Malathion Fate in Water and Catfish Technical Bulletin 225 -- December 1999 -- Printable .pdf version   Table 1. Concentration (ppb) of malathion in water from tanks dosed with various levels of malathion and sampled at various intervals after dosing. Sample time1 Concentration applied to water (ppb)2 60 12 2.4 0.48 0 day after dosing 53.00 a 11.100 a 2.30a 0.50 a 1 day after dosing 1.40 b 0.260 b 0.07 b 0.00 b3 2 days after dosing 0.36 b 0.072 b 0.00 b 0.00 b 3 days after dosing 0.00 b 0.000 b 0.00 b 0.00 b 5 days after dosing NA NA NA NA 7 days after dosing NA NA NA NA 14 days after dosing NA NA NA NA Log intercept (intercept) 3.61 (37.0) 2.15 (8.61) 1.02 (2.76) 0.34 (1.40) Log slope (per day)4 -2.92 A -1.83 AB -0.88 BC -0.30 C Slope (probability of F)5 0.0002 0.0036 0.0865 0.5264 Predicted day = 0.02 ppb 2.42 2.21 2.10 1.91 R2 0.92 0.84 0.82 0.78 1Concentrations at 0 day are averages of three sample analyses. All other concentrations are based on analysis of one composite sample for the three-replicate experiment. The 0-day sample was taken approximately 15 minutes after dosing. The study was conducted in fiberglass tanks. 2Means within a column followed by the same lowercase letter are not significantly different (LSD, p = 0.05). 30.00 = none detected (quantification limit = 0.02 ppb). 4Slopes followed by the same uppercase letter in this row are not significantly different (F, p < 0.05). Regression equation: log (concentration) = log (intercept) + Bi log (time), where Bi = log (slope). 5F-test of slope where Ho is slope = 0.   Table 2. Concentrations (ppb) of malathion in water from tanks with fish and tanks without fish dosed with 46 ppb malathion. Sample time1   No fish    Fish2    Mean3 0 hour after dosing    33.0    40.0    36.5a 6 hours after dosing    17.0    13.0    15.0b 24 hours after dosing    7.7    1.3    4.5bc 48 hours after dosing    1.4    0.0    0.7c Log intercept (intercept)    3.76 (42.95)    3.97 (52.98) Log slope (per hour)4    -0.62 A    -0.96A Slope (probability of F)5    0.0734    0.0244 Predicted hour = 0.02 ppb    416.7    60.2 R2    0.86    0.95 1The 0-hour sample was taken approximately 15 minutes after dosing. Water pH was 8.9. This study was conducted in fiberglass tanks. 20.0 = none detected (quantification limit = 0.02 ppb) 3Means followed by the same lowercase letter in this column are not significantly different (LSD, p = 0.05). 4Slopes followed by the same uppercase letter in this row are not significantly different (F, p < 0.05). Regression equation: log (concentration) = log (intercept) + Bi log (time), where Bi = log (slope). 5F-test of slope (Ho: slope = 0).   Table 3. Concentrations (ppb) of malathion in pH 7.0 and 8.5 well water dosed with 42 ppb malathion.1 Sample time2    pH 7.0    pH 8.5    Means3 0 hour after dosing    41.0    42.0    41.5 a 6 hours after dosing    32.0    24.0    28.0 ab 24 hours after dosing    23.0    8.6    15.8 bc 48 hours after dosing    5.2    1.1    3.2 c         Log intercept (intercept)    3.81 (45.2)    3.69 (40.1)   Log slope (per hour)4    -0.039 A    -0.061 B   Slope (probability of F)5    0.0014    0.0002   Predicted hour = 0.02 ppb    98.3    59.9   R2    0.95    0.99   1Water was held in glass containers with no fish. The unadjusted pH was 8.5, and the adjusted pH was 7.0. 2The 0-hour sample was taken approximately 15 minutes after dosing. 3Means followed by the same letter in this column are not significantly different (LSD, p = 0.05). 4Slopes not followed by the same uppercase letter in this row are significantly different (F, p = 0.03). Regression equation: log (concentration) = log (intercept) + Bi (time), where Bi = log (slope). 5F-test of slope where Ho is slope = 0.   Table 4. Concentrations (ppb) of malathion in pH 7.0 and 8.9 deionized distilled water in glass containers dosed with 12 or 60 ppb malathion. Sample time1 Water pH/initial malathion concentration (ppb)    7.0/12 7.0/60 8.9/60 Means2 0 hour after dosing 9.3 57.0 57.0 41.1a 1 hour after dosing 7.9 49.0 44.0 33.6ab 2 hours after dosing 12.0 56.0 40.0 36.0ab 4 hours after dosing 11.0 54.0 &emdash; 21.7b 8 hours after dosing 13.0 53.0 38.0 34.7ab 24 hours after dosing 12.0 59.0 36.0 35.7ab 48 hours after dosing 13.0 56.0 34.0 34.3ab           Log intercept (intercept) 2.32 (10.21) 3.99 (54.27) 3.27 (26.15)   Log slope (per hour)3 0.091 A 0.015 A 0.040 A   Slope (probability of F)4 0.0568 0.4361 0.9340   R2 0.55 0.13 0.002   1The 0-hour sample was approximately 15 minutes after dosing. 2Means followed by the same lowercase letter in this column are not significantly different (LSD, p = 0.05). 3Slopes followed by the same uppercase letter in this row are not significantly different (F, p < 0.05). Regression equation: log (concentration) = log (intercept) + Bi log (time), where Bi = log (slope). 4F-test of slope (Ho: slope = 0).   Table 5. Concentrations (ppb) of malathion in deionized distilled water, pond water, and pond water and sediment in glass containers dosed with 51 ppb malathion.1 Sample time2    Laboratory water (pH 7.0)     Pond water (pH 7.85)      Pond water sediment (pH 7.85)    Means3   0 hour after dosing    45.0    49.0    38.0    44.0 a 6 hours after dosing    33.0    34.0    28.0    31.7 b 24 hours after dosing    33.0    29.0    23.0    28.3 b 48 hours after dosing    27.0    21.0    16.0    21.3 c           Lop intercept (intercept)    3.81 (45.15)    3.93 (50.91)    3.70 (40.45)     Log slope (per hour)4    -0.11 A    -0.19 A    -0.20 A     Slope (probability of F)5    0.0499    0.0239    0.0369     R2    0.90    0.95    0.93     1Pond water and pond water and sediment samples came from earthen ponds containing channel catfish at the National Warmwater Aquaculture Center in Stoneville, MS. 2The 0-hour sample was approximately 15 minutes after dosing. 3Means followed by the same lowercase letter in this column are not significantly different (LSD, p = 0.05). 4Slopes followed by the same uppercase letter in this row are not significantly different (F, p = 0.05). Regression equation: log (concentration) = log (intercept) + Bi log (time),where Bi = log (slope). 5F-test of slope (Ho: slope = 0).   Table 6. Concentrations of malathion in pond water dosed with 35 ppb malathion (pond B).1 Sample time     Average malathion concentration (ppb)2 3 1 hour after dosing     7.7 a 6 hours after dosing     4.1 b 22 hours after dosing     1.2 c 48 hours after dosing     0.0 c 72 hours after dosing     0.0 c 168 hours after dosing 0.0 c     Log intercept (intercept)     2.54 (12.69) Log slope (per hour)     -0.55 Slope (probability of F)4     0.0001 Predicted hour = 0.02 ppb     100.23 R2     0.93 1Water samples came from earthen ponds containing channel catfish at the National Warmwater Aquaculture Center in Stoneville, MS. Water pH was 7.9 at the time of dosing, which was approximately 10 a.m. Pond B was one of two ponds used in this study; it was sampled at five sites. 2Means followed by the same letter are not significantly different (LSD, p = 0.05). 30.0 = None detected (quantification limit = 0.02 ppb). 4F-test of slope (Ho: slope = 0). Regression equation: log (concentration) = log (intercept) + Bi log (time), where Bi = log (slope).   Table 7. Concentrations of malathion in pond water dosed with 82 ppb malathion (pond A).1 Sample time     Average malathion concentration (ppb)2 3 1 hour after dosing     9.20 a 17 hours after dosing     10.50 a 48 hours after dosing     1.50 b 72 hours after dosing     0.49 b 168 hours after dosing     0.00 b     Log intercept (intercept)     2.98 (19.67) Log slope (per hour)    -0.55 Slope (probability of F)4     0.0722 Predicted hour = 0.02 ppb     218.24 R2     0.71 1Water samples came from earthen ponds containing channel catfish at the National Warmwater Aquaculture Center in Stoneville, MS. Water pH was 8.3 at the time of dosing, which was approximately 3:30 p.m. Pond A was one of two ponds used in this study; it was sampled at five sites. 2Means followed by the same letter are not significantly different (LSD, p = 0.05). 30.0 = None detected (quantification limit = 0.02 ppb). 4F-test of slope (Ho: slope = 0). Regression equation: log (concentration) = log (intercept) + Bi log (time), where Bi = log (slope).   Table 8. Malathion residues in channel catfish fillet and carcass samples taken at various times after dosing from pond B.1 Sample time     Type sample analyzed2        Carcass     Fillet 6 hours after dosing     0.03     0.0 24 hours after dosing     0.0     0.0 48 hours after dosing     0.0     0.0 72 hours after dosing     0.0     0.0 168 hours after dosing     0.0     NA 1Fish samples were taken from earthen ponds at the National Warmwater Aquaculture Center in Stoneville, MS. This pond was one of two used in the study; it was dosed with 35 ppb malathion. 2No statistical analysis. 30.0 = None detected (quantification limit = 0.02 ppm).   Table 9. Malathion residues in channel catfish fillet and carcass samples taken at various times after dosing from pond A.1 Sample time     Type sample analyzed2        Carcass     Fillet Pretreatment     0.03     0.0 17 hours after dosing     0.04     0.0 48 hours after dosing     0.0     0.0 72 hours after dosing     NA5     0.0 168 hours after dosing     NA     0.0 1Fish samples were taken from earthen ponds at the National Warmwater Aquaculture Center in Stoneville, MS. This pond was one of two used in the study; it was dosed with 82 ppb malathion 2No statistical analysis. 30.0 = None detected (quantification limit = 0.02 ppm). 4Trace detected < 0.01 ppm (quantification limit = 0.02 ppm). 5NA = Not analyzed.

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