How about ozone or microwave disinfection?

Dear Benjamin, thank you very much for your answer.

So far I understood, microwaves works only for moist soils and it destroys fungi but not heterotrophic bacteria. About ozone, should have I a specific equipment to apply the gas?

Hi Raffaella,

My experience with disinfecting soil is limited (I deal more with water and wastewater), but here is an example of what I was thinking for ozone. They use "5.8 ± 0.7 mg L−1 of dissolved ozone dose for 30 min in a continuous diffusion reactor."

Article Inactivation of Ascaris eggs in soil by microwave treatment ...

But, I'm not sure what this would do to the overall physico-chemical soil properties.

Hopefully some others can chime in as well!

Hi Benjamin,

I will have a look to the reference you suggest. Thanks a lot!

Hi, Raffaella,

there are multiple methods, and each one has its own problem. We are using very often sodium azide at the 200 mg/L level. This is very classic approach, its advantage is that (most probably) it has small effects on soil properties (not always) but it is not necessary effective. HgCl2....in your case it may be problematic since you have competing metals but perhaps concentrations are not comparable. HgCl2 is considered as biocide less affecting soil.

From my experience, in the past, seeing a strong biodegradation of phenol in peat solutions, we succeeded to deal with that by using simultaneously sodium azide, sterilizing glassware and performing sorption in the nitrogen atmosphere. But typically, I prefer gamma-irradiation of soils which is very effective. But....it may have effects on soil sorptive properties, in particular due to possible release of DOM. Yet, I would consider irradiation as a primary solution. If you do not work with organic amendments, soil per se might release limted DOM concentrations, if at all. For your possible interest, I have attached our paper (in that, you may find some discussions of the literature regarding use of irradiation).

Dear Mikhail,

thank you very much for your answer and for sending the paper. Unfortunately I have no Access to any instrumentation providing gamma radiation. That´s why I was thinking to use formaldehyde, do you have any idea about it? On the other hand, i think nitrogen atmosphere is a good option to limit degradation under energically favourable conditions.

Thanks again.

Cheers

Dear Raffaella,

I have no any experience to use formaldehyde, but am pretty sure it was compared with other methods in the paper by Wold (1989) I have quoted in our paper. From general vision (not necessarily correct), there are some reasons why I would not like formaldehyde. This compound is quite active in chemicall reactions, e.g., participating in redox reactions (as a reduction agent) and in condensation reactions (at least with amines but also with phenols). I do not know how it is effective as biocide and at which concentrations it works, but my expectation is that it should effectively become bound with soil organic matter, due to condensation, and might interfere with some solutes/[p;;utants of interest. For example, it might interact with some organic pharmaceuticals. and it would reduce some heavy metals and/or just make ciomplexes with them. In thisd sense, sodium azide seems to be as a simple alternative. It is rarely interacting with organic solutes (if at all), and quite inert with metals (but! some do not consider that azides of heavy metals have low water solubility; but this could be easily checked with solubility data sources).

Dear Mikhail,

thank you very much for your very helpful answer. So, it appears that formaldehyde is not a very good choice. As you suggest, we will test sodium azide and check if there not competition with target contaminants for sorption sites.

Thanks again.

good luck! and have controls of your solutes with sodium azide (without soil and any other sorbent), to rule out any chemical reaction between azide and solutes.

How about autoclaving the soil (maybe twice) before use.