Exchange of sulfur pollution between Bulgaria and Greece

The EMAP model (Eulerian Model for Air Pollution) is applied for calculating the sulfur concentration and deposition fields for 1995 as based upon Bulgarian and Greek sources. The country-to-country budgets show that about 4% of the sulfur oxides emitted by Bulgaria are deposited over Greek territory, estimated at 28 kt S. Only 2% of sulfur compounds emitted by Greece are deposited over Bulgaria, estimated at 6.2 kt S for 1995. This data is in agreement with EMEP/MSC-W estimates and provides more details concerning time and space. The results can be used in decision-making, negotiating and the development of contamination strategies.     

Photocatalytic degradation of gaseous perchloroethylene: products and pathway

Batch photocatalytic degradation of 1000-ppm gaseous perchloroethylene (PCE) was conducted with UV irradiation such that nearly 100% was decomposed within 10 min. The main intermediate and final product were identified as trichloroacetylchloride (TCAC) and hydrogen chloride (HCl), respectively, and minor ones as dichloroacetic acid (DCAC), monochloroacetic acid (MCAC), carbon tetrachloride, chloroform, and phosgene. More than 90% of Cl- equivalent, i.e., the sum of the chlorine number in PCE, intermediates, and HCl, was compensated for during the time of PCE degradation; a result indicating that no other major chlorinated intermediates are present during the time of PCE degradation. In a similar experiment, 500 ppm of gaseous TCAC degraded into HCl within 3 h without producing DCAC or MCAC, where like PCE, more than 90% of Cl- equivalent, i.e., the sum of the chlorine number in TCAC and HCl, was compensated for during time of TCAC degradation. Accordingly, gaseous PCE is concluded to predominantly follow a degradation pathway of PCE --> TCAC --> HCl.     

Accumulation of silver in the liver of three species of pinnipeds

Silver in the three species of pinnipeds [northern fur seal (Callorhinus ursinus), Steller sea lion (Eumetopias jubatus), and harbor seal (Phoca vitulina)] caught in the North Pacific Ocean were analyzed using inductively coupled plasma-mass spectrometry, in order to understand accumulation and distribution of silver in pinnipeds. In northern fur seals, relatively high concentrations of silver were observed in the liver and body hair. Some 70% of the silver burden was concentrated in the liver. Hepatic silver concentrations were significantly correlated to age in northern fur seals (r = 0.766, P < 0.001, n = 49) and Steller sea lions (r = 0.496, P < 0.01, n = 28). Levels of silver concentrations per wet weight (microgram g-1) in the three pinnipeds ranged from 0.04 to 0.55 for northern fur seals, from 0.1 to 1.04 for Steller sea lions and from 0.03 to 0.83 for harbor seals. Silver concentrations in liver for all pinnipeds were significantly correlated with mercury, and selenium (P < 0.001). Molar ratios between silver to selenium approximated 1:180 in northern fur seals, 1:120 in Steller sea lions, and 1:60 in harbor seals. The silver-mercury molar ratios were approximately 1:170 in northern fur seals, and 1:80 both in the other species. Increase in silver accumulation in the liver was caused by the retention in nuclei and mitochondria fraction together with mercury and selenium in the cells of northern fur seals.     

The use of amino compounds for binding 2,4,6-trinitrotoluene in water

Sites polluted with 2,4,6-trinitrotoluene (TNT) constitute a worldwide problem. In this work, chemical reactions for binding TNT to amino-compounds are proposed as an initial step for developing new remediation techniques to clean-up groundwater and soils contaminated with TNT. Indeed, addition of aniline and an amino acid-like cysteine caused a decrease in free TNT of 86% and 68-100%, respectively. Using 13C-NMR spectroscopy, it was shown that TNT chemically forms a Meisenheimer complex with cysteine and aniline in 1/1 (by vol.) H2O/d6-acetone.     

Oxidation of triphenylarsine to triphenylarsineoxide by Trichoderma harzianum and other fungi

Arsenic resistant strains of bacteria and fungi were isolated from soil contaminated by chemical warfare agents. Until now, no metabolic products of microbial attack against the phenyl residues of the model substrate triphenylarsine (TP) were found if it was incubated together with these strains in liquid culture assays. However, one of the isolated fungi, Trichoderma harzianum As 11, was found to oxidize TP to triphenylarsineoxide (TPO). The yeast Trichosporon mucoides SBUG 801 and the white-rot fungus Phanerochaete chrysosporium were also able to oxidize the As(III) in TP. In addition, P. chrysosporium transformed phenylarsineoxide (PAO) to phenylarsonic acid (PAA) under O2-atmosphere. By means of a respirometer system, the oxidation of TP by T. harzianum As 11 was confirmed by a significantly higher consumption of oxygen in the presence of these compounds. HPLC analysis of the oxidation products TPO and PAA in the medium of the assays provided evidence for the transfer reaction of As(III) to As(V) in organic bonds. The oxidation products TPO and PAA are more hydrophilic than TP and PAO. Therefore, it was concluded that particular fungi contribute to the mobilization of arsenic in soil contaminated by chemical warfare agents.     

Insecticide residues in cotton crop soil

Dimethoate, monocrotophos, triazophos, deltamethrin, cypermethrin and endosulfan were applied to a cotton crop soil located at Nurpur village, Punjab, India. The insecticides were applied sequentially at recommended dosages in cotton fields by foliar application in 1995, 1996 and 1998. Soil samples were collected from the cotton crop farms and extracted with acetone. The extracted material was analysed by a gas liquid chromatograph (GLC) equipped with an 63Ni electron-capture detector (ECD-63Ni). Recovery data was obtained by fortifying soil with insecticide. The average recoveries from the fortified soil samples were 76-92% for organophosphorous compounds and 90-98% for synthetic pyrethroids and organochlorines. The results showed that the insecticide residues under study were present in the range of 1.16 to 41.97 ng g(-1) d.wt.soil. The pattern of dissipation of the insecticides used was similar for the duration of the crop. Half lives of the insecticides ranged from 7 to 22 days. Except endosulfan none of the other insecticides used were leached below 15 cm. Endosulfan was found to be rapidly degraded in the soil and formed a sulfate metabolite. Persistence and dissipation pattern in soils with history of exposure to the insecticide compared to non-history soils were similar.     

Ozone predictions in Atlanta, Georgia: analysis of the 1999 ozone season

Ozone prediction has become an important activity in many U.S. ozone nonattainment areas. In this study, we describe the ozone prediction program in the Atlanta metropolitan area and analyze the performance of this program during the 1999 ozone-forecasting season. From May to September, a team of 10 air quality regulators, meteorologists, and atmospheric scientists made a daily prediction of the next-day maximum 8-hr average ozone concentration. The daily forecast was made aided by two linear regression models, a 3-dimensional air quality model, and the no-skill ozone persistence model. The team's performance is compared with the numerical models using several numerical indicators. Our analysis indicated that (1) the team correctly predicted next-day peak ozone concentrations 84% of the time, (2) the two linear regression models had a better performance than a 3-dimensional air quality model, (3) persistence was a strong predictor of ozone concentrations with a performance of 78%, and (4) about half of the team's wrong predictions could be prevented with improved meteorological predictions.     

Response of mosses to the heavy metal deposition in Poland--an overview

Concentrations of heavy metals (Cd, Cr, Cu, Fe, Ni, Pb, Zn) in Pleurozium schreberi (Brid.) Mitt., a common moss species, were used to indicate relative levels of atmospheric deposition in Poland in the years 1975-1998. Spatial and temporal differences in the heavy metal concentrations in mosses were found. The highest concentration of heavy metals was recorded in the moss samples from the southern, most industrialised part of the country, and the lowest from north-eastern Poland. A significant decrease of heavy metals over 20 years (1975-1998) was found.     

The use of sediment analogues to study the uptake of pollutants by chironomid larvae

A technique is described that uses artificial resin beads with known surface properties to investigate the factors influencing the bioaccumulation of pollutants from sediments. One advantage of this technique is that it provides a standard procedure against which it is possible to calibrate natural sediments with their diverse properties. The method has been used on third instar larvae of the midge Chironomus riparius and the results are compared with previous studies on the worm Lumbriculus variegatus. The use of a standard test using resin beads as a substitute for natural sediment allows comparisons to be made between species and substrates. Thus, the bioaccumulation factors for the midge larvae are much smaller than those of the worm and this correlates with the ability of the insect larva to detoxify many pollutants. It is also possible to use the test to identify if ingestion of the sediment increases the bioaccumulation of contaminants and whether this involves the release of pollutants by digestive processes or not.     

The sensitivity of PM2.5 source-receptor relationships to atmospheric chemistry and transport in a three-dimensional air quality model

Air quality model simulations constitute an effective approach to developing source-receptor relationships (so-called transfer coefficients in the risk analysis framework) because a significant fraction of particulate matter (particularly PM2.5) is secondary (i.e., formed in the atmosphere) and, therefore, depends on the atmospheric chemistry of the airshed. In this study, we have used a comprehensive three-dimensional air quality model for PM2.5 (SAQM-AERO) to compare three approaches to generating episodic transfer coefficients for several source regions in the Los Angeles Basin. First, transfer coefficients were developed by conducting PM2.5 SAQM-AERO simulations with reduced emissions of one of four precursors (i.e., primary PM, sulfur dioxide (SO2), oxides of nitrogen (NOx), and volatile organic compounds) from each source region. Next, we calculated transfer coefficients using two other methods: (1) a simplified chemistry for PM2.5 formation, and (2) simplifying assumptions on transport using information limited to basin-wide emission reductions. Transfer coefficients obtained with the simplified chemistry were similar to those obtained with the comprehensive model for VOC emission changes but differed for NOx and SOz emission changes. The differences were due to the parameterization of the rates of secondary PM formation in the simplified chemistry. In 90% of the cases, transfer coefficients estimated using only basin-wide information were within a factor of two of those obtained with the explicit source-receptor simulations conducted with the comprehensive model. The best agreement was obtained for VOC emission changes; poor agreement was obtained for primary PM2.5.