Effect of MSW leachate on soil consistency under influence of electrochemical forces induced by soil particles

Investigations on the effect of leachate from municipal solid waste on the soils in landfill sites usually focus on the effect of leachate compounds on the engineering properties of the soil. Leachate chemical composition and its effect on the consistency of soil are important factors for designing liner systems. Soil samples from the bottom of the Esfahan, Iran, landfill were collected. Leachate samples were collected within the a landfill and a composting factory leachate lagoon. Effects the leachates on cation exchange capacity, electrical conductivity, pH, and consistency of the soil samples were investigated. The chemical property of leachate showed that leachate from the compost factory was contaminated by higher concentrations of heavy metals (Cu, Zn, Pb, Cd, Ni, and Hg); higher concentrations of Na+,Ca+2, Mg+2, and K+; and higher EC; and were more acidic than the landfill leachate. Liquid limits and plastic limits of the soil were higher from the effect of the compost factory leachate in comparison with the values for landfill leachate

Shearing Rate Effect on Mechanical Behavior of MSW Materials

Recent catastrophic failure in different regions of the world is an indication on the poor level of engineering knowledge on the mechanical behavior of MSW materials which are the main materials in the landfill body. However extensive researches have been made to represent a clear frame work to describe the behavior of these materials but clearly all of these attempts had not been enough. In the region with high seismic activity, mechanical response of MSW materials under quick and dynamic loading condition is one of the issues which should be addressed however there are some evidences concerning the higher resistance of MSW materials under dynamic loading condition. As a part of an extensive research, using large triaxial apparatus and large direct shear box, the effect of shearing rate on the mechanical response of these materials were evaluated. Effect of this factor also estimated on the pore water pressure generation pattern using large triaxial tests performed in un-drained condition. The results confirmed the achievement of Augello et al. (1995, 1998), Zekkos (2005) and Zekkos et al. (2007) regarding higher level of shear resistance of MSW materials under dynamic loading condition. The results also showed that however the rate of pore water pressure generation decreases with increasing the loading rate but final level of pore water pressure is independent of loading rate

Efficiency of partial 16S rRNA gene sequencing as molecular marker for phylogenetic study of cyanobacteria, with emphasis on some complex taxa

At present, the analysis of 16S rRNA gene sequences is the most commonly used molecular marker for phylogenetic studies of cyanobacteria. However, in many studies partial sequences is used. To evaluate the performance of this molecular marker, phylogenetic relationship of several taxa from this phylum, especially some intermixed taxa, was studied. We analyzed a data set consisting of three categories of cyanobacterial strains, traditionally classified in three orders, by morphological and phylogenetic analyses. The phylogenetic analyses were performed with an emphasis on partial 16S rRNA gene sequences (600 bp) and the phylogenetic relationships were assessed using Maximum Parsimony, Maximum Likelihood and Bayesian Inference. In morphometric study, numerical taxonomy was performed on several morphospecies, and cluster analysis was performed using SPSS software. Based on the findings of this study, unlike the morphological analysis which was useful in several taxonomic ranks, this molecular marker is recommended for use only in high taxonomic levels such as order and family, because, contrary to our expectations, using partial 16S rRNA gene sequencing in the lower taxonomic levels, even in the genus level, was not necessarily successful. Inefficiency of this molecular marker in taxonomy of some genera, especially intermixed taxa, was another finding of the present study, which represents the genetic similarity of these taxa

Interactions of phosphates and selected organic molecules with palygorskite and sepiolite

Palygorskite and sepiolite are silicate clay minerals that commonly occur in soils of and semiarid regions. Despite the significance of these minerals in soil agrochemistry and in a variety of industrial applications, the sorptive behavior of palygorskite and sepiolite is not fully elaborated. The objectives of this work were to: (i) study the interactions of orthophosphate (Pi) and inositol hexaphosphate (IHP) with palygorskite and sepiolite in pure systems and in the presence of calcite and (ii) quantify the contribution of different sites in sorption of monovalent organic cations, crystal violet (CV) and methylene blue (MB), on palygorskite and sepiolite. The Pi sorption capacity of sepiolite and palygorskite amounted at about 0.7 and 1.5 cmol kg-1, respectively, which is higher than other crystalline silicate clays. Sepiolite has the potential to be a carrier for orthophosphate compounds. The IHP sorption capacity was 24 and 15 cmol kg'-'1 for sepiolite and palygorskite, respectively. The large surface area and Al-Mg contents, may explain the P sorptive behavior of these minerals. The availability of sorbed P by palygorskite and sepiolite in the presence of calcite was compared with that of a montmorillonite, using a sequential extraction technique. About 90% of total Pi sorbed on a sepiolite-calcite mixture was recovered over seven extractions, while the recovery of sorbed Pi was about 20%, 12%, and 2% for palygorskite-calcite, montmorillonite-calcite, and pure calcite, respectively. Application or presence of sepiolite in calcareous soils may favor the phosphate availability in these soils. The maximum sorption of MB and CV greatly exceeded the cation exchange capacity of these minerals. In sorption maxima, the neutral sites showed the highest contribution to the sorption of organic cations as compared to the free and complexed negative sites. This part of the study may help the modification of clay surfaces for different industrial applications

Phytosiderophore release by wheat genotypes differing in zinc deficiency tolerance grown with Zn-free nutrient solution as affected by salinity

There is limited information concerning the effect of salinity on phytosiderophores exudation from wheat roots. The aim of this hydroponic experiment was to investigate the effect of salinity on phytosiderophore release by roots of three bread wheat genotypes differing in Zn efficiency (Triticum aestivum L. cvs. Rushan, Kavir, and Cross) under Zn deficiency conditions. Wheat seedlings were transferred to Zn-free nutrient solutions and exposed to three salinity levels (0, 60, and 120 mM NaCl). The results indicated that Cross and Rushan genotypes exuded more phytosiderophore than did the Kavir genotype. Our findings suggest that the adaptive capacity of Zn-efficient ‘Cross’ and ‘Rushan’ wheat genotypes to Zn deficiency is due partly to the higher amounts of phytosiderophore release. Only 15 days of Zn deficiency stress was sufficient to distinguish between Zn-efficient (Rushan and Cross) and Zn-inefficient (Kavir) genotypes, with the former genotypes exuding more phytosiderophore than the latter. Higher phytosiderophore exudation under Zn deficiency conditions was accompanied by greater Fe transport from root to shoot. The maximum amount of phytosiderophore was exuded at the third week in ‘Cross’ and at the fourth week in ‘Kavir’ and ‘Rushan’. For all three wheat genotypes, salinity stress resulted in higher amounts of phytosiderophore exuded by the roots. In general, for ‘Kavir’, the largest amount of phytosiderophore was exuded from the roots at the highest salinity level (120 mM NaCl), while for ‘Cross’ and ‘Rushan’, no significant difference was found in phytosiderophore exudation between the 60 and 120 mM NaCl treatments. More investigation is needed to fully understand the physiology of elevated phytosiderophore release by Zn-deficient wheat plants under salinity conditions

Effect of Sewage Sludge on Some Macronutrients Concentration and Soil Chemical Properties

Sewage sludge as an organic fertilizer has economic benefits. Land application of sewage sludge improves some soil chemical and physical properties. The objective of this study was to evaluate the effect of sewage sludge on soil chemical properties and macronutrient concentration in acid and calcareous soils. The study was carried out in a greenhouse using factorial experiment design as completely randomized with three replications. Treatments included : four levels of 0 or control, 50, and 100, 200 ton ha-1 sludge and one level of chemical fertilizer (F) consisting of 250 kg ha-1 diammonium phosphate and 250 kg ha-1 urea, and soil including soils of Langroud, Lahijan, Rasht, and Isfahan. As a major vegetable , crop spinach (Spinacea oleracea) was grown in the treated soils. Soils samples were analyzed for their chemical properties after crop narvesting. Application of sewage sludge significantly increased plant available k, P, total N, organic matter, electrical conductivity and cation exchange in the soils. Soils pH significantly decreased as a result sewage sludge application. The effect of sewage sludge on plant yield was significant. Overall, the results indicated that sewage sludge is potentially a valuable fertilizer. However, the sludge effect on soil EC and heavy metals should be taken into consideration before its widespread use on cropland

Effects of Applied Biochar and Municipal Solid Waste Compost on Saline Soil Properties and Sorghum Plant Attributes

The hypothesis is that incorporating saline soil with biochar or compost reduces the deteriorating effects of salinity. The pot experiment was irrigated with waters with different salinities (4.5 and 9 dS m-1) and a silty clay soil in pots was thoroughly mixed with 1.5% w/w of biochar, 1.5% w/w of municipal solid waste compost and the mixtures of 0.5 × 0.5% w/w of the two mentioned substances. Irrigation was provided to realize 0.15 leaching fractions for equilibrating the soil salinity. Soil and plants were analysed after two months (T1) and three months (T2) after sowing. Saline irrigation water decreased SAR (~45%) and SOC (~5.5%), respectively for T2 compared with T1. The biochar treatment reduced the amount of ECe in T1 and T2. Both irrigating with saline water and amendments greatly changed the amount of leaf water potential (LWP), chlorophyll and proline leaf. LWP and proline were increased by 17 and 76%, respectively, with increasing irrigation water salinity, while the leaf chlorophyll content was significantly decreased (~52%). The overall finding was that incorporating the saline soil of the region with biochar showed more potential to enhance soil properties and sorghum production

Changes of hydraulic conductivity of silty clayey sand soil under the effects of municipal solid waste leachate

Effect of municipal solid waste (MSW) on the hydraulic conductivity of soil is an important factor for designing liner systems. Leachate samples were collected within a landfill and a composting factory leachate lagoon. Soil samples from the bottom of the Esfahan, Iran, landfill were collected. Effects of the leachates on permeability of the soil samples were investigated. The results of study showed that at the highest level of leachate concentration (100%), the soil showed 20% increase in permeability (k) value from compost leachate and 10% reduction in landfill leachates. Compost and landfill leachates had shown contrasting impact on the soil permeability