I have 2 ponds. The only difference between these 2 is that one has Nitrate and the other has UREA. I observed that each time i feed the pond with urea, the conductivity decreases. What can be the reason for this?
may be the result of Urea reaction gives type of hydrocarbon complex, which characterize by low conductance( more electrical resistivity).
Regards
Urea (CO(NH2)2) is an organic solute which does not participate in the electrical conductivity process hence either dilute other inorganic solutes or could interfere with the electrical conductivity.
However, give few more hours for urea to be hydrolysed by urease (which exists in most ponds), the conductivity will increase rapidly owing to NH3 (ammonia) release from urea and the subsequent NH4+ (ammonium) formation. Of the above two species, ammonia is not ionised hence may not participate in the conductivity process directly but once it has been converted to NH4+ (by accepting H+ in the solution), it can contribute to conductivity.
Urea is not amphoterically ionic but has a very high permanent dipole moment and in solution depending on the ambient temperature it can possess negligible to some conductivity as it exists as highly polar resonance hybrids. As both Bayan Hussien and Selva Selvarajah stated above it can form complexes, more readily with cyanates and thiourea as well as can get degraded by urease over time which should enable less or more conductivity respectively. To conclusively infer, you need to observe the changes over a longer period following the addition of urea, in my opinion.
I assume that the change in conductance is rapid? In addition to the previous suggestions, perhaps rapid microbial breakdown of the urea occurs (from the presence of urease), which would increase conductance. This step seems likely in some types of ponds - it occurs rapidly in sewers. However, in the presence of sufficient magnesium and phosphate, this can lead to precipitation of magnesium ammonium phosphate (struvite). This step seems less likely unless those concentrations are high, as they are in some anaerobic digesters. If I remember my aquatic chemistry, this would lead to an overall decrease in conductance.
Good luck with your work!
- Peter
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