Toxicity testing of sediment samples from the Rio Santiago and its main tributaries was performed using a battery of tests that included the ECHA dipstick biocide monitor, the MetPad test, the lettuce seed germination and the root elongation test, the nematode test, spot plate test, and the SOS Chromotest. Assessment was carried out on organic extracts, pore water, and direct sediment. Results of bioassays showed toxicity sources from tributaries and canals flowing into the river and areas being degraded by insults from industrial spills. 0 7995 by John Wiley & Sons, Inc.

Lethal effects of active ingredients and formulations of widely used soybean pesticides were assessed with the Hydra attenuata toxicity test. Studied pesticides were insecticides chlorpyrifos and cypermethrin, and herbicide glyphosate. Results indicate the following toxicity trend: chlorpyrifos > cypermethrin > glyphosate. Tested active ingredients of insecticides and respective formulations did not significantly differ between them. Glyphosate formulation exhibited higher toxicity at low concentrations (LC(1-10)) respect to active ingredient, reversing this behavior at higher concentrations (LC(50-90)). Comparing H. attenuata sensitivity with existent toxicity data for aquatic organisms indicates that this species is poorly sensitive to tested insecticides and highly sensitive to the herbicide.

Surface water bodies receive a basin's wide diversity of pollutants, especially when there are mixed land uses. Among the many environmental tools to assess a body water quality, most studies use only a few. In addition these studies, usually, are focused only on a set of pollutants and an environmental matrix. The Del Gato Stream a surface watercourse within of more populated area of Argentinaexemplifies the typically contrasting land uses around this area's streams. The predominant land uses along of the stream are agricultural in the upper, urban and industrial the middle, and animal husbandry in the lower subbasin. The aim of this study was to use a multidisciplinary approach to evaluate the environmental quality of that stream as a model of surface-water bodies within mixed-land-use regions in the Buenos-Aires metropolitan area. At each of the sampling sitesdistributed along the stream as follows: 3 in the upper, 4 in the middle, 3 in the lower subbasingeneral water parameters were measured; water and sediment samples taken for physical, chemical, microbiological, and ecotoxicological analysis; and the variables in each environmental matrix, analyzed separately and jointly. The stream presented a significant general deterioration, the middle subbasin with urban-industrial land use being the most impacted, where metals and metalloids recorded highest levels, and the rest of the measured parameters were also found at high levels. The upper subbasin had the highest quality, and the lower subbasin proved poor quality regarding microbiological variables, nutrients, and general water parameters. The tests included in the toxicity battery did not reflect a common pattern of toxicity along the watercourse. However, when they were integrated in the EDAR index, the middle subbasin was the most affected sector of the stream. Although, the usefulness of each analysis tool must be evaluated taking into account the objective of the study, if the aim is to know the general environmental quality of a stream, the multiple-factor analysis proved to be the most effective means in complex systems under the influence of great diversity of pollution sources. This study provides relevant information about the ecological quality of a stream representative of a region with scarce environmental information.