Mapping heavy metals in polluted soil by disjunctive kriging

The soil of some 50 km(2) around the town of Weinfelden in north-east Switzerland has been sampled and analysed to estimate and map the concentrations of heavy metals before an incinerator for the canton's waste is built. Given that the estimates are subject to error, the probabilities that true values exceed the maximum tolerable concentrations of the Swiss federal guide have also been estimated by disjunctive kriging. These may now be used by the local planners for making decisions. Of the metals examined, lead exceeded the guide value at several sampling points, and a moderate probability of excess of lead is fairly widespread. Copper exceeded the guide value in vineyards and orchards, but also in a few places elsewhere, and the estimated probabilities of excess were not negligible. The other two metals of concern, cadmium (with one exception) and zinc, had concentrations much less than the guide values. The patterns of distribution of the four metals were similar, the product-moment correlations among them are substantial, except in the vineyards and orchards, and it seems likely that they had common sources.     

Emission database for global atmospheric research (Edgar)

Atmospheric chemistry and climate modellers require gridded global emissions data as input into their models. To meet this urgent need a global emissions source database called EDGAR is being developed by TNO and RIVM to estimate for 1990, on a regional and on a grid basis, annual emissions of greenhouse gases (CO₂, CH₄, N₂O, CO, NO_x, non-methane VOC, SO_x), of NH₃, and of ozone depleting compounds (halocarbons) from all known sources. The aim is to establish at due levels of spatial, temporal and source aggregation the emissions from both anthropogenic and biogenic sources: a complete set of data required to estimate the total source strength of the various gases with a 1×1 ° resolution (altitude resolution of 1 km) and a temporal resolution of a month, supplemented by diurnal variation, as agreed upon in the Global Emissions Inventory Activity (GEIA) of the International Atmospheric Chemistry Programme (IGAC). In this way EDGAR will meet the requirements of present and future developments in the field of atmospheric modelling. The data comprise demographic data, social and economic factors, land use distributions and emission factors (with due emphasis on the uncertainty). As understanding in this field is still changing, due attention is paid to flexibility regarding the disaggregation of sources, spatial and temporal resolution and species. The objective and methodology chosen for the construction of the database and the structural design of the database system are presented, as well as the type and sources of data and the approach used for data collection. As an example, the construction of the N₂O inventory is discussed.     

Occurrence of dioxins in cow's milk in the vicinity of municipal waste incinerators and a metal reclamation plant in the Netherlands

Over 200 samples of cow's milk have been analysed for dioxins in a survey on the occurrence of dioxins in milk from the vicinity of municipal waste incinerators (MSWs) and other potential dioxin sources in The Netherlands. Levels in milk were found to vary considerably with time, depending on emission rates, the direction and distance to the source and the feeding and housing of cows. Highest levels of up to 13.5 pg TEQ/g of milk fat were found in the Lickebaert area and Zaandam near two incinerators with highest emission rates. The background level ranged between 0.7 and 2.5 pg TEQ/g of milk fat. Levels in winter were comparable to those found in summer and, in some areas, even higher, when cows were fed with hay and silage harvested on the same farm. After the closure of the MSW in Zaandam, cow's milk from neighbouring farms showed a significant decrease in dioxin levels to below the critical limit of 6 pg TEQ/g of milk fat. Dioxin levels in the vicinity of a metal reclamation plant were comparable to those in milk from the vicinity of a MSW with moderate emissions. Differences were observed in the ratio PCDF/PCDD, which was higher in milk near the metal reclamation plant. Principal component analysis has been applied on a large data set of patterns of the 2,3,7,8-chlorine substituted PCDDs and PCDFs in cow's milk. This technique has proved to be useful for distinguishing and identification of sources on the basis of the isomer pattern in milk.     

Pesticide residues in products of plant origin in the European Union

The results of a co-ordinated monitoring programme for pesticide residues in the European Union and Norway carried out in 1996 and 1997 are presented. The aim of this programme is to work towards a system, which makes it possible to estimate actual dietary pesticide intake for the population of the European Union. Based on a statistically dérived sampling plan and within the limited number of pesticides/commodities analysed, the most critical pesticides (benomyl group and dithiocarbamates) and commodities (mandarine and lettuce) were identified. In case of detected non-compliances, repeated sampling and, if necessary, enforcement actions are to be taken by national authorities. The programme will be continued in the next years.     

Evolution and function of auditory systems in insects

While the sensing of substrate vibrations is common among arthropods, the reception of sound pressure waves is an adaptation restricted to insects, which has arisen independently several times in different orders. Wherever studied, tympanal organs were shown to derive from chordotonal precursors, which were modified such that mechanosensitive scolopidia became attached to thin cuticular membranes backed by air-filled tracheal cavities (except in lacewings). The behavioural context in which hearing has evolved has strongly determined the design and properties of the auditory system. Hearing organs which have evolved in the context of predator avoidance are highly sensitive, preferentially in a broad range of ultrasound frequencies, which release rapid escape manoeuvres. Hearing in the context of communication does not only require recognition and discrimination of highly specific song patterns but also their localisation. Typically, the spectrum of the conspecific signals matches the best sensitivity of the receiver. Directionality is achieved by means of sophisticated peripheral structures and is further enhanced by neuronal processing. Side-specific gain control typically allows the insect to encode the loudest signal on each side. The filtered information is transmitted to the brain, where the final steps of pattern recognition and localisation occur. The outputs of such filter networks, modulated or gated by further processes (subsumed by the term motivation), trigger command neurones for specific behaviours. Altogether, the many improvements opportunistically evolved at any stage of acoustic information-processing ultimately allow insects to come up with astonishing acoustic performances similar to those achieved by vertebrates.     

利用寿命周期评估(LCA)进行的鲑科鱼饲料的环境影响评价

了解与水产饲料有关的环境负荷是评价和改进水产养殖环境性能的一项重要内容.本研究的目的是利用寿命周期评估(LCA)评价与法国用于硬头鳟生产的饲料有关的环境影响.所评价的各个阶段为:原材料的提取,所使用的原始配料的生产与改造,饲料的生产,饲料在养殖场的使用,各个阶段的运输以及能源的生产和使用.评价结果显示,渔业资源的利用(例如生物资源利用)以及养殖场中营养物的排放(例如富营养化潜能)对鲑科鱼饲料的潜在环境影响所起作用最大.改进饲料的组成以及管理做法看来是改善水产饲料环境概貌的最佳途径.