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We studied the interaction between toxic stress and accumulation in the earthworm Aporrectodea caliginosa, as induced by different soil copper pools and soil constituents (especially pH). Earthworms were exposed in quartz sand, spiked soils, and field soils with different Cu concentrations and varying soil composition. The copper content in the earthworms was determined in the following: the cytosolic fraction, a granular fraction and a fraction consisting of tissue fragments, cell membranes and intact cells. The highest amount of Cu was found in the cytosolic fraction. The other fractions varied only slightly in response to changes in any of the copper pools in soil. Cytosolic copper was the best predictor of Cu availability to earthworms collected from soils at constant pH, as statistically significant correlations were obtained with pore water pCu at constant pH in earthworms exposed in quartz sand. This correlation was lost for cytosolic Cu concentrations in earthworms exposed to spiked soils and field soils at differing pHs. Instead, cytosolic copper correlated well to Cu in either pore water or solid phase. Soil pH not only plays an important role in the availability of metals and therefore on their uptake fluxes, but internal competition of Cu2+ and H+ at physiologically active binding sites also explained these apparent contradictions and increased the predictability of body burdens significantly. [ABSTRACT FROM AUTHOR]

From May to September 2005, five passive air samples were deployed over five, 1-month periods at five elevations on the CN Tower in Toronto, Canada, to investigate the vertical distribution, seasonality, and sources of organochlorine pesticides. A strong seasonality was observed between spring and the end of summer. Vertical profiles differed for different pesticide classes. For instance, α- and γ-hexachlorocyclohexane exhibited higher concentrations (60°80 pg m-3, respectively) near the ground during the spring and early summer, suggesting that surface-air exchange within the city or nearby Lake Ontario may be important sources. The vertical profile for chlordane isomers was variable, suggesting that both advective and local inputs are important. For dieldrin, no obvious trend with elevation was observed, suggesting that concentrations could reflect a regional air mass contamination. Strongest seasonality was observed for the endosulfans, a widely used pesticide in North America, that reached peak concentrations of 750–850 pg m-3 during June/July. Advective inputs of endosulfan from regional or more distant agricultural regions can explain the relatively uniform concentrations with elevation throughout the study period. The approach used in this study demonstrates that monthly average vertical concentration profiles differ between pesticide groups and reflect their use as well as the relative magnitude of input from local versus regional sources. [ABSTRACT FROM AUTHOR]