Journal of Soil Science Society of Iran
Volume:1 Issue: 1, Summer 2022

The sustainability production of dryland agriculture is threatened by salt accumulation in soil due to irrigation practices by saline waters. However, the dynamic processes of secondary soil salinization depend on some factors varying in time and space. The aim of this research was to introduce an approach for the prediction of soil salinity in some irrigated pistachio (Pistacia vera L.) orchards facing secondary soil salinization. The study area was Ardakan (Yazd Province, Central Iran). In this approach, the Landsat 8 satellite data bands and satellite–based driven data (indices) were used. The Partial Least Square Regression (PLSR) method was used to predict the variability of soil salinity with minimum (zero) ground measurements. The predicted soil salinity (electrical conductivity) of soil saturated paste extract (ECe) were compared by the measured ECe. The existing conventional methods (e.g. WatSuit computation model) using ancillary measured data of irrigation water salinity (ECiw) and corresponding leaching fractions (LF) were also used for evaluation. The Results of the satellite-based PLSR method showed an R2 of about 64% between predicted and measured soil salinity, while this indicator was about 72% for the conventional model of WatSuit. The higher accuracy of the Watsuit model is owing to its dependence on ground measurements, while the introduced satellite-based PLSR approach was able to predict temporal changes of soil salinity in patterns fitted to the irrigation intervals with zero dependence on the ground truth data.

Extreme floods are able to execute river geomorphological variations with a wide and substantial geological changes. Former studies of extreme floods have reported a reach of geomorphic replies from negligible change to catastrophic channel change. This article provides an evaluation of the geomorphic effects of a scarce, great value event that occurred in the Ilam Dam upstearim, on 29 October 2015. Variations in geomorphic replies among reaches are examined in the context of changes in flood power, channel competence and lateral confinement index by the use of field survey and Satellite Images (IRS). In this research which is focused on the plan of spatial units, channel width variations and calculation of peak discharges were used to estimate cross-sectional stream power and unit stream power. The analysis was performed for the widening (width ratio) at reach scale. The total data set includes 38 reaches. Because of the 2015 flood, the largest value of widening was 29 m (Reach 13) and it demonstrated a 100% change in the channel width. Flood power peak was calculated 10631 W m−2 along the rather confined reaches (Reach 31) and was much lower along the unconfined reaches. The tendency of high stream power values, and resultant high erosion rates, within the confined and partly confined reaches is a subordinate of the higher energy slope of the steeper.

Textural components of soil play an essential role in erodibility and should be considered in many projects of conservation and environmental modeling processes. Traditional methods of determining soil texture are usually laborious, expensive and time consuming along with destructive effects on the environment. Meanwhile, spectroscopic technology using the spectral features and signatures from the whole reflected spectra of soil surface promises a competent method to study soil constituents. To investigate this issue, 113 points were selected and sampled randomly from 0-15 cm of soil surface in eastern parts of Mazandaran Province, Iran. Samples were haphazardly divided into 91 for model building and 22 for final verification and accuracy assessment processes. Applying the enhanced PLS-algorithm plus the FLOOCV approach along with spectral transformations and pre-processing, the modeling of each textural components were accomplished. Spectrally, sand and clay fractions were modeled with high accuracy as: R2c= 0.89, RMSEc= 7.42, SEc= 7.46 for sand and R2c= 0.82, RMSEc= 6.88, SEc= 6.92 for the clay content. Whereas, the silt predictive model was slightly weaker than the other constituents. The most effective spectral ranges involved in the modeling process, were also detected and recognized based on beta & spectral weight analyses and Marten’s uncertainty test. Additionally, the most influential spectroscopic ranges included were the visible, NIR and SWIR regions with the specified wavelengths. In general, the efficacy of spectroscopic technology in soil texture studies has been proven by this research. Using the computed spectral models, we are able to study the soil textural components at large scales faster, safer, timelier and also cheaper. That is absolutely true and applicable using the regionalized remotely sensed data but requires further investigation in different geographical regions.

One of the main ecosystem services of mangroves is enhancing carbon sequestration, most of which is done by sediments. Therefore, recognizing sediment properties is useful to evaluate the factors affecting carbon uptake in mangrove sediments. To identify the relationship between sediment organic carbon (SOC) content and sediment properties, sampling from three mangrove forests in Bushehr (Iran) coastal regions (Asalouyeh, Basatin, and Malegonzeh) was performed at 6 different stations, and the SOC of the samples were measured by Walkley and Black method. The particle diameters were performed by the sieving and hydrometer method and the results were analyzed (Gradistat. v8). The results showed that the highest percent of particles were silt, ranging from 93.6 to 96.6%. Several sediment grain size properties were correlated with SOC. Two factors were analyzed in principal component analyses, which were responsible for 75.8% of the samples attrinbutes. Factor 1 was organic carbon (SOC), skewness, sand, mean size, sediment density, clay, and silt summation (clay & silt). Factor 2 included clay, sorting, and kurtosis. Organic carbon was positively correlated to sorting, clay & silt percent, and grain size (ɸ). Meanwhile, the SOC was negatively correlated to sediment density, C, sand percent, and skewness. Generally, by decreasing the size of the sediment particles, the amount of SOC increased. Areas with fine-grained sediments appear to be able to absorb more organic carbon.

One of the main causes of soil pollution is the release of crude oil into the environment. Indigenous microorganisms with the capability of biodegrading hydrocarbon components can be used to improve the efficiency of microbial bioremediation technology. Here, oil-contaminated soils were collected from five oil refineries (Abadan, Isfahan, Tehran, Tabriz and Shiraz) for screening and isolation of geographically adaptive indigenous oil-degrading bacteria. Bacterial colonies from oil-contaminated soil samples were isolated, which were able to grow in a medium containing crude oil, light, and heavy diesel, as a sole carbon source. Twelve strains were isolated, purified, and identified, using the 16S rRNA gene sequencing analysis. The isolates belonged to five species, including Achromobacter spanius, Klebsiella quasipneumoniae, Ochrobactrum intermedium, Citrobacter amalonaticus, Pseudomonas aeruginosa. These bacterial strains were capable of growing in media containing crude oil, light and heavy diesel for 7 to 9 days and had the potential for biosurfactant production. These bacterial strains can be considered as geographically adaptive bacteria, creating preliminary data for further research to utilize their bioremediation potential.

In this study, total petroleum hydrocarbons (TPHs) decontaminating mechanisms for soils around the Rey refinery complex (South of Tehran, Iran) was investigated. Natural attenuation, biostimulation and bioaugmentation (separately and in combination) methods were evaluated TPHs and soil microbial respiration in 210 days, using laboratory treatments The modified methods were applied through 13 different treatments, including improving the environmental conditions for native bacteria (natural attenuation for treatments 1-8), adding non-native bacterial complex (bioaugmentation for treatment 9) and intensifying and stimulating growth while adding non-native bacterial complex (biostimulation-bioaugmentation for treatments 10-13). Although, overall of the treatments, a significant decreasing TPHs concentration were observed over the time, biostimulation-bioaugmentation treatments had the highest amount of TPHs decomposition, the highest rate of bio-respiration, the lowest half-life times (t1/2), and the highest remediation efficiency and biodegradation constants rate. Among natural attenuation treatments, modifiers with manure and sawdust had the greatest effect on reducing the TPHs concentration and the highest rate of bio-respiration. The first-order kinetic model was fitted to the data related to biodegradation in a satisfactory manner. The results showed that there was a strong and positive linear correlation between decreasing TPHs concentration and microbial respiration in all modifiers. Although for the bacterial treatments and at the early stages of inoculation, the rate of total respiration was low, but as the time passed and with adaptation of the effective inoculated bacteria to contaminated soil, the respiration rate gradually was increased. Due to its low cost and low environmental risk, the proposed bioremediation technique for oil contaminated soil can be recommended to the region.