Chemical Partitioning to Foliage: The Contribution and Legacy of Davide Calamari

- DOI: http://dx.doi.org/10.1065/espr2006.01.002 Background Davide Calamari and his colleagues were among the first to appreciate that vegetation could play a key role in determining the fate and effects of organic contaminants. They conducted pioneering experiments to investigate the uptake of contaminants by plants from the atmosphere and they sought to model the observed phenomena. In the nearly two decades since there has been a marked increase in understanding of these phenomena as a result of both experimental and modelling studies. - Goal. In this study we briefly review our current understanding of chemical partitioning between foliage and air. A model in both fugacity and concentration format is described, based on that of Tolls and McLachlan (1994), in which the leaf is treated as consisting of two layers, a waxy cuticle with an underlying 'reservoir' layer, the cuticle being surrounded by an air boundary layer and containing stomata that provide direct access from the air to the 'reservoir'. The model quantifies the dynamic penetration of a defined chemical into a defined leaf as a function of time. Main Features The model is applied for illustrative purposes to a hypothetical but typical leaf for a set of illustrative chemicals to demonstrate the effect of changes in physical-chemical properties and leaf characteristics. Discussion The results are compared qualitatively with a variety of field and laboratory studies of foliage uptake and clearance of chemicals. Conclusion It is concluded that the model yields results that are generally consistent with observations. It is suggested that with appropriate parameterisation and validation, the model can contribute to an improved understanding of the process of foliage uptake from the atmosphere and to the development of an improved predictive capability.     

Methane fluxes in aerobic soils

Aerobic soils are an important sink for methane (CH₄), contributing up to 15% of global CH₄ destruction. However, the sink strength is significantly affected by land management, nitrogen (N) fertilizers and acidity. The rates of uptake from the atmosphere of both enhanced (10 ppmv) and ambient (2 ppmv) concentrations of CH₄ were measured in laboratory incubations of soil cores under controlled conditions taken from sites in the U.K. and Germany. The most rapid rates of uptake were measured in soil from deciduous woodland at pH 4 (measured in water). Extended (150 years) cultivation of land for arable crops reduced uptake rate by 85% compared to that in the same soil under an adjacent woodland. The long-term application of ammonium (NH₄)-based fertilizer, but not nitrate (NO₃)-based fertilizer, completely inhibited CH₄ uptake, but the application for the same period of farmyard manure (FYM) that contained more N than the fertilizer had no inhibitory effect. Where a combination of FYM and inorganic fertilizer was applied there was a reduction in methane uptake rate compared to plots receiving solely FYM.Autoclaving showed that the uptake of CH₄ was microbially mediated. The most likely causes of the inhibitory effects seen are (i) insufficient concentrations of CH₄ in situ to activate methane monooxygenase; (ii) the direct inhibition of CH₄ oxidation by NH _inf4 ^sup+ ions; (iii) the suppression of methanotrophs by NH₄-based fertilizers; (iv) the requirement of methanotrophs for a stable soil architecture which is incompatible with the disturbance caused by regular arable cultivation.     

爆炸性气体环境危险区域划分方法改善探讨

本文在对当前爆炸性气体环境的危险区域划分存在的主要问题及其原因分析的基础上,探讨了通过建立爆炸性气体环境危险区域计算机辅助划分平台,提高危险区域划分的可操作性,从而实现爆炸性气体环境危险区域划分方法的改善.探讨了通过运用数值计算方法,基于fluent对爆炸性气体扩散进行研究,对非对称分布场所的危险区域划分提供划分辅助.     

Measurement of organic contaminants and biological effects in Scottish waters between 1999 and 2005

Concentrations of organic contaminants were determined in sediment and fish collected annually at six sites around Scotland between 1999 and 2005, as part of the UK National Marine Monitoring Programme. Polycyclic aromatic hydrocarbons (PAHs) and chlorobiphenyls (CBs) were measured in sediment, while CBs and ethoxyresorufin-O-deethylase (EROD) activities were measured in the fish. Highest PAH concentrations in sediment were found at sites where higher coastal influences would be expected (e.g., Clyde and Solway) and four of the six sites gave PAH concentrations above OSPAR background assessment concentrations (BACs). A significant downward trend in the median total PAH concentrations, normalised to total organic carbon (TOC), was found at one of the six sites (Minches). The PAH profiles at all sites were consistent over the 6 year period, indicating that the sites are relatively stable and PAH sources are not changing. There was an indication of a greater petrogenic input on the west coast, with sediment from the Clyde, Solway and Minches having a greater proportion of 2- and 3-ring PAHs and a lower proportion of 5-ring PAHs. CB concentrations at all sites were low compared with UK estuarine sites and similar to sediment from more remote areas: however, BACs were exceeded. No significant trends were detected in either the sediment CB concentrations or patterns at any of the six sites. CB concentrations were significantly higher in fish liver collected from the Clyde. Concentrations at the other five sites were low, with the majority of samples having concentrations for the ICES7 CBs of <500 microg kg(-1) lipid weight. However, individual CB concentrations were still above the BACs. Hepatic EROD activities were measured in male plaice from 2002-2005 and were generally low (<10 pmol min(-1) mg protein(-1)). No temporal trends were detected in either CB concentrations or the EROD activity.     

Long-term fate of polycyclic aromatic hydrocarbons (PAH) in sediments from Loch Leven after closure of an aluminium smelter

An aluminium smelter discharged polycyclic aromatic hydrocarbons (PAHs) into Loch Leven on the west of Scotland from 1907 until it closed in 2000, resulting in elevated PAH concentrations in the sediment. A temporal monitoring programme to investigate any recovery in sediment concentrations began in 2004, with sampling each year until 2008 and again in 2010. Cores were also collected to investigate temporal trends over a longer time scale and to estimate the sedimentation rate in the loch. The loch is divided into two basins, and PAH concentrations were significantly higher in the upper basin, closer to the smelter, than in the lower basin. The PAH distribution and concentration ratios were consistent with a pyrolytic source of PAHs, with a high proportion of heavier parent PAHs. There was no evidence of any recovery in PAH concentrations, perhaps due to the mixing and disturbances of the sediment, and the persistence of PAHs. Concentrations of all PAHs were above the Background Assessment Concentrations (BACs) in both basins. In the lower basin only the 5- and 6-ring PAHs were above the Effects Range Low (ERL) values, but in the upper basin all but naphthalene were above the ERLs. There is therefore still an unacceptable risk of chronic effects in marine species. Concentrations decreased down the cores, falling below BACs in the deepest sections. However, ERLs were exceeded as far down the core as 30 cm for some PAHs.     

The Costs of Corrosion: A Perspective

Until recently the materials engineer relied upon a combination of his experience and the use of economic analysis to make the proper choice of materials. His economic analyses required projection of useful life, probable obsolescence, eventual cost of equipment replacement—all seasoned with future predictions on the costs of money and labor.     

Determination of chlorinated paraffins in sediments from the Firth of Clyde by gas chromatography with electron capture negative ionisation mass spectrometry and carbon skeleton analysis by gas chromatography with flame ionisation detection

Short chain chlorinated paraffins (SCCPs) are a group of persistent organic pollutants (POPs) of increasing concern, but are to date not widely investigated in the environment, largely due to the challenges involved in their quantification. Here, SCCPs were quantified in marine sediments from the Firth of Clyde, Scotland, by gas chromatography with electron capture negative ionisation mass spectrometry (GC-ECNIMS) and through carbon skeleton analysis by gas chromatography with flame ionisation detection (GC-FID), and the analytical challenges encountered are discussed. Concentrations in the sediments ranged from 0.4 to 69 μg kg⁻¹ when determined by GC-ECNIMS, and from 5.6 to 379 μg kg⁻¹ when determined by GC-FID. For 8 out of 11 samples, analysis by GC-FID gave higher results than analysis by GC-ECNIMS. Unexpected aspects of the analysis, such as the presence of high concentrations of longer chain chlorinated paraffins in the samples, are also presented.     

Mapping aerial metal deposition in metropolitan areas from tree bark: a case study in Sheffield, England

We investigated the use of metals accumulated on tree bark for mapping their deposition across metropolitan Sheffield by sampling 642 trees of three common species. Mean concentrations of metals were generally an order of magnitude greater than in samples from a remote uncontaminated site. We found trivially small differences among tree species with respect to metal concentrations on bark, and in subsequent statistical analyses did not discriminate between them. We mapped the concentrations of As, Cd and Ni by lognormal universal kriging using parameters estimated by residual maximum likelihood (REML). The concentrations of Ni and Cd were greatest close to a large steel works, their probable source, and declined markedly within 500 m of it and from there more gradually over several kilometres. Arsenic was much more evenly distributed, probably as a result of locally mined coal burned in domestic fires for many years. Tree bark seems to integrate airborne pollution over time, and our findings show that sampling and analysing it are cost-effective means of mapping and identifying sources.     

Construction and economics of a pilot/full-scale biological trickling filter reactor for the removal of volatile organic compounds from polluted air

The design and the construction of an actual 8.7-m3 pilot/full-scale biotrickling filter for waste air treatment is described and compared with a previous conceptual scale-up of a laboratory reactor. The reactor construction costs are detailed and show that about one-half of the total reactor costs ($97,000 out of $178,000) was for personnel and engineering time, whereas approximately 20% was for monitoring and control equipment. A detailed treatment cost analysis demonstrated that, for an empty bed contact time of 90 sec, the overall treatment costs (including capital charges) were as low as $8.7/1000 m3air in the case where a nonchlorinated volatile organic compound (VOC) was treated, and $14/1000 m3air for chlorinated compounds such as CH2Cl2. Comparison of these costs with conventional air pollution control techniques demonstrates excellent perspectives for more field applications of biotrickling filters. As the specific costs of building and operating biotrickling filter reactors decrease with increasing size of the reactor, the cost benefit of biotrickling filtration is expected to increase for full technical-scale bioreactors.