Discussion on methods of soil dehydrogenase determination

Abstract

In this paper, we discuss the influence of different factors on the measured values of dehydrogenase activity. We focus on the incubation time of the sample and optimal 2,3,5-triphenyl-tetrazolium chloride concentration. We provide a comparison between results obtained from three methods: Casida method, standard method, and optimization method. Some disadvantages of traditional methods were critically discussed. We showed that the results of dehydrogenase activity determination strongly depend on the method used. To minimize these discrepancies, the increase in TPF concentration should be described with the kinetic model which allows determining tangent activity. Michaelis–Menten kinetics can be used to describe the relationship between TTC concentration and tangent activities. We suggest using the value of 4 km as the optimal TTC concentration.

Bacterial community dynamics during bioremediation of alkane- and PAHs-contaminated soil of Siri island, Persian Gulf: a microcosm study

Abstract

Studding the diversity of soil indigenous microorganisms, and monitoring effect of contaminants on microbial population, is very critical for understanding microbial activity during bioremediation and selecting successful remediation strategy. To simulate the natural environment, four microcosms were prepared by artificially contaminating clean soil with defined amounts of petroleum hydrocarbons including alkanes mixture (C₁₃–C₂₀), polyaromatic hydrocarbons (PAHs) mixture (anthracene, phenanthrene, fluoranthene, pyrene and benzo (α) pyrene) and both alkanes and PAHs. Contaminants degradation and heterotrophic bacterial count were measured during a 6-month study. Copy number of alkB and C23DO genes was studied using real-time PCR, and bacterial diversity was monitored by 16S rRNA gene PCR and denaturing gradient gel electrophoresis (DGGE). Results indicated that all types of contaminants (except the five ring benzo (α) pyrene) were totally degraded after 6 months and the increase in hydrocarbon degradation rate coincided with the enhancement of total heterotrophic bacterial count in each microcosm. Real-time PCR results showed a significant increase in the copy number of both alkB and C23DO genes in alkane- and PAHs-contaminated microcosm comparing with the control microcosm, indicating selection for special hydrocarbon degraders in hydrocarbon-amended microcosms. The results of DGGE revealed that the type of contaminant in the same soil has a remarkable influence on soil bacterial community structure. Sequencing of DGGE bands suggested that most of the dominant members of the microbial community of contaminated soil are unculturable bacteria from Proteobacteria and the genus Bacillus.

H 3 PO 4 -activated sawdust and rice husk as effective decolorizers for textile wastewater containing Reactive Black 5

Abstract

Textile wastewater contains significant amounts of dyes and chemicals, which makes it very difficult to be treated. Reactive Black 5 is one of the most widely used azo dyes that cause severe impact on environment and aquatic life. Activated carbons are known for their high adsorption capacities, and the objective of the current study was to prepare an effective low-cost adsorbent. H₃PO₄ acid-activated sawdust and rice husk which were prepared using a simple and low-cost method successfully adsorbed Reactive Black 5 (RB 5) in hypersaline synthetic and real textile dye bath wastewaters. SEM analysis of activated carbon made from these two materials showed an enhanced pore structure. 0.10 g of activated sawdust carbon decolorized 88, 97 and 75% of neat RB 5 solution, synthetic textile wastewater and real textile dye bath wastewater, respectively. RB 5 adsorption is pH dependent, and low pH facilitates the dye adsorption. Langmuir and Freundlich isotherm models were used to analyze the equilibrium adsorption data, and only the Langmuir isotherm model shows a good correlation (R² = 0.99). Kinetic data match well with the pseudo-second-order model, and the calculated rate constants are 6.09 × 10⁻³ g mg⁻¹ min⁻¹ and 9.88 × 10⁻³ g mg⁻¹ min⁻¹ for activated carbon of sawdust and rice husk, respectively. Thermodynamic parameters, ΔG⁰, ΔH⁰ and ΔS⁰, for both types of activated carbon show that the adsorption process is favorable, endothermic and spontaneous.

Effect of foliar application of compost water extract, humic acid, EDTA and micronutrients on the growth of fenugreek plants under sandy soil condition

Abstract

Foliar application of liquid organic fertilizer, compost water extract, combined with micronutrients solution in sulfate form, EDTA form or humic acid form gave the highly significant values for fenugreek plants height and weight of seeds. Seven treatments such as compost tea, every three forms of micronutrients and three combinations (1:1) of compost tea with each micronutrients form besides untreated control were applied as foliar spray twice to Trigonella plants at 35 days and at 70 days from sowing. The plant height increments were by 48 and 50% for sulfate form with compost tea, by 67 and 69% for humic acid form with compost tea and by 66% for EDTA form with compost tea for the first and second season, respectively. The values of fenugreek weight of seeds for combined compost tea in both seasons were by (63 and 41%) with sulfate mineral solution, by (76 and 50%) with EDTA and by (90 and 65%) with humic acid, respectively. It is obvious from the results that using compost tea in a combination with micronutrients forms can reduce the chemical fertilizer dose by 50% and enhance the fenugreek growth better than the chemical fertilizer does.

Application of biochar from agro-industrial waste in solid-phase extraction for the determination of 17β-estradiol from aqueous solution

Abstract

In this study, the biochar produced from coffee wastes and eucalyptus sawdust was employed as an adsorbent in solid-phase extraction devices for the determination of 17β-estradiol from aqueous solution. Parameters such as adsorbent mass, solvent type, eluent volume, ionic strength, breakthrough volume, and the cartridge reuse were evaluated. The best experimental conditions for solid-phase extraction concerning adsorbent mass, elution solvent, eluent volume, ionic strength, breakthrough volume, and cartridge reuse were established. The most suitable conditions for 1.0-mL cartridge were: mass of 50 mg, elution solvent 5.0 mL of acetonitrile/water 90:10 (v:v), 0.003 mol L⁻¹ NaCl concentration, and 17β-estradiol solution volume 50.0 mL. The solid-phase extraction results showed that, although 17β-estradiol recovery was about 60%, the removal efficiency was 100% and the cartridges of 200 and 500 mg can be reused eight and four times, respectively, without any decrease in adsorption capacity. The results demonstrate the potential use of biochar as new adsorbent in solid-phase extraction devices for the removal of estrogens in aqueous solution.

Glyphosate in vitro removal and tolerance by Aspergillus oryzae in soil microcosms

Abstract

Argentinian agriculture is based on a technological package that includes the application of significant amounts of pesticides. Glyphosate is the active ingredient of several glyphosate herbicides which are frequently used for weed control. Fungi can use glyphosate both as a nutrient and an energetic source. Therefore, the aim of the present study was to evaluate the in vitro glyphosate removal as the only source of phosphorus or nitrogen by two non-toxigenic Aspergillus oryzae strains. A. oryzae AM1 and AM2 were successfully able to use the herbicide both as phosphorus or nitrogen source. The degradation percentages were higher than 50% at the end of the incubation period (15 days) with glyphosate concentrations of 1 and 1.5 mM. In addition, AM1 strain was able to remove 57% of 10 mM of glyphosate at 0.99 of a_W. Soil microcosm assay was performed in order to study the GP tolerance, permanence and competitiveness of A. oryzae AM1 in the presence of native mycota. A. oryzae count remained constant along the incubation period and was not significantly affected by the different glyphosate concentrations tested (10, 20 and 50 mM). This strain showed great in vitro removal ability, and it was also able to remain viable on soil microcosms contaminated with glyphosate. Therefore, these results encourage future studies in order to evaluate the ability of these strains to degrade glyphosate on soil and then promote them as potential bioremediation agents.

Project portfolio selection for construction contractors by MCDM–GIS approach

Abstract

In this paper, project portfolio selection (PPS) is considered as one of the main steps in project portfolio management (PPM). PPS which depends on different criteria such as strategic, financial, as well as project specifications is also suggested for construction contractors. Although it is difficult to consider all these criteria, the decision will be inaccurate when some of them are ignored. The most common multi-criteria decision-making (MCDM) methodologies and geographic information system (GIS) are combined as a method, by which the potential projects obtain a strategic score by the analytical hierarchy process (AHP). Then, they are ranked according to technical criteria by the technique for order preference by similarity to ideal solution (TOPSIS). The proposed approach includes three ordinal phases. First, scoring potential projects due to the company strategy is conducted by the AHP to determine strategic-aligned projects (SAPs). Then, SAPs are ranked by TOPSIS. Finally, the final GIS sheet is prepared by the obtained technical score and communal criteria. This paper provides a clear and comprehensive insight to accept or reject SAPs by form a weighted sheet in GIS. It suggests that CCs select project portfolio according to all the financial and non-financial criteria. This approach can satisfy the PPM principals and resolve some of the shortcomings related to MCDM methods by GIS capacities to reduce complexity so that the decision-makers form project portfolios easily and effectively. This approach is described in a case study.

Development of soil pollution risk index in the vicinity of a waste dam in Chadormalu iron ore mine

Abstract

Soil pollution caused by anthropogenic activities or natural factors results in reduced quality of environment. Fourteen elements, including Ti, Al, Fe, Cr, V, Pb, As, Sc, Zn, Cu, Co, Mn, Ca and Mo, in 20 soil samples and a wildflower called Anabasis Setifera on the tailing pond of Chadormalu iron ore in Iran were assessed. Metals were measured using inductively coupled plasma mass spectrometry (ICP-MS). Enrichment factor and contamination factor were employed to assess the ecological risk. C_fⁱ value within the range of 1.00–1.12 indicates the mean contamination of the soil, and E_rⁱ value within the range of 1–10 represents the low ecological risk of the elements in the soil. Transfer factor (Tr_i) was also used to calculate the transfer of heavy metals from soil to plant. Tr_i value within the range of 1.63–29.01 shows that the plant induces the transfer of contaminants from soil. The order of the transferred elements in terms of amount is as: Co > Ti > Cr > Al > Mn > Fe > Ca > V>Cu > Pb > Zn > As > Mo > Sc. Geo-accumulation (I_geo) and pollution indices have showed some weaknesses in assessing the high values of the elements. Therefore, in this study, a new index as level of pollution, Ln (LP), was developed to evaluate the contamination of soil by various concentrations of the elements. Based on I_geo and I_POLL, the pollutants fall within the class of 0 which indicates no pollution. The Ln (LP) index calculated as 0.069–1.166 shows that the studied elements, except for cobalt, had no pollution.

The efficacy of the ozonation process in the presence of activated carbon impregnated with magnesium oxide in the removal of benzene from the air stream

Abstract

The main purpose of this study was to investigate the catalytic ozonation process with GAC–MgO in removal of benzene in air streams. The flow diagram of the experimental bench-scale setup included a glass column (internal diameter = 3 cm) packed for 10 cm with granular activated carbon coated with magnesium oxide. Different initial concentrations of benzene (80, 200 and 400 ppm) were used to evaluate the removal efficiency. The synthesized granular activated carbon coated by magnesium oxide was a microporous adsorbent with the BET specific surface area of 1028 m²/g. Hydroxyl, methylene, methyl, carboxylic groups and aromatic C=C bonds were some of the several functional groups identified on the its surface. In the catalytic ozonation process, the breakthrough time for the inlet concentration of 200 ppm increased from 36 h for granular activated carbon to 53 h for granular activated carbon ozonation. In other words, the concomitant use of activated carbon and ozone enhanced (from 36 h to 53 h) the removal efficiency of the system by 17 h in comparison with activated carbon alone. In the ozonation process for the bed, the benzene breakthrough time of the bed, for the inlet concentration of 200 ppm, increased from 44 h in the granular activated carbon coated by magnesium oxide system to 78 h in the granular activated carbon coated by magnesium oxide and ozonation. Eventually, the results showed the ozonation process in combination with the granular activated carbon coated by magnesium oxide catalyst.