Aerosol light-scattering in The Netherlands

The relation between the (midday) aerosol light-scattering and the concentrations of nitrate and sulfate has been assessed at a site near the coast of the North Sea in The Netherlands. Midday was selected for the measurements because this is the time at which the aerosol is most effective in the scattering of solar radiation. Automated thermodenuders were used for the hourly measurement of the concentration of nitrate and sulfate with a lower detection limit of 0.1 μ m⁻³. The site is operational since October 1993. The first-year average dry aerosol light-scattering (measured with an integrating nephelometer at a wavelength of 525 nm) was 0.71 × 10⁻⁴ m^1̄. In arctic marine air the aerosol light-scattering was a factor of 10 lower than the average value, in polluted continental air it was up to a factor of 10 higher. The ratio of the total aerosol light-scattering to the concentration of sulfate was 20 m² g⁻¹. The contribution of nitrate to the aerosol light-scattering was higher than that of sulfate in the winter and of about equal magnitude in the summer period. In November and December of 1993, the humidity dependence of the aerosol light-scattering was investigated. Two types of (continental) aerosol were found with respect to the humidity behavior. One type showed a significant increase in light-scattering at the deliquescence points of ammonium nitrate and ammonium sulfate, with that of ammonium nitrate the most pronounced. The second type of continental aerosol did not show deliquescence, but followed the typical humidity dependence of aerosol in a supersaturated droplet state. In this latter aerosol type, nitrate dominated over sulfate. It was concluded from the study that the aerosol light-scattering in The Netherlands, in particular its humidity dependence, is governed by (ammonium) nitrate.     

Leaching study of polycyclic aromatic hydrocarbon bioavailability from a coal-derived solid product

The leaching behavior of selected four- to six-ring polycyclic aromatic hydrocarbons (PAH) from a tumorigenic coal-derived solid product was determined using three media to evaluate their potential bioavailabilities. Equilibrium PAH concentrations generally exceeded the aqueous solubilities after less than five days of leaching. PAH selectively accumulated in phospholipid vesicles at individual concentrations greater than 1 μg/g, which is ca. 100-fold over that in the bulk aqueous leachate. The results suggest that the PAH are quite bioavailable from the solid product, and that cell membranes can be exposed to considerable quantities of these PAH over an extended bioassay.     

Perspectives of a large scale environmental survey for chlorinated dioiins: water analyses

During 1983 and 1984, The Dow Chemical Company conducted a study to determine the extent of dioxin contamination at its Midland, Michigan plant and the surrounding area. The primary objectives of this study were to identify, rank order, and when possible quantify potential sources of dioxins to the environment and also to determine the extent of contamination in areas affected by the Dow facility. Early in the study, it was estimated that approximately 0.6g/year of 2378-TCDD was being emitted in 2.5 × 10¹⁰L of wastewater effluent. Data will describe observed sources of TCDD (both current and historical), environmental levels, existing water treatment methods, control measures taken, and future improvements on the water system to reduce TCDD in the effluent.     

Pharmacokinetics of 2,3,7,8-TCDD in man

A single dose of 1.14 ng of ³H-2,3,7,8-TCDD/kg bw, ingested by a human volunteer, was absorbed almost completely from the intestine (> 87 %). The resulting adipose tissue levels, measured 13 and 69 days after dosage were 3.09±0.05 and 2.85±0.28 ppt, respectively. The dioxin was cleared from the body with a half life of elimination of 2120 days.     

Dibutylphthalate degradation in estuarine and freshwater sites

Biotic and abiotic degradation of di-$\text{n}$-butylphthalate (DBP) in water and sediment/water systems from six different sites was investigated under laboratory conditions. DBP disappearance was rapid in all microbially active systems and substantially reduced under sterile conditions. Adaptation of microbial populations to degrade DBP was indicated in six of nine evaluations conducted. The presence of sediment significantly increased biodegradation rates in five of the six sites.     

Elimination of 2-halogenobenzanilides

The elimination of 2-halogenobenzanilides has been studied in the rat, over 75% of the oral dose being excreted in 3 days. The higher the molecular weight of the compound, the more important was the faecal elimination route. No such association was seen for biliary secretion.     

Distribution of organotin compounds in tissues of mussels Mytilus edulis and clams Mya arenaria

Concentrations and composition of butyltin (BT) and phenyltin (PT) compounds were compared in tissues of mussels Mytilus edulis and clams Mya arenaria collected from the Mersey Estuary. Tributyltin (TBT) concentrations were consistently highest in digestive gland and low in muscular tissues such as siphons (Mya) and adductor muscle (Mytilus). Lowest concentrations were found in the periostracum surrounding the siphons of Mya. Ratios of monobutyltin (MBT), dibutyltin (DBT) and TBT to total BT content of Mytilus tissues were in the ranges 25-34%, 21-28% and 44-51%, respectively. Much higher proportions of TBT:total BT were characteristic of Mya (>80% in the digestive gland, remaining tissue and gonad) implying that slow degradation rates account for the relatively high levels of TBT in this species. TPT was the only phenyltin compound detected (albeit at relatively low levels), and, like TBT, was present in highest concentrations in the digestive gland of clams--suggesting an important dietary component in the accumulation of OTs in these bivalves.     

A laboratory study of the mineralization and binding of 14C-labeled herbicide rimsulfuron in a rendzina soil.

The fate of pyrimidine-2-14C-rimsulfuron in a rendzina soil was investigated using a laboratory microcosm approach. Measurement of CO2 evolution suggested that rimsulfuron applied at 5 times the recommended dose did not affect soil respiration. Under abiotic conditions, no mineralization of 14C-rimsulfuron into 14C-CO2 occurred and under biotic ones it was very low reaching 0.75% of the applied 14C-rimsulfuron after 246 days of incubation. The analysis of data showed that a three-half order model provided the best fit for the mineralization curve. Extractable 14C-residues decreased over time to 70-80% of the applied 14C-rimsulfuron at the end of the incubation. After 246 days of incubation, non extractable residues (NER) accounted for up to 24.7% of the applied 14C-rimsulfuron and were distributed according to organic carbon in soil size fractions, suggesting a progressive incorporation process of NER to soil humus.