Lead bioimmobilization in contaminated mine soil by Aspergillus niger SANRU.

Lead (Pb) contamination in soils is becoming one of the most serious environmental issues in recent years. For this reason, amendment induced immobilization of Pb in contaminated soils has been considered as an eco-friendly and cost-effective technique to minimize soil Pb availability. This study aims at evaluating efficacy of the newly discovered Aspergillus niger strain, SANRU in bioimmobilization of Pb in contaminated mine soil. To conduct bioimmobilization, phosphate rock (PR) at various P/Pb ratios of 0 (T1), 2 (T2), 4 (T3), or 6 (T4) molars was inoculated with the A. niger strain SANRU and subsequently introduced into the soil. The soil sample inoculated with A. niger SANRU and P/Pb molarity ratio of 0 (T1) in this study showed the highest Pb bioimmobilization efficiency, as well as a significant reduction up to 65 % in the unimmobilized Pb concentration and an increase in residual Pb fraction. Our in-depth Fourier transform infrared spectra (FTIR) and X-ray diffraction (XRD) studies revealed that the successful Pb bioimmobilization in this sample was attributed to Pb oxalate formation in the soil. In T2 treated soil with A. niger and P/Pb molarity ratio of 2, the Pb oxalate was precipitated solely as Pb minerals in spite of the presence of available phosphate. In the samples with A. niger and higher amounts of PR (T3 and T4) the Pb bioimmobilization efficiency was significantly lower than T1 but hydroxypyromorphite was formed in these samples. Our data thus propose that A. niger SANRU alone suffice to bioimmobilize Pb in contaminated soil.

An approach for land suitability evaluation using geostatistics, remote sensing, and geographic information system in arid and semiarid ecosystems.

This study was undertaken to incorporate geostatistics, remote sensing, and geographic information system (GIS) technologies to improve the qualitative land suitability assessment in arid and semiarid ecosystems of Arsanjan plain, southern Iran. The primary data were obtained from 85 soil samples collected from tree depths (0-30, 30-60, and 60-90 cm); the secondary information was acquired from the remotely sensed data from the linear imaging self-scanner (LISS-III) receiver of the IRS-P6 satellite. Ordinary kriging and simple kriging with varying local means (SKVLM) methods were used to identify the spatial dependency of soil important parameters. It was observed that using the data collected from the spectral values of band 1 of the LISS-III receiver as the secondary variable applying the SKVLM method resulted in the lowest mean square error for mapping the pH and electrical conductivity (ECe) in the 0-30-cm depth. On the other hand, the ordinary kriging method resulted in a reliable accuracy for the other soil properties with moderate to strong spatial dependency in the study area for interpolation in the unstamped points. The parametric land suitability evaluation method was applied on the density points (150 x 150 m(2)) instead of applying on the limited representative profiles conventionally, which were obtained by the kriging or SKVLM methods. Overlaying the information layers of the data was used with the GIS for preparing the final land suitability evaluation. Therefore, changes in land characteristics could be identified in the same soil uniform mapping units over a very short distance. In general, this new method can easily present the squares and limitation factors of the different land suitability classes with considerable accuracy in arbitrary land indices.

Effect of shifting cultivation on distribution of nutrient elements and carbohydrates within water-stable aggregates in northern Iran.

This study attempts to evaluate the nutrient element and carbohydrate distribution within Water-Stable Aggregates (WSA) of two natural ecosystems, native forest and pasturelands, under different land uses. Soil samples were collected from depths of (0-20) cm in Typic Haploxeroll soils. The overall pattern indicated that Mean Weight Diameter (MWD) and WSA were greater in the pasture and forest soils compared with the adjacent cultivated soils and aggregates of > 1.0 mm size were dominant in the uncultivated soils, whereas the cultivated soils comprised aggregates of the size < or = 0.5 mm. Distribution of organic carbon, nitrogen, phosphorus and carbohydrates within the WSA showed preferential enrichment of these parameters in the macroaggregate fraction (4.75-1.0 mm) for the uncultivated soils and microaggregate fraction (> 0.25 mm) for the cultivated soils. Average distribution of total exchangeable bases within WSA showed that cultivation of forest pastureland soils significantly led to reduce in these nutrient in the 4.75-2.0 mm fraction and increase in concentration of these cations in < 0.25 mm fraction. Since smaller aggregates are preferentially removed by erosion, this study emphasizes the need for sustainable soil management practices that they will minimize nutrient loss when forest or pastures lands are converted to cropland.

Assessment of some soil properties by spatial variability in saline and sodic soils in Arsanjan plain, Southern Iran.

Spatial patterns for several soil parameters such soil texture, Exchangeable Sodium Percentage (ESP), Electrical Conductivity (ECe), soil pH, Cation Exchange Capacity (CEC) were examined in saline and sodic soils in Arsanjan plain, Southern Iran, in order to identify their spatial distribution for implementation of a site-specific management. Soil samples were collected from 0-30, 30-60 and 60-90 cm soil depths at 85 sampling sites. Data were analyzed both statistically and geostatistically on the basis of the semivariogram. The spatial distribution model and spatial dependence level varied between soil parameters. Soil pH and ESP had the minimum and maximum variability at all depths, respectively. Soil properties indicated moderate to strong spatial dependence. ECe exhibited moderate spatial dependence at three depths; pH and ESP had a moderate spatial dependence at 0-30 cm and strong spatial dependence at 30-60 and 60-90 cm depths. Clay and CEC exhibited strong spatial dependence for the 0-30 cm and weak spatial dependence at 30-60 and 60-90 cm depths. Sand and silt had a non-spatial dependence at 0-30 cm and weak spatial dependency at 30-60 and 60-90 cm depths. The spatial variability in small distances of ECe, CEC, pH and ESP generally increased with depth. All geostatistical range values were greater than 1168 m. The results reported herein indicated that the strong spatial dependency of soil properties would lead to the extrinsic factors such as ground water level and drainage. It is important to know the spatial dependence of soil parameters, as management parameters with strong spatial dependence will be more readily managed and an accurate site-specific scheme for precision farming more easily developed.