Hydrogen peroxide is not a good reagent for the removal of soil organic matter

Organic matter (OM) is the most important cementing agent of soil particles. Soils containing high amount of OM (like the limestone soil from Leyte in the picture below) generally have good aggregation (i.e. the sand, silt and clay particles are glued together by the OM). Removal of OM using chemical reagents is thus an important pretreatment in textural or particle size analysis as well as in the evaluation of soil mineralogy, cation exchange capacity, and surface area.
Soil in Leyte having a dark surface horizon due to OM 
Hydrogen peroxide (H2O2) which was first used in 1923 by G.W. Robinson to destroy soil organic matter, is the most widely used chemical reagent for removing OM in soil laboratories worldwide. However, there have been some scientific reports indicating that it may not be a good reagent for that purpose due to some unwanted effects on the mineral soil particles. In the Philippines, it is not also easy to procure large volumes of hydrogen peroxide since it requires clearance from the Philippine National Police.
Robert Mikutta and colleagues from the Institute of Soil Science and Plant Nutrition of the University of Halle-Wittenberg, Germany in a study published in the Soil Science Society of American Journal, Vol. 69 (2005), compared the performance of the three most accepted reagents for OM removal: hydrogen peroxide, sodium hypochlorite (NaOCl), and disodium peroxodisulfate (Na2S2O8).
The old soil mineralogy lab at the Univ Halle-Wittenberg
They found that: 1) removal of OM from soil is mostly incomplete with efficiency of removal varying with reaction conditions and sample properties; 2) sodium hypochlorite and disodium peroxodisulfate are generally more effective in removing OM compared with hydrogen peroxide; 3) alkaline conditions and additives favoring dispersion and/or decomposition of OM such as sodium pyrophosphate, are crucial for OM removal; and 4) OM removal can be little in soils containing high amounts of clay-sized minerals like Fe oxides, poorly crystalline Fe and Al phases, and expanding clay types.
The authors also found that the use of hydrogen peroxide to remove OM should be avoided for the determination of mineral particle properties since the treatment may promote organic-assisted dissolution of poorly crystalline minerals at low pH, disintegration of expandable clay minerals, and transformation of vermiculite into mica-like products due to ammonium (NH4+) fixation.
Clay collection for mineralogical analysis 
They concluded that sodium hypochlorite and disodium peroxodisulfate are less harmful for soil minerals than hydrogen peroxide; prolonged heating to 40 degrees Celsius during any pretreatment may transform poorly crystalline minerals into more crystalline ones; and sodium hypochlorite can be used at 25 degrees Celsius and can thus prevent heat-induced soil mineral changes.
Simply put: sodium hypochlorite is better than hydrogen peroxide in removing OM from soil samples.

Reference

Mikutta R, Kleber M, Kaiser K and Jahn R. 2005. Organic matter removal from soil using hydrogen peroxide, sodium hypochlorite, and disodium peroxodisulfate. Soil Science Society of America Journal 69: 120-135.

Comments

Post a Comment

Popular posts from this blog

Tropical soils: some important aspects of these less understood soils

Image
Tropical regions occur between the Tropic of Cancer and the Tropic of Capricorn. The tropics include approximately 40% of the land surface and is the largest ecozone of the earth. According to Köppen (1931), the tropics are characterized by an annual mean air temperature above 18°C through­out the whole year. The largest climatic variation is introduced by the variability of precipita­tion, reaching from nearly 0 mm in the Saharan and Atacama Desert to 11,700 mm on Mt. Waialeala in Hawaii (Eswaran et al., 1992). An Afisol (Luvisol) soil derived from mudstone in Eastern Samar, Philippines According to Uehara and Gillman  (1981), "t ropical soils" is a common name used to identify any soil that occurs in the tropics. They noted that like most common names, the term lacks precision, but it is more readily understood by a larger audience than are the scientific names. In contrast, Sanchez (1976) argued against the use of the term "tropical soils" since it does not accur
Read more

The causes of the Guinsaugon landslide

Image
On 17 February 2006, a catastrophic landslide buried the village of Guinsaugon, the second largest village of St. Bernard town (Southern Leyte, Philippines) killing more than a thousand residents and displacing approximately 19,000 people. The landslide originated on an approximately 800 m high escarpment produced by the Philippine Fault that bisects Leyte and the major islands of the Philippines. In a recent article which synthesized the papers presented during an international conference in Leyte 2008 and published in the international journal Bulletin of Engineering Geology and the Environment, Guthrie and co-workers (2009) arrived at the following conclusions: "The approximately 15 million m3 landslide was a result of progressive failures and tectonic weakening in a region made especially vulnerable by the inter-reaction of geological/tectonic, climatic and cultural factors. In southern Leyte, geology and tectonics (including historical seismicity, the progressive disintegr
Read more