| Summary: | The objective of this research was to investigate the use of leeches as in situ monitors of the biological availability of chlorophenols and degree of contamination in the North Arm of the Fraser River Estuary, British Columbia, where chlorophenols are used as wood preservatives by several forest industry operations. The objective was accomplished by : 1) an integrated series of grab and continous samples to determine the spatial and temporal variability in chlorophenol contamination, 2) in situ and laboratory experiments to compare leech bioconcentration to water levels of pollutants and to determine environmental factors( temperature, pH, leech size) that regulate and affect bioassay interpretation.
Grab samples were not representative of the average level of pollution in the river. High concentrations such as the one reported for Mitchell Island on October 4 (11 ppb TTCP and 2.25 ppb PCP) could give a false impression of the pollution level in the river. Also, plumes of high concentration of chlorophenols could be missed easily if the sampling time does not coincide with the pollutant discharge.
High frequency( every 2 hours) automatic water sampling showed a high variability in chlorophenol contamination( 0.278 ppb to 3.678 ppb TTCP for the March 31- April 6 field experiment) which demonstrated . the sporadic nature of chlorophenol discharges. Changes in the river flow also affected the level andthe pattern of chlorophenol variation. A method capable of integrating concentration versus time seemed to be the only way to elucidate the irregular pattern of pollutant levels.
Leeches were exposed to the contaminants by submersion in cages at various locations along the North Arm. On the basis of the levels of chlorophenols found in the leech, estimation of the average chlorophenol concentration in the water were made. Concentrations as high as 3.2 9 ug/g TTCP and 1.11 ug/g PCP were found in leeches exposed in the Mitchell Island area( TTCP and PCP were the only chlorophenols found in the area of study at any time during our sampling program carried out between August 1984 and September 1985). An average concentration higher than 2 ppb TTCP and 2 ppb PCP was estimated in the water for the duration of the leech exposure( 7 days) at that location using bioconcentration levels determined in the laboratory.
Laboratory experiments showed that lower pH increased
bioconcentration of chlorophenols. Higher bioconcentration
factors were achieved at higher temperatures and regression equations( R= 0.96 to 0.99) were calculated for the five chlorophenols used in the experiments( 2,4-DCP; 2,4,5-TCP; 2,4,6-TCP; 2,3,4,6-TTCP and PCP). Temperature affected the time needed to achieve steady state which was 4 days at 4 C, 5 days at 12 C and 7+ days at 22 C. Four out of the five chlorophenols tested( 2,4-DCP exhibited different bioconcentration characteristics) were bioconcentrated to the same level by leeches, regardless of their Po/w values. This contradicted the linear, relationships established by various researchers between the bioconcentration factor and Po/w of various compounds including chlorinated phenols in other organisms.
Recommendations for setting up a method to use leeches in a
biomonitoring program of the chlorophenol pollution in the Fraser
River Estuary are proposed from the results of this research. The
cost of the analyses using a biomonitoring program could be an order of magnitude lower than an adequate water sampling program to assess the chlorophenol pollution level. === Applied Science, Faculty of === Civil Engineering, Department of === Graduate
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