Environmental Pollution Series B, Chemical and Physical最新文献

Competitive adsorption, by activated carbon, of phenolic compounds from 2- and 3-solute mixtures was studied. Phenols with 2 or 3 chlorine substituents (2,4-dichlorophenol and 2,4,6-trichlorophenol) were strongly adsorbable and adsorbed preferentially to 2-chlorophenol, phenol and m-cresol. Data generally fit Freundlich adsorption isotherms. The dichloro- and trichlorophenols adsorbed more strongly than predicted by the Polanyi-based model when in competition with other phenolics. The cumulative adsorption capacities for the mixtures containing all phenolic compounds were lower than those for individual compounds.

The rhodizonate spot test for Pb has been adapted to the detection of Pb contamination of soil. Depending upon the method of extraction chosen, Pb is detectable to 400–700 μg g⁻¹ in the dry soil sample. Extraction is carried out by heating or shaking with nitric acid, followed by filtration. The filtrate is brought to pH 1·5 with citrate using a pH meter or an indicator. The extract is spotted on filter paper and treated with freshly prepared aqueous sodium rhodizonate. Heating extracts more Pb than shaking, but a relatively stable percentage of the Pb present is extracted by shaking for 30 s. This latter method of extraction may be used as part of a rapid, simplified procedure requiring a minimum of apparatus. Use of citrate for pH adjustment eliminates the problem of crystallisation encountered with tartarate, as specified in the original procedure. Soil extracts with pH < 1 showed rapid fading of the pink Pb-rhodizonate spot, and those with pH > 3 gave the intense yellow colour of free rhodizonate, which tended to obscure the pink Pb-rhodizonate colour. Differences in the effect of heating and the effect of extraction time on Pb and Fe levels were observed, with Pb more readily extracted than Fe. Use of extracts with low levels of Fe made possible visual endpoint detection for the adjustment of pH. Using the shaken extraction method with a series of 107 samples, positive results were obtained for 82 samples with > 700 μg Pb g⁻¹, negative results for 10 samples with < 400 μg Pb g⁻¹ and mixed results for 15 samples in the range 400–700 μg Pb g⁻¹. Selection of a cutoff value of 500 μg Pb g⁻¹ eliminated false negative results in a pilot screening trial of 38 samples prepared by the heated extraction method.

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.