Polycyclic aromatic hydrocarbons in Recent lake sediments—I. Compounds having anthropogenic origins

Polycyclic aromatic hydrocarbons (PAH) in sediment cores from Lake Lucerne, Lake Zürich, and Greifensee, Switzerland, and Lake Washington, northwest U.S.A., have been isolated, identified and quantified by glass capillary gas chromatography and gas chromatography/mass spectrometry. Surface sediment layers are greatly enriched in PAH—up to 40 times—compared to deeper layers. In addition, concentration increases in upper sediments generally correspond to increasing industrialization and urbanization in the catchment basins of the lakes. Few PAH could be detected in pre-industrial revolution sediments, indicating that background levels for most PAH in aquatic sediments are extremely low.These results are consistent with an anthropogenic source for most of the aromatic hydrocarbons present in the modern sediments. A comparison of PAH distributions in the sediments and in possible source materials shows that urban runoff of street dust may be the most important PAH input to these lacustrine sediments. There is evidence that a significant contribution to the PAH content of street dust comes from material associated with asphalt.     

PCBs in the Hudson River

Hydrocarbon distribution in sediments from three lakes are related to the level of human activity in the respective drainage basins. Petroleum hydrocarbon contamination is found in surface sediments of a lake surrounded by a major city, compared to no detectable contamination in a lake located in a National Park.     

Global detailed geoid computation and model analysis

This paper presents a survey of recent work on the gravimetric geoid. The gravity models considered are those published in the past few years by the Goddard Space Flight Center (GSFC), the Smithsonian Astrophysical Observatory (SAO) and the Ohio State University (OSU). Comparisons and analyses have been carried out through the ose of detailed gravimetric geoids which we have computed by combining the above-mentioned models with a set of 26 000, 1^ox1^o mean free air gravity anomalies. The accuracy of the detailed gravimetric geoid computed using the most recent Goddard Earth Model (GEM-6) in conjunction with the set 1^ox1^o mean free air gravity anomalies is assessed at 2 m on the continents of North America, Europe And Australia, 2 to 5 m in the North-East Pacific and North Atlantic areas and 5 to 10 m in other areas where surface gravity data are sparse. Rms differences between this detailed geoid and the detailed geoids computed using the other satellite gravity fields in conjunction with same set of surface data range from 3 to 7 m. The maximum differences in all cases occurred in the Southern Hemisphere where surface data and satellite observations are sparse. These differences exhibited wavelengths of approximately 30^o to 50^o in longitude. Detailed geoidal heights were also computed with models truncated to 12th degree and order as well as 8th degree and order. This truncation resulted in a reduction of the rms differences to a maximum of 5 m. Comparisons have been made with the astrogeodetic data of Rice (United States), Bomford (Europe), and Mather (Australia) and also with geoidal heights from satellite solutions for geocentric station coordinates in North America and the Caribbean.