An analysis of the environmental mobility of radiostrontium from weapons testing and Chernobyl in Finnish river catchments

The mobility of radiostrontium within the Arctic environment and surrounding area has been studied by analysing the mobility of 90Sr in river catchments that are within Finland. The environmental mobility of 90Sr deposited by both nuclear weapons testing and the Chernobyl accident has been investigated in five Finnish river catchments. Different models assessing the time-dependent mobility of 90Sr have been evaluated. No significant differences were found between the mobility of 90Sr from nuclear weapons tests and from the Chernobyl accident. Model parameters obtained by fitting to the measurements of the deposition and runoff rates of the nuclear weapons test fallout gave predictions which were consistent with the mid- and long-term contamination by the Chernobyl fallout. A comparison of 90Sr with 137Cs showed that they had similar mobility on deposition but, as time passed, the relative mobility of 90Sr increased with respect to 137Cs over a period of 5-8 years. Once the relative migration of 90Sr with respect to 137Cs reached equilibrium, its runoff rate was, on average, approximately an order of magnitude greater than 137Cs.     

The specification of sustainable urban transport strategies

Transport strategies have been developed for nine European cities to achieve optimum performance in terms of a range of objective functions. The functions selected represent economic efficiency, sustainability and a combination of these. The strategies have been based on combinations of a standard set of policy instruments, including public transport infrastructure, frequency and fares, road capacity increases, low cost road pricing and parking charges. The optimisation method is described, and results presented. The reactions of city authorities to the proposed strategies are discussed and implications for transport policy outlined.     

Hazards equal trips or alarms or both

Anyone who has been involved in the application of IEC 61508 and IEC 61511 by undertaking the Safety Integrity Level (SIL) determination for Safety Instrumented Systems (SIS) will appreciate the amount of effort and tenacity that is required to undertake the task. SIL determination of Safety Instrumented Systems requires considerable commitment and tenacity to get the job done, but it is like climbing to the top of a hill only to be faced with a mountain when we come to consider what is involved in reviewing or configuring a typical alarm system.A medium sized process facility may have a few hundred or so primary Safety Instrumented Functions (SIF) or trips configured into a Safety Instrumented System, but the number of alarms configured into a process control system (PCS), that need to be assessed and prioritised, can often run into the thousands.There is synergy between safety instrumented functions and alarms because they both make a contribution to reduce the risk of having unwanted events, and both need an assigned appropriate criticality.This paper details various methods of criticality assessment which have been successfully applied to set the appropriate priority, identify the critical alarms that need to be upgraded to trips and to rationalise those of no value. It will also cover the use of software tools which can significantly reduce the effort involved in this process.     

A new method to account for the depth distribution of 137Cs in soils in the calculation of external radiation dose-rate

This work reports a new method for calculating the external dose-rate as a function of height above land that has been contaminated with a surface deposition of (137)Cs. Unlike previous work this method accounts for vertical migration of (137)Cs using the Advection Dispersion Equation (ADE) with appropriate parameters. The results have been successfully verified with field measurements from the (137)Cs contaminated regions within the Republic of Belarus. The method also correctly predicts the observed variation of dose-rate with elevation above the soil surface and it is shown how this method can be used to predict the reduction in surface dose-rate after remediation measures such as deep ploughing have taken place.     

Dioxins: Sources of environmental load and human exposure

Polychlorinated dibenzo‐p‐dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) represent a class of tricylic, almost planar, aromatic ethers with 1 to 8 chlorine atoms. Congeners with substituents in the positions 2, 3, 7, and 8 are of special concern due to their toxicity, stability, and persistence. These compounds have been identified in almost all environmental compartments and humans.

Dioxins are a potent carcinogen for animals and—at the moment—considered a probable carcinogen for humans. Actual toxicological risk assessment for humans are based on 2,3,7,8‐Cl4DD carcinogenicity studies on rodents. Tumorigenic effects were found for 2 strains of rats and 2 strains of mice. All dioxins and furans elicit common toxic and biological responses, starting with a specific binding to a protein receptor, but existing epidemiologic data do not provide definitive data on human health effects.

Toxicity equivalency factors (TEFs) have been developed by several agencies as a provisional method of risk assessment for complex mixtures of PCDD/PCDF.

Dioxins have never been produced intentionally and have never served any useful purpose. They are formed in trace amounts as by‐products in industrial processes; for instance within the chemical industry, of the pulp and paper industry, metallurgical processes, processes for reactivation of granular carbon, dry cleaning, and the manufacture of flame‐retarded plastics.

The main pathway for dioxins to enter the environment is via combustion processes. Incineration is of special importance since PCDD/PCDF are directly released to the atmosphere from either stationary sources, such as municipal, hazardous and hospital waste incinerators, the combustion of sewage sludge, and scrap metal recycling, or diffuse sources, e.g. automobile exhausts, private home heating with fossil fuels, forest fires, and cigarette smoking. Furthermore, fires with PCB and PVC have additionally contributed to the total dioxin load. The emission gases can undergo long‐range transport, so that dioxins have been found even in remote areas.

Besides the two primary sources (industrial processes and combustion processes) the release of dioxins from contaminated areas and waste dumps via the leachate and the application of sewage sludge for fertilization represents a third source of PCDD/PCDF.

After more than 10 years of dioxin research the most important sources of PCDD/PCDF have been identified and analytical methods have been developed for their quantification in trace levels and in complex matrices.

Various efforts have been undertaken to reduce the emission of dioxins: for example, optimization of combustion processes for municipal waste incineration, use of unleaded gasoline, ban of chemicals, such as polychlorinated biphenyls (PCBs) and pentachlorophenol (PCP). More detail is provided in the pulp and paper section where changes have been initiated to significantly reduce the sources of PCDD/PCDF.

However, relatively little is known about transport and transformation processes, so only rough estimates can be made. Photodegradation has been found to be the primary process for 2,3,7,8‐Cl4DD breakdown. A half‐life of 3–4 days has been estimated for photochemical degradation under oxidative conditions. Field studies on the fate of 2,3,7,8‐Cl4DD in soil gave a half‐life of 9.1 (Seveso) and 12 years (under special conditions: sand, erosion), respectively. Biodegradation seems to be negligible. Transfer factors soil‐plants for PCDD/PCDF have been determined—with a high degree of uncertainty—to be less than 0.1.

Human exposure primarily occurs via ingestion whereas inhalation is a minor pathway. Dermal absorption can be neglected although skin contact to polluted surfaces may occur. Due to the lipophilicity of PCDD/PCDF and their potential for accumulation, foods such as meat and especially dairy products contribute most to the dioxin body burden of humans.

Both national agencies and international organizations have recognized the significance of this problem and as a result have initiated regulations, recommendations and research programmes (1) to understand where and how PCDD/PCDF are formed, (2) to reduce their impact on the environment and to humans, and (3) to start remedial action on contaminated areas.     

Measuring dissolved organic carbon δ13C in freshwaters using total organic carbon cavity ring-down spectroscopy (TOC-CRDS)

This article reports the first application of coupled total organic carbon cavity ring-down spectroscopy (TOC-CRDS) for the analysis of the ??¹³C signature of dissolved organic carbon (DOC) in freshwater samples. DOC represents a major, dynamic component of the global carbon cycle. The export of DOC from soils into rivers and groundwaters may be highly climate sensitive, and much of this export may occur in ephemeral fluxes. Thus, a robust, simple and inexpensive method for the continuous determination of DOC concentration and quality is urgently needed. We detail recent advances made in the analysis of the ??¹³C signature of DOC using a TOC-CRDS system optimised for the analysis of DOC with natural abundances greater than 2.5?mg?L^?1 with no sample pre-concentration required and sample volumes of 40?mL. Precision between replicated samples was comparable to conventional analysis by gas-source isotope ratio mass spectrometry, yielding ??¹³C values with standard deviations of?±?0.5??? for DOC concentrations higher than 1.5?mg?L^?1. The utility of this technique for the analysis of DOC in samples with a broad range of compositions and concentrations (2.5?C25?mg?L^?1 DOC) is demonstrated. Since DOC ??¹³C can be measured continuously, ca. 45?min per measurement, this method enables the online monitoring of DOC in river water, water intakes and treated waters, allowing changes in DOC fluxes to be monitored in real time.