Modeling phosphorus transport in an agricultural watershed using the WEPP model

The Water Erosion Prediction Project (WEPP) model has been tested for its ability to predict soil erosion, runoff, and sediment delivery over a wide range of conditions and scales for both hillslopes and watersheds. Since its release in 1995, there has been considerable interest in adding a chemical transport element to it. Total phosphorus (TP) loss at the watershed outlet was simulated as the product of TP in the soil, amount of sediment at the watershed outlet, and an enrichment ratio (ER) factor. WEPP can be coupled with a simple algorithm to simulate phosphorus transport bound to sediment at the watershed outlet. The objective of this work was to incorporate and test the ability of WEPP in estimatingTP loss with sediment at the small watershed scale. Two approaches were examined. One approach (P-EER) estimated ER according to an empirical relationship; the other approach used the ER calculated by WEPP (P-WER).The data used for model performance test were obtained from two side-by-side watersheds monitored between 1976 and 1980. The watershed sizes were 5.05 and 6.37 ha, and each was in a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation. Measured and simulated results were compared for the period April to October in each year. There was no statistical difference between the mean measured and simulated TP loss. The Nash-Sutcliffe coefficient was 0.80 and 0.78 for the P-EER and P-WER methods, respectively. It was critical for both methods that WEPP adequately represent the biggest sediment yield events because sediment is the main driver for TP loss so that the model can adequately simulate TP losses bound to sediment. The P-WER method is recommended because it does not require use of empirical parameters to estimate TP loss at the watershed outlet.     

Wie gef?hrlich ist Feinstaub?

Ohne Zusammenfassung     

Deposition, Verteilung sowie Bedeutung für den Menschen und sein Nahrungsnetz

Since the introduction of automotive exhaust catalysts in 1984, an intensive discussion started about the emission of platinum group metals and their effect on mankind and the environment. Several platinum compounds are known to be potent sensitizers, even at very small doses. In spite of both the scientific and public interest in this important field, the collection and coordination of scientific research and its conclusions continues to be a lacking. The present results from analytical chemistry, ecology, toxicology and occupational medicine are summarized here. This state of the art indicates the great need for further investigations concerning especially the assessment of emission sources and bioavailability studies for platinum as well as palladium and rhodium.     

Anthropogenic platinum fluxes: Quantification of sources and sinks, and outlook

Employing the data available to date, anthropogenic Pt fluxes are calculated for Germany with special emphasis on the Pt emitted by cars equipped with catalytic converters. Pt fluxes are quantified using five different methods (street deposition, automobile emission rate, sewage sludges, atmospheric load, industrial consumption). During the first and the second methods, approx. 100 kg of emitted Pt are seen to result for both for the mid 1990’s. Up to the year 2018, a total of 2100 kg of Pt will be emitted by cars equipped with catalytic converters. The diffuse atmospheric Pt deposition amounts to 0.73 – 4.4 μg/m²y or 260 kg Pt/year. Industrial sources emitting Pt into the atmosphere are likely but difficult to quantify. The enrichment of Pt in soils during agriculture fertilization with sewage sludges and during diffuse atmospheric deposition result in a level of 46 – 460 ng/kg up to the year 2018. Although this is slightly below the geogenic background, a comparison with the pollution history of Pb implies that forthcoming environmental Pt enrichment should not be neglected.     

Distribution of platinum group elements (Pt, Pd, Rh) in environmental and clinical matrices: Composition, analytical techniques and scientific outlook

Trace concentrations of the platinum group elements (PGE; here: Pt, Pd and Rh) play an important role in environmental analysis and assessment. Their importance is based on 1. their increasing use as active compartments in automobile exhaust catalysts, 2. their use as cancer anti-tumor agents in medicine. Due to their allergenic and cytotoxic potential, it is necessary to improve selectivity and sensitivity during analytical investigation of matrices like soil, grass, urine or blood. This paper summarizes the present knowledge of PGE in the fields of analytical chemistry, automobile emission rates, bioavailibility, toxicology and medicine.