Soil Extract Solution Research Articles

Effect of Alternating Current and Sulfate-Reducing Bacteria on Corrosion of X80 Pipeline Steel in Soil-Extract Solution.

AC corrosion has been considere d as a threat to the corrosion of buried pipelines. Effects of sulfate-reducing bacteria (SRB) and alternating current (AC) on corrosion of X80 pipeline steel in soil-extract solution were investigated by electrochemical and surface analysis techniques. AC current can inhibit the growth of planktonic and sessile SRB. The corrosion current density of steel with 10 mA/cm2 AC current is about nine times bigger than that without AC current. Corrosion morphology changes from small pitting to large pitting holes with increasing AC current density. Corrosion of steel with SRB and AC current is controlled by both active dissolution of iron and film degradation.

Closing the gap - inclusion of ultrashort-chain perfluoroalkyl carboxylic acids in the total oxidizable precursor (TOP) assay protocol.

An improved protocol of the total oxidizable precursor (TOP) assay was developed for precursors to C2-C14 perfluoroalkyl carboxylic acids (PFCAs) and C4-C8 and C10 perfluoroalkyl sulfonic acids (PFSAs). The proposed protocol was tested and validated for contaminated soil samples. The perfluoroalkyl acids (PFAAs) present in the soil extract solutions after oxidation with persulfate were separated from the inorganic salts by vacuum-assisted drying of the digestion solution followed by solid-liquid extraction of the PFAAs with acetonitrile from the dry residue. Ion chromatography (for C2-C4 PFCAs) and reversed phase liquid chromatography (for all other PFASs), both coupled to tandem mass spectrometry, were used for quantification. High procedural recoveries of PFAAs between 68% and 123% with RSDs between 0.2% and 25% (n = 3) were achieved. The method was validated using selected polyfluoroalkyl phosphoric acid esters (PAPs) and bis-[2-(N-ethyl perfluorooctane-1-sulfonamido)ethyl] phosphoric acid ester (diSAmPAP) as model precursors in pure solutions and in the presence of soil matrix. The oxidation led to characteristic and reproducible PFCA patterns (in the case of PAPs) or PFOA (in the case of diSAmPAP) with total reaction yields between 92 ± 4% and 123 ± 13% (n = 3). The impact of the soil matrix on transformation yields was negligible. In a soil core from a PFAS-polluted agricultural site, precursors were concentrated in the upper 40 cm with long-chain precursors being prevalent. After oxidative digestion, the total molar PFAA-concentrations increased by factors of 1.6 to 5.0. More than 40 cm below ground precursors of TFAA, PFPrA and PFBA accounted for ∼50% of the reaction products, underlining the importance of their inclusion in mass balances based on the TOP assay.

Optimization of sodium extraction from soil by using a central composite design (CCD) and determination of soil sodium content by ion selective electrodes

Rapid determination of sodium (Na) ions in soil samples using ion selective electrodes (ISE) was investigated in this study. The compatibility of ISEs with soil extraction solution is a challenging subject as various effects such as pH, ionic strength and other interferences have to be considered as well as efficiency of the extraction solution. Because almost every type of sodium salt is soluble in water, and the pH of water is suitable for ISE studies, it was chosen as the soil extractant. Firstly, the extraction parameters were optimized by using a central composite design (CCD), secondly thirty agricultural soil samples were extracted with water and the extracts were measured by Na-ISE in a previously developed flow system. The results were compared with ion chromatography (IC) as the reference method, and the regression analysis between IC and ISE results yielded a high correlation (R² = 0.9408). It was concluded that, ion selective electrodes can be used with water as an extraction solution for rapid determination of sodium in soil samples.

Three-dimensional macroporous cellulose-based bioadsorbents for efficient removal of nickel ions from aqueous solution

We present a simple synthetic method for the preparation of cellulose-g-poly(acrylic acid-co-acrylamide) materials with three-dimensional macroporous structure, which can be used for the environmental application as the reusable bioadsorbents. In the grafting copolymerization process, the acrylic acid and acrylamide are cross-linked with cellulose molecules to form three-dimensional interconnected porous structure. Due to the macropores and the abundant functional groups, the cellulose-based bioadsorbents exhibit excellent adsorption performance for the removal of nickel ions from aqueous solution with a maximum adsorption capacity of 171.8 mg/g. The adsorption of bioadsorbents to Ni2+ is accurately described by a pseudo-second-order kinetic model and the initial concentration-dependent adsorption isotherm suggests a Langmuir isotherm model. Furthermore, the cellulose-based bioadsorbents can be easily separated from the aqueous solution after adsorption and regenerated using 0.2 M HCl solution, which exhibits high adsorption capacity after six adsorption–desorption cycles. Importantly, the biodegradation rate of 53.1 wt% for the bioadsorbents is found after being incubated in the soil extraction solution for 90 days. Therefore, the eco-friendly cellulose-based bioadsorbents could be used for water purification effectively.

First Report of Phytophthora megasperma Causing Decline and Death on Celtis australis in Italy.

European hackberry (Celtis australis L.) is a popular shade tree mainly planted in southern Europe and known to be tolerant to dry and poor soils. In early autumn 2013, hackberry plants grown in soil in a commercial nursery located in the floodplain in Umbria region showed symptoms of wilting, dieback, and death. Up to 100% of the canopy was affected, and over 60% of the plants were symptomatic or dead. A Phytophthora species was consistently isolated from symptomatic 6-year-old plants by plating small pieces of collar and root tissues, cut from the margin of dark-brown necrotic lesions, onto P5ARPH selective medium (4). Pure cultures were obtained by single-hyphal transfers on potato dextrose agar (PDA). Sporangia, produced on pepper seeds in soil extract solution (3), were nonpapillate and noncaducous, measuring 34.0 to 85.0 × 22.0 to 50.0 μm. Oospores had an average diameter of 44 μm with mostly paragynous antheridia. On the basis of morphological features, the isolates were identified as P. megasperma Drech. (2). The identity was confirmed by sequencing the cytochrome c oxidase subunit II (Cox II) (5), which gave 100% identity with P. megasperma sequences available in GenBank (GU222070), and by sequencing the internal transcribed spacer (ITS) using the universal primers ITS4 and ITS6, which gave 99% identity with the AF266794 sequence from Cooke et al. (1). The sequences of one isolate (AB239) were deposited in the European Nucleotide Archive (ENA) with accession numbers HG973451 and HG973450 for Cox II and ITS, respectively. Pathogenicity tests were conducted in the greenhouse with isolate AB239 on eight 2-year-old potted European hackberry plants. Mycelial plugs (5 mm diameter) cut from the margins of actively growing 8-day-old cultures on PDA were inserted through the epidermis to the phloem at the collar level. Two plants were used as controls and treated as described above except that sterile PDA plugs replaced the inoculum. Inoculated plants were kept for 4 weeks in a greenhouse at 24 ± 2°C. During that period, inoculated plants showed wilting symptoms similar to those observed in the field. Lesions were evident at all the inoculation points progressing downward to the roots. Colonies of Phytophthora were isolated from the margins of lesions and identified as P. megasperma, thus fulfilling Koch's postulates. Controls remained symptomless. P. megasperma taxonomy is rather complex since it embraces different subgroups, including host specialized forms (formae speciales), some of which are recognized as biological species. Based on morphological and molecular data presented here, the Phytophthora isolates from hackberry belong to P. megasperma sensu stricto, which is included in the "pathogenic to a broad range of hosts" (BHR) group (1). This pathogen is rather polyphagous, attacking mainly fruit and ornamental woody plants, commonly Prunus spp., Malus spp., and Actinidia deliciosa. Like other homothallic Phytophthora species, it is particularly dangerous due to its abundant production of thick-walled resting oospores that enable long-term survival in the soil. To our knowledge this is the first report of P. megasperma sensu stricto (1) on C. australis and its family Ulmaceae/Cannabaceae.

Corrosion of Carbon Steel Q235 in a Crevice Under a Simulated Disbonded Coating

Variations of the environmental parameters were studied in a crevice under a simulated disbonded coating in soil extract solutions (SES) with and without sulfate-reducing bacteria (SRB). Results show that the crevice blocks the penetration of cathodic currents and weakens the cathodic polarization of the steel. The potential of carbon steel Q235 in the presence of SRB does not reach a standard of cathodic protection (CP) in the deeper crevice. SRB leads to the increasing of the cathodic current and pH values of the SES. Metabolic sulfide is formed between a corrosion product film and a biofilm.

Corrosion monitoring of galvanized steel in soil extract solutions by electrochemical impedance spectroscopy

The chemical and structural complexity of soils, coupled with their heterogeneity, contributes to the increase in soil aggressiveness, which can in turn result in severe corrosion of underground materials. The understanding of corrosive processes of underground structures is important in aiding the development of methods, as well as in monitoring and maintenance, in an attempt to minimize environmental, social, and economic impacts. In this work, electrochemical impedance spectroscopy (EIS) was used to monitor the corrosive process of galvanized steel when in contact with soil extracts, aimed at evaluating the potentiality of applying electrochemical impedance spectroscopy when monitoring underground structures. To accomplish this, the behavior of the galvanized steel when undergoing corrosion was studied for 105 days, examining the variations in the eletrochemical parameter values obtained through EIS assays over this period. EIS proved to be effective in the study of corrosive processes of galvanized steel when in contact with soil extracts, identifying the different stages of the corrosive process, controlled by mass and/or charge transfer reactions.

In Situ Production of Zoospores by Five Species of Phytophthora in Aqueous Environments for Use as Inocula

The goal of this study was to develop a procedure that could be used to evaluate the potential susceptibility of aquatic plants used in constructed wetlands to species of Phytophthora commonly found in nurseries. V8 agar plugs from actively growing cultures of three or four isolates of Phytophthora cinnamomi, P. citrophthora, P. cryptogea, P. nicotianae, and P. palmivora were used to produce inocula. In a laboratory experiment, plugs were placed in plastic cups and covered with 1.5% nonsterile soil extract solution (SES) for 29 days, and zoospore presence and activity in the solution were monitored at 2- or 3-day intervals with a rhododendron leaf disk baiting bioassay. In a greenhouse experiment, plugs of each species of Phytophthora were placed in plastic pots and covered with either SES or Milli-Q water for 13 days during both summer and winter months, and zoospore presence in the solutions were monitored at 3-day intervals with the baiting bioassay and by filtration. Zoospores were present in solutions throughout the 29-day and 13-day experimental periods but consistency of zoospore release varied by species. In the laboratory experiment, colonization of leaf baits decreased over time for some species and often varied among isolates within a species. In the greenhouse experiment, bait colonization decreased over time in both summer and winter, varied among species of Phytophthora in the winter, and was better in Milli-Q water. Zoospore densities in solutions were greater in the summer than in the winter. Decreased zoospore activities for some species of Phytophthora were associated with prolonged temperatures below 13 or above 30°C in the greenhouse. Zoospores from plugs were released consistently in aqueous solutions for at least 13 days. This procedure can be used to provide in situ inocula for the five species of Phytophthora used in this study so that aquatic plant species can be evaluated for potential susceptibility.

Investigation on corrosion control of mild steel buried in soil by spent FCC catalyst coating

Effects of aerobic and anaerobic bacteria on corrosion behaviour of mild steel coated with modified spent FCC catalyst have been examined in soil extract solutions (SES) and that buried in soil. Coating of modified spent FCC catalyst was found to inhibit the growth of bacterial isolates from the soil which is represented as zone of inhibition. Efficacy of spent FCC catalyst was studied for the coated coupons immersed in SES. Cracks and interstices were found on uncoated coupons due to corrosion whereas coated surface remained unaffected. This is confirmed by the SEM analysis. It was also seen that coated coupon was undamaged under buried-in-soil conditions for 30 days.

Electrochemical behavior of steel A36 under disbonded coating in the presence of sulfate-reducing bacteria

Variation and distribution of the environmental parameters (potential, current, pH and [Cl−]) and electrochemical behavior of steel A36 were studied in a crevice under a disbonded coating in soil extract solutions in the presence and absence of sulfate-reducing bacteria (SRB). Results show that the crevice blocks the penetration of cathodic currents, and weakens the cathodic polarization of the steel in the crevice. The presence of SRB in the crevice leads to alkalization of the solution and increases energy consumption of the cathodic protection system. The forming of the reversed potential increases the cathodic current. SRB restrains corrosion of the steel in the earlier period due to the protective biofilms, whereas it SRB corrosion of the steel in the later period because of exfoliation of the films and the formation of the corrosive microcell.

Variations of Microenvironments with and without SRB for Steel Q 235 under a Simulated Disbonded Coating

Distributions of potential and current and variations of crevice environments are studied in a crevice under a simulated disbonded coating in soil extract solutions (SES) with and without sulfate-reducing bacteria (SRB). Results show that forming of the crevice blocks the penetration of cathodic currents in the crevice and weakens the cathodic polarization of the steel Q 235. The cathodic currents in the presence of SRB are nearly three times more than those without SRB at the same cathodic protective potential, which indicates that SRB increases the energy consumption of the cathodic protection systems. SRB leads to basification of the solution in the crevice. The forming of inner electric field enhances the anionic migration into the crevice. The forming of the reversed potential increases the cathodic current.

Biosusceptibility of historical bricks from the Bac fortress: part I

The significance of the conservation of cultural heritage objects has led to a greater interest in the appearance of biocorrosion. The aim of this paper is to point out the correlation between the growth of fungi isolated from the fortress of Bac and the contact angle value of the bricks from the fortress in order to determine the brick susceptibility to biodegradation. Three types of bricks (red, yellow and roan) and three isolates of Penicillium spp., as well as one isolate of Cladosporium sp., were used during the experiments. A suspension of fungi in soil extract solution was inflicted on the surface of the bricks and then the samples were incubated. The study showed that the red bricks with cut surface and the roan bricks with broken surface are the most susceptible to the biocorrosion process. Based on the obtained results, Cladosporium sp. can be considered as the most important biodeteriogenic factor on the bricks built in the walls of the Bac fortress.

First Report of Phytophthora megasperma Associated with Decline and Death of Common Walnut Trees in Italy.

Common walnut (Juglans regia L.) is an important nut crop in Italy, which is the fifth largest producer of walnut in Europe. In recent years, walnut decline and subsequent death has increased in many Italian commercial orchards. In the summer of 2010, several declining trees were present in waterlogged area of a walnut orchard located in the Veneto region. Symptoms included sparse foliage, wilting, and shoot and branch dieback. By the next year, a larger area of about 1 ha with 20% of dead trees was present, and soil/root samples were subjected to azalea leaf baiting and successively cultured on PARBH medium (3). Isolates were identified as Phytophthora megasperma based on morphological characteristics (2) and DNA sequence analysis. Sporangia were 35.0 to 62.0 × 12.0 to 30.0 μm, nonpapillate, and noncaducous when produced in soil extract solution. Oogonia had an average diameter of 36 μm with mostly paragynous antheridia. Identity was confirmed by sequence comparison in NCBI database with 99% and 100% identity for internal transcribed spacer (ITS) and mitochondrial partial COI (4) for cytochrome oxidase subunit 1, respectively. The sequences of the isolate AB199 were deposited in GenBank with the accession nos. HE805270 and HE805269 for ITS and COI, respectively. Pathogenicity tests were conducted in the greenhouse on six 1-year-old walnut shoots with two inoculation points each. Mycelial plugs cut from the margins of actively growing 8-day-old cultures on PDA were inserted through the epidermis to the phloem. Controls were treated as described above except for inoculation with sterile PDA plugs. After inoculation, shoots were incubated in test tubes with sterile water for 1 week in the dark at 22 ± 2°C. Lesions were evident at the inoculation points. P. megasperma was consistently reisolated from the margin of symptomatic tissues. Controls remained symptomless. P. megasperma is a polyphagous, ubiquitarious Phytophthora species that attacks many crops and fruit species including walnut. Although several other species of Phytophthora have been reported from Italy (1), to the best of our knowledge, this is the first report of Phytophthora decline on common walnut in Italy caused by P. megasperma.

Effects of Sulfate Reducing Bacteria on Corrosion of Carbon Steel Q235 in Soil-Extract Solution

Effects of Sulfate Reducing Bacteria on Corrosion of Carbon Steel Q235 in Soil-Extract Solution

First Report of Phytophthora cryptogea on Potato Tubers in Turkey.

Potato (Solanum tuberosum L.) is an important agricultural crop in Turkey, with 150,000 ha and a production of about 4 million tons per year. There are numerous pathogens that limit potato production. In 2011, a new disease was observed on the potato cultivar Ramos in Erzincan Province in Turkey. Disease symptoms were similar to pink rot. Infected tubers had a rubbery texture and when cut, infected areas were cream colored. When the infected area was exposed to air for 10 min, the color turned to salmon pink and after 15 to 20 min it turned black. A funguslike organism was isolated from diseased tubers on carrot agar. The colonies were uniform and there were no petaloid patterns. Soil extract solution was prepared using 1,000 ml of distilled water and 15 g of field soil according to Jeffers and Aldwinckle (2) and used for sporangia production. Agar discs from 5-day-old colonies were placed in soil extract solution and incubated under continuous fluorescent light at room temperature. Sporangia began forming after 24 h and were abundant after 48 h. Oogonia were not observed on corn meal agar plates supplemented by beta-cytosterol. Sporangia were nonpapillate and noncaducous, mostly ovoid, but some were obpyriform. The mean size of the sporangia was 43 ± 4 × 30 ± 2 μm. The Oomycete was identified as Phytophthora cryptogea Pethybr. & Laff., according to its morphological characters (1). Isolate identity was confirmed by sequence analysis of the ribosomal DNA internal transcribed spacer using primers ITS1 and ITS4. The ITS sequence was a 99% match to P. cryptogea strains (GenBank Accession Nos. AF087475.1, AF228101.1, GU111626.1, AY995400.1, GU111624.1, AY995400.1, and GU111624.1). The isolate from Turkey was deposited in GenBank as Accession No. JQ071495. Pathogenicity tests were conducted on potato tubers (cv. Ramos). Tubers were surface disinfected with 0.5% NaOCl for 5 min., then washed twice with sterile water. When dried, 20 tubers were wounded with a shallow cut made parallel to the surface by a sterile knife. An agar disc from a 1-week-old colony was placed on the artificial wound on each of 10 potatoes. For controls, agar discs without fungal mycelia were placed on the wounds of the other 10 potatoes. Each inoculated and uninoculated potato was incubated for 5 days at 24°C in the dark and in separate plastic cups containing moistened filter paper at the bottom. Tubers were then cut open and examined for disease. Cream colored lesions were first observed; after 10 min lesions turned salmon pink and after 20 min they turned black. Cream colored lesions were not observed inside uninoculated potatoes. To the best of our knowledge, this is the first report of P. cryptogea causing pink rot of potato in Turkey. Pink rot disease of potato is commonly caused by P. erytroseptica, but P. cryptogea can cause similar symptoms (3) and severe tuber rot. This pathogen could cause important losses of potato in Turkey, especially during storage of tubers.

A Comparative Study of the Effects of Sulfate Reducing Bacteria on Corrosion of Carbon Steel Q235 under Simulated Disbonded Coating with Different Width of Aperture

The effect of sulfate reducing bacteria (SRB) on the corrosion of Q235 steel has been investigated in the crevice under the simulated disbonded coating with aperture width of 1.0 and 0.5mm in the soil-extract solutions (SES) by using electrochemical methods. The results show that the existence of SRB in SES can cause corrosion potential of the working electrode to shift to a more negative value, and the formation of pitting on the surface of the electrode. Compared with the crevice width of 1.0mm, the corrosion potential of the electrode shows a little more positive at the crevice width of 0.5mm. The corrosion rate of the electrode increases with the increase of aperture width in the SES without SRB, however, decreases with the increase of aperture width in the SES with SRB. The results obtained indicate that either bio-film on the surface of the electrode formed by SRB in SES or aperture width has obvious influences on the crevice corrosion process of the carbon steel.

The Effects of Sulfate Reducing Bacteria on Crevice Corrosion Behavior of Q235 Steel

The crevice corrosion behavior of Q235 carbon steel has been studied under the simulated disbonded coating with an aperture of 1.0mm in the soil-extract solution (SES) with and without sulfate-reducing bacteria (SRB) by using the electrochemical impedance spectroscopy (EIS). The surface morphologies of the steel after experiment were observed by scanning electron microscopy (SEM).The results showed that the capacitive arc of the Q235 steel electrode in SRB containing solution is smaller than that in the aseptic solution at the initial stage of test. However, after 19 days, the capacitive arc of the steel in bacteria containing solution becomes bigger than that in the aseptic solution, and corrosion rate of the steel was smaller in the SES with SRB than that without SRB. The degree of the corrosion on the surface of steel Q235 was more severe after 44 days in the SES without SRB than that with SRB. However, corrosion pits were found on the surface of Q235 steel in the SES with SRB.

Interaction of Sulfate-Reducing Bacteria and Carbon Steel Q 235 in Biofilm

The effect of sulfate-reducing bacteria (SRB) on corrosion of carbon steels and interaction between SRB and the carbon steel Q 235 are investigated in soil-extract solutions (SES). The results show that corrosion rates are smaller in the SES with SRB during growing period of SRB, but bigger during dying period. The procedures of interactions of SRB and the steel are studied by scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDXA). SRB do not aggregate on the surface of the steel until an anaerobic space is formed. SRB defend themselves against free oxygen by absorbing substances containing nonfree oxygen.

The effects of sulfate reducing bacteria on corrosion of carbon steel Q235 under simulated disbonded coating by using electrochemical impedance spectroscopy

The effect of sulfate reducing bacteria (SRB) on the corrosion of the carbon steel Q235 has been investigated in the crevice under the simulated disbonded coating in the soil-extract solutions (SES). The results of electrochemical impedance spectroscopy (EIS) show that the corrosion rate is inhibited in the SES with SRB during the stationary phase of SRB, but enhanced during the death phase. The comparison of the polarization ( R p ) and the charge transfer resistances ( R t ) has indicated that the biofilm seriously influences the reactive procedure of metal/solution interface. SRB is found in the pits on the surface of the steel.

Electrochemical EDTA recycling with sacrificial Al anode for remediation of Pb contaminated soil

Recycling chelant is a precondition for cost-effective EDTA-based soil remediation. Extraction with EDTA removed 67.5% of Pb from the contaminated soil and yielded washing solution with 1535 mg L −1 Pb and 33.4 mM EDTA. Electrochemical treatment of the washing solution using Al anode, current density 96 mA cm −2 and pH 10 removed 90% of Pb from the solution (by electrodeposition on the stainless steel cathode) while the concentration of EDTA in the treated solution remained the same. The obtained data indicate that the Pb in the EDTA complex was replaced by electro-corroded Al after electro-reduction of the EDTA and subsequently removed from the solution. Additional soil extraction with the treated washing solution resulted in total removal of 87% of Pb from the contaminated soil. The recycled EDTA retained the Pb extraction potential through several steps of soil extraction and washing solution treatment, although part of the EDTA was lost by soil absorption.