed by UVA and visible light (VIS: 400–700 nm), respectively. UVB produced 4.89 and 0.69 pM m2 W−1 radioisotopic Fe(II) followed by UVA with 0.33 and 0.10 pM m2 W−1 radioisotopic Fe(II) and VIS with 0.04 and 0.03 pM m2 W−1 radioisotopic Fe(II).  相似文献   
8.
Transplants of the epiphytic lichen Parmelia sulcata were suspended in nylon bags in a special device allowing a fixed orientation of the lichen towards the wind direction, viz. facing the wind (F orientation) or shielded from the wind by its substrate (T orientation). The F- and T-orientation data were mutually compared and also with reference values (= time zero values of the transplants). The data were analysed via Monte Carlo added target transformation factor analysis (MCATTFA) to get information on possible emission-source profiles and their contributions to total-element levels in transplants, in F- and T-orientations. Both orientations did not differ for Na, Mg, P, Cl, K, Fe, Co, Ni, Ga, Se, Br, Sr, Ba, La, Nd, Sm, Lu and Ta, but showed some time-related differences for Cr and Zn. For the remaining elements the data presents a high variability. Under the conditions of the experiment, F- and T-oriented transplants generally did not result in differences in source profiles reflected, nor in differences in source contributions to element levels in the transplants.  相似文献   
9.
The present paper addresses Kriging-based approaches to estimate survey quality, thereby using data on biomonitoring surveys of trace element air pollution. Data were used of a 1995 moss monitoring study in The Netherlands, thereby taking sodium (Na), arsenic (As) and bromium (Br) to illustrate the points made. Survey quality was expressed as the survey signal-to-noise ratio (SSNR), with the survey variance as the signal and the local variance as the noise. The Kriging approaches were regarded in parallel to direct approaches where local variances are determined from multi-fold local sampling.The paper addresses the uncertainties in SSNR associated to the uncertainties in local values and variances if based on pooled samples and a limited 5-fold sub-sampling in a restricted number of sampling sites. It further introduces a Kriging approach to SSNRK (K for Kriging), by Kriging-assisted recalculation of local values and variances, in turn based on fitted experimental variograms. The outcomes suggest that the Kriging approach may yield reliable SSNRK values; the approach implies that SSNRK depends on survey set-up, site density and sampling grid characteristics. The discussion of the paper addresses the points made and further suggests the use of large sample analytical facilities to permit a change in survey approach from mixing and milling of pooled sub-samples to bulk analyses of all sampled material in higher site-density surveys.  相似文献   
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