Anthropogenic and Natural Influences on Soil Organic Carbon Fractions: A Case Study on Soils of Meyghan Lake in Arak, Iran

Monitoring and assessment of soil organic carbon (SOC) in the soils of arid areas are very important. The objectives of the study were to evaluate the responses of extractable and particulate organic matter in soils around Meyghan Lake in Arak (Iran) to surface water-inflows. Two layers (0-30 cm and 30-60 cm) of soils were sampled in the release sites of municipal wastewater and 3 rivers. Different fractions of SOC were measured and statistically analyzed. The soil sampled from the release sites of municipal wastewater had the highest total organic carbon (14.1 mg TOC g-1 topsoil) and free particulate organic matter (8.07 mg FPOM g-1 topsoil) due to better soil condition for plant growth. In contrast, the soil sampled from the release sites of wastewater of sodium sulfate plant had the lowest the total organic carbon (3.50 mg TOC g-1 topsoil) and all of the fractions. The cold water extractable OC (CWEOC), occluded particulate organic matter (OPOM) and the heavy fraction (HF) as slow fractions responded to soil sampling time better than active fractions. They significantly increased in the soils sampled in fall. The means of CWEOC, hot water extractable OC (HWEOC) and OPOM were higher in the soils sampled from the eastern part of the lake with higher clay and moisture contents and lower elevation. They responded better to the soil properties controlling the biological activity and biodegradation. The best fraction for the study of short-term changes of SOM by anthropogenic and natural effects was FPOM in these non-agricultural lands

The relative effects of some elements on the DNS method in cellulase assay

For evaluating the relative effects of some polluting salts on the measurement of cellulase activity assayed by 3,5-dinitrosalicylate (DNS) this study was done. Glucose and cellulase solutions have been treated with salts. Exoglucanase and endoglucanase were assayed by 3,5-dinitrosalicylate reagent. Measurement of reducing sugar by DNS indicator in the presence of Ca+2, Ba+2, Fe+3, Mn+2, Pb+2, Fe+2, Ag+1, Zn+2, Co+2, and Al+3 salts overestimated and in the presence of Mg+2, Cu+2, Cd+2, and Hg+2 salts underestimated the real contents. The intensity of DNS color and/or the reducing power of glucose increased by decreasing radius of hydrated cation of alkaline-earth elements (from Mg+2 to Ba+2) in glucose solution. Exoglucanase and endoglucanase activities increased in the presence of Na+, K+, Ca+2, Ba+2 and Mn+2 salts and decreased in the presence of NH4+ and Mg+2 salts. Among the trace elements studied, Fe+3, Pb+2, Fe+2, Ag+1, Zn+2, Co+2, and Al+3 were the most effective inhibitors of cellulase activity. These ions inhibited exoglucanase more than endoglucanase. The effect of most ions on cellulase activity may be related to negative or positive effect of them on the method of cellulase assessment. So, for a better data interpretation in the study of ion effects on the soil enzyme activity, both the effects of ions on the method of enzyme assay, and the effects of ions on the enzyme activity should be studied

Factors affecting cellulase sorption in soil

The sorption of cellulase proteins of Trichoderma viride on calcareous soils was investigated, and the soil factors affecting cellulase sorption were also studied. The study on some arid, semiarid and humid soils of Isfahan, Hamadan and Gilan provinces of Iran revealed that the sorption of cellulase on the calcareous soils obey both the Freundlich and the Langmuir isotherms. The maximum binding levels of cellulase on the Isfahan, Hamadan and Gilan soils estimated by the Langmuir model were 58.72, 41.64 and 74.07 g kg-1, respectively. The association binding constants were 3.32, 2.17 and 1.86 ml mg-1 for cellulase sorption on the Isfahan, Hamadan and Gilan soils, respectively. The observed differences may be due to the deferent clay and carbonate contents of soils, because the correlation tests revealed that the sorption capacity of soils was significantly related to the soil clay and carbonates contents. Cellulase sorbed on the soils was not correlated with soil organic mater contents. Sorbed cellulase washed out more easily from the Hamadan soils than from the other soils, probably due to their lower clay contents.Keywords: Sorption, calcareous soils, cellulas

The relative effects of some elements on the DNS method in cellulase assay

For evaluating the relative effects of some polluting salts on the measurement of cellulase activity assayed by 3,5-dinitrosalicylate (DNS) this study was done. Glucose and cellulase solutions have been treated with salts. Exoglucanase and endoglucanase were assayed by 3,5-dinitrosalicylate reagent. Measurement of reducing sugar by DNS indicator in the presence of Ca+2, Ba+2, Fe+3, Mn+2, Pb+2, Fe+2, Ag+1, Zn+2, Co+2, and Al+3 salts overestimated and in the presence of Mg+2, Cu+2, Cd+2, and Hg+2 salts underestimated the real contents. The intensity of DNS color and/or the reducing power of glucose increased by decreasing radius of hydrated cation of alkaline-earth elements (from Mg+2 to Ba+2) in glucose solution. Exoglucanase and endoglucanase activities increased in the presence of Na+, K+, Ca+2, Ba+2 and Mn+2 salts and decreased in the presence of NH4 + and Mg+2 salts. Among the trace elements studied, Fe+3, Pb+2, Fe+2, Ag+1, Zn+2, Co+2, and Al+3 were the most effective inhibitors of cellulase activity. These ions inhibited exoglucanase more than endoglucanase. The effect of most ions on cellulase activity may be related to negative or positive effect of them on the method of cellulase assessment. So, for a better data interpretation in the study of ion effects on the soil enzyme activity, both the effects of ions on the method of enzyme assay, and the effects of ions on the enzyme activity should be studied. Journal of Applied Sciences and Environmental Management Vol. 10(3) 2006: 93-9

Temporal And Spatial Variability Of Lead Levels In Salsola Kali Near Razan-hamadan Highway

The contribution to environmental pollution of heavy metals from automotive emissions has been the subject of intensive investigation in recent years. Airborne metal particulates, such as Pb, have been attributed mainly to emissions from motor vehicle exhausts. The objectives of this study were to evaluate the temporal and spatial variability of lead levels in Salsola kali in the vicinal soils of Razan-Hamadan highway, Iran. In both sides of the highway sampling was carried out on a transect (200-m long), in vertical direction from highway with a separation distance of 20 m, thereby providing 10 actual sampling locations for each side of highway. During 2 seasons of 2002, plant samples were taken from shoots and roots with 3 replicates. Root and shoot organs of samples separately analyzed for Pb concentration with dry ash method by atomic absorption spectroscopy. Lead levels in most of the analyzed plant samples were higher than the natural levels. Lead concentration in the plant organs was decreased exponentially with distance from the road. In both seasons the decrease constant for Pb in root organ was higher than that for shoot organ. The decrease constants for Pb in root and shoot organs of the plant were higher in spring compared to those in autumn. Lead accumulation was significantly higher in shoot organs compared to root organs. The highest lead contents may exceed 37.66 \u3bcgg-1 in the shoot organs of the plant in east side of the road. In both organs of the plant especially in shoot organs lead concentration in autumn compared to that in spring was relatively higher. Translocation factor for lead in the plant sampled in autumn was also higher than that for those sampled in spring

The effects of water potential on some microbial populations and decrease kinetic of organic carbon in soil treated with cow manure under laboratory conditions

The moisture content of the soil habitat is an important stress factor and effects on soil microbial population and activity. The objectives of this study were to test the effects of water potential on the decrease kinetic of soil organic carbon (OC), some microbial populations and their activities in a soil treated with cow manure. A semiarid soil was treated with raw cow manure (CM) at a rate of 20 g kg-1. Three water potentials established for soil incubation were: saturation (SAT, 0 bars), field capacity (FC, -0.3 bars), and permanent wilting point (PWP, -15 bars). Fourth irrigation treatment was drying-rewetting cycle (D-W) between -0.3 to -15 bars. After 0, 10, 20, 40, 60 and 90 days of incubation, soils were sampled for analysis. Colony forming units of bacteria, actinomycetes and fungi and soil OC, basal respiration (BR) and substrate induced respiration (SIR) were measured. The effects of soil moisture, incubation time and their interactions on all of the studied properties and kinetic parameter for OC decrease were significant. The populations of bacteria and fungi were the highest in the soils incubated in DWC and PWP respectively. The population of bacteria decreased significantly with increasing time of incubation. The population of fungi was the lowest in soil incubated in SAT condition and decreased continuously. However fungal population in soil incubated in other moisture increased significantly with increasing time of incubation. The population of actinomycetes was the highest in soil incubated in SAT condition in the early stages of incubation but it was decreased significantly with increasing time in soils incubated in SAT, FC, and DWC. Soil BR and SIR were significantly higher in SAT condition and lower in PWP condition compared to those in other water potentials. However both BR and SIR decreased significantly during soil incubation. Soil OC was significantly higher in SAT and PWP conditions due to unsuitable soil aeration and moisture for OC mineralization. The power function equation was the best model for decrease kinetic of OC in soil incubated in SAT and PWP conditions. However the second order equation was the best model for decrease kinetic of OC in soil incubated in FC and DWC conditions

The effects of water potential on some active forms of phosphorus in a calcareous soil amended with sewage sludge

Immobilization and mobilization reactions of soil phosphorus depend on biological properties of soil and these soil properties strongly depend on the soil water potential. The objective of this study was to test the effects of water potential on some active forms of soil P. A semiarid soil classified as Calcic Haploxerept was treated with raw sewage sludge at a rate of 20 g kg-1. Water potentials established for soil incubation were: saturation (SA, 0 bar), field capacity (FC, -0.3 bar), and permanent wilting point (PWP, -15 bar). An irrigation treatment was dryingrewetting cycle (DWC) between -0.3 to -15 bars. After 0, 20, 60 and 90 days of incubation soils were sampled for analysis. The addition of sewage sludge increased soil total P, organic P, available P, microbial P, soluble and easily soluble P contents. The increase of soluble P was relatively higher. The effects of soil moisture, incubation time and their interaction on all active forms of soil P were significant. During 20 days of incubation, available P and soluble P decreased, whereas microbial P, easily soluble P and dicalcium phosphate increased significantly. After that, available P and easily soluble P increased continuously, but microbial P, soluble P and dicalcium phosphate fluctuated during incubation. Microbial P had negative and significant correlations with available P and easily soluble P. Soils incubated in DWC and FC compared to soils incubated in SA and PWP had significantly higher available P, soluble P and easily soluble P contents. However microbial P and dicalcium phosphate were significantly higher in soils incubated in higher water potential. @ JASE

Detection of Beta-lactamase gene in the culturable bacteria isolated from agricultural, pasture and mining soils around mines in Hamedan, Iran

Introduction: Growing evidence exists that agriculture affects antibiotic resistance in human pathogens. Beta-lactam antibiotics are the most commonly used antimicrobial agents in many countries. The abundance of beta-lactamase encoding genes can be used as an indicator of antibiotic resistance in the environment. So, to determine the beta-lactamase resistance genes, the abundance of culturable bacteria having bla-TEM genesin the soils under different land uses wasexamined. Materials and methods: 44 Gram-positive and 34 Gram-negative bacteria plated on nutrient agar were isolated from agricultural, pasture and mining soils and selected to study the presence of TEM-class gene using PCR amplification. Antibiotic sensitivity test of bla-TEM+isolateswas done adopting the Kirby-Bauer disk diffusion method and antibiotic discs used were: ampicillin, amoxicillin, vancomicin, streptomycin, tetracycline and gentamicin. Finally, five multi-drug resistant and bla-TEM+ isolates were identified using universal primers. Results: The highest level of beta-lactamase genes was observed in the Gram-positive and Gram-negative isolates from the pasture soils. In the agricultural and mining soils, a high abundance of bla-TEM+ isolateswasfound which also showed resistance to beta-lactam antibiotics. The identified multi-drug resistant and bla-TEM+ isolates were from these genera: Achromobacter, Bacillus, Brevibacillus, Aminobacter and Brevundimonas. Discussion and conclusion: The high number of bla-TEM+ bacteria in all the soils may be attributed to the other important feature of bla genes which is their capability to extrude toxic compounds like heavy metals in contaminated environments. Sensitivity of some bla-TEM+ bacteria to beta-lactam antibiotics was interesting. This result shows that bla-TEM genes confer resistance to beta-lactamase inhibitors in a different degree. Some of the identified isolates were pathogen. These pathogens in soils can transfer to plants and human which induce health problems. A high abundance of bla-TEM+ bacteria in the agricultural soil indicates the inefficiency of beta-lactam antibiotics

Biodegradation of Chlorpyrifos and Diazinon Organophosphates by Two Bacteria Isolated from Contaminated Agricultural Soils

Introduction: The organophosphate insecticides such as chlorpyrifos and diazinon have been widely used to control insects in home, agriculture, and veterinary. These compounds are a threat to public health and the environment; on the other hand, they have low degradation rate and therefore can be stable for a long time in soil. A major factor determining the fate of organophosphate insecticides in soil and water is biodegradation. Materials and methods: Two diazinon and chlorpyrifos degrading bacterial strains were isolated from pesticides contaminated soils. The isolated bacterial strains were identified by 16S ribosomal RNA gene and fatty acid methyl ester analysis. Results: Strong correlation was seen between microbial growth and the two organophosphates degradation. On average, bacterial strain 1 and 2 degraded 88.27% and 82.45% of initial applied diazinon in medium and degraded 81.07% and 88.35 % of initial applied chlorpyrifos during 20 days, respectively. The isolated bacterial strains were identified as Acinetobacter and Pseudomonas sp. The highest diazinon degradation were found by Acinetobacter and the highest chlorpyrifos degradation were found by Pseudomonas when cultivated in the mineral salt medium. Discussion and conclusion: The identified pure bacterial strains utilized chlorpyrifos and diazinon as a source of carbon. They were able to degrade most of the parental molecule in 20 days. Therefore, the isolated bacterial strains may have the potential for use in the bioremediation of diazinon and chlorpyrifos-contaminated soils