Removal of heavy metals by biosorption using freshwater alga Spirogyra hyalina.

The use of biosorbents for heavy metal removal has revealed enormous potential of algae for biosorption. The dried biomass of Spirogyra hyalina was used as biosorbent for removal of cadmium (Cd), mercury (Hg), lead (Pb), arsenic (As) and cobalt (Co) from aqueous solutions at different initial concentrations of the heavy metals and contact time of the biomass. The results showed that highest amount of Cd, Hg and As was adsorbed when the initial heavy metal concentration was 40 mg l-1 whereas Pb and Co exhibited greatest removal at 80 mg l-1. The value of Freundlich model constant (1/n) for different metals ranged from 0.342 to 0.693 and the values of Langmuir separation factor values (RL) varied between 0.114 and 0.719 that indicated favorable biosorption by the biomass. The order of metal uptake for the dried biomass was found to be Hg>Pb>Cd>As>Co. The finding of the study revealed that dried biomass of S. hyalina has much potential as a biosorbent for the sorption of Cd, Hg, Pb, As and Co.

Short term diurnal and temporal measurement of methane emission in relation to organic carbon, phosphate and sulphate content of two rice fields of central Gujarat, India.

Methane emission from two rice fields of Lambhvel village, Anand district, central Gujarat, India, was measured for whole cultivation period during pre-summer season. Along with the methane emission, soil chemistry of the two rice fields (Organic carbon, PO4 -2 and SO4 -2) was determined. The methane emission ranged from 105.67 to 720.64 mg m-2hr-1, having maximum emission during noon period (11 am to 1 pm) of the day at the rice field 1. Besides, at rice field 2, the methane emission ranged between 201.59 to 430.94 mg m-2hr-1, having maximum peak during same period (11 am to 1 pm) of the day. The results of the current investigation confirm that the methane emission vary substantially between two rice fields, and suggest that soil chemistry and flood water depth might control the methane emission in both the rice fields and suppressed by the phosphate and sulphate concentrations. The greater methane emission was gradually declined from first trip to fourth trip. Correlation analysis, ANOVA and F-test showed that the methane emission from both the sites has positive correlation with organic carbon and negative correlation with sulfate and phosphate content of the soil and the details of these reasons are discussed in this paper.