Environmental Pollution Series B, Chemical and Physical最新文献

This study reports an investigation into fluvial contamination by the Cwm Rheidol ZnPb mine near Aberystwyth, Wales. This mine was last worked at the end of the last century, but acidic drainage waters are still a major source of water-borne contamination to the River Rheidol, despite the installation of a static treatment plant below the mine over twenty years ago.

Acidity in the main discharge stream often approaches pH 3, causing the precipitation of hydrated ferric oxides and subsequent sorption of metals along its length. The concentrations and movement of Ag and other metals (Cd, Cu, Pb and Zn) before and after treatment are reported.

The fate of these metals after discharge into the River Rheidol was also studied, using a sequential extraction procedure performed on the sediments. Much of the discharged Cd remained ‘easily or freely leachable and exchangeable’ (Badri & Aston, 1983), non-lithogenic forms (i.e. not bound in the mineral lattice) of Ag and Cu were released from sediments by oxidation, while Cd and Zn were solubilised predominantly by an acid-reduction extraction. Studies of the distribution and partitioning of metals in sediments at and near the mine suggest similarities in the behaviour of Zn and Cd and of Ag, Cu and Pb. However, the data indicate that caution should be exercised when interpreting the chemical partitioning of elements solubilised by so-called ‘selective’ extractants.

Dutch sparrowhawk populations were seriously affected by organochlorines during the 1960s. In particular, the role of DDE in suppressing the reproductive output has been often stressed, an effect which was said to prevent sparrowhawk populations from recovering, even after bans on the use of most organochlorines had been enacted.

In the present study residue levels of DDE in eggs were monitored over the period 1975-83, during which time most sparrowhawk populations recovered. Fresh eggs were sampled in three study areas and the contents were analysed for organochlorine compounds.

Since DDE affects egg shells, Ratcliffe indices for shell thickness were measured. Egg breakage frequency was recorded from 1970 to 1983.

From 1975 to 1983 no significant trend in DDE residues, nor in egg-shell thickness, is apparent. The decline in the proportion of clutches with broken eggs suggests a decrease in contamination levels during the early 1970s.

Several causes of the continuing contamination are discussed. DDE is a very persistent compound, and it is likely that considerable amounts are still to be found in the soil and, therefore, in the food chain of the sparrowhawk.

The seasonal variations in the water quality indices of dissolved oxygen, biological oxygen demand (BOD), turbidity, total solids, nitrates, phosphates, hydrogen-ion concentration (pH), temperature and faecal coliforms of the Warri River at five sampling points were investigated from July 1981 to July 1982.

With respect to nitrate and phosphate levels, the waters are oligotrophic and therefore excellent throughout the period of investigation. Water quality indices for hydrogen-ion concentration (pH) and temperature also showed that the waters were medium to good from month to month. However, water quality indices for dissolved oxygen, turbidity and total solids revealed a seasonal effect on these parameters, although the waters were generally medium to good. With respect to faecal coliforms, however, there was a longitudinal gradient whereby the waters deteriorated from Udu Bridge (near the source) to Warri, where they are very polluted as a result of indiscriminate disposal of human wastes into the river.

The application of the weighted mean index to all nine parameters showed the Warri River waters to be medium to good. The immediate source of pollution in the Warri River is sewage, rather than industrial.

The baseline levels of mercury in fish and sediments from the Niger delta area of Nigeria have been examined. The measured concentrations in fish varied from less than 10 μg kg⁻¹ to 410 μg kg⁻¹ wet weight and those in the sediments varied between 0·024 and 1·54 μg g⁻¹ dry weight. The levels found in the samples from this area were generally low in comparison with levels found in other regions of the world and the 0·5 μg g⁻¹ Hg in fish recommended for human consumption by the World Health Organisation. These results indicate that the Niger delta area of Nigeria is relatively unpolluted with mercury.

Eggs from herring gull Larus argentatus were collected at seven different locations along the Norwegian coast in 1969 and again in 1979–1981. Hexachlorobenzene (HCB), octachlorostyrene (OCS), DDE, PCB and decachlorobiphenyl (DCB) were determined in each of the 200 eggs. In order to obtain additional information on the time trend of the PCB levels, the relative distribution of four selected PCB components was determined to see if there had been a shift towards the more persistent PCB isomers. Such a shift may indicate a decreasing tendency in PCB levels. Mean levels of HCB in 1969 and 1979–1981 were 0·19 and 0·12 μg g⁻¹ wet weight, respectively. When excluding the results from Telemark, an area with local contamination with HCB, OCS and DCB, there were no statistical differences in HCB levels between the two sampling periods. OCS and DCB were only detected in eggs from Telemark. Significant decreases in DDE levels and DDE/PCB ratios but not in PCB levels were observed between 1969 and 1979–1981. Only for the most persistent of the PCB isomers recorded was there a small increase in the relative amount from 1969 to 1979–1981.

Corn (Zea mays L.) and soybean (Glycine max L.) were grown on sandy loam alluvial soil amended with fly ash at rates ranging up to and including 25% by weight. Plant analysis data for 7 elements showed enhanced absorption of B, Cu, Mn and Zn with increasing rates of fly ash application. Phosphorus, potassium and calcium concentrations in the two crops were not affected by fly ash application.

Measurements have been made to determine the levels of radioactivity in silt in the River Lea using the gross beta count rate method and γ-ray spectrometry. The results show that the environmental levels are very low and appear to be due to naturally occurring potassium, uranium and thorium and a small amount of ¹³⁷Cs, probably from fallout. The evidence suggests that pollution due to radioactivity present in the river is negligible.

Traces of cadmium ion in solution, alone and together with different cadmium bonding agents (K₂CO₃, CaCO₃, KH₂PO₄, Ca₃(PO)₄, Fe(NO₃)₃ and Fe(OH)₃), were added to three soils of pH 5·0, 7·0 and 7·6, respectively, and incubated aerobically at 45°C for 6 days.

The extent to which the different binding agents immobilised cadmium in the treated soils was determined by measuring the amounts extracted by CH₃COONH₄, CaCl₂, NH₄Cl, Ca(NO₃)₂, (CH₃COO)₂Ca or KNO₃ solutions. The extracted cadmium was determined by AAS. Recoveries by the different extractants, which are representative of those proposed for the determination of ‘available cadmium’ in soils, showed a systematic variation for each of the treated soils. The extent to which these differences arise from pH and the complexation of the cadmium is discussed.

Markedly different amounts of cadmium were immobilised in the different soils, under the same conditions and treatments. CaCO₃ and Ca₃(PO₄)₂ were the most efficient in immobilising cadmium in the acid soil, K₂CO₃ and Ca₃(PO₄)₂ were best with the neutral soil and Fe(NO₃)₃, Fe(OH)₃ and Ca₃(PO₄)₂ with the calcareous soil. Thus, under the aerobic conditions likely to be found in dry farmlands, the cadmium immobilisation mechanisms appear to be associated with precipitation on carbonate and phosphate surfaces; in calcareous soils, the surface hydrolysis of cadmium on ferric hydroxide seems most important.

Aluminium concentrations in water have been measured at several points in time for more than 50 sites distributed along the Rivers Esk and Duddon, Cumbria, and their tributaries. Total aluminium (Al_total), inorganic monomeric aluminium (Al_inorg) and organic monomeric aluminium (Al_org) were measured using a modified Driscoll technique. Concentrations were found to vary with season (flow rate) and geographical variation was often high. High Al_inorg concentrations (200–300 μg litre⁻¹), associated with low pH levels, were commonly found in tributaries in the upper reaches of the valleys, at high flow rates, and in catchments containing little or no improved agricultural land. Two catchments in the Duddon valley appear to be affected by afforestation and had even higher levels of Al_inorg (400–600 μg litre⁻¹). Two catchments in Eskdale were sampled in more detail. It was found that water quality changed markedly after the tributaries flowed through improved pasture land. Al_inorg concentration fell and pH values rose. Those changes were associated with increased Ca concentrations, possibly the result of agricultural liming.