Effects of Fe3+ and Ca2+ on sorption of phenanthrene by Humin in karst soil,Southwest China

Humin(HM) is the main organic matter component to af fect the migration and transformation of polycyclic aromatic hydrocarbons(PAHs) in soil. The study on infl uence of the morphology change of inorganic ions on the adsorption of PAHs in soil and its organic matter is still rare at microscopic scale. In this paper, yellow soil humin(YS-HM) and lime soil humin(LS-HM) were chosen as samples, then Fe^(3+) and Ca^(2+) were added into samples to facilitate the precipitation by changing the existing conditions of ions, and the mechanism by which inorganic precipitation changed adsorption capacity of karst soil was analyzed from the microscopic scale. The results showed that the adsorption capacity of HM reduced with the inorganic precipitation increasing. The precipitation of Ca^(2+)and Fe^(3+) both reduced the adsorption capacity of YS-HM and LS-HM by 61.71% and 71.83% on average, respectively. The results of scanning electron microscope-energy dispersive spectrometry(SEM-EDS) and pore analysis showed that the HM porosity decreased after formation of Ca^(2+) and Fe^(3+) precipitation. According to the value of Freundlich parameter n, it may be because the precipitation or colloid of Ca^(2+) and Fe^(3+) fi lled micropores and covers high-energy adsorption sites of the HM. This research provides theoretical support for studying the PAHs migration and bioavailability of Calcium-rich in karst soil.

Effects of Groundwater with Various Salinities on Evaporation and Redistribution of Water and Salt in Saline-sodic Soils in Songnen Plain,Northeast China

Groundwater mineralization is one of the main factors affecting the transport of soil water and salt in saline-sodic areas.To investigate the effects of groundwater with different levels of salinity on evaporation and distributions of soil water and salt in Songnen Plain,Northeast China,five levels of groundwater sodium adsorption ration of water(SARw)and total salt content(TSC mmol/L)were conducted in an oil column lysimeters.The five treated groundwater labeled as ST0:0,ST0:10,ST5:40,ST10:70 and ST20:100,were prepared with NaCl and CaCl2 in proportion,respectively.The results showed the groundwater evaporation(GWE)and soil evaporation(SE)increased firstly and then decreased with the increase of groundwater salinity.The values of GWE and SE in ST10:70 treatment were the highest,which were 2.09 and 1.84 times the values in the ST0:0 treatment with the lowest GWE and SE.There was a positive linear correlation between GWE and the Ca^(2+)content in groundwater,with R^(2)=0.998.The soil water content(SWC)of ST0:0 treatment was significantly(P<0.05)less than those of other treatments during the test.The SWC of the ST0:0 and ST0:10 treatments increased with the increase of soil depth,while the other treatments showed the opposite trend.Statistical analysis indicated the SWC in the 0–60 cm soil layer was positively correlated with the groundwater TSC and its ion contents during the test.Salt accumulation occurred in the topsoil and the salt accumulation in the 0–20 cm soil layer was significantly(P<0.05)greater than that in the subsoil.This study revealed the effects of the salinity level of groundwater,especially the Ca^(2+)content and TSC of groundwater,on the GWE and distributions of soil water and salt,which provided important support for the prevention and reclamation of soil salinization and sodificaton in shallow groundwater regions.

Geogenic Pollution of Groundwater Quality in Gampaha District, Sri Lanka: A Case Study of Groundwater Acidification from Rathupaswala

Over recent decades, Gampaha district, Sri Lanka, has experienced significant urbanisation and industrial growth, increasing groundwater demand due to limited and polluted surface water resources. In 2013, a community uprising in Rathupaswala, a village in Gampaha district, accused a latex glove manufacturing factory of causing groundwater acidity (pH < 4). This study evaluates the spatial and temporal changes in geochemical parameters across three transects in the southern part of Gampaha district to 1) assess the impact of geological formations on groundwater;2) compare temporal variations in groundwater;and 3) explain acidification via a geochemical model. Seventy-two sample locations were tested for pH, electrical conductivity (EC), and anion concentrations (sulphate, nitrate, chloride and fluoride). Depth to the water table and distance from the sea were measured to study variations across sandy, peaty, lateritic, and crystalline aquifers. Results showed pH readings around 7 for sandy and crystalline aquifers, below 7 for peaty aquifers, and below 5 for lateritic aquifers, with significant water table fluctuations near Rathupaswala area. Principal component analysis revealed three principal components (PCs) explaining 86.0% of the variance. PC1 (40.6%) correlated with pH, EC, and sulphate (saltwater intrusion), while PC2 (32.0%) correlated with nitrates and depth to the water table (anthropogenic nutrient pollution). A geochemical transport model indicated a cone of depression recharged by acidic groundwater from peat-soil aquifers, leading to acidic groundwater in Rathupaswala area. Previous attributions of acidic pH to the over-exploitation of groundwater by the latex factory have been reevaluated;the results suggest natural acidification from prolonged water-rock interactions with iron-rich lateritic aquifers. Groundwater pH is influenced by local climate, geology, topography, and drainage systems. It is recommended that similar water-rock interaction conditions may be present throughout the wet zone of Sri Lanka, warranting detailed studies to confirm this hypothesis.

Interaction Between Charge Characteristics and Cu^(2+) Adsorption-Desorption of Soils with Variable or Permanent Charge

Charge characteristics and Cu2+ adsorption-desorption of soils with variable charge (latosol) and permanent charge (brown soil) and the relationship between them were studied by means of back-titration and adsorption equilibrium respectively. The amount of variable negative charge was much less in variable-charge soil than in permanent-charge soil and increased with the pH in the system, but the opposite trend occurred in the points of zero charge (PZCs). The amount of Cu2+ ions sorbed by permanent-charge soil was more than that by variable-charge soil and increased with the increase of Cu2+ concentration within a certain range in the equilibrium solution. The amount of Cu2+ ions desorbed with KC1 from permanent-charge soil was more than that from variable-charge soil, but the amount of Cu2+ ions desorbed with de-ionized water from permanent-charge soil was extremely low whereas there was still a certain amount of desorption from variable-charge soil. The increase of PZC of soils with variable or permanent charge varied with the increment of Cu2+ ions added. When the same amount of Cu2+ ions was added, the increments of PZC and variable negative surface charge of permanent-charge soil were different from those of variable-charge soil.

Free cupric ions in contaminated agricultural soils around a copper mine in eastern Nanjing City, China

To determine the environmental free metal ion activity was a recent hot issue. A method to measure low-level free cupric ion activity in soil solution extracted with 0.01 mol/L KNO3 was developed by using cupric ion-selective electrode （ISE） and calibrating with Cu-buffer solution. Three copper buffers including iminodiacetic acid （IDA）, ethylenediamine （EN）, and glycine （Gly） were compared for calibrating the Cu-ISE curves in the range of free cupric ions （pCu^2＋） 7-13. The Cu-EN buffer showed the best electrode response and thus was applied as the calibration buffer. The pCu^2＋ of 39 contaminated agricultural soils around a copper mine was measured, ranging from 5.03 to 9.20. Most Cu in the soil solutions was found to be complexed with dissolved soil organic matters, averaging 98.1%. The proportion of free Cu^2＋ ions in the soil solutions decreased with the increasing of solution pH. Soluble Cu and free Cu^2＋ ions concentrations were analyzed by multiple linear regressions to evaluate the effects of soil properties on metal levels and speciation. The results showed that soil solution pH was the most significant factor influencing pCu^2＋ （with R^2 value of 0.76）, while not important for the soluble Cu concentration.

Chemical Species of Aluminum Ions in Acid Soils *1

Soil samples collected from several acid soils in Guangdong, Fujian, Zhejiang and Anhui provinces of the southern China were employed to characterize the chemical species of aluminum ions in the soils. The proportion of monomeric inorganic Al to total Al in soil solution was in the range of 19% to 70%, that of monomeric organic Al (Al OM) to total Al ranged from 7.7% to 69%, and that of the acid soluble Al to total Al was generally smaller and was lower than 20% in most of the acid soils studied. The Al OM concentration in soil solution was positively correlated with the content of dissolved organic carbon (DOC) and also affected by the concentration of Al 3+ . The complexes of aluminum with fluoride (Al F) were the predominant forms of inorganic Al, and the proportion of Al F complexes to total inorganic Al increased with pH. Under strongly acid condition, Al 3+ was also a major form of inorganic Al, and the proportion of Al 3+ to total inorganic Al decreased with increasing pH. The proportions of Al OH and Al SO 4 complexes to total inorganic Al were small and were not larger than 10% in the most acid soils. The concentration of inorganic Al in solution depended largely on pH and the concentration of total F in soil solution. The concentrations of Al OM, Al 3+ ,Al F and Al OH complexes in topsoil were higher than those in subsoil and decreased with the increase in soil depth. The chemical species of aluminum ions were influenced by pH. The concentrations of Al OM, Al 3+ , Al F complexes and Al OH complexes decreased with the increase in pH.

Effects of Inorganic Sodium Salt in Soil on Concentration of Zinc Ion in Different Patterns

[Objective] The aim was to study on effects of inorganic sodium salt in soil on concentration of zinc ion in different patterns. [Method] Tessier sequential extraction was used to study on effects of inorganic sodium salts （in different species and different concentrations） on concentration of zinc ion in different patterns. [Result] Different inorganic sodium salts had different effects on zinc form. Content of ex- changeable Zn would reduce if Na2CO3 or Na2SO4 was added and the content would increase if NaCI was added. Content of carbonate zinc, which was significantly influ- enced by Na2SO4, would increase if NaCI or Na2SO4 was added, and would decrease if Na2CO3 was added. For Zn bound to Fe-Mn oxides and organic matters, and residual Zn, the contents would decrease if NaCI or Na2SO4 was added and the decrease showed much more significantly if high concentration sodium salts were added. In addition, content of Zn bound to Fe-Mn oxides decreased if Na2CO3 was added. If low concentration Na2CO3 was added, Zn bound to organic matters and residual would increase in content but would lower if high concentration one was added. [Conclusion] The research provided references for measurement of heavy metal ion content in soil in different places.

Adsorption of Potassium and Sodium Ions by Variable Charge Soils

Adsorption of potassium and sodium ions by four typical variable charge soils of South China was studied. The results indicated that the variable charge soils saturated with H and Al showed a much higher preference for potassium ions relative to sodium ions, and this tendency could not be changed by such factors as the pH, the concentration of the cations, the dielectric constant of solvent, the accompanying anions and the iron oxide content etc., suggesting that this difference in affinity is caused by the difference in the nature of the two cations. It was observed that a negative adsorption of sodium ions by latosol and lateritic red soil in a mixed system containing equal amount of potassium and sodium ions at low pH, which is caused by a competitive adsorption of potassium and sodium ions and repulsion of positive charge on the surfaces of soil particles for cations. The adsorption of potassium and sodium ions increased with the decreases in the dielectric constant of solvent and the iron oxide content. Sulfate affected the adsorption of potassium and sodium ions through changing the surface properties of the soils.

Diffusion of Chloride Ions in Soils:I.Influences of Soil Moisture, Bulk Density and Temperature

Diffusion coefficients of chloride ions in four soils of different texture with varying effective moisture content and varying bulk density from 1.1 to 1.6 g cm3 under three different temperatures were determined by the diffusion-cell method using 36Cl-labelled CaCl2 solution. The results showed that activation energy decreased with water content, which indicated that the threshold for diffusion was lower at a higher soil moisture rate. Therefore, the diffusion coefficient (D) of chloride ions in soil increased consistently with soil moisture. Although a near linear increase in the diffusion coefficient with increasing soil moisture or bulk density in all the soils was observed, the increase rate in different soils was not the same. The D value increased with temperature, and with temperature increased by 10℃ in the range from 5 "C to 45℃ theD valve increased by 10%～30%, averaging about 20%.

Exchange Reaction Between Selenite and Hydroxyl Ion of Variable Charge Soil Surfaces: Ⅱ. Kinetics of Hydroxyl Release

A self-made constant pH automated titration instrument was used to study thekinetics of hydroxyl release during selenite reacting with variable charge soils. The rate ofhydroxyl release was very rapid at the first several minutes, then gradually slowed down, and atlast did not change any more. The experimental data was well fitted by the Langmuir kineticequation, arid with increasing selenite concentration or decreasing solution pH, the reaction lastedlonger, the maximum of hydroxyl release (x_m) increased, and the binding constant (k) decreased.The time of hydroxyl release with Xuwen latosol was much longer than that with Jinxian red soil.

Adsorption of Potassium and Calcium Ions by Variable Charge Soils

Interactions of potassium and calcium ions with four typical variable charge soils in South China were examined by measuring pK-0.5pCa value with a potassium ion-selective electrode and a calcium ion-selective electrode,and pK value with a potassium ion-selective electrode.The results showed that adsorption of potassium and calcium ions increased with soil suspension pH,and the tendency of the pK-0.5pCa value changing with pH differed with respect to pH range and potassium to calcium ratio.Adsorption of equal amount of calcium and potassium ions led to release of an identical number of protons,suggesting similar adsorption characteristics of these two ions when adsorbed by variable charge soils.Compared with red soil,latosol and lateritic red soil had higher adsorption selectivities for calcium ion.The red soil had a greater affinity for potassium ion than that for calcium ion at low concentration,which seems to result from its possession of 2:1 type minerals,such as vermiculite and mica with a high affinity for potassium ion.The results indicated that adsorption of potassium and calcium ions by the variable charge soils was chiefly caused by the electrostatic attraction between the cations and the soil surfaces.Moreover,it was found that sulfate could affect the adsorption by changing soil surface properties and by forming ion-pair.

Interactions of Heavy Metal Ions with Paddy Soils as Inferred from Wien Effect Measurements in Dilute Suspensions

Interactions of three heavy metal ions, Cu^2＋, Cd^2＋, and Pb^2＋, and, for comparison, Na^＋ with electrodialytic clay fractions （less than 2μm in diameter） of four paddy soils as well as a yellow-brown soil as a control soil were evaluated based on measurements of the Wien effect in dilute suspensions with a clay concentration of 10 g kg^-1 in four nitrate solutions of 2 × 10^-4/z mol L^-1, where z is the cation valence, and a nitric acid solution of 3 × 10^-5 mol L^-1, Field strengths ranging from 15 to 230 kV cm^-1 were applied for measuring the electrical conductivities （ECs） of the suspensions. The mean free binding energies between the various cations and all of the soils determined from exchange equilibrium increased in the order： Na^＋ 〈 Cd^2＋ 〈 Cu^2＋ 〈 Pb^2＋. In general, the ECs of the suspensions in the sodium nitrate solution were smaller than those of the suspensions in the heavy metal solutions because of the lower electrophoretic mobility of sodium compared to the divalent cations. In terms of relative electrical conductivity-field strength relationships, relative electrical conductivity （REC） of suspensions containing various cations at field strengths larger than about 50 kV cm^-1 were in the descending order： Na^＋ 〉 Cu^2＋ 〉 Cd^2＋ 〉 Pb^2＋ for all tested soils. A characteristic parameter of the REC-field strength curves, AREC200, REC at a field strength of 200 kV cm^-1 minus that at the local minimum of the concave segment of the REC-field strength curves, characterized the strength of adsorption of the cations stripped off by the applied strong electrical field, and for all soils the values of AREC200 were generally in the order： Na^＋ 〈 Cu^2＋ ≤ Cd^2＋ 〈 Pb^2＋.

Analysis of Macro and Micronutrients in Soils from Palestine Using Ion Exchange Membrane Technology

Ion Exchange membrane technology (IEM) is a method that allowed a single extraction process and a single subsequent measurement of different elements that are available in soil. The values of the available forms of the different macro- and micronutrients obtained by IEM extraction were compared with the values of the soluble form obtained by conventional extraction methods. In surface soil sample, the concentrations of available potassium, nitrate, phosphate, iron and boron were 37.7 mg kg–1, 17.5 mg kg–1, 3.6 mg kg–1, 171.0 μg kg–1, and 4.2 μg kg–1 respectively were greater than that of soluble forms of the same elements which were 7.0 mg kg–1, 9.2 mg kg–1, 0.4 mg kg–1, 109.0 μg kg–1, and 1.9 μg kg–1 respectively.

Studies on Heavy Metal Pollution in Soil-Plant System:A Review

Heavy metal pollution in soil-plant system is of major environmental concern on a world scale and in China in particular with the rapid development of industry. The heavy metal pollution status in soil-plant system in China, the research progress on the bioavailability of heavy metals (affecting factors, extraction methods, free-ion activity model, adsorption model, multivariate regression model, Q-I relationship, and compound pollution), and soil remediation are reviewed in the paper. Future research and monitoring is also discussed.

Effects of red-yellow soil acidification on seed germination of Chinese pine

Acid treatments significantly change the physical and chemical properties of red yellow soil by lowering its pH value and leaching out aluminum(Al) ions that are harmful to the growth of plants. The structure of soil will be damaged, resulting in higher viscosity, higher water retention rate and lower air permeability of the soil. The germination rate of Chinese pine( Pinus tabulacformic Carr. ) seeds sowed in soil treated with sulphuric acid(H 2SO 4) decreased compared to that for untreated soil. The direct cause was the large amount of Al ions leached out because of low pH values(≥3.5). The added acid decreased the soil aggregation and increased the number of micro aggregates(under 250 μm in diameter). Such changes increased the soil's viscosity, which tied the pine needles to the soil after the seeds had germinated and prevented the seedlings from fully developing.

Determination of Diffusion Coefficient and Analysis of Diffusion Factors of Cr(Ⅵ) Ion in Clay Soil

Some laboratory diffusion tests were conducted with diffusion device to determine the diffusion coefficient of Cr(Ⅵ) ion passing through Dalian red clay samples. The concentrations of Cr(Ⅵ) at different places of the samples were then measured spectrophotometrically after a standing time of 1 000 d. A one-dimensional solute transport equation was used to simulate the transport of Cr(Ⅵ) through clay samples. Back-calculation of diffusion coefficient of Cr(Ⅵ) was made with finite difference method. Parametric analysis was conducted to simulate variations in soil dry density, temperature, pH and standing time. The results show that the method used in this paper is simple and effective. The diffusion coefficient of Cr(Ⅵ) in Dalian red clay varies from 1.50×10-7 cm2/s to 2.08×10-7 cm2/s. After 1 000 d diffusion, the concentration of the source solution drops down to 1.27 mg/L from 62.5 mg/L, and the diffusion distance is only 3.5 cm. Under the assumption that diffusion coefficient is constant, the diffusion effect becomes more obvious with lower density, lower temperature, higher pH value, and much more time.

Variation of soil physical-chemical characteristics in salt-affected soil in the Qarhan Salt Lake,Qaidam Basin

Soil salinization has adverse effects on the soil physical-chemical characteristics.However,little is known about the changes in soil salt ion concentrations and other soil physical-chemical characteristics within the Qarhan Salt Lake and at different soil depths in the surrounding areas.Here,we selected five sampling sites(S1,S2,S3,S4,and S5)alongside the Qarhan Salt Lake and in the Xidatan segment of the Kunlun Mountains to investigate the relationship among soil salt ion concentrations,soil physical-chemical characteristics,and environmental variables in April 2019.The results indicated that most sites had strongly saline and very strongly saline conditions.The main salt ions present in the soil were Na^(+),K^(+),and Cl^(-).Soil nutrients and soil microbial biomass(SMB)were significantly affected by the salinity(P<0.05).Moreover,soil salt ions(Na^(+),K^(+),Ca2+,Mg^(2+),Cl^(-),CO_(3)^(2-),SO_(4)^(2-),and HCO_(3)^(-))were positively correlated with electrical conductivity(EC)and soil water content(SWC),but negatively related to altitude and soil depth.Unlike soil salt ions,soil nutrients and SMB were positively correlated with altitude,but negatively related to EC and SWC.Moreover,soil nutrients and SMB were negatively correlated with soil salt ions.In conclusion,soil nutrients and SMB were mainly influenced by salinity,and were related to altitude,soil depth,and SWC in the areas from the Qarhan Salt Lake to the Xidatan segment.These results imply that the soil quality(mainly evaluated by soil physical-chemical characteristics)is mainly influenced by soil salt ions in the areas surrounding the Qarhan Salt Lake.Our results provide an accurate prediction of how the soil salt ions,soil nutrients,and SMB respond to the changes along a salt gradient.The underlying mechanisms controlling the soil salt ion distribution,soil nutrients,and SMB in an extremely arid desert climate playa should be studied in greater detail in the future.

Novel Inorganic Pyrophosphatase from Soil Metagenomic and Family and Subfamily Prediction

Inorganic pyrophosphatase (PPase) is widely studied, to be extremely important for survival of plants and microorganisms. PPases catalyze an essential reaction the hydrolysis of inorganic pyrophosphate (PPi) to inorganic phosphate (Pi). Studies involving the mechanism of PPase were performed in microorganisms culture. We didn’t found reports of PPase derived from soil meta-genomic libraries. Soil environment has immense diversity of microorganisms, yet most remains unexplored and the metagenome are the technologies used and investigate uncultured microorganisms potential. The aim is to identify novel genes using the metagenomic approaches from a bioinformatics perspective and hopefully will serve as a useful resource. With this purpose, we used the metagenomic library of Eucalyptus spp. arboretum (EAA). We did a screening to select a positive clone and submitted them to the process of shotgun. The data obtained was submitted to bioinformatics analyses. These analyses identified were the novel MetaPPase gene and were classified according to the predict family and subfamily.

Chloride transport and its sensitivities to different boundary conditions in reclaimed soil solutions filled with fly ash

Chloride ion transport in reclaimed soil solutions filled with fly ash （FA） was investigated by measuring the hydraulic parameters （i,e. water retention curves and hydraulic conductivity） of three substrates, namely GSL, GFA, and CFA. Similar simulations were carried out under certain weather conditions. The different boundary conditions of chloride transport were also discussed from FA texture, cover soil thickness, groundwater table level, and initial chloride concentration. Furthermore, the sensitivities of chloride ions to these effect factors were analyzed. The results show that the different top soil thickness and initial chloride concentration have no effect on salinity of topsoil solution in the monitoring points, but they can clearly change the chloride concentration of FA layers. The sensibilities from top soil thickness and initial chloride content are exceedingly weak to the salinity balance based on two dimensions of the time and concentration. While the different FA texture and groundwater table not only affect the salinity equilibrium process of the whole reclaimed soil profile, but also change its balance state. Generally, coarse FA particles and high groundwater table can defer the salinity balance process of the reclaimed soil solution, and they also increase the chloride concentration of FA layer solutions, and even topsoil ones.