Elevated mid-trimester hCG and maternal lupus anticoagulant

An association is described between women with lupus anticoagulant and abnormal prenatal serum screening results. Three cases of positive second-trimester serum screening for Down syndrome, with karyotypically normal fetuses, in women demonstrated to have lupus anticoagulant are presented. Serum screening positivity was principally due to a disproportionately elevated maternal serum human chorionic gonadotrophin (hCG) level. In each case, early, severe intrauterine growth restriction was documented, with only one fetus surviving the neonatal period. As maternal lupus anticoagulant may have a profoundly adverse effect on the course of pregnancy, we suggest that an elevated hCG level on prenatal screening prompt consideration of maternal lupus anticoagulant testing if ultrasonography demonstrates an otherwise normal singleton gestation and the fetal karyotype is normal.     

Monitoring air,soil, stream and fish for aerial drift of permethrin

Permethrin drift from two aerial applications at each of two sites in a potato growing area in Ontario were measured to a maximum distance of 61 m outside the treatment area. Droplet drift did not enter the adjacent surface water streams at either study site, since there was little or no wind on the four occasions. The concentration of the insecticide in soil as a result of drifting off site was significantly lower than the amount deposited on the treatment area. The spray drifting off-target was generally made up of droplets <100 m. Permethrin residues were detected in the water and sediment samples collected after treatment along the Bailey Creek and Beeton Creek; however, these levels did not cause lethal or sublethal effects to aquatic invertebrates and fish species. Based on the conditions and results of this study, it is concluded that a buffer zone of 65 m around sensitive and productive bodies of water would be effective and practical.     

Carbon dioxide fluxes over a grazed prairie and seeded pasture in the Northern Great Plains

Temperate grasslands are vast terrestrial ecosystems that may be an important component of the global carbon (C) cycle; however, annual C flux data for these grasslands are limited. The Bowen ratio/energy balance (BREB) technique was used to measure CO2 fluxes over a grazed mixed-grass prairie and a seeded western wheatgrass [Pascopyrum smithii (Rybd) L?ve] site at Mandan, ND from 24 April to 26 October in 1996, 1997, and 1998. Above-ground biomass and leaf area index (LAI) were measured about every 21 days throughout the season. Root biomass and soil organic C and N content were determined to 110 cm depth in selected increments about mid-July each year. Peak above-ground biomass and LAI coincided with peak fluxes and occurred between mid-July to early August. Biomass averaged 1227 and 1726 kg ha(-1) and LAI 0.44 and 0.59, for prairie and western wheatgrass, respectively. Average CO2 flux for the growing season was 279 g CO2 m(-2) for prairie and 218 g CO2 m(-2) for western wheatgrass (positive flux is CO2 uptake and negative flux is CO2 loss to the atmosphere). Using prior measured dormant season CO2 fluxes from the prairie sites gave annual flux estimates that ranged from -131 to 128 g CO2 m(-2) for western wheatgrass and from -70 to 189 g CO2 m(-2) for the prairie. This wide range in calculated annual fluxes suggests that additional research is required concerning dormant season flux measurements to obtain accurate estimates of annual CO2 fluxes. These results suggest Northern Great Plains mixed-grass prairie grasslands can either be a sink or a source for atmospheric CO2 or near equilibrium, depending on the magnitude of the dormant season flux.     

Declining biodiversity in agricultural landscapes and the effectiveness of agri-environment schemes

Agricultural intensification, greatly accelerated as a result of the EU Common Agricultural Policy (CAP), has led to drastic reductions in the populations of many wild plant and animal species that used to be characteristic of farmland. In 1992, the EU provided the member states with its Agri-environment Regulation 2078/92 to help member states reverse these developments by means of agri-environment schemes. The question is: will the implementation of these schemes be sufficient to restore the biological diversity on farmland? Most studies that have examined the effectiveness of agri-environment schemes have focussed on farmland birds in Great Britain and The Netherlands. So far, the positive effects appear to be limited. Continuous evaluation and adaptation of these schemes is needed to enable the biodiversity on farmland to recover from the EU's former policy.     

Spatial variability in compartmental fate modelling

A new approach is presented which is designed to address the spatial heterogeneity of the environment in compartmental mass balance models of chemical fate in the environment. It rests on the assumption of chemical equilibration within one phase despite prevailing environmental heterogeneity. Composite D- and Z-values are derived from sub-unit specific environmental parameters and are used to solve mass balance equations which can be adopted essentially unchanged from existing compartmental fugacity models. With the resulting common fugacity value for each compartment, sub-unit specific concentrations and process rates can be calculated. The approach is illustrated using the QWASI lake model to calculate the fate of hexachlorobenzene in a hypothetical lake sub-divided in four distinct sub-units. The approach allows the subdivision of each compartment in a large number of sub-units with distinct environmental characteristics without substantially increasing model complexity. This is a necessary condition for linking fugacity models to geographical information systems.     

The effect of export to the deep sea on the long-range transport potential of persistent organic pollutants

BACKGROUND: Export to the deep sea has been found to be a relevant pathway for highly hydrophobic chemicals. The objective of this study is to investigate the influence of this process on the potential for long-range transport (LRT) of such chemicals. METHODS: The spatial range as a measure of potential for LRT is calculated for seven PCB congeners with the multimedia fate and transport model ChemRange. Spatial ranges for cases with and without deep sea export are compared. RESULTS AND DISCUSSION: Export to the deep sea leads to increased transfer from the air to the surface ocean and, thereby, to lower spatial ranges for PCB congeners whose net deposition rate constant is similar to or greater than the atmospheric degradation rate constant. This is fulfilled for the PCB congeners 101, 153, 180, and 194. The spatial ranges of the congeners 8, 28, and 52, in contrast, are not affected by deep sea export. With export to the deep sea included in the model, the spatial ranges of the heavier congener are similar to those of the lighter ones, while the intermediate congeners 101 and 153 have the highest potential for long-range transport. CONCLUSIONS: Transfer to the deep ocean affects the mass balance and the potential for LRT of highly hydrophobic chemicals and should be included in multimedia fate models containing a compartment for ocean water.