In the biodegradation process microorganisms will transform or mineralize organic contaminants, through metabolic or enzymatic processes, into less harmful, non hazardous substances, which are then integrated into natural biogeochemical cycles. Organic material can be degraded by two biodegradation mechanisms aerobically, with oxygen, or anaerobically, without oxygen. This process will alter the soil pH.

What is being degraded?

Paul is right it is important to know what is being degraded. Normally the soil has buffering capacity which also depends on soil type too. So it is important to address which contaminant is being degraded what is soil type. 

As rightly pointed out by Dr. Safdar, soil has buffering capacity to adjust with the pH, however the contaminant and soil characteristics and environmental conditions should be known to give a clear answer.  Soil pH is an important factor, which determines the activity of microbes for degrading the contaminant. Hence for degradation of contaminant also it is important to know the pH.

Yes, most of the soil has strong buffering capacity. Therefore, to change the pH depends on the type of contaminants which is degrading, type of soil, microbial and moisture status. Moreover, soil organic matter has a great role to play to change in pH. 

It depends on the type and nature of the compound undergoing degradation as well as the nature and properties of the soil. Unless the above information is available it's hardly possible to make a comment on the issue asked.

Its degradation of petroleum hydrocarbons. 

Soil type: Loamy

Thanks

OK, I suppose that you want to perform biodegradation of petroleum hydrocvarbons under aerobic conditions. In that case the organic acids are produce as byproducts which can decrease pH of soil. The pH decrease depends on soil characteristics, buffering capacity and many more parameters.

From the practical point of view: we have experince with treatment of 500 thousand tons of soil contaminated with petroleum hydrocarbons (in The Czech Republic, Sweden, The Netherlands, Slovakia), but we never recognized very substantial pH decrease after treatment.

Best regards

Vit

 I agree with last statement by  Vit . Please have a look at these PDFs...

In the biodegradation process microorganisms will transform or mineralize organic contaminants, through metabolic or enzymatic processes, into less harmful, non hazardous substances, which are then integrated into natural biogeochemical cycles. Organic material can be degraded by two biodegradation mechanisms aerobically, with oxygen, or anaerobically, without oxygen. This process will alter the soil pH.

I think, soil pH is the last soil chemical property that undergoes  any  significant change , regardless of any input..

It depends on type of contaminants, for example, in case of hydrocarbons, the biodegradation process creates an acid environment, so, pH decreases.

Thank you everyone.

Yes, off course

At least for the case of oil pollution, yes, of course.

The formation process of a hydrocarbon contaminated area is linked to chemical reactions and variations in physical characteristics of the affected medium (Sauck, 1998; 2000; Atekwana et al., 2001). According to Sauck (1998), the low resistivity anomaly is due to an increase of Total Dissolved Solids (TDS) in the ACID environment created by the bacterial action in the inferior part of the vadose zone or below groundwater table (GWT).

ATEKWANA, E. A., D. P. CASSIDY, C. MAGNUSON, A. L. ENDRES, D. D. WERKEMA JR. and W. A. SAUCK, 2001. Changes in geoelectrical properties accompanying microbial degradation of LNAPL. Proceedings of SAGEEP, OCS_1.

SAUCK W. A., 1998. A conceptual model for the geoelectrical response of LNAPL plumes in granular sediments. Proceedings of SAGEEP, 805-817.

SAUCK, W. A., 2000. A model for the resistivity structure of LNAPL plumes and their environs in sandy sediments. J. App. Geophys., 44, 151–165.

The soil pH is a substantial parameter that could be involved for effective improvement of biodegradation process. Good luck

thank you Omar & Jawad.