Assessment of spatial variation of cesium-137 in small catchments

Surface contamination by bomb-derived and Chernobyl-derived 137Cs has been subject to changes due to physical decay and lateral transport of contaminated soil particles, which have resulted in an on-going transfer of radionuclides from terrestrial ecosystems to surface water, river bed sediments, and flood plains. Knowledge of the different sources of spatial variation of 137Cs is particularly essential for estimating 137Cs transfer to fluvial systems and for successfully applying 137Cs as an environmental tracer in soil erosion studies. This study combined a straightforward sediment redistribution model and geostatistical interpolation of point samples of 137Cs activities in soil to distinguish the effects of sediment erosion and deposition from other sources of variation in 137Cs in the small Mochovce catchment in Slovakia. These other sources of variation could then be interpreted. Besides erosion and deposition processes, the initial pattern of 137Cs deposition, floodplain sedimentation, and short-range spatial variation were identified as the major sources of spatial variation of the 137Cs inventory.     

Odor concentration decay and stability in gas sampling bags

This paper presents results of an experimental study into factors contributing to decay of odor samples during storage, between 4 and 40 hr after sample collection. The odor studied was sampled from a tobacco processing plant as part of collaborative research with a view to establishing a manual outlining methods for odor annoyance management, specifically for the tobacco industry. In August and September 1997, an experimental program was carried out in which two types of tobacco odor were sampled: Burley Toaster and Mix. The dependent variable was odor concentration in the bag, measured by dynamic olfactometry in accordance with the draft Comité Européen de Normalisation (CEN) standard EN13725 "Air Quality-Determination of Odor Concentration by Dynamic Olfactometry." The independent variables were sampling bag material, degree of dilution during sampling, dilution gas used, particle removal during sampling, and age of sample in hours. In the first phase, 94 odor analyses were carried out. In a second test, 32 samples were analyzed for odor concentration. In addition, 16 samples were analyzed using gas chromatography-mass spectrometry (GC-MS). Analysis of the results (analysis of variance) led to the unexpected conclusion that Nalophan film bags performed significantly better than metalized Cali-Bond layered film as a bag material. The odor concentration of samples in Nalophan bags remained relatively stable between 4 and 12 hr after sampling. After 30 hr, decay to about half the initial concentration, as measured at 4 hr, was observed. Particle removal during sampling caused the odor concentration in the bags to be reduced by approximately 20%. For practical reasons, particle removal remains useful, to avoid contamination of equipment. Using air or nitrogen as the neutral gas for pre-dilution during sampling or the dilution factor used (between factor 2 and 6) did not appear to have an effect on the decay characteristic of odor samples. The following recommendations are suggested for the practice of collecting odor samples and apply specifically to tobacco processing emissions: Analyze samples as soon as possible, preferably within 12 hr; When samples age for more than 12 hr, decay is likely to cause a reduction in odor concentration to half the original concentration at age 30 hr; Use sampling bags made of Nalophan NA or benchmark performance of other materials against Nalophan NA before using alternative materials; Use pre-dilution when sampling only for the purpose of avoiding condensation during sample storage. Use an appropriate minimum dilution factor to avoid condensation; Both nitrogen and high-purity (synthetic) air are suitable to use as neutral gas for pre-dilution; and When sampling tobacco odors, use an odorless filter to remove particles. This practice removes a source of variation and avoids contamination of equipment. The effect on results, despite being consistently lower in odor concentration, is not meaningful in terms of perceived intensity or annoyance potential.     

Tillage, intercrop, and controlled drainage-subirrigation influence atrazine, metribuzin, and metolachlor loss

Atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] have been found with increasing occurrence in rivers and streams. Their continued use will require changes in agricultural practices. We compared water quality from four crop-tillage treatments: (i) conventional moldboard plow (MB), (ii) MB with ryegrass (Lolium multiflorum Lam.) intercrop (IC), (iii) soil saver (SS), and (iv) SS + IC; and two drainage control treatments, drained (D) and controlled drainage-subirrigation (CDS). Atrazine (1.1 kg a.i. ha-1), metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazine-5(4H)-one] (0.5 kg a.i. ha-1), and metolachlor (1.68 kg a.i. ha-1) were applied preemergence in a band over seeded corn (Zea mays L.) rows. Herbicide concentration and losses were monitored from 1992 to spring 1995. Annual herbicide losses ranged from < 0.3 to 2.7% of application. Crop-tillage treatment influenced herbicide loss in 1992 but not in 1993 or 1994, whereas CDS affected partitioning of losses in most years. In 1992, SS + IC reduced herbicide loss in tile drains and surface runoff by 46 to 49% compared with MB. The intercrop reduced surface runoff, which reduced herbicide transport. Controlled drainage-subirrigation increased herbicide loss in surface runoff but decreased loss through tile drainage so that total herbicide loss did not differ between drainage treatments. Desethyl atrazine [6-chloro-N-(1-methylethyl)-1,3,5-triazine-2,4-diamine] comprised 7 to 39% of the total triazine loss.     

A quantitative evaluation of monitoring networks for region-specific nitrate reduction policies

Modern environmental policy implementation in many developed countries is increasingly regionally oriented. Regional governments have undertaken measures designed for the specific needs of the region but, so far, the resulting change in environmental quality has hardly been monitored. This study develops a method for the quantitative evaluation of region-specific environmental policy. Two forms of monitoring are distinguished: monitoring of performance of policy measures and monitoring of environmental quality. This study investigates two regions in the Netherlands where region-specific policy has been implemented. Performance monitoring focused on reduction of nitrate leaching to groundwater. Leaching reductions were calculated with simple models or rules of thumb. Quality monitoring focused on nitrate concentrations under grassland and other land use. An analysis of variance showed significant differences between different soil units. Stratified kriging was applied for spatial interpolation, showing within-unit variability. The current monitoring network could be improved by using a more regular type of grid.     

ESF Workshop

Dioxin and PCB monitoring programs for food and feeding stuff in most countries of the world, including many European Countries are currently inadequate. Better control of food production lines and food processing procedures is needed to minimize entry of dioxin to the food chain and will help to avoid dioxin contamination accidents. This would also improve the ability to trace back a possible contamination to its source. European guidelines for monitoring programs should be established to ensure comparable and meaningful results. These guidelines should define the minimum requirements for the design of monitoring programs, analytical methods, and quality assurance. Though data from Northern Europe shows that the general population exposure to dioxin and PCB has decreased during the last ten years these compounds continue to be a risk of accidental contamination of the food chain. The most prominent recent example is the Belgian dioxin contamination of feeding stuff in 1999. The Belgian dioxin contamination was not detected due to dioxin monitoring programs but by their direct biological effects seen in animals. Four other cases of dioxin contamination have been detected in Europe since 1997 due to local monitoring programs. One of them (citrus pulp pellets 1998) was in a much larger scale than the Belgian dioxin contamination. The general population's exposure to dioxins and PCBs is still in the same range (1-4 pg WHO-TEQ/kg body weight and day) as the recently revised WHO tolerable daily intake (TDI). There is concern that short-term high level exposure to dioxins, furans, and PCB may cause biological effects on the human fetal development and further research is required. Further actions to control sources building on considerable advances already made in many countries may need to be supplemented by measures to prevent direct contamination of feeding stuff or food to reduce general population exposure further.     

Application of a purge and trap TDS-GC/MS procedure for the determination of emissions from flame retarded polymers

Emissions of volatile organic compounds (VOCs) from different thermoplastic polymers used in electrotechnical applications were investigated using a purge and trap procedure that involved adsorption on Tenax GR. Results were compared to those for an operating TV set monitored in a test chamber. The analyses were in both cases carried out using thermodesorption gas chromatography with mass spectrometric detection (TDS-GC/MS). Substances identified were monomers, volatile additives, or related compounds. Special attention was given to the detection of halogenated compounds. Their origin was studied using reference samples and synthetic standards.     

Nitrogen recovery in an integrated system for wastewater treatment and tilapia production

An integrated system, consisting of Up-flow Anaerobic Sludge Blanket (UASB)-duckweed-tilapia ponds was used for recovery of sewage nutrients and water recycling. A UASB reactor with 40 liter working volume was used as pre-treatment unit followed by a series of three duckweed ponds for nitrogen recovery. The treated effluent and duckweed biomass was used to feed fishponds stocked with Nile tilapia (Oreochromis niloticus). The UASB reactor was fed with raw, domestic sewage at 6 h hydraulic retention time. The three duckweed ponds were stocked with Lemna gibba and fed with UASB effluent at 15 days hydraulic retention time. Nitrogen recovery from UASB effluent via duckweed biomass represented 81% of total nitrogen removal and 46.5% from the total nitrogen input to the system. In subsequent fishponds the nitrogen recovery from duckweed as fish feed was in the range of 13.4–20%. This nitrogen in fish biomass represented 10.6–11.5 g N from the total nitrogen in the raw sewage fed to the UASB reactor. The growth performance of tilapia (Oreochromis niloticus) showed specific growth rates (SGR) in the range of 0.53–0.97. The range of feed conversion ratio (FCR) and protein efficiency ratio (PER) were 1.2–2.2 and 2.1–2.28, respectively. The results of the experiments showed total fish yield and net fish yield in the range of 17–22.8 ton/ha/y and 11.8–15.7 ton/ha/y respectively. In conclusion UASB-duckweed-tilapia ponds provide marketable by-products in the form of duckweed and fish protein, which represent a cost recovery for sewage treatment.     

Fish bioassay monitoring of waste effluents

Spills of toxic materials into bodies of water receiving industrial waste discharges can be prevented only if frequent or continuous assessments of effluent quality can be made. Currently available methods can automatically measure individual physical or chemical waste components but cannot assess toxicity caused by the interaction of components or the presence of an unsuspected material. Aquatic organisms, in contrast, respond to their total environment and in this way integrate the effects of all the various chemical and physical waste parameters.This study evaluates the possibility of using the continuously and automatically recorded responses of fish to monitor the toxicity of industrial waste effluents. A review of previously developed toxicity monitoring systems is followed by a field evaluation of a method that uses the computer-monitored ventilatory patterns of 12 bluegills (Lepomis macrochirus Rafinesque) to monitor the toxicity of an industrial waste effluent as it flows into a river. No known toxic spills occurred in the effluent during the operation of this system, but acetone added to the effluent waste caused responses from the fish at concentrations which peaked near the 96-hr LC₅₀ level. Some responses were also noted when no known toxicant was present; these were related to environmental disturbances and system design problems. Recommendations are made for the design of future biologic monitoring units.     

The stable isotope signature of methane emitted from plant material under UV irradiation

Recent experiments have shown that dry and fresh leaves, other plant matter, as well as several structural plant components, emit methane upon irradiation with UV light. Here we present the source isotope signatures of the methane emitted from a range of dry natural plant leaves and structural compounds. UV-induced methane from organic matter is strongly depleted in both ¹³C and D compared to the bulk biomass. The isotopic content of plant methoxyl groups, which have been identified as important precursors of aerobic methane formation in plants, falls roughly halfway between the bulk and CH₄ isotopic composition. C3 and C4/CAM plants show the well-established isotope difference in bulk ¹³C content. Our results show that they also emit CH₄ with different δ¹³C value. Furthermore, δ¹³C of methoxyl groups in the plant material, and ester methoxyl groups only, show a similar difference between C3 and C4/CAM plants. The correlation between the δ¹³C of emitted CH₄ and methoxyl groups implies that methoxyl groups are not the only source substrate of CH₄.Interestingly, δD values of the emitted CH₄ are also found to be different for C3 and C4 plants, although there is no significant difference in the bulk material. Bulk δD analyses may be compromised by a large reservoir of exchangeable hydrogen, but no significant δD difference is found either for the methoxyl groups, which do not contain exchangeable hydrogen. The δD difference in CH₄ between C3 and C4 plants indicates that at least two different reservoirs are involved in CH₄ emission. One of them is the OCH₃ group, the other one must be significantly depleted, and contribute more to the emissions of C3 plants compared to C4 plants. In qualitative agreement with this hypothesis, CH₄ emission rates are higher for C3 plants than for C4 plants.