Salt Dynamics in Rhizosphere of Puccinellia ciliata Bor. in a Loamy Soil

A glasshouse experiment using a rhizobox technique was conducted to examine salt dynamics in the rhizosphere of a salt-tolerant grass, Puccinellia ciliata Bor. ’Irwin Hunter’, grown in a loamy soil, and to study the effect of rainfall flush on salt accumulation in the rhizosphere. The rhizobox (10 × 5.5 × 50 cm) had a nylon mesh (1 μm) positioned vertically in the middle to create two compartments filled with soil amended with 1 g NaCl kg-1. The plants were grown in one compartment only. Flushed treatments received 275 mL of deionized water two days before harvest. In the plant-growing compartment, soils were sectioned vertically at 5 cm intervals. Significant differences in soil electrical conductivity (EC) (P < 0.05) and pH (P < 0.05) were observed for depths, but not between flushed and non-flushed treatments. In the no-plant compartment (rhizosphere), soil cores were taken horizontally at depths of 5, 20 and 40 cm and sliced at 1, 2, 3, 4, 5, 7, 10, 15 and 20 mm away from the roots. Soil EC and Cl- concentration at the 5 and 20 cm depths, and Na+ concentration at the 5 cm depth significantly decreased (P < 0.05) with the distance away from the root, but no significant differences were observed in soil pH and concentrations of the K+ and Ca2+. The flush treatment only had significant influence on soil EC, pH, and Cl- concentration at the 20 cm depth. Thus, salt accumulation could occur in the rhizosphere of salt-tolerant species on saline soils, and the periodic low rainfall might not have a strong influence on salt distribution in the rhizosphere and/or root zone.

Dynamic Water and Salt Changes in Saline Wasteland on the Lower Edge of Plain Reservoirs in the Desert Oasis Region

In order to reveal the distribution characteristics of water and salt in the non-irrigated saline wasteland and the growth zone of the windbreaks surrounding the plain reservoir,the groundwater and soil monitoring points were set up around the south area of Duolang Reservoir in the desert oasis.Monthly groundwater depth monitoring and soil water content and salt content fixed-point sampling for a period of 2 years were conducted.The results showed that the groundwater depth of salt wasteland in the area around the reservoir area changed slightly during the monitoring period of 2 years,and the average is 1.28 m.The soil moisture content increased with the increase of soil depth,and soil water content of 60-100 cm was larger than that of other soil layers.The salt content of the soil in the salt wasteland varied between 0.48 g/kg and8.86 g/kg in the two years,and the total salt content of different soil decreased with the increase of soil depth.The soil salt content changed greatly in 0-40 cm soil layers,with significant salt accumulation phenomenon.The soil salt content of windbreaks was significantly lower than that of the natural ecological forest.

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.

Preface:Value and dynamics of salt lakes in a changing world

The statement that the world’s ecosystems are rapidly deteriorating due to human intervention and global warming is nowadays commonplace.Some of the ecosystems most heavily impacted are inland salt lakes.The salt lakes are among the most valuable and fascinating ecosystems on Earth,and their study has both basic scientifi c interest as well as applied aspects.

Soil salt leaching under different irrigation regimes: HYDRUS-1D modelling and analysis

Field irrigation experiments were conducted in the Hetao Irrigation District of Inner Mongolia,China,to study the effects of irrigation regimes on salt leaching in the soil profile.The data were used to calibrate and validate the HYDRUS-1D model.The results demonstrated that the model can accurately simulate the water and salt dynamics in the soil profile.The HYDRUS-1D model was then used to simulate 15 distinct irrigation scenarios.The results of the simulation indicated that irrigation amount did not have a significant effect on soil water storage but that increases in irrigation amount could accelerate salt leaching.However,when the irrigation amount was larger than 20 cm,the acceleration was not obvious.Compared with irrigating only once,intermittent irrigation had a better effect on increasing soil water storage and salt leaching,but excessive irrigation times and intervals did not improve salt leaching.In addition,we found that the irrigation regime of 20 cm,irrigated twice at 1-d intervals,might significantly increase salt leaching in the plough layer and decrease the risks of deep seepage and groundwater contamination.

Interaction of cetyltrimethylammonium bromide with drug in aqueous/electrolyte solution:A combined conductometric and molecular dynamics method study

Interaction between beta-lactum antibiotic drug ciprofloxacin hydrochloride(CFH)and cationic surfactant cetyltrimethylammonium bromide(CTAB)was performed conductometrically in aqueous as well as in the occurrence of different salts(NaCl,KCl as well as NH_4Cl)over the temperature range of 298.15–323.15 K at the regular interval of 5 K.CFH drug has been suggested for the treatment of bacterial infections such as urinary tract infections and acute sinusitis.A clear critical micelle concentration(CMC)was obtained for pure CTAB as well as(CFH+CTAB)mixed systems.The decrease in CMC values of CTAB caused by the addition of CFH reveals the existence of the interaction between the components and therefore it is the indication of micelle formation at lower concentration of CTAB and their CMC values further decrease in attendance of salts.A nonlinear behavior in the CMC versus T plot was observed in all the cases.The ΔG_m^0 values are found to be negative in present study systems demonstrated the stability of the solution.The values of ΔH_m^0 and ΔS_m^0 reveal the existence of hydrophobic and electrostatic interactions between CFH and CTAB.The thermodynamic properties of transfer for the micellization were also evaluated and discussed in detail.Molecular dynamic simulation disclosed that environment of water and salts have impact on the hydrophobic interaction between CFH and CTAB.In water and salts,CTAB adopts spherical micelle in which charged hydrophilic groups are interacted with waters whereas hydrophobic tails form the core of the micelle.This hydrophobic core region is highly conserved and protected.In addition,micelle formation is more favorable in aqueous Na Cl solution than other solutions.

Brownian Dynamics Simulations of Rigid Polyelectrolyte Chains Grafting to Spherical Colloid

Brownian dynamics simulations are employed to explore the effects of chain stiffness and trivalent salt concentration on the conformational behavior of spherical polyelectrolyte brush. The rigid brush adopts bundle-like morphology at a wide range of trivalent salt concentration. The number variation of bundles pinned on the colloid surface shows a non-monotonic profile as a function of the chain stiffness. The radial distributions of monomers and ions and the charge ratio between condensed ions and monomers are calculated. The charge inversion is observed for the high salt concentration regardless of chain rigidity. Furthermore, the pair correlation functions of monomer-monomer and monomer-salt cation are used to elucidate the aggregated mechanism of the bundle-like structure.