Saline Soil Samples Research Articles

Investigation of Salt-Frost Heaving Rules and Mechanical Properties of Chlorite Saline Soil along the Duku Highway under Freezing-Thawing Action

Aiming to investigate salt-frost heaving rules and the mechanical properties of natural saline soil along the Duku Highway subjected to multiple freezing-thawing cycles, we collected natural saline soil samples from the alluvial-proluvial plain in front of the Dushanzi Mountain at the starting point of the Duku Highway. Then, we conducted mineral composition analysis tests, essential laboratory physical property measurement, large scale multiple freezing-thawing cyclic salt-frost heaving tests, shear strength tests, and unconfined compressive strength tests on the samples. According to the test results presented, the collected saline soil differed from saline soil in other regions and fell into “chlorite saline soils.” As the number of freezing-thawing cycles increased, the overall salt-frost heaving capacity increased and then decreased in the freezing process but first reduced and then increased in the thawing process. Thus, the salt-frost heaving capacity was cumulative in freezing/thawing cycles. The peak salt-frost heaving capacity reached a maximum after 1 freezing-thawing cycle and then dropped drastically and fluctuated regularly. After 6 freezing-thawing cycles, the displacement deformation and time formed a new equilibrium. After 7 freezing-thawing cycles, the displacement and deformation of the soil no longer appear negative. As the number of freezing-thawing cycles increased, the cohesive force of saline soil first increased and then dropped steadily, the internal friction angle first dropped and then increased steadily, and the unconfined shear strength first increased and then decreased. These research results provided data supporting the prevention and controlling highway saline soil disasters with insightful references for the other projects in this region.

Isolation and selection of salt-tolerant bacterial strains capable of solubilizing phosphorus and synthesizing phosphatase enzyme from rice-shrimp soil in Mekong River Delta, Vietnam

The aim of this study was to isolate and select salt tolerant bacteria having both functions in phosphorus solubilization and phosphatase synthesis from rice-shrimp farming soil in saline areas in Mekong River Delta of Vietnam. Phosphorus solubilizing bacteria were isolated on National Botanical Research Institute's Phosphate (NBRIP) agar medium containing 1% NaCl and the activity of phosphatase enzyme was determined by disodium p-nitrophenyl phosphate reagent method at a wavelength of 420 nm. The result showed that from 15 saline soil samples, a total of 95 strains of phosphorus solubilizing bacteria were isolated and 19 of them showed their good phosphorus solubilization. The results about phosphatase activities of these 19 strains illustrated that TBT5-3 bacterial strain was the highest phosphatase producing strain with an amount of 0.377 U/mL after 10 days of incubation. This strain showed its best phosphatase producing capacity when cultured in the liquid culture medium containing pH 5, 1% NaCl, glucose and urea under the shaking speed of 120 rpm. Based on 16S rRNA gene sequence analysis this phosphatase synthesizing bacterial strain was genetically identified as species of Bacillus sp. TBT5-3 since 100% of this train sequence is affiliated with Bacillus megaterium.

Amycolatopsis aidingensis sp. nov., a Halotolerant Actinobacterium, Produces New Secondary Metabolites.

A novel actinobacterium, strain YIM 96748T, was isolated from a saline soil sample collected from the south bank of Aiding Lake in Xinjiang Province, Northwest China. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain YIM 96748T is closely related to Amycolatopsis cihanbeyliensis BNT52T (98.9%) and Amycolatopsis jiangsuensis KLBMP 1262T (97.2%). The DNA–DNA relatedness between strain YIM 96748T and its closest type strain A. cihanbeyliensis BNT52T was 59.6%. The average nucleotide identity between strain YIM 96748T and its neighbor strain was 88.97%. Based on the genotypic and phenotypic characteristics, it is concluded that strain YIM 96748T represents a novel species of the genus Amycolatopsis, whose name was proposed as Amycolatopsis aidingensis sp. nov. The type strain is YIM 96748T. To investigate the biosynthetic potential of producing secondary metabolites, the complete genome of YIM 96748T was sequenced and analyzed. The complete genome sequence of YIM 96748T consists of a 7,657,695-bp circular chromosome, comprising 7,162 predicted genes with a DNA G + C content of 70.21 mol%. Fifty-one putative biosynthetic gene clusters of secondary metabolites were found, including the antibacterial/antitumor agent TLN-05220, the antibacterial agent nocardicin A, the antifungal agent nystatin A1, and the osmolyte ectoine. The investigation of the secondary metabolites of A. aidingensis YIM96748T led to the discovery of two new phenylpropyl acetate enantiomers, amycoletates A (1) and B (2), and five known compounds: 4-hydroxy phenethyl acetate (3), 2-p-acetoxyphenylethanol (4), (S)-ethyl indole-3-lactate (5), (R)-ethyl indole-3-lactate (6), and p-hydroxybenzoic acid (7). One of the gene clusters 14, 36, and 43, which contain a single module of polyketide synthase, might be responsible for the biosynthesis of compounds 1 and 2 from compound 7 as a precursor. Further studies, including the one strain many compounds approach (OSMAC) and genetic modification, are needed to explore novel compounds from this talented halophilic Amycolatopsis strain.

Absorbed carbon dioxide in saline soil from northwest China

Saline soil can both absorb and release atmospheric carbon dioxide (CO2); however, the factors underlying the mechanisms that drive CO2 transport and transformation in saline soils remain unclear. This study examined the absorption of atmospheric CO2 by saline soil in an effort to better understand the factors that contribute to this exchange. We investigated the relationship between carbon sources and sinks using in-situ observations of saline soil in the Hetao Irrigation District, Inner Mongolia, China. Eight saline soil samples, each of which exhibited different electrical conductivities (EC), were collected from 2014 to 2018. CO2 was sampled and analyzed by closed static-chamber-gas chromatography. We found that atmospheric CO2 was absorbed by all eight soil samples, but EC levels influenced the carbon exchange between the soil and the atmosphere. Between 2014 and 2018, cumulative CO2 absorbed by the two soil samples with the lowest EC values was 662.03 g·m−2 and 1322.17 g·m−2; whereas for the same period, the cumulative CO2 absorbed by the six soil samples with the highest EC values ranged from 55.05 g·m−2 to 600.52 g·m−2. Diurnal and nocturnal observations showed that saline soil absorbed atmospheric CO2 at night and released it into the atmosphere during the day, with a maximum night-time absorption value of −41.4 mg·m−2·h−1. Eighty-nine percent of the differences observed in dissolved inorganic carbon (ΔDIC) values across the soil samples were explained by differences in CO2 accumulation (ΔCO2) (r2 = 0.8922, n = 7). CO2 was absorbed by saline soil, where it was converted into DIC. As soil salinity increased, the cumulative amount of CO2 in the soil-atmosphere system increased significantly. As a result, we conclude that saline soils with high EC exhibit an enhanced ability to absorb carbon.

Halobaculum halophilum sp. nov. and Halobaculum salinum sp. nov., isolated from salt lake and saline soil

Two halophilic archaeal strains, Gai3-2T and NJ-3-1T, were isolated from salt lake and saline soil samples, respectively, collected in PR China. The 16S rRNA gene sequences of the two strains were 97.5% similar to each other. Strains Gai3-2T and NJ-3-1T had the highest sequence similarities to 'Halobonum tyrrellense' G22 (96.7 and 97.8%, respectively), and displayed similarities of 91.5-93.5% and 92.3-94.7%, respectively, to Halobaculum members. Phylogenetic analysis revealed that the two strains formed different branches and clustered tightly with 'H. tyrrellense' G22 and Halobaculum members. The average nucleotide identity (ANI), in silico DNA-DNA hybridization (isDDH) and amino acid identity (AAI) values between the two strains were 83.1, 26.9 and 77.9%, respectively, much lower than the threshold values proposed as a species boundary. These values between the two strains and 'H. tyrrellense' G22 (ANI 77.9-78.2%, isDDH 22.5-22.6% and AAI 68.8-69.3%) and Halobaculum members (ANI 77.53-77.63%, isDDH 21.8-22.3% and AAI 68.4-69.4%) were almost identical, and much lower than the recommended threshold values for species delimitation. These results suggested that strains Gai3-2T and NJ-3-1T represent two novel species of Halobaculum. Based on phenotypic, chemotaxonomic and phylogenetic properties, strains Gai3-2T (=CGMCC 1.16080T=JCM 33550T) and NJ-3-1T (=CGMCC 1.16040T=JCM 33552T) represent two novel species of the genus Halobaculum, for which the name Halobaculum halophilum sp. nov. and Halobaculum salinum sp. nov. are proposed.

Isolation and screening of carotenoid-producing Bacillus spp. from seashore saline soil and seawater at Hon Son islet

Carotenoids are natural pigment compounds with a variety of colors. They are antioxidants and boost the immune system. It is interesting to examine strains of bacteria capable of producing carotenoids applied in the food industry, animal feed, and aquaculture. Rach Gia bay of Kien Giang province has a good ecosystem, and the carotenoid-producing microorganisms in these regions are very plentiful. However, there are fewer studies about them in this region. This study was conducted to isolate and select carotenoids-producing Bacillus from Hon Son islet of Rach Gia bay. Seashore saline soil and seawater samples were shocked at 65°C in 1 hour and plated on Difco sporulation medium. Colored colonies of bacteria were selected and incubated at 37°C on Difco sporulation medium. Pigments from these isolates were extracted in the mixture of methanol and chloroform (with the ratio 1:2 of v/v). The extracted solutions were scanned absorbance by spectrophotometer at the wavelength range from 400 to 600 nm. Bacterial isolates were identified by 16S rRNA sequencing. Twenty carotenoid-producing bacterial species were isolated, including five colony colors such as pale yellow, yellow, yellow-orange, pale pink, and pink. They were Gram-positive, positive - catalase test, motile, and endospore-forming. The results of extracted solutions from 20 bacterial species indicate that all the extracts have absorbance from 400-600 nm, this is the popular absorbance of carotenoids. Two high-carotenoid-producing species (HS3-7 and HS8-3) were analyzed the 16S rRNA gene sequence. They were showed high similarity with Bacillus vietnamensis species Marseille-P799 and Bacillus infantis species NRRL B-14911,...

Microwave-assisted single-step extraction method for determination of heavy metals in saline soil and compare with conventional sequential extraction method

The present research assesses the chemical fractionation of cadmium (Cd), chromium (Cr), and lead (Pb) detected in saline soil samples of Hyderabad Pakistan. Based on the reagents used in the BCR three-step conventional sequential extraction (CSE) for partitioning Cd, Cr, and Pb in saline soil samples, a Microwave induced single-step extraction (MSE) method was developed. The validity of the method was confirmed using certified reference material (CRM) BCR-483 and the standard method of addition (recoveries 96–102%). The data provided by the BCR- CSE method for Cd, Cr and Pb partition were compatible with MSE using the same operating conditions applied and checked in BCR fraction by the Certified Reference Material (CRM) BCR-483. Using compromised sonication and microwave conditions steps 1–3 of the sequential extraction (excluding hydrogen peroxide digestion in step 3) could be accomplished with ultrasonic bath between 15 and 30 min, whereas 60–120 s needed for MSE. The total concentrations of Cd, Cr, and Pb extractable metals produced by three separate extractions ranged 1.02–3.30, 5.02–9.95 and 3.97–8.01 μgg−1, respectively. The accuracy of the proposed BCR single extraction methods (expressed as RSD %) for all metals was found within the range of (4.99–8.61%).

Evaluation and speciation of cobalt, copper, and zinc in saline soil bymicrowave‐assistedsingle extraction

AbstractThe present research assessed the chemical fractionation of Cobalt (Co), Copper (Cu), and Zinc (Zn), detected in saline soil samples of Hyderabad Pakistan. The partitioning of Co, Cu, and Zn in soil samples was carried by single‐step extraction using microwave irradiation energy. The validity of the methods was confirmed using the same operating conditions applied and checked as in BCR sequential extraction fractionation using certified reference material BCR‐701 and the standard method of addition (recoveries 96%–102%). Atomic absorption spectrometry was used to test extractable Co, Cu, and Zn contents obtained by the comparative method. Using compromised microwave conditions steps 1–3 of the sequential extraction (excluding hydrogen peroxide digestion in step 3) could be accomplished with an ultrasonic bath between 15 and 30 min, whereas 60–120 s were needed for microwave single‐extraction (MSE). The total concentrations of Co, Cu, and Zn extractable metals produced by three separate extractions ranged from 1.02–3.30, 5.02–9.95, and 3.97–8.01 μg/g respectively. Consequently, the use of single‐step extraction with the aid of microwave and ultrasound energy to reduce the time required for single‐step extraction based on the BCR sequential extraction method. However, with the aid of developed single‐step extraction methods, the obtained results were comparable to those values obtained from BCR sequential extraction method. For further study, the MSE can be frequently used to know the metal‐bound intensity with a different chemical fraction on environmental solid samples.

The effects of the recombinant YeaZ of Vibrio harveyi on the resuscitation and growth of soil bacteria in extreme soil environment.

Numerous bacteria entered the viable but non-culturable state due to the stresses of dry and salt in soils. YeaZ of Gram-negative bacteria is a resuscitation promoting factor (Rpf) homologous protein could resuscitate bacteria of natural environment in VBNC state. To investigate the promoting effect of YeaZ on the isolation of viable but non-culturable (VBNC) bacteria from soil samples in extreme environments, the recombinant YeaZ of Vibrio harveyi was prepared and added to the soil samples from volcanic soil and saline soil in Northwest China. The study has shown that YeaZ can promote the recovery and growth of soil microorganisms, and the number of cultivable bacteria in volcanic and saline soil has increased from 0.17 × 103 and 2.03 × 103 cfu⋅ml−1 to 1.00 × 103 and 5.55 × 103 cfu⋅ml−1, respectively. The 16S rDNA gene sequencing and phylogenetic analysis showed that YeaZ played an essential role in the increase of composition and diversity of bacteria. A total of 13 bacterial strains were isolated from the volcanic soil samples, which belong to phyla Actinobacteria, Firmicutes and Gamma-proteobacteria. Four species, including Ornithinimicrobium kibberense, Agrococcus citreus, Stenotrophomonas rhizophila and Pseudomonas zhaodongensis were found in the control group, while Micrococcus antarcticus, Kocuria rose, Salinibacterium xinjiangense, Planococcus antarcticus, Ornithinimicrobium kibberense and Pseudomonas zhaodongensis were isolated from the treatment groups (addition of YeaZ). Twenty-one strains were isolated from the saline soil samples, including eight species from the control group and thirteen species from the treatment groups, among which nine species were only found, including Bacillus oceanisediminis, Brevibacillus brevis, Paenibacillus xylanilyticus, Microbacterium maritypicum, B. subtilis, B. alcalophilus, B. niabensis, Oceanimonas doudoroffii and Zobellella taiwanensis. The results suggest that addition of YeaZ to soil samples can promote the recovery of VBNC. This method has the implications for the discovery of VBNC bacteria that have potential environmental functions.

Isolation and Identification of Biosurfactant Producing Bacterial Strain from Saline Soil Samples in Iran; Evaluation of Factors on Biosurfactant Production

Background: Biosurfactants are a group of valuable amphiphilic molecules that have been widely used in different industries such as pharmaceuticals and cosmetics. Objectives: The current study aimed to screen and identify a bacterial strain able to produce biosurfactant from environmental soil samples, followed by evaluating factors that contribute to biosurfactant production. Methods: The biosurfactants production was evaluated every 24 hours by emulsification index (EI), oil spreading ability, and surface tension measurement. Thereafter, the sequences of 16S rDNA genes and biochemical tests were performed to identify the isolated bacterial. Furthermore, the effect of different factors, including nitrogen, vegetable oil, and cations on biosurfactant productivity of the selected bacterial strain, was also evaluated. Results: In primary screening, out of the six bacterial strains, only one isolate was found to produce a hemolytic zone on the blood agar plate. The EI index was increased in a time-dependent manner with a maximum EI of 10% after 12h. Surface tension measurement revealed decreased surface tension (51 mN/m) after 12 hours' incubation compared to that of the blank sample. The selected isolate was recognized as Bacillus atrophaeus by 16S rDNA gene sequencing and biochemical test. All applied factors in culture media could decrease the surface tension of culture broth compared to that of the blank sample. Conclusions: This study demonstrated a Bacillus strain able to produce biosurfactants. Such biosurfactant producers would have great potentials in bioremediation activities and microbial enhanced oil recovery.

Paenibacillus turpanensis sp. nov., isolated from a salt lake of Turpan city in Xinjiang province, north-west China.

Strain YIM B00363T, a Gram-positive, aerobic, non-motile, rod-shaped, spore-forming bacterium, was isolated from saline soil samples collected from a salt lake in Xinjiang province, north-west China, and was characterized using a polyphasic approach. The optimum growth temperature was 37°C and the optimum pH was 7.5-8.0. The major menaquinone was MK-7; anteiso-C15:0 (53.52%), iso-C15:0 (15.04%) and C16:0 (12.76%) were the predominant cellular fatty acids. The diagnostic diamino acid of the cell wall peptidoglycan was meso-diaminopimelic acid. The phospholipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, unidentified phospholipids, unidentified glycolipids and unknown lipids. The DNA G + C content of the type strain was 50.4mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain YIM B00363T belonged to a cluster comprising species of the genus Paenibacillus. The nearest relatives were P. residui MC-246T and P. senegalensis JC66T, with 93.2% and 92.8% gene sequence similarities, respectively. On the basis of its phenotypic characteristics and phylogenetic distinctivenes, strain YIM B00363T represents a novel species of the genus Paenibacillus, for which the name Paenibacillus turpanensis sp. nov. is proposed. The type strain is YIM B00363T (= CGMCC 1.17507T = KCTC 43184T).

Production, characterization and bioactivities of biosurfactants from newly isolated strictly halophilic bacteria

Eight distinct halophilic bacteria isolated from extreme saline soil samples of Khewra Salt Mines, Pakistan, were investigated for biosurfactant production. Isolates were identified by physiological, phenotypic and genetic characterization. Using 16S rDNA sequence analysis, the strains MB590, MB591, MB593, MB594, MB595 and MB596 were identified as Halomonas elongata, MB588 as Halobacillus karajiensis, and MB589 as Alkalibacillus almallahensis. Preliminary screening of biosurfactant production in halophilic bacteria was done by multiple screening assays. All biosurfactants showed significant emulsification properties and remarkably low surface tension values (up to 16.5 dynes/cm). Structural characterization of partially purified biosurfactants using Gas chromatography–mass spectrometry (GC–MS) and Fourier-transform infrared spectroscopy (FTIR) techniques indicated different fatty acids, glycolipid derivatives and a novel antimicrobial peptide furanomycin. These biosurfactants exhibited strong bioactivities against bacterial/fungal pathogens i.e. Klebsiella pneumoniae (86.5 %), Staphylococcus aureus (97.75 %), Bacillus subtilis (97 %), Enterococcus faecalis (97.6 %), E. coli (54.5 %), Aspergillus niger (87.75 %), Aspergillus fumigatus (93.1 %), Aspergillus flavus (80.4 %), and Fusarium solani (89.05 %). Additionally, biosurfactants also showed 85 % free radical scavenging activity indicating their antioxidant potential. The present study revealed the potential of halophilic bacterial biosurfactants as effective antimicrobial agents against various pathogens, and their possible applications in the biomedical field.

Influence of gin trash bacteria broth treatment on cotton fibres

Purpose Bacterial exopolysaccharides (eps) have fascinating chemical compositions, properties and structures which could be used in the modification of natural fibres. Bacterial eps have therefore been used to modify plant cellulose fibre surface and impart desired properties. The purpose of this paper is therefore to investigate the influence of gin trash cultured bacteria eps on the physical and structural properties of cotton fibres. Design/methodology/approach Gin trash soil sample was collected from a ginnery in Kenya, and physiochemical and microbial characterization was done. The soil sample was then fermented for 24 h before being used to treat raw cotton fibres at varied conditions of temperature, pH and treatment time periods. Physical and structural properties of the treated fibres were then determined using USTER HVI-1000 M700, Fourier transform infrared, scanning electron microscope (SEM) and X-ray diffraction (XRD) and compared with those of the raw fibres. Findings The bacteria broth treated fibres were found to have increased in strength, spinning consistency index, elongation and fineness by 25.44, 24.30, 11.70 and 3.60%, respectively. The variations were attributed to interactions of bacterial eps with cotton cellulose through hydrogen bonding. SEM and XRD analysis revealed an increase in fibre surface roughness and crystallinity, respectively. Originality/value Bacterial eps have been used to modify plant cellulose fibre surface and impart desired properties. Eps producing bacteria have been isolated from different habitats such as saline water, soil samples, food wastes and petroleum-contaminated soil. To the best of the authors’ knowledge, bacterial eps cultured from gin trash soil sample for modification of cotton fibres have however not been previously done, hence the originality of the current study.

Gracilibacillus salitolerans sp. nov., a moderate halophile isolated from saline soil in Northwest China.

A moderately halophilic strain, designated SCU50T, was recovered from a saline soil sample and characterized by a polyphasic approach. The 16S rRNA gene sequence analysis showed that strain SCU50T belonged to the genus Gracilibacillus and was most closely related to Gracilibacillus thailandensis TP2-8T (98.1 % similarity) and Gracilibacillus orientalis XH-63T (97.7 %). Genomic average nucleotide identity and digital DNA-DNA hybridization analyses confirmed the separate species status of the new isolate relative to other recognized Gracilibacillus species. The genome size was about 5.09 Mbp and the DNA G+C content was 36.7 mol%. The strain grew optimally at 10-15 % (w/v) NaCl, pH 6.5-7.5 and 25-30 °C. It contained anteiso-C15 : 0, iso-C15 : 0 and anteiso-C17 : 0 as the dominant fatty acids and menaquinone-7 as the major respiratory quinone. The polar lipid profile was examined and found to comprise diphosphatidylglycerol, phosphatidylglycerol, one unidentified phospholipid and one unidentified lipid. The cell-wall peptidoglycan type was A1γ based on meso-diaminopimelic acid. Combining the data from phenotypic, chemotaxonomic, genomic and phylogenetic characterization, it was concluded that strain SCU50T should be assigned as representing a novel species within the genus Gracilibacillus. Thus, a novel taxon named Gracilibacillus salitolerans sp. nov. was first established, with SCU50T (=CGMCC 1.17336T=KCTC 43107T) as the type strain.

Hygroscopic properties of sodium and potassium salts as related to saline mineral dusts and sea salt aerosols

Mineral dust, soil, and sea salt aerosols are among the most abundant primary inorganic aerosols in the atmosphere, and their hygroscopicity affects the hydrological cycle and global climate. We investigated the hygroscopic behaviors of six Na- and K-containing salts commonly found in those primary organic aerosols. Their hygroscopic growths as a function of relative humidity (RH) agree well with thermodynamic model prediction. Temperature dependence of deliquescence RH (DRH) values for five of those salts was also investigated, which are comparable to those in literature within 1%–2% RH, most showing negative dependence on temperature. Hygroscopic growth curves of real-world soil and sea salt samples were also measured. The hygroscopic growths of two more-hydroscopic saline soil samples and of sea salt can be predicted by the thermodynamic model based on the measured water-soluble ionic composition. The substantial amounts of water-soluble ions, including Na+ and K+, in saline soil samples imply that even nascent saline soil samples are quite hygroscopic at high-RH (>80%) conditions. For three less-hygroscopic dust samples, however, measurements showed higher water uptake ability than that predicted by the thermodynamic model. The small amount of water taken up by less-hygroscopic dust samples suggests that dust particles might contain thin layers of water even to very low RH. The results of this study provide a comprehensive characterization of the hygroscopicity of Na- and K-containing salts as related to their roles in the hygroscopic behaviors of saline mineral dusts and sea salt aerosols.

Analysis of the pore structure characteristics of freeze-thawed saline soil with different salinities based on mercury intrusion porosimetry

The pore structure characteristics of soil are closely related to soil engineering properties. For saline soil distributed in seasonally frozen areas, existing studies have focused on the influence of freeze–thaw cycles on pore structure, while the influence of soluble salt in the soil is not well understood. This study aims to explore the influence of salt content and salt type on the pore structure of freeze-thawed soil. Soil samples with different salt contents (0–2%) and types (bicarbonate salt and sulfate salt) were subjected to 10 freeze–thaw tests, and their pore size distributions (PSDs) were obtained by mercury intrusion porosimetry tests. In addition, the PSDs were quantitatively analyzed by fractal theory. For both salts, the PSDs of the tested soil samples were bimodal after the freeze–thaw cycles, and the porosity of saline soil samples increased with increasing salt content overall. However, the contents of various types of pores in soil samples with two salt types were quite different. The variation in bicarbonate salt content mainly affected the mesopore and macropore contents in the soil samples, and their change trends were opposite to each other. For soil samples with sulfate salt, the porosity and macropore content increased significantly when the salt content exceeded 1%. In addition, the pore structures in saline soil presented fractal characteristics after the freeze–thaw cycles, and the fractal dimension was positively correlated with macropore content. This study may provide references for understanding the engineering properties of saline soil in seasonally frozen areas at the microscale.

Apply biochar to ameliorate soda saline-alkali land, improve soil function and increase corn nutrient availability in the Songnen Plain

Soda saline-alkali soils are characterized by high concentration of sodium cations on the exchange complex or in soil-water resulting in soils which are physically as well as nutritionally challenging for crop production. Biochar application has received growing interest as a sustainable technology to improve physicochemical properties in non-saline and non-alkali soils. However, information is inadequate regarding potential of using corn straw derived biochar as an organic material to reduce soda saline-alkali stress. Based on the established model of corn straw biochar-soda saline alkali soil-corn system, soil and plant samples were collected from long-term field experiment in soda saline-alkali land with different addition rates of corn straw biochar (CK: control, T5: 5 ton ha−1, T10: 10 ton ha−1, T15: 15 ton ha−1, T20: 20 ton ha−1, T25: 25 ton ha−1, T30: 30 ton ha−1). In the seedling and harvest period, addition of corn straw biochar enhanced the contents of cation exchange capacity (CEC), organic matter, and nutrients of 0–20 cm and 20–40 cm saline-alkali soil layers and the above ground and underground parts of corn. However, the results were contrary as far as pH, salt, and Na+ were concerned, and the effect of T20 was the most significant. Principal component analysis showed that CEC, pH, salinity, and organic matter could be used as indicators to evaluate the improvement effect of biochar on soda saline-alkali soil. Irrespective of the application of biochar, pH, salt content, Na+, and nutrients concentrations at seedling stage were higher than those at harvest stage, indicating that planting corn could improve soda saline-alkali soil. It may be concluded that corn straw biochar can be used as an organic amendment for reducing adverse effects of salinity and alkalinity on soil functions governed by their rates of addition.

Displacement of Sodium, Potassium, Calcium, Magnesium and Improvements in a Saline Soil Treated with Organic and Chemical Amendments

The accumulation of salts in the soil produces conditions that affect the growth of most crops. Currently, soil amendments have been used to improve the texture and chemical & biological reactions of the soil. The objective of this work was to simulate the transport of sodium, potassium, calcium and magnesium in columns of saline soil through the use of organic and chemical amendments. Saline soil samples of the municipality of Tlahuelilpan, Hidalgo state, Mexico were studied. Compost, vermicompost, phosphogypsum and malting barley husk were used as amendments. The results showed that the highest metal element removal was obtained with the combined treatment of vermicompost at 4 % and phosphogypsum at 2 % (V4FY2) (59 %). Improvements in soil physico-chemical properties were also observed. These findings indicated that the combination of organic and chemical amendments promotes the leaching of metals, (mainly sodium). Therefore, the amendments evaluated in this study can be a good alternative for the remediation and improvement of saline soils.

Soil Desalination via Poly(vinyl alcohol) Borate Hydrogel

Saline and sodic soil sample was collected from salty beach. Polyvinyl alcohol borate hydrogel due to its cation attracting ability was utilized as an adsorbent for the removal of excess cations responsible for the salinity and sodicity of soil. Experimental data were collected before treatment and after each treatment using 1 : 2 by weight soil to water extract method. Electrical conductivity and pH were observed. The amounts of sodium, potassium, magnesium, and calcium ions were determined by flame photometry and atomic absorption spectrometry. From data it was evaluated that there is the decrease in electrical conductivity and amounts of cations after desalinating soil that was previously categorized as saline. Sodium adsorption ratio and exchangeable sodium percentage were also determined and found to decrease after treatment of soil sample with polyvinyl alcohol borate hydrogel. After treatment, soil becomes nonsaline but remains sodic. This was due to the fact that it has the higher sodium ion content in comparison with other cations. Thus, further remediation to decrease the sodicity of soil was suggested before its application for agricultural purposes.

Correlation between Electrical Resistivity and Suction for Unsaturated Coastal Saline Soil

An experimental research on joint application of engineering-geological and geophysical measurements is presented in this paper. Experimental results obtained from the filter paper method and four electrode resistivity measurements were presented to characterize unsaturated saline soil samples collected in a test area in Lian Yungang City (in Jiangsu Province), which aimed at defining both soil suction and electrical resistivity curves versus water content at different salt contents. From the matching of the experimental data, the relationships between electrical resistivity and suctions were retrieved for the investigated soil. It was concluded that suctions increase with the increase of electrical resistivity and the increase of soil salt content. The outcomes of the study would provide proper understanding about the influence of physical characteristics of unsaturated soils on their electrical responses.