Effect of bioremediation or organic treatments of soil contaminated with some heavy metals on the biological and L- glutaminase activity

Abstract

For the purpose of identify the ability of bioremediation or organic treatments of soil to reduce the harmful effect of heavy metals including Zn, pb and cd on the biological activity such as soil respiration, the total number of fungi and the activity of the L-glutaminase enzyme have been studied. A laboratory incubation experiment was applied in the Soil Microbiology Laboratory in the Department of Soil Sciences and Water Resources in the College of Agriculture– Basrah University. The soil of the surface layer (0-30 cm) from Qurna district, north of Basrah province was contaminated with the critical levels of the heavy metals cd, Pb, Zn and were placed in an incubator at 30°C for 14 days. The biological and organic treatments process was applied by inoculating soil contaminated with Aspergillus niger or humic acid (40 L ha-1) or sterilized cow manure (4%), incubated at 25°C for 30 days, then some biological parameters were estimated at the periods of 10, 20 and 30 days. Results have been showed that an inhibitory effect of the studied heavy metals on the biological parameters, and the Cd has been recorded the highest percentage of inhibition of total number of fungi (30.67%), the amount of CO2 released (13.93%) and the activity of the L-glutaminase enzyme (45.33%) compared to the control treatment. The ability of the treatments materials to remove heavy metals were (89.02%) for A. niger compared to humic acid (63.48%) and cow manure (48.71%). It was reflected in an increase in the number of fungi, which recorded 152, 167.75, 174.5 cfu g-1 when treated with A. niger, cow manure and humic acid, respectively compared to the control treatment which was (65.92 cfu g-1). The biological and organic treatments also increased the level of liberated CO2 from the polluted soil to 268.62, 253.86, 303.59 mg CO2 g-1, respectively compared to the control treatment. The activity of the L-glutaminase enzyme has increased due to application of treatments. It was 57.02, 48.97, 70.41 µg NH4+ g-1 2hr.-1 for inoculated with A. niger or treated with cow manure and humic acid, respectively, while the control treatment was 37.19 µg NH4+ g-12hr.-1.