Untreated Soil Samples Research Articles

Effect of Cement Kiln Dust on the Geotechnical Properties of Clay in Ede, South-western, Nigeria

This paper investigated the effect of cement kiln dust (CKD) on the geotechnical properties of clay. Soil sample was collected from clay deposit at Ede North Local Government Area, Osun State, which lies within the geographical coordinates of 7N and 4E, was treated with up to 10% CKD. Sieve analysis, specific gravity, consistency limits, compaction (British Standard Light, BSL and West African Standard, WAS) and California Bearing Ratio (CBR) tests were carried out on both treated and untreated soil samples. Results showed that Ede clay is an A-7- 6 soil. Specific gravity increased from 2.61 to 2.91 with increase in CKD from 0 to 10%, maximum dry density (MDD) of the natural soil sample increased from 1.72 and 1.76 g/m’ to 1.84 and 1.85 g/m’ at 8% CKD for BSL and WAS, respectively. The unsoaked CBR of the specimen increased from 17 to 35% for 0-10% addition of CKD, and a similar trend was observed for the 24 hours soaked CBR values. This study indicated that CKD, though regarded as waste material, can be used to improve the geotechnical properties of Ede clay.

Dissipation kinetics and risk assessment of chlorfenapyr on tomato and cabbage.

A field experiment was conducted over two seasons to evaluate the dissipation kinetics and assess the risks of chlorfenapyr in tomato and cabbage following foliar application of chlorfenapyr 10% SC at 100 and 200ga.i.ha-1. Samples of tomato, cabbage, and soil were analyzed and quantified by gas chromatography-electron capture detector (GC-ECD). The limit of detection (LOD) and limit of quantification (LOQ) of chlorfenapyr were found to be 0.01 and 0.03mgkg-1, respectively, in tomato, cabbage, and soil. The dissipation of chlorfenapyr followed first-order kinetics. The compound showed less persistence in both the vegetables and soil as the calculated half-life values of chlorfenapyr ranged between 4.54 and 7.74days considering two different doses and seasons. The residue was below detection limit in all the untreated plant and soil samples. The pre-harvest interval (PHI) of chlorfenapyr in both the vegetables was determined to be 9-14days regardless of dose or season. The theoretical maximum residue contribution (TMRC) of chlorfenapyr was calculated for tomato and cabbage and was found to be lower than the maximum permissible intake (MPI) of the compound. Therefore, the application of chlorfenapyr at the recommended dose in tomato and cabbage for crop protection seems to be safe from both environmental contamination and consumer safety standpoints.

THE USE OF HEU-TYPE ZEOLITIC TUFF IN SUSTAINABLE AGRICULTURE: EXPERIMENTAL STUDY ON THE DECREASE OF NITRATE LOAD IN VADOSE ZONE LEACHATES

A HEU-type zeolitic tuff of very-high quality (88 wt.% clinoptilolite-heulandite) has been used as an additive to natural soils, aiming to reduce the produced nitrate load in leachates, following a common irrigation scheme. Zeolitic tuff has been added and mixed with agricultural soil in three different proportions (0.2, 0.4 and 0.6%) corresponding to an application of 500, 1000 and 1500 kg per acre. The control soil (without zeolitic tuff) and the three mixtures were exposed in a ten weeks experiment, in which, specific doses of irrigation water enriched in nitrates were added. Results of leachates analyses revealed that the addition of 0.2% zeolitic tuff is not effective and the mixture of soil-zeolitic tuff appears to have similar behaviour with the untreated (reference) soil sample. On the contrary, zeolitic tuff additions by 0.4% and 0.6% showed remarkable results and reduced the nitrate load of leachates by 81 and 86%, respectively. Hence, the impacts from the application of very-high quality HEUtype zeolitic tuff in agricultural soils could be rather positive towards environmental protection and rational farming, an in line with the goals and objectives of the new common agricultural policy imposed by European Union

Effect of cyclic loading on the compressive strength of soil stabilized with bassanite–tire mixture

This study investigates the effect of static and cyclic loading on the performance of soil stabilized with recycled bassanite, produced from gypsum wastes, mixed with waste tire shreds. Recycled bassanite was mixed with furnace cement in different proportions to prevent the solubility of bassanite. Different percentages by weight of this admixture were mixed with the test soil. In addition, different percentages and sizes of waste tire shreds along with a fixed content of bassanite admixture were mixed with the tested soil. The static and cyclic strength and stiffness parameters of soil specimens treated using the different schemes were measured from cyclic triaxial tests. The results obtained showed that recycled bassanite improved the strength of the treated soil, but the increase in compressive strength was much higher compared to the tensile strength. The strength of the treated soil increased as the admixture content and proportion of cement in the admixture increased. Shredded waste tire improved the tensile strength of the treated soil, but slightly reduced its compressive strength. Cyclic loading resulted in significant degradation of strength for samples treated with bassanite admixture; however, incorporation of shredded tire reduced this degradation. It was also noted that the size of shredded tire had negligible effect on cyclic strength of the treated soil. The results also showed that the fatigue life of stabilized soil increased with the increase of shredded tire content and bassanite admixture. As expected, the number of load cycles had a negative effect on the strength of treated soil: as the number of load cycles increased the strength degradation increased for both treated and untreated soil samples. The effect of number of cycles was more pronounced in the case of unreinforced soil sample while it reduced when tire shreds were incorporated in soil mixture.

Influence of tebuconazole and copper hydroxide on phosphatase and urease activities in red sandy loam and black clay soils.

The efficacy of two selected fungicides i.e., tebuconazole and coppoer hydroxide, was conducted experiments in laboratory and copper hydroxide on the two specific enzymes phosphatase and urease were determined in two different soil samples (red sandy loam and black clay soils) of groundnut (Arachis hypogaea L.) from cultivated fields of Anantapuramu District, Andhra Pradesh. The activities of the selected soil enzymes were determined by incubating the selected fungicides-treated (1.0, 2.5, 5.0, 7.5 and 10.0 kg ha−1) and -untreated groundnut soil samples at 10 day intervals. By determining the effective concentration, the rate of selected enzyme activity was estimated by adding the suitable substrate at 10, 20, 30 and 40 days of soil incubation. Both the enzyme activities were increased up to 5.0 kg ha−1 level of fungicide in both soil samples significantly at 10 days of soil incubation and further enhanced up to 20 days of incubation. The activity of the phosphatase and urease decreased progressively at 30 and 40 days of incubation. From overall studies, higher concentrations (7.5 and 10.0 kg ha−1) of both tebuconazole and copper hydroxide were toxic to phosphatase and urease activities, respectively, in both soil samples.

Permeability of lime- and cement-treated clayey soils

The permeability (k) of lime- and cement-treated clayey soils was investigated in the laboratory by flexible-wall permeability tests and oedometer tests. Test results indicate that for the cement-treated soils (with up to 8% cement content by dry weight), the value of k is almost equal to that of untreated soils under identical void ratio (e) conditions, and the k value decreases significantly when the cement content is higher than 8%. For lime-treated soils, the threshold lime content is about 4%. Investigation of the soil microstructure using the mercury intrusion porosimetry (MIP) test and scanning electron microscope (SEM) imaging indicates that when the cementation products formed by the pozzolanic reaction fill mainly the intra-aggregate pores, the value of k is comparable for the treated and untreated samples. When the cementation products begin to fill the interaggregate pores, the value of k of the treated sample becomes smaller than that of the untreated soil sample under the identical e value condition. An indication that the cementation products have filled the interaggregate pores is the rapid increase in strength of the treated soil.

Identification of geochemical processes controlling the neutralization of abandoned coal mine drainage using integration of geochemical modelling, geochemical analysis, and batch test: an example from the south of Bochum, Germany

Geochemical modelling, geochemical analysis, and batch extraction test were used to determine the geochemical processes controlling neutralization of the abandoned coal mine drainage of a Ruhr hard coal coalfield, presented in the south of Bochum. The geochemical modelling was performed on the surface water and the groundwater samples collected from the vicinity of the abandoned coal mines, while the geochemical analysis and the batch extraction test were performed on man-made materials, untreated soil samples, treated fertilized soil samples, and rock samples collected from the study area. The geochemical analysis, represented by pH and carbonate test, and the batch test aimed to classify the buffering systems existing in the study area, to identify the buffering level of each system, and to determine the potential sources and reactions controlling the buffering levels. Conversely, the geochemical modelling aimed to determine the source of the carbonate alkalinity. The results of experiments and methods used in this study showed that the neutralization of the abandoned coal mine drainage in this area is controlled by dissolution of carbonate minerals (calcite, aragonite, and dolomite), weathering of silicate and clay minerals, and redissolution of secondary minerals (hydroxides). Furthermore, the buffering systems in this area were divided into geogenic and anthropogenic. The anthropogenic buffering system includes the man-made materials and the treated fertilized soil covers, while the geogenic buffering system consists of the untreated soil cover, the hydroxides and the rock formations. The anthropogenic system has a buffering level of 5.6–11.71 identifying a highly effective short-lived buffer system, while the geogenic system has a buffer level of 4.01–7.17 identifying a moderately effective long-lived buffer system. The importance of this research is related to being a foundation that must be taken into account when making plans for the management of water in the coal mines that will be closed in the near future all over Germany.

Reducing the bioavailability of cadmium in contaminated soil by dithiocarbamate chitosan as a new remediation.

Dithiocarbamate chitosan (DTC-CTS) was used as a new amendment for remediation of cadmium (Cd)-contaminated soils to reduce the Cd bioavailability. Arabidopsis thaliana was chosen as a model plant to evaluate its efficiency. It was found that DTC-CTS could effectively improve the growth of A. thaliana. The amount of Cd up-taken by A. thaliana could be decreased by as much as 50% compared with that grown in untreated Cd-contaminated soil samples. The chlorophyll content and the aerial biomass of Arabidopsis also increased substantially and eventually returned to a level comparable to plants grown in non-contaminated soils, with the addition of DTC-CTS. These findings suggested that DTC-CTS amendment could be effective in immobilizing Cd and mitigating its accumulation in plants grown in Cd-contaminated soils, with potential application as an in situ remediation of Cd-polluted soils.

Research on Wetting-Drying Cycles’ Effect on the Physical and Mechanical Properties of Expansive Soil Improved by OTAC-KCl

Expansive soil experiences periodic swelling and shrinkage during the alternate wet and dry environments, which will result in severe damage to the slope stability. In this study, a promising modifier OTAC-KCl is introduced, which has a good diffusivity and is soluble in water or other solvents easily. Firstly, a reasonable combination of ameliorant 0.3% STAC and 3% KCl is chosen referring to the free swell test. Then, the best curing period, 14 days, is gotten from UCS tests. The effect of wetting and drying cycles on engineering properties of expansive soil improved by OTAC-KCl admixtures after 14-day curing is also studied accordingly. Both treated and untreated expansive soil samples are prepared for the cyclic wetting-drying tests which mainly include cyclic swelling potential and cyclic strength tests. Experimental results show that the swelling potential of expansive soil samples stabilized with OTAC-KCl is suppressed efficiently, and the untreated soil specimens will collapse when immersed in water while the treated specimens keep in good conditions. Moreover, expansive soil samples modified with 0.3% OTAC + 3% KCl show enough durability on the swelling ability, shear strength, and unconfined compressive strength, which means, that both the physical and the mechanical properties of stabilized expansive soil have been improved effectively.

Free swell potential of lime-treated gypseous soil

Lime treatment generally enhances the geotechnical properties of the soils. However, some studies have reported an adverse effect, especially in the presence of gypsum. To develop an understanding of the underlying mechanisms, a study of fine-grained soil with different amounts of gypsum was carried out. The influence of curing conditions (curing period and curing temperature) and wetting-drying cycles on the swell potential of fine-grained soil with (0, 5, 15 and 25%) gypsum was investigated to assess the long-term behavior of this type of soil (i.e. gypseous soil) when used in the construction of road and pavement structures. Mineralogical and microstructural studies (porosimetry, X-ray diffraction and scanning electron microscopy) were carried out to evaluate the cementitious materials and the presence of ettringite. The results show that increasing the gypsum content decreased the swell potential of the untreated soil samples. On the other hand, the swell potential values of soil samples started decreasing after the first wetting–drying cycle then reached equilibrium. Lime treatment results show that the suppression of swelling in lime-treated soil samples without gypsum was partly lost after the first cycle, especially for short curing periods and for both temperature values (20°C and 40°C), while long-term curing periods (more than 28days) gave good results with respect to the suppression of swell potential values. Lime treatment of gypsum-containing samples showed an adverse effect on swell potential. The swell potential values increased with curing period and curing temperature, due to the formation of ettringite. Lastly, wetting–drying cycles caused an increase in the swell potential values of gypsum-containing samples, cancelling out the beneficial effect of lime treatment to control swell.

Effects of a sulfonylurea herbicide on the soil bacterial community

Sulfonylurea herbicides are widely used on a wide range of crops to control weeds. Chevalier® OnePass herbicide is a sulfonylurea herbicide intensively used on cereal crops in Algeria. No information is yet available about the biodegradation of this herbicide or about its effect on the bacterial community of the soil. In this study, we collected an untreated soil sample, and another sample was collected 1month after treatment with the herbicide. Using a high-resolution melting DNA technique, we have shown that treatment with Chevalier® OnePass herbicide only slightly changed the composition of the whole bacterial community. Two hundred fifty-nine macroscopically different clones were isolated from the untreated and treated soil under both aerobic and microaerobic conditions. The strains were identified by sequencing a conserved fragment of the 16S rRNA gene. The phylogenetic trees constructed using the sequencing results confirmed that the bacterial populations were similar in the two soil samples. Species belonging to the Lysinibacillus, Bacillus, Pseudomonas, and Paenibacillus genera were the most abundant species found. Surprisingly, we found that among ten strains isolated from the treated soil, only six were resistant to the herbicide. Furthermore, bacterial overlay experiments showed that only one resistant strain (related to Stenotrophomonas maltophilia) allowed all the sensitive strains tested to grow in the presence of the herbicide. The other resistant strains allowed only certain sensitive strains to grow. On the basis of these results, we propose that there must be several biodegradation pathways for this sulfonylurea herbicide.

Removal of organic matter and oxides of iron and manganese from soil influences boron adsorption in soil

The influences of specific soil components such as organic matter and oxides of Fe and Mn on B adsorption characteristics are not understood well. In the present study, we compared B adsorption behavior of two acidic soils after removal of organic matter, and Fe- and Mn-oxides with that of untreated soil samples. The B adsorption capacity of the soils before and after removal of different components was low; the average values of maximum B adsorption obtained from nonlinear least square optimization of Langmuir adsorption isotherm being 20.61mgkg−1 for Mallerbari soil and 27.15mgkg−1 for Sikarpur soil. Removal of organic matter by NaOCl treatment from the soils increased B adsorption. This indicates that Fe- and Al-oxides and other available adsorption sites on the mineral surfaces are coated by organic matter and are activated only after removal of organic matter. Removal of Fe- and Mn-oxides, however, resulted considerable decrease in B adsorption in the soils. It is, therefore, suggested that B adsorbing surfaces in soil decrease on removal of Fe- and Mn-oxides, since these oxides are known to have good adsorptive capacity for B.

Amino acid treatment enhances protein recovery from sediment and soils for metaproteomic studies

Characterization of microbial protein expression provides information necessary to better understand the unique biological pathways that occur within soil microbial communities that contribute to atmospheric CO2 levels and the earth's changing climate. A significant challenge in studying the soil microbial community proteome is the initial dissociation of bacterial proteins from the complex mixture of particles found in natural soil. The differential extraction of intact bacterial cells limits the characterization of the complete representation of a microbial community. However, in situ lysis of bacterial cells in soil can lead to potentially high levels of protein adsorption to soil particles. Here, we investigated various amino acids for their ability to block soil protein adsorption sites prior to in situ lysis of bacterial cells, as well as their compatibility with both tryptic digestion and mass spectrometric analysis. The treatments were tested by adding proteins from lysed Escherichia coli cells to representative treated and untreated soil samples. The results show that it is possible to significantly increase protein identifications through blockage of binding sites on a variety of soil and sediment textures; use of an optimized desorption buffer further increases the number of identifications.

Measured effects on engineering properties of clayey subgrade using lime–Homra stabiliser

The engineering properties of clayey subgrade soils may need to be improved for suitability in construction using appropriate stabilisation methods. Stabilisation of pavement subgrade soils has traditionally relied on treatment with lime, cement and sometimes special additives, which are regarded as waste materials. Alternatively, the Egyptian bricks/ceramic industry generates large amount of calcined-clay waste or crushed clay bricks (known as Homra). In this study, standard laboratory soil tests were conducted to measure changes in the engineering properties of clayey soils when treated with a lime+Homra (L+H) blend. Tests were conducted on untreated control soil samples and on varieties of treated samples with L+H ranging from 1% to 11% for lime and 5% to 15% for Homra. The results showed that the L+H clay samples exhibit low plasticity, swelling, maximum dry density and consolidation settlement. On the other hand, results showed a significant increase in California Bearing Ration, soil cohesion and soil strength. The internal friction angle concerning shear strength parameters is also enhanced. It can be summarised that engineering properties of clayey soils can be enhanced using lime and Homra. This is advantageous for work construction in the civil engineering field.

Assessment of ability of three chemical oxidants to remove hydrocarbons from soils polluted by Bonny Light crude oil.

Three prominent hydrocarbon groups found in crude oil- Polycyclic Aromatic Hydrocarbon (PAH);Benzene,Toluene,Ethylbenzene and Xylene(BTEX) and Total Petroleum hydrocarbon(TPH) were used to study the ability of three chemical oxidants-Fenton’s reagent, Potassium permanganate, and Potassium persulfate to degrade hydrocarbons in crude oil inundated soils. This was done by spiking soil samples with Bonny light crude oil and subsequently treating the mixture with the different chemical oxidants at acidic, neutral and basic pH media for each of the oxidants. Oil extracts from the treated and untreated soil samples were later analyzed for the three hydrocarbon groups using a gas chromatograph (GC). Treatment with Fenton’s reagent proved very efficient in the removal of the hydrocarbons especially at the acidic pH with some components of TPH experiencing complete disappearance. Also the four ringed-PAHs were depleted more than the three ringed- ones at the indicated pHs. For the treatment with potassium persulfate, while the oxidant was good in the removal of BTEX at the different pHs, it was found to be very inefficient for the removal of PAHs. Generally, Four and five ringed–PAHs were degraded more than the three and two ringed-PAHs, an indication that degradation of PAHs by oxidants may be a function of hydrocarbon structure. Treatment with potassium permanganate was found to be pH dependent with most of the depletions occurring at acidic pH. Even though potassium permanganate was not as good as the other oxidants in the removal of aliphatic hydrocarbons(TPH), it was found to be effective in the removal of aromatic hydrocarbon(BTEX and PAH). Also the four ringed-PAHs such as pyrene, benzoanthracene, and chrysene were seriously attacked at all pHs. BTEX was also attacked more at acidic pH with above 90% removal at the acidic pH.

Nanotechnology as a Preventive Engineering Solution to Highway Infrastructure Failures

AbstractThis paper reports the results of research on the application of nanomaterials to improve the quality and durability of road infrastructure. The research investigated road transportation infrastructure failures and the feasibility of preventive engineering solutions using nanotechnology. Laboratory experiments were conducted on different treated and untreated Nigerian soil samples (laterite, clay, and black soils) to study the changes in their fundamental geotechnical properties. Common engineering standards were used for the experiments and results analysis. Laboratory tests showed that treated laterite and clay soils had improved the liquid limit, plastic limit, and shrinkage index, including hydrophobic properties. The California bearing ratio (CBR) improved by as much as 87–125%. However, the black soil sample only passed the hydrophobicity test. The black soil did not exhibit any bearing strength in the CBR test, even after treatment with the nanomaterial. The paper contributes to understandi...

Feasibility of Estimating Cu Contamination in Floodplain Soils using VNIR Spectroscopy—A Case Study in the Le’an River Floodplain, China

Heavy metal accumulation can influence the physical, chemical, and ecological processes in the soil ecosystem, and the accumulation of heavy metals has become a serious environmental issue in China, especially in the floodplains downstream from mining and smelting sites. A novel method of estimating the heavy metal contamination of soil is proposed using visible and near-infrared (VNIR) spectroscopy and partial least squares regression (PLSR). Our study focuses on the Le’an river floodplain, Jiangxi Province, China, which houses the largest copper mining operation in China and has suffered a series of environmental setbacks from the extraction of copper. Our study employs PLSR to summarize the relationship between VNIR reflectance spectra and the copper content of collected soil samples, and then estimates copper contamination of the soil using VNIR spectroscopy and the calibrated model. More specifically, with 71 soil samples collected from the Le’an River floodplain, our study aims at (1) exploring the correlation between VNIR and soil constituents, including soil organic matter, total copper, and iron content; (2) assessing the relationship between VNIR determination of copper and the pre-processing of soil samples; and (3) evaluating the performance of data transformation methods in PLSR. The correlation analysis revealed that the mechanism of estimating Cu content lay in its correlation with Fe content. The PLSR model with logarithmic scale transformed copper content and the standard normal variate spectra was chosen for estimating copper contamination from untreated soil samples; the model with logarithmic scale transformed copper content and reflectance spectra was selected for pretreated soil samples. The correlation analyses and regression results in the PLSR models both suggest that the main mechanism for estimating Cu content in this case study lies in its correlation with Fe content. Therefore, the coupling of VNIR spectroscopy and PLSR could serve as an alternative method of monitoring heavy metal contamination of soil.

Toluene sorption behavior on soil organic matter and its composition using three typical soils in China

The effect of soil organic matter (SOM) content and composition on sorption behavior of toluene for fluvo-aquic, red and black soils in China was investigated in batch experiments. Tested SOM was fractionated into two primary sorptive domains (‘soft’ and ‘hard’) to explain the dependence of sorption behavior on SOM composition. All the tested soils exhibited similar sorption kinetics and nonlinear sorption isotherms. Soils with high SOM content possessed a high sorptive capacity. Clay minerals also contributed to the sorptive capacity, especially for fluvo-aquic and red soils with low SOM content. In comparison, after removing most ‘soft’ SOM fraction from soils through hydrogen peroxide treatment, the residual ‘hard’ SOM fraction of three soil samples exhibited a slower sorption rate and a less sorption capacity compared to the untreated soil samples. The nonlinear degree of sorption was positively correlated with the content of ‘hard’ SOM for all soil samples. This is explained by the combined effect of SOM content and the composition on toluene sorption rates, sorption capacity and nonlinear degree of sorption of three typical soils in China.

Metal immobilization and phosphorus leaching after stabilization of pyrite ash contaminated soil by phosphate amendments

In this study we would like to show the importance of a holistic approach to evaluation of chemical stabilization using phosphate amendments. An extensive evaluation of metal stabilization in contaminated soil and an evaluation of the leaching of phosphorus induced after treatment were performed. The soil was highly contaminated with Cu (2894 mg kg(-1)), Zn (3884 mg kg(-1)), As (247 mg kg(-1)), Cd (12.6 mg kg(-1)) and Pb (3154 mg kg(-1)). To immobilize the metals, mixtures of soil with phosphate (from H(3)PO(4) and hydroxyapatite (HA) with varying ratios) were prepared with a constant Pb : P molar ratio of 1: 10. The acetic acid extractable concentration of Pb in the mixture with the highest amount of added phosphoric acid (n(H(3)PO(4)) : n(HA) = 3 : 1) was reduced to 1.9% (0.62 mg L(-1)) of the extractable Pb concentration in the untreated soil, but the content of water extractable phosphorus in the samples increased from 0.04 mg L(-1) in the untreated soil sample up to 14.3 mg L(-1) in the same n(H(3)PO(4)) : n(HA) = 3 : 1 mixture. The high increase in arsenic mobility was also observed after phosphate addition. The PBET test showed phosphate induced reduction in Pb bioavailability. In attempting to stabilize Pb in the soil with the minimum treatment-induced leaching of phosphorus, it was found that a mixture of soil with phosphate addition in the molar ratio of H(3)PO(4) : HA of 0.75 : 1 showed the most promising results, with an acetic acid extractable Pb concentration of 1.35 mg L(-1) and a water extractable phosphorus concentration of 1.76 mg L(-1). The time-dependent leaching characteristics of metals and phosphorus for this mixture were evaluated by a column experiment, where irrigation of the soil mixture with the average annual amount of precipitation in Slovenia (1000 mm) was simulated. The phosphorus concentration in the leachates decreased from 2.60 mg L(-1) at the beginning of irrigation to 1.00 mg L(-1) at the end.

The effect of glyphosate application on soil microbial activities in agricultural land

In recent years, intensive use of herbicides has increasingly become a matter of environmental concern partially because of the effects of these chemicals on soil microorganisms. Glyphosate [N- (phosphonomethyl) glycine] (GP) is a broad-spectrum, non-selective, post emergence herbicide that is widely used in agriculture. In this study, glyphosate effects as N, P and C nutrient sources on microbial population and the effect of different concentration of it on dehydrogenease activity and soil respiration were investigated. The results show that in a soil with a long historical use of glyphosate (soil 1), the hetrotrophic bacterial population was significantly (p<0.05) increased. Also, by increase in the bacterial population, the herbicide existence as the possible nutrient source is enhanced. According to results, bacterial populations in the presence of glyphosate as P source was significantly (p<0.01) higher than N and C sources. The application of GP to the soil led to a significant increase in dehydrogenase activity with respect to untreated control soil samples. Also, respiration rates increased with increasing glyphosate application up to 50 mM but in 500 mM the inhibitory effect of glyphosate was observed. It can be concluded that glyphosate application may alter (increase) soil microbial activity and population. Increased microbial activity may be beneficial or detrimental toward plant growth, soil microbial ecology, and soil quality. Key words : Glyphosate, bacterial population, dehydrogenease activity, soil respiration.