Impact of sulphur dioxide exposure on conidial germination of powdery mildew fungi

The impact of sulphur dioxide, in two different concentrations (286 microg m(-3) and 571 microg m(-3)) for various exposure periods, on conidial germination of some powdery mildew fungi was investigated in artificial treatment conditions. SO(2) in general was inhibitory for conidial germination of all the studied powdery mildew fungi and the species did not differ much from each other in their sensitivity to SO(2). The per cent conidial germination was increasingly inhibited with an increase in the concentration of SO(2). The concentration of SO(2) and the exposure period were important determinants of the inhibitory effect.     

Impact of repeated application on the binding and persistence of [14C]-DDT and [14C]-HCH in a tropical soil

An Indian sandy loam soil was initially treated with 1 kg a.i. ha(-1) of either [(14)C]-p,p'-DDT or [(14)C]-gamma-HCH during winter. DDT concentration after 30 days declined to 75.3%, which included 2.1% soil-bound residues. After 150 days, DDT levels further decreased to 42.4% with a concomitant increase in bound residues amounting to 5.9%. Identical treatment with HCH caused the residue levels to be reduced to 67.4 and 23.6%, after 30 and 150 days, respectively. During this period, the soil-bound residues of HCH increased from 5.2 to 12.8%. Repeat application to pre-treated soils in summer and subsequent field exposure for 30 days reduced the concentration of DDT to 52.1% and that of HCH to 42.4% of the total concentration following the second treatment. In parallel control experiments, which received only a single treatment, DDT levels declined to 61.3%, while HCH slumped to 45.3%, indicating a slower dissipation rate than in the corresponding repeated treatments. In repeat experiments, the soil-bound residues of DDT and HCH showed only a 1.07 to 1.08-fold increase in 30 days, as compared to three to ten-times increase in the control experiments. The results amply demonstrate that pre-treatment of tropical soils with DDT or HCH enhances their rate of dissipation and significantly reduce the formation of their soil-bound residues.     

Criteria for the evaluation of dioxins in the environment

In FRG and other countries unequivocal criteria for the limitation of dioxins (PCDD's/PCDF's) in food like vegetables and fruits are lacking. These have to be directly associated with the limitation of dioxins in the soil and the deposition of particulate matter as the two main pathways for plant contamination. Based on recent investigations in the vicinity of cable-waste incinerators in Northrhine-Westphalia with comparatively high contents of dioxins in garden plants and soils and other sources of dioxins, considerations are given for the establishment of the criteria urgently needed.     

Field studies of ethoprop movement and degradation in two Florida soils

Unsaturated- and saturated-zone field studies were conducted under two different agricultural conditions in Florida, U.S.A., to measure the movement and degradation of ethoprop.When ethoprop was applied to a sand soil in an orange grove located on the Florida central ridge, soil residues declined with a half-life of 13 days to near the limit of detection (0.01 μg g⁻¹ within 2 months. Ethoprop residues were generally contained in the upper 2 m of soil. Although low levels of ethoprop were found in four groundwater samples within the first 3 months after application, the cause of these isolated and transient residues could not be determined. The data show that there was no widespread plume of ethoprop residues beneath or downgradient from the treated area.On a flatwood soil on the west coast of Florida, ethoprop was incorporated into raised beds and protected by a plastic mulch in which tomatoes were grown. When the plastic mulch was present, ethoprop soil residues declined with a half-life of 40 days and were confined to the upper 0.3 m of soil. After the mulch was removed at crop harvest, the remaining ethoprop dissipated with a half-life of 12 days. Groundwater residues in excess of 1 μg L⁻¹ were confined to a single sample collected after the well had been damaged during a rototilling operation. Resides of < 1 μg L⁻¹ were present in three later samples from this well. At the sampling interval where the highest residues were detected in the damaged well, ethoprop residues of < 1 μg L⁻¹ were also found in three other wells but no residues were detected in these wells in later samples.     

A natural analogue of high-pH cement pore waters from the Maqarin area of northern Jordan: Comparison of predicted and observed trace-element chemistry of uranium and selenium

Current design concepts for low-/intermediate-level radioactive waste disposal in many countries involve emplacement underground in a cementitious repository. The highly alkaline groundwaters at Maqarin, Jordan, are a good analogue for the cementitious pore waters that will be present within such a repository. A geochemical modelling study of these groundwaters has been carried out in order to test the applicability of equilibrium models in geochemical programs and their associated thermodynamic databases in such hyperalkaline conditions. This was achieved by comparison of elemental solubilities and speciations predicted by the programs with observations in the natural system. Five organisations took part in the study: AEA Technology, U.K.; Chalmers University of Technology, Sweden; MBT Tecnología Ambiental, Spain; Nagra, Switzerland; and SKB, Sweden. The modelling study was coordinated by the University of Berne.The results of the study showed good agreement between the predictions of the programs employed. Comparison of the observed solids with those predicted by the models has allowed limited validation of the databases. The results for U and Se are presented here.     

Secondary air pollutants

The study has been performed in a supposedly clean-air region of a Northern Finnish forest with a homogeneous stand of Scots pine. Stomatal epicuticular wax layer erosion is described using a classification system of five erosion stages. The percentage of stomatal wax within each erosion stage is calculated and the results are treated statistically, which makes the morphological study of the needle surface semi-quantitative. Severe wax degradation has already been found in the current year, increasing with the age of the needles. In this area, the wax layer erosion is correlated with secondary air pollutants, as analyses have shown high trichloroacetate (TCA) levels in needles from the same trees. The wax layer analyses are in accordance with earlier findings which have demonstrated differences in tolerance to TCA.