Spatial analysis and mapping the annual mean concentrations of acidity and major ions in precipitation over the United Kingdom in 1986

The composition of precipitation is being monitored in collectors sited throughout the United Kingdom. In the first year, 1986, hydrogen ion, nitrate, ammonium and non-marine sulphate were measured in samples from 47 sites and annual mean concentrations determined. Spatial analysis based on Regionalized Variable Theory revealed autocorrelation in all four ions and reasonable bounded models were fitted to the sample variogram of all four. These were then used to estimate values of a fine mesh grid by simple kriging, and the estimates were then contoured. The estimation errors were similarly mapped, and both sets of maps are presented. The maps show that concentrations of these ions are greatest in eastern parts of the country, as expected from consideration of European emissions and weather patterns. For the first time estimation errors were also mapped and show how the network could be improved.     

The characteristics of size distribution of suspended particulates in the air for sulphates and selected metals in different areas and seasons

The characteristics of the distribution of particles by size were investigated for sulphates and selected metals (Pb, Fe, Mn, and Cu) in the air in two urban and an industrial area during the winter and summer periods using an Andersen cascade impactor.In the case of metals, but not sulphates, the character of the area affected the value of mass median diameter. Lowest values were obtained in a sparsely populated urban area, whereas in a densely populated urban area and in the industrial area the values were higher.In the industrial area a high correlation coefficient was found between sulphate and manganese, and between sulphate and lead, as well as a high value of the equivalent Mn²⁺/SO _inf4 ^sup2- ratio for the total sample. It may therefore be assumed that in the industrial area manganese produces a catalytic effect on SO₂ conversion to sulphate. Among the investigated metals lead stands out as a dominant cation which binds to the sulphate ion in the industrial and densely populated areas.     

An evaluation of in situ microcosms for validating aquatic fate and transport models

The fates of two compounds, 2,4 Dichlorophenoxy Acetic Acid Butoxyethyl Ester (2,4-DBEE) and 1,4 Dichlorobenzene (1,4-DCB), were examined in in situ microcosms placed in a pond and compared with the fates in the pond itself. Results also were compared with predictions of an aquatic fate and transport model (EXAMS). Decay rates of 2,4-DBEE were not significantly different among the microcosms, pond and model predictions. The decay rate of 1,4-DCB in the microcosms was significantly lower than the rate for the pond, and lower than the rate predicted by the model. The low volatility of 1,4-DCB in the microcosms is attributed primarily to lack of water surface turbulence in the microcosms.     

Determination of the working level of radon/thoron mixtures by personal α-dosimeters and environmental α-monitors using gross α-counting

Analytical procedures are presented which permit the determination of the Working Levels of the radon and thoron progenies with personal α-dosimeters and α-particle environmental monitors, operating on time integrating principles, from gross α-counts. Experiments have been carried out in an underground uranium mine and in a radon/thoron environmental chamber, specially designed for calibration purposes, to verify theoretical data. In general, and notwithstanding a number of complicating factors, fair to good agreement has been found between theoretical and experimental data. Experimental values have been found to be lower than theoretical values, an observation which is partly ascribed to plate-out of decay products in the instrument's sampling heads.     

Dose-time-response functions for toxic chemicals

In many situations, the effect of a toxic chemical on a biological system depends on both the intensity and the duration of exposure. The dependence on the time dimension can be the expression of a range of processes including the physical accumulation of toxic chemicals or their metabolites and the functional accumulation of damage. Measures and functions that have been used to describe this dependence are reviewed.Some of these functions are compared through a case study of the neurotoxicity of methylmercury. Use is made of data that indicates a dependency between the blood concentration at which monkeys were exposed and the length of time before damage was detected. Several exposure functions are fitted to these data and their appropriateness is compared. Using the most appropriate function, an exposure-response relationship is developed using probit analysis. An alternative data analysis procedure is also investigated. The apparent threshold after a 100 day exposure is estimated to be greater by a factor of 3–5 compared to the threshold for chronic exposure. Applying this factor to man, the blood concentration threshold for chronic exposure is estimated to be 40–170 ppb, a finding consistent with recent reports of neurological damage in humans exposed below the generally accepted threshold.     

Determination of biomass burning emission factors: Methods and results

Biomass burning, in a broad sense, encompasses different burning practices, including open and confined burnings, and different types of vegetation. Emission factors of gaseous or particulate trace compounds are directly dependent both on the fuel type and the combustion process. Emission factors are generally calculated by stoichiometric considerations using the carbon mass balance method, applied either to combustion chamber experiments or to field experiments based on ground-level measurements or aircraft sampling in smoke plumes. There have been a number of experimental studies in the last 10 years to investigate wildfires in tropical, temperate, or boreal regions. This article presents an overview of measurement methods and experimental data on emission factors of reactive or radiatively active trace compounds, including trace gases and particles. It focuses on fires in tropical regions, that is, forest and savanna fires, agricultural burns, charcoal production, use of fuelwood, and charcoal combustion.     

Effects of exposure of aquatic snails to sublethal concentrations of waste drilling fluid

Static bioassays were carried out using two aquatic snails (Pilia sp. and Lanistes sp.) as test organisms in soft natural dilution water, with waste drilling fluid as the test material, at 28±2°C. Comparison of results for the control and different concentrations of the waste drilling fluid were made by means of the F-statistic method. The waste drilling fluid was practically non-toxic to the two aquatic snails.