Effect of anion composition of simulated acid rain on nutrient behavior in reclaimed saline soils

Abstract

The purpose of this study is to demonstrate the relative influence of the anion composition of simulated acid rain on the behavior of nutrients in three reclaimed saline soils. Reclaimed saline soil samples used for this study were collected from surface soils of the Saemangeum and Koheung soils in Korea and the Hachirogata soil in Japan. The Hachirogata soil behaved as a high variable charge soil which was derived from sediments and reclaimed from the deposits of the lake Hachirogata, while the Saemangeum and Koheung soils behaved as permanent charge soils with the cation exchange capacity (CEC) being largely independent of the pH. The simulated acid rain at pH 3.0 was prepared with nitrate-to-sulfate mol ratios of 0.75 : 0.25, 0.5 : 0.5, 0.25 : 0.75, and control (pH 5.7). The influence of the anion composition of simulated acid rain on the changes in the contents of nutrients in reclaimed saline soils was as follows: The soil organic matter content decreased from 36.8 to 24.1 g kg⁻¹ for the Saemangeum soil, from 29.0 to 19.8 g kg⁻¹ for the Koheung soil, and from 137.7 to 85.6 g kg⁻¹ for the Hachirogata soil, respectively: The CEC and point of zero charge (PZC) values in the Saemangeum and Koheung soils were not significantly different, whereas in the Hachirogata soil the CEC decreased by about 15% and the PZC decreased by 1.1 unit. The content of ammonia nitrogen decreased by about 20 to 30%. The content of nitrate nitrogen increased by about 10% for the Hachirogata soil but there was no appreciable difference in the case of the Saemangeum and Koheung soils. The contents of Al-P and Ca-P were not significantly different from the original values in the untreated soil, whereas that of Fe-P decreased by about 30%. The content of inositol phosphate decreased by about 35% in the Hachirogata soil but did not change appreciably in the case of the Saemangeum and Kohueng soils. Different mechanisms were involved in the behavior of anions and cations between the soils with predominant aluminosilicates and the soil rich in hydrous oxides of iron and aluminum. Also, the contents of most of the nutrients changed considerably with the increase of the nitrate content of the simulated acid rain.

Key Words:

• acid rain
• nitrogen
• phosphate
• reclaimed saline soil