摘要:

AbstractLaboratory experiments and analysis of field samples showed that clay minerals, Fe and Mn oxides, and humic matter (colloids) have complex and often dramatic effects on the microbial methylation and demethylation of Hg, and on other microbial activities, in lake sediments. Depending on the nature, abundance, and surface chemistry of the colloids, the source of the sediment, the nature of the microbes, and synergistic/antagonistic effects of environmental variables, the colloids either strongly inhibited or stimulated the Hg transformations, had little or no effect, or alternated in their effects. Most of the results suggest specific effects on particular kinds of microbes, and are not attributable to general inhibition or stimulation of microbial growth or to effects due to the binding of Hg by the colloids. The colloids probably alter the species composition of the microbial community and affect the course of ecological succession, upsetting the dynamic balance between methylation and demethylation and causing alternate increases and decreases in methyl mercury (CH3Hg+) levels along with changes in other indicators of microbial activity [CO2and CH4production and oxidationreduction potential (Eh)].The role of clays was critically dependent on surface coatings. Clays often interfered with methylation (while in some cases strongly promoting subsequent demethylation); but iron oxide (FeOOH) often promoted methylation, and FeOOH coatings on clay tended to counterbalance the negative influence of the clay. Removal of oxide coatings depressed both methylation and demethylation. Manganese oxide (MnOOH) coatings sometimes promoted methylation, but larger amounts of MnOOH (unlike FeOOH) strongly suppressed methylation. On addition of organic nutrients, oxide coatings enhanced methylation and impeded demethylation; without nutrient enrichment, the reverse tended to occur. Humic matter in solution tended to stimulate methylation; but humic coatings on clay impeded methylation and fostered demethylation. Thus, the effects of natural colloids on Hg speciation are vitally important but variable, inconsistent, and not altogether predictable.

ISSN:0268-2605    

DOI:10.1002/aoc.590030103

出版商:Longman Group UK Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractTributyltin (TBT) has been measured in water in 12 of 15 harbors studied during US Navy baseline surveys. The highest concentrations of TBT (some exceeding laboratory toxicity limits) have been found in yacht harbors and near vessel repair facilities. Many sites (75%) in harbors and estuaries had no detectable (<5 ng dm−3) TBT. TBT monitoring studies with increased detection limits (<1 ng dm−3) have documented a high degree of TBT variability associated with tide, season and intermittent point source discharges. Although yacht harbors were shown to be the principal TBT source in most regions, dry‐docks can be significant sources. Tributyltin degradation studies were conducted using unfiltered seawater from four geographic regions and incubated under natural conditions. Degradation half‐lives were always in the range of 4–19 days, providing evidence that TBT is not highly persistent in the water column at environmental concentrations. Preliminary degradation experiments suggest that TBT has a longer residence time in sediment with a half‐life of several months. Tributyltin is primarily in the dissolved form in unfiltered seawater, although the association with particulate fractions may increase in samples collected near yacht repair facilities, Partition coefficients for particulate TBT versus bulk water are frequently near 3000 and vary with the particulate concentration, salinity and presence of natur

ISSN:0268-2605    

DOI:10.1002/aoc.590030104

出版商:Longman Group UK Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractEvidence is presented in favour of a natural environmental alkylation process as a source of atmospheric vapour‐phase alkyllead. Several species of marine flora have been cultured under laboratory conditions with added doses of inorganic lead, and production of alkyllead, predominantly trimethyllead (Me3Pb+), has been measured. Atmospheric concentrations and ratios of alkyl and inorganic lead at urban, rural and remote sites suggest that differential decay and deposition processes for different species, together with an environmental alkylation source, may explain enhanced ratios of total alkyllead/total lead in maritime air masse

ISSN:0268-2605    

DOI:10.1002/aoc.590030105

出版商:Longman Group UK Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractAnalyses of fish and other environmental samples (clams, macrophytes, sediments and waters) from areas upstream and downstream from two alkyllead manufactures beside the St Lawrence and St Clair Rivers, Ontario, show a clear indication of elevated alkyllead levels in samples near the industries. Most species of fish contained alkyllead compounds with tetraethyllead and triethyllead as the predominant forms. Most fish from the contaminated areas contained 50–75% of total lead as alkylleads. Carp, yellow perch and white sucker were generally the most contaminated species while pike, alewife and rock bass were the least contaminated. Average alkyllead levels varied from year to year but declined steadily after 1981. For example, the geometric mean of alkyllead compounds in carp from the St Lawrence River decreased from 4207 μg kg−1in 1981 to 2000 μg kg−1in 1982 and to 49 μg kg−1in 1987, reflecting the reduction of alkylleads in the effluents and the closure of one of the manufactures in 1985. Alkyllead levels were consistently lower in muscle and carcass samples in comparison with whole fish containing fatty intestines. However, muscle levels were generally equal to carcass levels.The concentrations of alkyllead compounds were generally low in clams, macrophytes, sediments and waters except from the immediate vicinity of the manufactures' final effluent

ISSN:0268-2605    

DOI:10.1002/aoc.590030106

出版商:Longman Group UK Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractMethylarsine oxide and sulfide are more toxic toCandida humicolathan arsenite; the sulfide is rapidly metabolized to trimethylarsine (Me3As) and methylarsine (MeAsH2) and the oxide to dimethylarsinic acid [Me2AsO(OH)]. Cell‐free extracts ofC. humicolaalso convert the oxide to Me2AsO(OH). The glutathione (RSH) derivative Me2AsSR is metabolized byC. humicolato Me3As and Me2AsH, but some other Me2AsSR′ compounds are unaffected. Studies involving the interaction of the arsenic(III) compounds with natural ecosystems and other micro‐organisms such asScopulariopsis brevicaulis,Straptococcus sanguis,Escherichia coli, andVeillonella alcalescensare desc

ISSN:0268-2605    

DOI:10.1002/aoc.590030107

出版商:Longman Group UK Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe water‐soluble arsenic compounds in five species of clams – Butter clam (Saxidomus giganteus), Horse clam (Schizothoerus nuttalli), Soft‐shelled clam (Mya arenaria), Native littleneck clam (Protothaca staminea), and Manila clam (Venerupis japonica) – are described. Varying amounts of arsenobetaine and tetramethylarsonium ion are the major arsenicals found in all species. Butter clams show the presence of a third compound which appears to be trimethylarsine oxide. Small amounts of as‐yet‐unidentified arsenicals can also

ISSN:0268-2605    

DOI:10.1002/aoc.590030108

出版商:Longman Group UK Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractAn improved synthetic route to [210Pb]‐(CH3)3PbCl is described in which chelated210Pb2+is methylated to [210Pb]‐(CH3)4Pb with methylmagnesium bromide (CH3MgBr) in the presence of methyl iodide. Controlled oxidation of the product with anhydrous hydrochloric acid and purification of the crude product by reversed‐phase high‐pressure liquid chromotography (HPLC) resulted in [210Pb]‐(CH3)3PbCl in 71% radiochemical yield. Whereas storage of the purified product at −10 °C resulted in complete conversion to Pb2+during one year, storage in 20% acetic acid at 4 °C resulted in less than 15% decomposition during six months. Periodic complexometric extractions to remove210Pb radioactive daughters (210Bi, 100% β,Emax= 1.16 MeV;210Po, 100% α,E= 5.305 MeV) from the storage solution did not alter the rate of decomposition. The rate of translocation of [210Pb]‐(CH3)3Pb+across an isolated tomato cuticle was approximately twice the rate of transfer of inorganic lead(II) and was not influenced by the presence of increasing amounts of disodium ethylenediam

ISSN:0268-2605    

DOI:10.1002/aoc.590030109

出版商:Longman Group UK Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA systematic study of the biomethylation of selenium and the determination of the methylated species indicates preliminarily that selenium is susceptible to natural biomethylation under certain environmental conditions. Detectable levels of methylated selenium species, including dimethyl selenide [(CH3)2Se], dimethyl diselenide [(CH3)2Se2] and dimethylselenone [(CH3)2SeO2] have been detected by gas chromatography – graphite furnace atomic absorption spectrophotometry (GC – GF AA) from a variety of environmental samples. Findings of naturally methylated selenium species from both soil samples and related air samples suggest that there may exist a localized cycle of selenium between ground soil and the ambient air.Factors that influence the sensitivity and accuracy for the determination of alkyl selenide compounds by GC – GF AA have also been investigated. Flashlike injection mode and addition of about 10% of hydrogen gas to the argon carrier gas provide for highly sensitive detection. Reproducible determination can be obtained with a precision of about 6% and the detection limits are 0.3 ng S

ISSN:0268-2605    

DOI:10.1002/aoc.590030110

出版商:Longman Group UK Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractOptimized techniques for measuring butyltins at the sub‐part‐per‐trillion (ppb; 1:1012) level in seawater and at the part‐per‐billion (ppb; 1:109) level in tissues and sediments are presented. Purge and trap/hydride derivatization followed by atomic absorption (AA) detection was optimized to give better sensitivity than was previously attained for seawater, yielding environmental detection limits of 0.08–0.2 ng dm−3. Improvement in precision and reproducibility in measurement of butyltins in tissues and sediments was attained by adjustment of the concentration in an organic extract to minimize matrix effects and by use of internal standards. The tissues and sediments were homogenized and extracted with methylene chloride (CH2Cl2) after acidification. The butyltins in the organic layer were derivatized with hexylmagnesium bromide and analyzed by gas chromatography (GC) with a flame photometric detector (FPD). The absolute detection limits in tissues and sedimets were 0.1 ng for tributyltin (TBT), 0.12 ng for dibutyltin (DBT) and 0.29 ng for monob

ISSN:0268-2605    

DOI:10.1002/aoc.590030111

出版商:Longman Group UK Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe methylation of tin(II) [Sn(II)] by iodomethane (CH3I) under environmental conditions has been further demonstrated by a13C carbon isotope tracer method. Methylation products are mainly monomethyltin, and very small amounts of dimethyltin. The reaction of Sn(II) and CH3I was investigated at pH 2, 4, 6, 8, 10 and salinity (S) 8, 15, 22, 28, 35%; it has been found the reaction was affected by pH and salinity, the tin methylation activity being highest at about pH 6 andS= 28% . The methylation reaction is first‐order for both CH3I and Sn(II), and the rate equation has been obtained as follows:\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{{\rm d}\left[{{\rm CH}_3 {\rm Sn}} \right]}}{{{\rm d}t}} = \left({k' + k''\left[{{\rm CH}_3 {\rm I}} \right]} \right)\left. {\left[{{\rm SnY}_2 } \right]} \right) $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm where}} \hfill & {k' = 9.10 \times 10^{ - 7} \min ^{ - 1},} \hfill \\ {} \hfill & {k'' = 1.11 \times 10^{ - 6}\; {\rm mmol}^{ - 1}\; {\rm dm}^3\; \min ^{ - 1},} \hfill \\ {} \hfill & {{\rm Y} = {\rm tin\;counterion}} \hfill \\ \end{array} $$\end{document

ISSN:0268-2605    

DOI:10.1002/aoc.590030112

出版商:Longman Group UK Ltd    

年代:1989

数据来源: WILEY