A reliability index for models

Since the prediction of environmental changes depends heavily on mathematical models, environmental planners have a definite need for a general test that can be easily applied to determine the reliability of a model or to choose between available models. In this paper a ‘reliability index’ for a model is defined. This index is a number k ? 1 which is determined from a set x₁,x₂,…,x_n of model predictions and a corresponding set y₁,y₂,…,y_n of observations. One interpretation of the index k is that the model predictions agree with observations, in some sense, within a factor of k. The index k is defined using an intuitive, geometric approach and is justified through agreement with another index developed using statistical techniques. Examples are given for a model which predicts the atmospheric movement of radon-222 originating from a concentrated source of radium-226, such as a uranium tailings pile.     

Comparing Forecasts of the Global Impacts of Climate Change

This paper utilizes the predictions ofseveral Atmosphere-Ocean GeneralCirculation Models and the Global ImpactModel to create forecasts of the globalmarket impacts from climate change. Theforecasts of market impacts in 2100 varyconsiderably depending on climate scenariosand climate impact sensitivity. The modelsdo concur that tropical nations will behurt, temperate nations will be barelyaffected, and high latitude nations willbenefit. Although the size of theseeffects varies a great deal across models,the beneficial and harmful effects areoffsetting, so that the net impact on theglobe is relatively small in almost alloutcomes. Looking only at market impacts,the forecasts suggest that while the globalnet benefits of abatement are small, thedistribution of damages suggests a largeequity problem that could be addressedthrough a compensation program. The largeuncertainty surrounding these forecastsfurther suggests that continued monitoringof both the climate and impacts isworthwhile.     

Water quality issues in the Nakdong River Basin in the Republic of Korea

A framework for evaluating alternative management strategies for the Nakdong River Basin in the Republic of Korea (South Korea) was developed and applied jointly by Argonne National Laboratory in Argonne, Illinois, USA, and the Research Institute of Industrial Science and Technology in Pohang, South Korea. Water from this basin, the second largest in South Korea, supports a total population of more than 13 million people. Rapid industrial expansion, urbanization, and population growth have dramatically increased the demand for water and have severely degraded water quality, particularly near large industrial complexes and in the lower portion of the basin. Management strategies for the entire basin through to the year {dy2011} were evaluated with a computer model for basin-wide predictions of water flow and quality (HSPF). This continuous-event model was developed and calibrated using site-specific data for the basin over a two-year period (1994-1995) that included periods of both high (monsoonal) and low (drought) flows. Water quality impacts for different wastewater treatment strategies were assessed in terms of biochemical oxygen demand (BOD), nitrogen (N) and phosphorous (P) levels. The results of the study indicate that BOD levels in the main stem of the Nakdong River below the Kumhogang (a major tributary with low flow and heavy pollution loads) cannot be significantly improved by reducing direct BOD loads from point sources along the river. To reduce main stem BOD levels, the nutrient loading to the river must be reduced. In order to reduce these loads, additional advanced treatment methods (i.e., tertiary treatment) must be incorporated in the treatment facilities to remove N and P. The discharge inventory data further suggest that a large portion of N and P loads are derived from non-point agricultural practices. Reduction of these loads is difficult to accomplish and may require extensive modifications in agricultural and land-use practices. The modeling frame-work developed provides a means to evaluate these and other basin management strategies.     

Soil phosphorus extractability and uptake in a Cirsio-Molinietum fen-meadow and an adjacent Holcus lanatus pasture on the culm measures, north Devon, UK

The seasonal pattern of extractable soil P and soil solution P was determined for topsoil samples taken from a Cirsio-Molinietum fen-meadow community, and also for an adjacent agriculturally improved pasture in Devon, UK. Phosphorus concentration was investigated using three methods during 1993; Olsen's reagent (sodium bicarbonate) for soil P, centrifuging and polymeric suction cups for soil solution P. Solutions were extracted at two-weekly intervals during the spring and at monthly intervals during the summer. Phosphorus removed from both sites by centrifuging was in the range 5–30 μg dm⁻³ soil, in comparison with 1–6 mg kg⁻¹ for Olsen P. Olsen P on the Cirsio-Molinietum was significantly lower than on the improved pasture in mid-March and mid-June. The concentration of P in soil solution removed by suction cups was below the level of detection (<2 μg dm⁻³) on the Cirsio-Molinietum. Suction cup P on the improved pasture peaked in April and May at 16–19 μg dm⁻³ soil. Herbage yield and P concentration were measured throughout the growing season. Above-ground standing crop was greater on the Cirsio-Molinietum than the improved pasture at the beginning of the grazing season, because of the large litter component on the former. Total P content of this material was only 1.81 kg P ha⁻¹ on the Cirsio-Molinietum, in comparison with 5.58 kg P ha⁻¹ on the improved pasture. Phosphorus concentration of plant material obtained by repeated defoliation was approximately 1.0 mg P g⁻¹ DM on the Cirsio-Molinietum, whereas a clear seasonal trend, peaking at 3.5 mg P g⁻¹ DM, was observed on the improved pasture. Phosphorus concentration of litter, grass and sedge from ungrazed plots on the Cirsio-Molinietum indicated distinct seasonal variations for the grass, with no seasonal pattern for the sedge component.     

沿海和海洋生态系统与人类人口系统间的相互作用:关于消费如何调解这种相互作用的看法

人口、环境及可持续发展的困境 20世纪的80和90年代,环境工作者和普通公众普遍认为,不加控制的人口增长是造成各类环境退化的根本原因.这种新马尔萨斯人口论的观点最初出现在20世纪60年代Ehrlich所著的<人口炸弹>的文章中,该文以危言耸听的语气解释了那十年空前高的人口增长率[1～3].     

Maternal cell contamination in cultured chorionic villi: Comparison of chromosome Q-polymorphisms derived from villi,fetal skin,and maternal lymphocytes

Maternal cell contamination of chorionic villi (CV) samples used for first trimester prenatal diagnosis can cause obvious and/or unrecognized diagnostic dilemmas. The purpose of this investigation is to assess the frequency of maternal cell contamination (MCC) in chorionic villus samples and to evaluate selected parameters which might predict where contamination is more likely to have occurred. Maternal lymphocytes, chorionic villi from ultrasonically directed transcervical catheter aspiration, and fetal tissue were obtained at 8–11 weeks gestation from 45 patients undergoing elective termination. Quinacrine (Q) banded metaphases were compared from duplicate direct preparations of chorionic villi; cultured chorionic villi, fetal fibroblast tissue cultures, and maternal lymphocyte cultures. Q-polymorphisms in metaphase chromosomes were 100 per cent concordant between fetal tissue and direct CV preparation. However, evidence for maternal cell contamination occurred in 13.1 per cent of cultured chorionic villi preparations where polymorphisms were found to be identical between maternal and cultured CV and both distinct from fetal tissue preparations. Where MCC was identified, it was noted that CV cell cultivation interval was prolonged (24.2±6.8 days) compared with non-contaminated cultures (14.1±4.4 days) (p <0.05). We conclude that maternal cell contamination is a significant problem with chorionic villus sampling. Where direct preparations are not employed or when cultures are ‘slow growing’, MCC may be a significant and unrecognized complication re: fetal diagnosis. Direct preparations, multiple cultures, quinacrine banding, and maternal Q-polymorphism comparisons can minimize diagnostic dilemmas secondary to maternal cell contamination. Q-polymorphism comparisons between maternal and fetal chromosomes should be included in all instances where cultured chorionic villi are utilized for fetal diagnosis and where direct preparations are not available.     

Characterization of i(18p) in prenatal diagnosis by fluorescence in situ hybridization

A case is presented in which chorionic villus direct preparation and cultured chorionic villus cells revealed a 47,XX, + mar karyotype. The marker was a small metacentric chromosome and appeared to be i(18p)—isochromosome 18p. Follow-up studies in both amniotic fluid and fetal fibroblasts confirmed the karyotype. In order to characterize the marker, a panel of biotinylated DNA probes was used, including a whole chromosome 18 probe, chromosome 18-specific alpha satellite DNA, Yac clones, and a pan-telomeric probe. These studies show that the marker is a monocentric i(18p) in which about 80 per cent of chromosome 18 alpha satellite DNA has been lost.     

Dissolved inorganic nitrogen budget for a forested catchment at Beddgelert, North Wales

An input-output budget for dissolved inorganic-N in a small forested catchment in North Wales is presented. From 1982 to 1990, bulk precipitation inputs averaged 10.3 kg ha(-1) year(-1), whereas throughfall inputs in 1983-1984 were 20.3 kg ha(-1) year(-1). Streamwater outputs were consistently larger than bulk precipitation inputs, averaging 14.6 kg ha(-1) year(-1). Inorganic-N in the forest stream was predominantly nitrate and concentrations were substantially higher than in a nearby moorland stream. Both streams showed seasonal trends in nitrate concentration, with highest concentrations occurring in summer in the forest stream but in winter in the moorland stream. Nitrate concentration in the forest stream increased with increasing soil temperature up to approximately 7 degrees C and decreased at higher temperatures. Nitrification is thought to be responsible for nitrate production at temperatures both below and above 7 degrees C, but root uptake becomes significant only at the higher temperatures. In the forest, dry deposition and cloudwater inputs of inorganic-N are responsible for increased nitrogen fluxes in throughfall compared with wet deposition. Mineralization and nitrification in excess of plant needs causes the organic soil horizons to act as a net source of dissolved inorganic-N. Nitrogen transformations in the soil lead to soil acidification at a rate of 1.0 keq ha(-1) year(-1).     

Apparent non-mosaic trisomy 16 in chorionic villi: Diagnostic dilemma or clinically significant finding?

A case is presented in which apparent non-mosaic trisomy 16 was found in chorionic villi (direct and culture) obtained from a patient undergoing first-trimester prenatal diagnosis. The fetal karyotype subsequently was determined to be 46,XX by follow-up amniocentesis. Serial ultrasonographic examinations revealed placental sonolucencies and intrauterine growth retardation. At 37 weeks, a small-for-gestational-age female was delivered by Caesarean section for fetal distress. Postnatal cytogenetic studies revealed a normal female karyotype in cord blood and mosaic trisomy 16 in plaental tissues. These findings suggest that in cases where aneuploidy is confined to placental tissues, it may have biological significance, as evidenced by the apparent placental dysfunction and poor fetal growth in this case.