Environmental Pollution Series B, Chemical and Physical最新文献

Ion chromatography is a technique which has developed rapidly in the last few years. The development of the method and instrumentation is considered. Particular emphasis is given to applications of significance in environmental analysis. Ion chromatography is shown to have significant advantages over alternative techniques in the analysis of anions. The advantages are in the speed of analysis, the range of species which may be determined in a single analysis and the lower concentrations which can be detedted.

Cations can also be analysed readily. The technique has some advantages over alternative methods but these are not as marked as for anion analysis.

Samples of brown seaweed Fucus vesiculosus from the south bank of the Humber Estuary have been analysed for Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. Distribution of Cd, Cu, Ni and Zn along the estuary are represented graphically. Cd and Ni are conservative, but the plots for Cu and Zn suggest inputs of these metals in the lower estuary. Elevated Fe levels are considered to result from contamination by suspended sediment, but concentrations at one site in the lower estuary are indicative of an input of] soluble iron. All Pb and Cr results can be accounted for entirely by particulate contamination. Data from the Humber is compared with figures available in the literature. Concentrations of Cd, Cu and Zn are much greater than ‘background’ levels and compare with contaminated conditions elsewhere, whilst Ni concentrations include the highest values reported for any location. It is concluded that Fucus vesiculosus in the Humber exhibits substantially elevated levels of heavy metals.

Uranium mining has increased the gamma radioactivity by up to 80 times in some areas. The activity also varies, by a factor of 5, with rock composition. The most important problems arise from the dispersion of unshielded radioactive material and the lack of rehabilitation of old mining areas. The continued existence of these problems reveals the inadequacy of existing laws, the past absence of social responsibility and a serious gap in the measures for the protection of public health.

Predictions of the emissions of airborne total viable particle (TVP) concentrations from sewage are of concern due to possible adverse human health effects. The work presented here is an assessment of the feasibility of using environmental data to develop a plume dispersion model for the prediction of airborne TVP concentrations in the vicinity of an activated sludge sewage treatment plant. The monitoring data used were collected during an epidemiology study of the health of residents in the vicinity of an activated sludge sewage treatment plant located in a suburb of Chicago. Two types of modelling approaches were explored: dispersion modelling such as the Gaussian plume dispersion model and statistical modelling. The results of the statistical model have been reported elsewhere. The Gaussian modelling approach was limited because emission rates and rate of microbial die-off could not be measured, and techniques for their estimation proved inadequate. The die-off rate is normally expressed as a negative rate of change, but only positive coefficients were found. Although microbial growth in air is possible under certain conditions, it is thought that high background TVP concentrations due to many undefined sources of TVP in the study area were chiefly responsible for the positive coefficients. Until a better method is found for estimating the ambient total viable decay rate and defining background concentrations, the Gaussian plume dispersion modelling technique does not appear to provide a more useful approach for estimating TVP concentrations downwind from an activated sludge sewage treatment plant than does statistical modelling. Rather, the modelling process served to identify deficiencies in the application of the Gaussian plume model to ground level source aerobiological emissions when there is a significant background concentration.

Water disinfected by chlorine produces trihalomethanes (THM), while chlorine dioxide, an alternative to chlorine, is reduced mainly to undesirable chlorite. Mixtures of ClO₂ and Cl₂ may successfully reduce the formation of both THM and chlorite in the absence of bromide. When Lake Kinneret water in Israel was studied, however, it was found that such mixtures caused only a minor reduction in the formation of THM compared with chlorine alone. This is attributed to the effect of bromide present in the water of Lake Kinneret. The formation of THM and chlorite could, however, be satisfactorily reduced (by about 60% and 90%, respectively), if chlorine dioxide were allowed to react in water with the THM precursors before chlorine was introduced.

Manganese(IV) oxide avidly adsorbed mercury(II) species, with freshly prepared material (HMO; capacity, 280 mmol kg⁻¹ abstracting most of the Hg present in 1 to 12 mg litre⁻¹ Hg(II) solutions. α cryptomelane also adsorbed in accordance with a Langmuir isotherm (capacity, 250 mmol kg⁻¹) but the binding constant (4400) was only 1% of the HMO value. A λ MnO₂ sample had an adsorption capacity of 15 mmol kg⁻¹. Uptake was not influenced by pH over the range 5 to 11, but decreased in the 5 to 3 region due to protonation of sites. The amount adsorbed was reduced in the presence of chloride ions, with the extent, and pH of minimum uptake, being a function of Cl⁻ level. As HgCl₂ and Hg(OH)₂ are the dominant solution species, and as protons were not released in the adsorption process, it is proposed that the adsorption mechanism involves migration of the Hg(II) species into the internal structure of the Mn(IV) oxide, where they either undergo ligand exchange with surface hydroxyl groups or are transformed into a solid hydroxy phase. The presence of sulphate ions further lowered Hg uptake. Extraction studies showed that adsorbed Hg could be totally released by EDTA, DTPA or 0·5m HCl. Decreasing quantities were displacedby 1m HNO₃, Na₄P₂O₇, Na₃cit. Equilibration with 0·5m NaCl extracted about half, while 1m NH₄NO₃ or CH₃COONH₄ recovered < 5%. It was concluded that the formation of manganese(IV) oxides in waterways would aid the maintenance of low solution-Hg levels.

The factors which promote retention or release of soluble fluoride species by soils have been reviewed with the aim of identifying key processes. The topics considered include fluoride levels in soils, mobility as demonstrated in leaching studies, and fluoride adsorption by soils. The role of competing chemical equilibria has been considered, through discussion of chemical interactions involving fluoride species and soil components such as clays, hydrous oxides (Al, Fe, Mn), organic matter, calcite and quartz.

The mobility of fluoride tends to be a function of soil type, system pH and F levels, with retention being favoured in acidic sediments containing clays and poorly ordered hydrous oxides of aluminium.

Lead in house dust may be an important source of this metal for children and it has been suggested that the mineral components of dust as well as lead and other trace elements are derived, in part, from garden soil. This proposed relationship between soil and dust trace metal composition was investigated in north Wales, in an area where lead mining has caused intensive and extensive heavy metal contamination of agricultural and garden soils, and in a control area. Paired garden and house dust samples were collected from the houses of random samples of 90 subjects and were analysed for Cd, Cu, Pb and Zn. Compared with soils from the control village the contaminated soils were enriched (ratios of geometric means) by factors of Cd = 6·7, Cu = 1·1, Pb = 14·1 and Zn = 3·8. The similar ratios for dust were Cd = 1·2, Cu = 1·1, Pb = 1·9 and Zn = 1·1. Correlation analysis suggested that soil contributes little Cd, Cu or Zn to dust but 27% of the variability in dust Pb could be explained by soil Pb and the gradient of the log-dust Pb/log-soil Pb regression was 0·3. Subsequent resampling in 11 houses demonstrated little change over two months in dust Cd, Cu or Zn concentrations. Pb levels did change and were poorly correlated in the two sample sets, which may be explained by differences in the amounts of contaminated soil carried into the house before the dust was sampled.

Uptake of Hg(II) (1–10 mg litre⁻¹) by two humic acids varied with pH, with >98% being sorbed at pH 4–5. Langmuir plots yielded adsorption capacity and bonding values of ∼50 mmol kg⁻¹ and 3 × 10⁶ litre mol⁻¹ respectively. The addition of increasing amounts of chloride reduced uptake (10–20%) and shifted the maximum sorption region to higher pH values. The presence of 10⁻² M levels of Ca²⁺, Mg²⁺ and NH₄⁺ promoted near total adsorption and reduced the pH effect; 10⁻⁴ levels slightly increased the amount of Hg(II) sorbed. Sulphate additions reduced Hg uptake. Much of the Hg(II) is considered to be chemisorbed, since while most of the sorbed species was extractable in 0·005 m EDTA, only half was released into 1 m HNO₃ and molar salt solutions retrieved less than a third.

The environmental significance of the results are discussed.