Phosphate sorption and desorption by Thai upland soils

Geoderma 01/2009; 153:408-415. DOI: 10.1016/j.geoderma.2009.09.005

ABSTRACT Phosphate (P) sorption and desorption characteristics have been investigated for sixty-two representative
samples of the major Thai upland agricultural soils which are Oxisols and Ultisols formed on diverse parent
materials and under various climatic conditions. P sorption characteristics are well described by Langmuir and
Freundlich equations. Values of Langmuir P sorption maximum (Xm) and b coefficient range from 47 to
1250 μg g−1 soil and 0.5 to 30 mL μg−1, respectively and the Freundlich k varies between 12 and 1694 μg g−1
and B coefficient 0.09 and 0.67. Soils derived from basalt have larger values of P sorption maximum than soils
on other parent materials. Both P sorption maximum and Freundlich k are closely related to pH (NaF), SSA,
total titanium, aluminum and iron, dithionite and oxalate extractable Fe and Al, and other soil properties that
reflect specific surface area. Soil pH in NaF is highly effective in predicting the P sorption capacity of Thai upland
soils explaining 79% of the variation in P sorption by these soils. P desorption curves for adsorbed P are well
described by the Freundlich equation. The Freundlich kd coefficient for P desorption is highly, linearly related to
the Freundlich k coefficient of P sorption indicating that the above soil factors that contribute to P sorption
similarly affect P desorption.

  • [Show abstract] [Hide abstract]
    ABSTRACT: This study was designed to survey the reservoir sediment properties, assess the phosphorus (P) sorption isotherm, and analyze the relationship between sediment properties and sorption parameters. Physicochemical analysis indicated that sediment from the FUSHI reservoir in Zhejiang Province, China, has similar physical and chemical properties and has been contaminated by P. Sorption isotherm experiments showed that the sorption process could be described by Langmuir and Freundlich models. The parameters of Q max (Phosphorus sorption maximum) and K (Freundlich adsorption isotherm constant) ranged from 618.98 to 825.70 mg kg−1 and 114.18 to 170.74 l kg−1, respectively. EPC0 (zero P equilibrium concentration) ranged from 0.14 to 0.24 mg l−1, more than the total P concentration in the water of the reservoir. Thus, the reservoir sediment releases P into the water and acts as a “P resource”. The clay, Feo, Alt, and Fet + Alt content were the main active components in P sorption. Q max had a highly significant positive relationship with some properties and could be estimated by a combination of these.
    Environmental earth sciences 67(1). · 1.45 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Coronary artery disease is fast emerging as the major concern for afflicting people across the globe. The Indian subcontinent is highly predisposed to this condition due to distinctive risk factor profile of this population. This fact has led to a condition where the current preventative and management protocols that have worked well in the non-Asian Indian Caucasian populations, have failed to bring about the anticipated control over the incidence and progression of CAD in Asian Indians. Metabolic syndrome has been identified as a major determinant of CAD in this population. The prevalence of metabolic syndrome was determined in 431 patients undergoing coronary angiography through various diagnostic algorithms. The Asian modified diagnostic criteria were also implemented to estimate the metabolic syndrome prevalence in patients with different levels of stenosis. We observed a high incidence of metabolic syndrome in the patients with coronary artery disease. The prevalence of MS increased with increase in severity of coronary artery involvement. The IDF guideline with Asian modification was the most successful diagnostic algorithm. It is now imperative to acknowledge the unique pattern of CAD and risk factor profile prevalent among South Asians. This will facilitate more focused and individualized management protocols directed to this population. Metabolic syndrome is a major syndrome prevalent in this population. Hence, effective control of MS may help in reducing the morbidity and mortality due to CAD in a great way.
    Diabetes & metabolic syndrome. 04/2011; 5(2):53-60.
  • [Show abstract] [Hide abstract]
    ABSTRACT: PurposeAccumulated soil phosphorus (P) in agricultural lands due to long-term organic manure and mineral phosphate fertilizer input is considered one of the main non-point pollution sources to surrounding surface water bodies. A chronosequence of soils is a potent instrument for pedological investigation and allows assessment of the effect of duration of agricultural cultivation on the environmental risk to water bodies of P loss from soil. Materials and methodsThe present study was conducted to evaluate the impact of pedogenesis on the retention of P in a chronosequence (25, 100, 300, 700, and 2,000years) of rice paddy soils located on the south bank of Hangzhou Bay. Batch sorption–desorption experiments were performed on the samples of surface horizons from this chronosequence. Results and discussionP retention differed moderately among the studied soils ranging from 17.8% to 22.6% when 2,500mgPkg−1 was added. Subsequent desorption experiment revealed that 11.2% to 21.9% of the recently sorbed P might move into solution. The maximum P sorption capacity as estimated by Langmuir isotherm ranged from 521.9 to 850.9mgkg−1, with a mean value of 726.2mgkg−1, while the degree of P saturation was less than 5%. The results indicate that P sorption is influenced by soil development with the maximum sorption capacity of studied soils significantly positively correlated to the organic carbon content of these soil materials. ConclusionsThe pH of the soil decreased from alkaline to neutral with increasing duration of rice cultivation due to continuing decalcification. The organic carbon content in the paddy surface soil materials increased with increasing duration of rice cultivation. The maximum P sorption capacity also slightly increased with increasing duration of rice cultivation likely due to organic carbon accumulation in topsoils. There is a very low risk of P in these paddy soils moving to the surrounding surface water bodies. This study of some possible long-term impacts helps to indicate that rice paddy agriculture is an environment friendly and sustainable land use. KeywordsDegree of phosphorus saturation–Maximum phosphorus sorption capacity–Non-point pollution–Paddy soil chronosequence
    Journal of Soils and Sediments 11(2):249-259. · 1.97 Impact Factor