Publications by authors named "Andrew M Riddle"

2 Publications

  • Page 1 of 1

Modeling the impact of direct phototransformation on predicted environmental concentrations (PECs) of propranolol hydrochloride in UK and US rivers.

Chemosphere 2007 Jan 7;66(4):757-66. Epub 2006 Sep 7.

AstraZeneca Global Safety Health and Environment, Brixham, Devon TQ5 8BA, UK.

There is currently uncertainty on the persistence of active pharmaceutical ingredients (APIs) and on their depletion mechanisms in natural surface waters such as rivers, and hence predictions of their fate are often poor. In this study, a beta-adrenergic receptor, propranolol hydrochloride, was selected as a model API to explore the relative significance of direct phototransformation as a potential removal process of hydrophilic APIs in rivers. Phototransformation kinetics of propranolol was measured under simulated solar irradiation in the laboratory, which were then converted to the kinetics applicable in UK and US rivers. The effects of light intensity, light penetration, river size and flow were examined. The extrapolated phototransformation half-lives were applied in the river catchment models of GREAT-ER and PhATE. Results demonstrated that direct phototransformation significantly reduced the predicted environmental concentrations of propranolol in the water phase. Predicted reductions of mean concentrations in the River Aire (UK) were 27% in summer and 3% in winter; and for the US rivers simulated, reductions were 28-68% in summer and 11-41% in winter. The highest reductions were predicted for long rivers with low turbidity and low flow conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.chemosphere.2006.07.047DOI Listing
January 2007

Estimating spatial patterns of effluent exposure concentrations in direct toxicity assessment studies.

Ecotoxicology 2004 Jul;13(5):449-61

Environmental Consultant, The Barn and Oast, North Lane, South Street, Boughton-under-Blean, Faversham, Kent ME13 9NN, UK.

Hydrodynamic models of differing scale and complexity were used to estimate spatial patterns of effluent concentration in discharge plumes in the River Esk and the Lower Tees Estuary. The output from the Tees model was used, in conjunction with measurements of toxicity determined in short-term oyster embryo tests, to predict contours/zones of toxicity in the estuary associated with effluent discharges from four chemical processing sites. One of the discharges also combined the input from a municipal sewage treatment works. The models appeared to be effective in predicting patterns of dilution and dispersion of the effluent discharges in the respective receiving environments. Confirmation of the predictive capabilities of the Tees model was achieved by comparing predicted and measured toxicity in different regions of the plumes associated with the four discharges. Differences between predicted and measured toxicity for two of the four discharges were explicable in terms of failure to take account of the effects of real-time wind conditions when test samples were collected or overlap of adjacent discharge plumes. Suggested refinements to the models and measurement of effluent toxicity would further enhance the utility of this approach for determining the extent and significance of the effects of effluent discharges in receiving environments.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1023/b:ectx.0000035295.97557.6bDOI Listing
July 2004