The mussel monitor at Beegden monitoring station along the River Meuse generated 360 CloseAlarms in a 15-month period (July 2006 through October 2007), with a total duration of more than600 hours. Maintenance, malfunctioning and tests caused "false" Close Alarms in 13.9 % (50) ofthe cases. Data evaluation using the data of the online sensors and the bbe Algae Toximeterillustrated the effects of slowly decreasing oxygen levels and turbidity on the valve movement ofthe Zebra Mussel. A correlation between these parameters and the valve movement was foundin 8.9% (32) and 18.1% (65) of the cases respectively. These 40.8% (147) Close Alarms wereleft out of the further data analysis. Of the remaining 213 Close Alarms, 75 (32.5%) wereanalyzed further, and (extra) samples at the beginning of the Close Alarm were screened forpollutants. Based on the data evaluation, putting effort into the identification of the unknowncompounds that caused the alarms is recommended. The results are used to propose a prioritylist for unknown compounds to be identified. Includes 7 references, tables, figures.
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Edition: Vol. - No. Published: 11/01/2009 Number of Pages: 15File Size: 1 file , 1.8 MB