The effect of clay minerals on cadmium toxicity to bacterial production.


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The effect of clays on cadmium toxicity to bacterial production and specific production was investigated in Lake Brazos, McLennan County, Texas. Bacterial production calculated from ^H-thymidine incorporation rates in samples without added cadmium ranged from 5.3x10"^ to 2.13x10"^ jj.g c 1"1 hr~l. Specific production varied between 8.1x10"® and 3.32x10"4 (Ig C ^lg C"1 hr". Cadmium significantly reduced bacterial productivity at low levels (1 mg Cd 1"--) . The response was non-linear. Reduction ranged from 79% at 1 mg Cd 1"1 to 98.4% at 20 mg 1"1. Reduction at 5 and 10 mg Cd 1"^ was 62.4% and 65.1%, respectively. Specific production dropped by 70.5% at 1 mg Cd 1"1, 82.2% at 20 mg 1"-*-, 55% at 5 mg l"-'-, and 50.4% at 10 mg Cd 1"1. Added clays increased cadmium toxicity to bacteria. Bacterial production and specific productivity were reduced by 90.7% and 85.9%, respectively, at 1 mg Cd 1"1 in samples amended with 20 mg 1"^ clay. Cadmium toxicity decreased with further additions of clay, approaching that observed in the untreated samples.



Cadmium toxicity, Lake Brazos, McLennan County