SPATIAL VARIATION AND DISTRIBUTION OF PHOSPHORUS FORMS IN BOTTOM SEDIMENTS OF TWO CANADIAN SHIELD LAKES

Nutrient dynamics in lake systems are influenced by the loading of sediment-associated phosphorus (P) from both internal and external sources. Despite efforts to control lake productivity through reductions in external P loading, water quality problems persist in some lakes due to high internal loading of P from bottom sediment. The present study examines the spatial distribution of chemically defined P forms (NH₄Cl-RP, BD-RP, NaOH-RP, HCI-RP, and NaOH_(S5)-RP) in bottom sediments of two noncalcareous Canadian Shield Lakes. Sediment P data are related to some of the physical and chemical variables that control internal P loading in lakes. The BD-RP and NaOH-RP forms are related to water depth and nonresidual iron and aluminum content of sediment. Approximately 80% of the total extractable P in the Muldrew Lakes sediment was bioavailable P (NH₄Co-RP + BD - RP + NaOH - RP), which is about twice that reported in the literature for calcareous lakes. In order to model P cycling in the Muldrew Lakes, further research is required to determine the internal supply of P from the lakes' sediments and potential anthropogenic inputs ofP from private sewage disposal systems. La dynamique des nutriments dans un lac est influenceé par I'apport en phosphore (P) provenant de sources internes et externes. Malgré les efforts déployés pour contrôler le taux de P par réduction de I'apport externe, la qualityé de I'eau demeure un problème dans certains lacs à cause de la contribution interne provenant de la sédimentation de fond. Cette étude examine la distribution spatiale de formes chimiquement définies de P (NH₄CI-RP, BD-RP, NaOH-RP, HCI-RP, and NaOH₍₈₅₎-RP) présentes dans les sédiments de fonds de deux lacs non-calcaires du Bouclier Canadien. Les contenus en P des sediments sont reliés à certaines variables physiques et chimiques qui contrôlent I'apport interne des lacs. Le Bd-RP et le NaOH-RP sont reliés à la profondeur de I'eau ainsi qu'aux contenus non-résiduels de fer et d'aluminium du sédiment. Environ 80% du P pouvant être extrait du sédiment des lacs Muldrew éait du P (NH₄Cl-RP + BD-RP + NaOH-RP) biodisponible. Ceci représente le double de ce qui est rapporté dans la littéature pour des lacs calcaires. Afin de construire un modèle du cycle du P dans les lacs Muldrew, il est important de déterminer I'apport interne de P provenant de la sédimentation et les sources anthropiques potentielles provenant des systèmes d'égouts privés.     

PRE-COLUMBIAN METALLURGY: TECHNOLOGY,MANUFACTURE, AND MICROPROBE ANALYSES OF COPPER BELLS FROM THE GREATER SOUTHWEST*

Twenty-four cast copper crotals (commonly called bells), one 'spilled bell’, one tinkler bell and a number of minerals from locations throughout the Greater Southwest were analysed for their elemental composition by a PIXE nuclear microprobe at Los Alamos National Laboratory, New Mexico, USA. Sixteen bells contained minor and trace amounts of silver, antimony, arsenic, lead, and in some cases tin, strontium, and selenium. Nine bells contained little or no detectable amounts of these elements. This suggests that several workshops throughout the Greater Southwest and Mexico might have manufactured these bells.