Die Bodenkultur - Journal for Land Management, Food and Environment

B. M. Dahal, A. Mentler, W. E.H. Blum:

Arsenic distribution in soil aggregate fractions of two different cropping fields in Nepal


The groundwater of Nawalparasi District of Nepal is severely contaminated with arsenic which can add in to soils during irrigation. The aggregate fractions are a major part of soil which holds various elements which were uptaken by plants. Therefore, arsenic contents in different aggregate fractions and their correlation with Fe, Mn, Al and Ca were studied in two agricultural cropping fields (rice and vegetable). The investigated soil particle size fraction was < 2 mm.

Within this fraction, 4 different aggregate sizes were separated by sonification and sieving. Most amount of arsenic was found in the more abundant smaller aggregates; however, arsenic concentrations were highest in larger aggregates.

The element content of each aggregate fraction was measured after microwave digestion. Under rice no distinct correlation of arsenic with Fe, Mn, Al and Ca was found. Under vegetables As showed a significant correlation with Fe, Mn and Ca in the smaller aggregate fractions (≤ 0.63 mm). Hence, the arsenic distribution in soil is affected by the distribution of soil aggregate fractions.

Key words:  Arsenic, soil aggregate fractions, rice field, vegetable field.