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Toxicity to soil microorganisms

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Description of key information

SOIL MICROORGANISMS - NITROGEN TRANSFORMATION TEST

Key value for chemical safety assessment

Short-term EC50 for soil microorganisms:
2 987 mg/kg soil dw

Additional information

Test systems were dosed with Phosflex 71B (tBuTPP) at nominal concentrations of 0, 30, 100, 300, 1000, and 2987 mg/kg dry soil, and incubated at approximately 20º C for 28 days. Soil samples were collected on days 0, and 28; and analyzed to determine nitrate concentrations.

The percent inhibition of nitrate formation, compared to untreated controls, was

calculated for each treatment level. Results are presented in the following table:

Application Rate

Days 0-28

Rate

Inhibition

0 mg/kg

4.45

--

30 mg/kg

4.68

-5.1%

100 mg/kg

5.25

-18.0%

300 mg/kg

4.76

-6.9%

1000 mg/kg

5.15

-15.7%

2987 mg/kg

4.43

0.6%

The EC50 value for inhibition of nitrate formation after 28 days was greater than 2987 mg Phosflex 71B

(tBuTPP)/kg dry soil, the highest concentration tested. Phosflex 71B (tBuTPP) did not have an adverse effect

on nitrogen transformation in aerobic surface soil.