Polychlorinated biphenyls in digested UK sewage sludges

Twelve sewage sludges from rural, urban and industrial waste water treatment works in north west England were analysed for polychlorinated biphenyls by capillary GC-ECD. The total polychlorinated biphenyl content ranged between 106 to 712 μg/kg, with a mean of 292 μg/kg. Di- and penta-chlorinated congeners made the greatest contribution to the ΣPCB concentrations at most sites. The 6 IUPAC congeners were found in the following order of abundance, 101>180>153>138>52>28. Industrial inputs would appear to influence levels of ΣPCB in the sludge.

If these sludges were ploughed into arable land at typical rates only a slight elevation in soil ΣPCB levels would result. Alternatively, if the same quantity of sludge were applied to the surface of pasture grassland, significant elevations in the potential transfer of PCBs to grazing livestock may result.     

The global re-cycling of persistent organic pollutants is strongly retarded by soils

'Persistent organic pollutants' (POPs) are semi-volatile, mobile in the environment and bioaccumulate. Their toxicity and propensity for long-range atmospheric transport (LRAT) has led to international bans/restrictions on their use/release. LRAT of POPs may occur by a 'single hop' or repeated temperature-driven air-surface exchange. It has been hypothesised that this will result in global fractionation and distillation-with condensation and accumulation in polar regions. Polychlorinated biphenyls (PCBs)--industrial chemicals banned/restricted in the 1970s--provide a classic illustration of POP behaviour. A latitudinally-segmented global PCB inventory has been produced, which shows that approximately 86% of the 1.3 x 10(6) tonnes produced was used in the temperate industrial zone of the northern hemisphere. A global survey of background surface soils gives evidence for 'fractionation' of PCBs. More significantly, however, very little of the total inventory has 'made the journey' via primary emission and/or air-surface exchange and LRAT out of the heavily populated source regions, in the 70 years since PCBs were first produced. Soils generally occlude PCBs, especially soils with dynamic turnover of C/bioturbation/burial mechanisms. This limits the fraction of PCBs available for repeated air-soil exchange. The forested soils of the northern hemisphere, and other C-rich soils, appear to be playing an important role in 'protecting' the Arctic from the advective supply of POPs. Whilst investigations on POPs in remote environments are important, it is imperative that researchers also seek to better understand their release from sources, persistence in source regions, and the significant loss mechanisms/global sinks of these compounds, if they wish to predict future trends.     

Estimation of PCDD/F distribution and fluxes in the Venice Lagoon,Italy: combining measurement and modelling approaches

The available experimental information on the occurrence of PCDD/Fs in the Venice Lagoon, Italy, was compiled and used to calculate fugacities for the environmental compartments of sediment, suspended particulate matter (SPM), water and air and then used to estimate fugacity ratios and assess the likely net direction of flux between media. The bottom sediment: SPM fugacity ratios for different PCDD/Fs indicate conditions close to equilibrium, suggestive of the close coupling of SPM with re-suspended sediment. Sediment/water and the sediment/air fugacity ratios suggest that net flux directions vary depending on the congener and the location within the lagoon. Net sediment-water-air movement (i.e. re-mobilisation/volatilisation) is suggested for the lighter congeners from the industrial canals, where the highest PCDD/F concentrations in the lagoon occur. The tendency to volatilise increases with decreasing congener molecular weight. In contrast, net deposition (air-water-sediment) appears to be occurring for the heaviest (hepta- and octa-) substituted PCDD/Fs. OCDF represents a marker of the industrial district of the lagoon, decreasing in concentration and as a fraction of total PCDD/Fs with increasing distance. The fugacity-based quantitative water air sediment interaction (QWASI) mass-balance model was applied to the central part of the lagoon. The key parameters for the determination of the model output, identified by a sensitivity analysis, were: the sediment active depth, the sediment re-suspension and deposition rates, and the total input of PCDD/Fs to the system. The QWASI model also indicates the tendency for the lighter PCDD/Fs to be released from surface sediment to the water column.     

Evidence for the "grasshopper" effect and fractionation during long-range atmospheric transport of organic contaminants

Although there is indisputable evidence that long-range atmospheric transport (LRAT) of organic contaminants occurs on a global scale, uncertainties remain about the detailed mechanism and extent of this phenomenon as well as the physical-chemical properties which facilitate LRAT. In this study, we discuss how mass balance models and monitoring data can contribute to a fuller understanding of the mechanism and extent of LRAT. Specifically we address the issues of "grasshopping" or "hopping" (the extent to which molecules are subject to multiple hops as distinct from a single emission-deposition event) and "global fractionation" (the differing behavior of chemicals as they are transported). It is shown that simple mass balance models can be used to assist the interpretation of monitoring data while also providing an instrument that can be used to assess the LRAT potential and the extent of hopping that organic substances may experience. The available evidence supports the notion that many persistent organic pollutants experience varying degrees of "hopping" during their environmental journey and as a consequence become fractionated with distance from source.     

Summer-time distribution of air pollutants in Sequoia National Park, California

Concentrations of air pollutants were monitored during the May November 1999 period on a network of forested sites in Sequoia National Park, California. Measurements were conducted with: (1) active monitors for nitric oxide (NO), nitrogen dioxide (NO2) and ozone (O3); (2) honeycomb denuder/filter pack systems for nitric acid vapor (HNO3), nitrous acid vapor (HNO2), ammonia (NH3), sulfur dioxide (SO2), particulate nitrate (NO3-), ammonium (NH4+), and sulfate (SO4(2-)); and (3) passive samplers for O3, HNO3 and NO2. Elevated concentrations of O3 (seasonal means 41-71 ppb), HNO3 (seasonal means 0.4-2.9 microg/m3), NH3 (seasonal means 1.6-4.5 microg/m3), NO3 (1.1-2.0 microg/m3) and NH4+ (1.0-1.9 microg/m3) were determined. Concentrations of other pollutants were low. With increasing elevation and distance from the pollution source area of O3, NH3 and HNO3 concentrations decreased. Ammonia and NH4+ were dominant N pollutants indicating strong influence of agricultural emissions on forests and other ecosystems of the Sequoia National Park.     

Bound pesticide residues in soils: a review

This article is a review of the current state of knowledge regarding the formation and biological/environmental significance of bound pesticide residues in soils. We begin by defining various terms used in our discussions and identifying the types/classes of pesticides which may be added to soil and interact with it. We then consider various soil properties and aspects of land management which will influence the nature and degree of the soil-pesticide association and discuss the possible physical and chemical binding mechanisms. We then move on to consider the role of microorganisms and other forms of soil biota in bound residue formation and the bioavailability of soil-borne pesticide residues. The review ends with a consideration of the significance of bound pesticide residues.     

Methods for the analysis of PCBs in human food, faeces and serum.

A method was developed to determine trace concentrations of a range of individual PCB congeners in biological samples (serum, food and faeces) using GC-MS, to prepare a mass balance of PCBs in humans. A simple method for the analysis of PCBs in human serum, which excluded an extraction step, was first employed. Results indicated that the recoveries of 13C12 PCB spikes were variable. A soxhlet extraction step was added and was found to be efficient and reproducible. A quality control routine and method validation results are presented. In batch tests of the methods presented it was found that the serum analysis method gave within batch mean 13C12 spike recoveries of 98-120% and standard deviations between 6 and 20%. The food/faeces analysis method gave within-batch mean 13C12 spike recoveries of 88-100%, and within batch standard deviations between 4 and 12%. The batch to batch mean recovery for serum analysis was 100%, with an RSD of 9% for high spikes and 10% for low spikes. For food/faeces analysis the batch to batch average recovery was 110%, with an RSD of 5% for high spikes and 9% for low spikes.     

Development and Evaluation of a Multiplexed Real-Time TaqMan RT-PCR Assay with a Sample Process Control for Detection of F-specific RNA Coliphage Genogroups I and IV

There are increasing concerns of zoonotic transmission of some animal enteric viruses, such as calicivirus, hepatitis E virus, and rotavirus, which are closely related to human pathogenic strains. Most enteric viruses are detected by molecular techniques because they cannot be cultured. Surrogates such as F-RNA coliphages are cultivable but few molecular methods exist. Individual real-time TaqMan RT-PCR assays for the replicase gene of F-RNA coliphage genogroups I and IV were developed and multiplexed with a real-time TaqMan RT-PCR assay for feline calicivirus as a sample process control for the simultaneous detection and enumeration of genogroup I and IV F-RNA coliphages. Genogroup IV were successfully detected with the multiplexed assay in 80% of fecal samples that contained F-RNA coliphage levels ≥3.2 log plaque forming units (pfu). F-RNA coliphage were at or below the limit of detection in most fecal samples when levels were ≤4 log pfu/g.     

Cover crop effects on nitrous oxide emission from a manure-treated Mollisol

Agriculture contributes 40–60% of the total annual N₂O emissions to the atmosphere. Development of management practices to reduce these emissions would have a significant impact on greenhouse gas levels. Non-leguminous cover crops are efficient scavengers of residual soil NO₃, thereby reducing leaching losses. However, the effect of a grass cover crop on N₂O emissions from soil receiving liquid swine manure has not been evaluated. This study investigated: (i) the temporal patterns of N₂O emissions following addition of swine manure slurry in a laboratory setting under fluctuating soil moisture regimes; (ii) assessed the potential of a rye (Secale cereale L.) cover crop to decrease N₂O emissions under these conditions; and (iii) quantified field N₂O emissions in response to either spring applied urea ammonium nitrate (UAN) or different rates of fall-applied liquid swine manure, in the presence or absence of a rye/oat winter cover crop. Laboratory experiments investigating cover crop effects N₂O emissions were performed in a controlled environment chamber programmed for a 14 h light period, 18 °C day temperature, and 15 °C night temperature. Treatments with or without a living rye cover crop were treated with either: (i) no manure; (ii) a phosphorus-based manure application rate (low manure): or (iii) a nitrogen-based manure application rate (high manure). We observed a significant reduction in N₂O emissions in the presence of the rye cover crop. Field experiments were performed on a fine-loamy soil in Central Iowa from October 12, 2005 to October 2, 2006. We observed no significant effect of the cover crop on cumulative N₂O emissions in the field. The primary factor influencing N₂O emission was N application rate, regardless of form or timing. The response of N₂O emission to N additions was non-linear, with progressively more N₂O emitted with increasing N application. These results indicate that while cover crops have the potential to reduce N₂O emissions, N application rate may be the overriding factor.