Some effects of diazinon on the microflora of submerged soils
SummaryThe application of diazinon, an organophosphorus insecticide, at the rate of 2 kg and 20 kg active ingredient per hectare to submerged Maahas clay significantly stimulated the actinomycete population. A distinct zone of brown pigmentation formed in that part of the profile commonly referred to as the oxidized layer. A profuse growth of actinomycetes developed from the soil samples of this pigmented zone when streaked onto the nutrient agar. A visible increase in algal populations was noted in the standing water of the diazinon-treated soil.
Diazinon-chemistry and environmental fate: a California perspective.
Diazinon, first introduced in USA in 1956, is a broad-spectrum contact organophosphate pesticide that has been used as an insecticide, and nematicide. It has been ond of the most widely used insecticides in the USA for household and agricultural pest control. In 2004, residential use of diazinon was discontinued; as a result, the total amount applied has drastically decreased. [corrected]. Consequently, the amounts of diazinon applied have been drastically decreased. For example, in California, the amount of diazinon applied decreased from 501,784 kg in 2000 to 64,122 kg in 2010. Diazinon has a K(oc) value of 40-432 and is considered to be moderately mobile in soils. Diazinon residues have been detected in groundwater, drinking water wells, monitoring wells, and agricultural well. The highest detection frequencies and highest percentages of exceedance of the water quality criterion value of 0.1 μg/L have been reported from the top five agricultural counties n California that had the highest diazinon use. Diazinon is transported in air via atmospheric processes such as direct air movement and wet deposition in snow and rain, although concentrations decrease with distance and evaluation from the source. In the environment, diazinon undergoes degradation by several processes, the most important of which is microbial degradation in soils. The rate of diazinon degradation is affected by pH, soil type, organic amendments, soil moisture, and the concentration of diazinon in the soil, with soil pH being a major influencing factor in diazinon degradation rate. Studies indicate tha soil organic matter is the most important factor that influences diazinon sorption by soils, although clay content and soil ph also play an important role in diazinon sorption. Diazinon is very highly to moderately toxic aquatic arganisms, Diazinon inhibits the enzyme acetylcholinesterase, which hydrolyzes the neurotransmitter acetylcholine and leads to a suite of intermediate syndromes including anorexia, diarrhea, generalized weakness, muscle tremors, abnormal posturing and behavior, depression, and health. Differences in metabolism among species and exposure concentrations play a vital role in diazinon's bioaccumulation among different aquatic organisms in a wide range of accumulating rates and efficiencies.
Residual activity of organophosphorus insecticides in soil as tested against the eye gnat,Hippelates collusor.
The long-tern activity of 20 organophosphorus insecticides in soil was studied against Hippelates collusor (Townsend), the predominant species of eye gnats in the southwestern United States. Soil lots treated with three dosages of each material were stored in a glasshouse maintained at 88°±2° F. and bioassayed against the eye gnat at from 2- to 8-month intervals of storage.

Trithion®, Diazinon®, Bayer 25141, Co-Ral®, ethion, GC-4072, and Ethyl Guthion® at the intermediate or high dosage levels manifested appreciable residual activity against the gnat after 6 to 8 months of storage. Bayer 22408, phorate, American Cyanamid Experimental Nematocide 18133, GC-3583, and GC-3582 showed a great deal of biological activity at the intermediate or high dosage levels after 2 months of storage, but were not active at later intervals of testing.

The other materials, Methyl Trithion®, Bayer 29493, Guthion ®, Di-Syston®, ronnel, dimethoate, parathion, and Bayer 22684 did not, even at the highest dosage levels, show any appreciable residual activity when they were tested 2 months after storage.