No abstract

An investigation was conducted on the pollutant removal performance of a constructed wetlands treating stormwater runoff from a residential townhome complex in northern Virginia. Constituent event mean concentrations for 33 runoff events between April 1996 and May 1997 were measured based on flow‐weighted composite samples collected at the facility's inlet and outlet. With the results from a limited number of grab samples representing ungauged overland drainage from an adjacent wooded area, estimated removals were positive for most constituents and typically exceeded those obtained at a nearby companion wetland study site, consistent with expectations based on the relative ratios of wetland area to drainage area at the two sites. Median load removals of all constituents were greater for a subset of 22 storms that had inflow volumes less than the maximum volume of the marsh. Orthophosphate phosphorus and ammonia removals were significantly better during spring of 1996 than spring of 1997. Lysimeter data suggest a possible explanation for this, which is development of anaerobic conditions in the shallow sediments in 1997. Outlet concentrations of oxidized nitrogen were consistently lower in base flow than in storm samples, suggesting that removal of this constituent occurred primarily between, rather than during, storm events.

Rebreathing of expired air may be a lethal hazard for prone sleeping infants. This paper describes a mechanical model to simulate infant breathing, and examines the eVects of bedding on exhaled air retention. Under simulated rebreathing conditions, the model allows the monitoring of raised carbon dioxide (CO 2 ) inside an artificial lung-trachea system. Resulting levels of CO 2 (although probably exaggerated in the mechanical model compared with an infant, due to the model's fixed breathing rate and volume) suggest that common bedding materials vary widely in inherent rebreathing potential. In face down tests, maximum airway CO 2 ranged from less than 5% on sheets and waterproof mattresses to over 25% on sheepskins, bean bag cushions, and some pillows and comforters. Concentrations of CO 2 decreased with increasing head angle of the doll, away from the face down position. Recreations of 29 infant death scenes also showed large CO 2 increases on some bedding materials, suggesting these infants could have died while rebreathing.

No abstract

No abstract