Soil Remediation – Mercury Speciation in Soil and Vapor Phase During Thermal Treatment

Spectroscopic (XRD, XPS, ICP-MS and AAS) and microscopic (ESEM) techniques have been used in order to study the chemical effects with emphasis on mercury speciation, during thermal treatment of a mercury contaminated soil. In the untreated soil, mercury was found concentrated in spherical particles, which were successively broken down upon thermal treatment. Hg⁰ and inorganic mercury compounds (presumably HgO(s) and HgSO₄(s)) could be detected. No (CH₃)₂Hg and only traces of CH₃Hg⁺ could be found. The dependence on temperature and heating time indicated that the evaporation of mercury from the soil was partly controlled by diffusion mechanisms. Mercury volatilized in two separate stages during heating; initial elemental vaporization, and subsequent volatilization of the oxide or sulfate phase at higher temperatures (>230°C). By thermal treatment at 470°C and 20 min, a removal of >99% of the mercury could be achieved.     

Soil Micronutrients and Citrus Growth

By using nutritional diagnosis of citrus leaves and determining soil micronutrients,the relationship between soil micronutrients and citrus growth in southern China has been studied.Studies showed that there was a significant positive correlation between available micronutrients (such as Zn,Mo,Cu)in the soil and the corresponding nutrients in citrus leaves.Thus,one can roughly learn of the sufficiency or deficiency of certain nutrients in soils by analyzing citrus leaves.Rational spray of Zn B or Mo fertilizer not only improved citrus yields but also increased the total sugar of Satsuma mandarin and of Xinhui orange by 2.9 and 17.2% respectively compared with the control.Spraying Mo fertilizer increased the vitamin C content of Satsuma mandarin juice by 4.7%-8.4%,maturated fruits 7-10 days earlier and gave the peel a brighter color.The ultramicroscopic characteristics of Zn-deficient citrus leaves were investigated under an electron microscope.Results showed that the Zn-deficient leaf cell was characterized mainly by poor cytoplasm,endoplasmic reticula and ribosomes and by big starch grains in the chloroplast.As a result of spraying Zn fertilizer the structure of the cell returned to normal,the cytoplasm became rich and the amount of chloroplast increased.There also appeared a great deal of multiform endoplasmic reticula,thus promoting the photosynthesis of Zn-deficient plants.This provides a cytologico-theoretical basis for fertilization of high-yielding citrus trees.     

Soil Microbiomes—a Promising Strategy for Contaminated Soil Remediation: A Review

Bioremediation is a process mediated by microorganisms and represents a sustainable and eco-friendly way to degrade and detoxify environmental contaminants. Soil microbiomes clearly become a key component of bioremediation as they are more stable and efficient than pure cultures, being recognized as one of the scientific frontiers of the soil environmental science and technology fields. Recently, many advancements have been made regarding the investigation of remediation mechanisms by soil microbiomes and the interactions inside them. This has greatly expanded our ability to characterize the remediating function of soil microbiomes and identify the factors that influence their efficiency for remediation. Here, we suggest that soil microbiomes are a promising strategy for soil remediation. Research is now needed to identify how we can manipulate and manage soil microbiomes to improve remediation efficiency and increase soil fertility at the same time. Therefore, this review aims to emphasize the importance of soil microbiomes in bioremediation and promote further development of this strategy into a widely accepted technique.     

Soil Cover with Organic Mulch and Its Influences on Soil Physical Parameters (Ⅲ)——Soil Temperature Regime under Organic Mulch

以田间实验为基础，分析了在不同厚度的有机物覆盖层下土壤温度变化的机制并与未覆盖条件下的土壤温度进行了比较。实验结果表明，有机物覆盖使土壤的日最高温度和日平均温度降低，但却使土壤的日最低温度得以提高。     

The Relationship Between pH Value and Magnetic Susceptibility of Soil——A Case Study of Mountain Red Soil and Red Limestone Soil

通过对昆明西山山原红壤和红色石灰土的pH值和磁化率测试研究发现,山原红壤的pH值在4.0～5.8之间,呈酸性,质量磁化率在56 × 10-8～ 174× 10-8 m3/kg之间,pH值与磁化率呈明显的正相关关系;而红色石灰土pH值在6.0～8.4之间,磁化率为752× 10-8 ～5056×10-8m3/kg,pH值和磁化率呈负相关关系.该研究表明,在我国西南地区,土壤pH值和磁化率既存在明显的负相关关系也存在正相关关系.结合前人在其他地区的研究资料,进一步发现,土壤的酸碱环境可能是决定这些关系的重要因素.     

Location of Bare Soil Surface and Soil Line on the RED–NIR Spectral Plane

Soil as a separate natural body occupies certain area with its own set of spectral characteristics within the RED–NIR spectral space. This is an ellipse-shaped area, and its semi-major axis is the soil line for a satellite image. The spectral area for a bare soil surface is neighboring to the areas of black carbon, straw, vegetating plants, and missing RED–NIR values. A reliable separation of the bare soil surface within the spectral space is possible with the technology of spectral neighborhood of soil line. The accuracy of this method is 90%. The determination of the bare soil surface using vegetation indices, both relative (NDVI), and perpendicular (PVI), is incorrect; the accuracy of these methods does not exceed 65%, and for most of the survey seasons it may be lower than 50%. The flat part of the “tasseled cap” described as the soil line, is not a synonym for the area of the bare soil surface. The bare soil surface on the RED–NIR plots occupies significantly smaller areas than the area of soil line according to Kauth and Thomas.     

Humble View on Soil Water Resources

Soil water is one of renewable water resources.Some properties of soil water concerning with its availability to plant are briefly described.An equation for estimating the amount of soil water resource is presented.Based on the evaporation demand of atmosphere,the evaluation coefficient for soil water resource is suggested.     

Soil Delineations on Public Cadaster Maps as Elements of the Soil–Land Cover Mapping

Eurasian Soil Science - The depiction of soil delineations on a public cadastral map clearly demonstrates the potentialities of large-scale soil mapping. The development of land legislation...     

Crop and Soil Responses to Fertilization with Distillers’ Grains–Derived Manure in a Saskatchewan Soil

A 2-year field trial was conducted to evaluate crop and soil responses to application of manure from cattle fed distillers’ grain (DGM) in comparison with manure from cattle fed regular barley grain (BGM). Manure addition in general promoted grain and straw yield and increased plant nitrogen (N) and phosphorus (P) uptake in both years by approximately 30–50%. In the first year, effect of manure type on crop responses was insignificant, which is consistent with the similar chemical composition of both manures. In the second year, P recovery was greater in DGM treatments, presumably related to a relatively greater P in DGM. Manure application in general increased soil residual nitrate nitrogen (NO₃^– N) and available P contents at 0–15 cm deep. The high background fertility of studied soil together with the excess moisture during the second year may have masked the significant effects of manure type on most crop and soil responses during this study.     

How Can Organic Amendments Help to Bind Sulfadiazine in the Soil? – An Iranian Soil Study

ABSTRACT

Veterinary antibiotics can enter the environment especially agricultural soils via animal manure application in which Sulfadiazine (SDZ) is considered as one of the most used antibiotic. After soil application, it may be transported into subsurface water. The sorption behavior of SDZ is not only influenced by the soil type but also by soil organic matters as well. Hence, an experiment was executed aimed to study sorption/desorption processes of SDZ under experimental conditions in three various soils treated by different bio fertilizers including rice husk compost (RHC), rice husk biochar (RHB) and Micrococcus yunnanensis (My) bacterium. Sorption/desorption data of soils with and without bio-fertilizers were well fitted with Freundlich model (R² = 0.97). Results showed that bio-amended soils had higher values of k_d sorption ranged from 1.16 to 52.4 without and with bio-fertilizers application respectively, proposing low sorption of SDZ with substantial risk of leaching without bio-fertilizers application. Also for the desorption cycle values of K_d increased from 1.03 to 39.1 without and with bio-fertilizers application, respectively. Furthermore, there was a hysteresis effect using organic matter. As a result of bio-fertilizers application, a significant value of SDZ was strongly adsorbed on the soil particles which was not desorb through desorption process.     

Soil Water Balance Measurement in Field Scale

A 5-year experiment on water balance has been conducted in a flat rainfed wheat field with an area of 66×100m² in Fengqiu, Henan Province in China. Based on the analysis of semi-variance functions conducted with soil moisture samples taken from 77 nodes of a 10×10m² grid, the soil moisture distribution in the field was structural with a temporal stability. According to the autocorrelation range of the semi-variance function, S sites were selected for the determination of soil water conditions. The characteristic of probability density function of the differences of water storage in two sets of measurements showed that the distribution of these variables in the field was a normal one. The error in the estimation of the average of S random samples was 14% (α=0.10), and the errors of water consumption by wheat during the experiments were estimated to be 6-13%.Since the experimental field was large enough to avoid any edge effect, the results obtained should tally with the actual situation.     

Soil mineralization: An emergent process?

This paper argues that soil mineralization should be seen as an emergent process. While it is effecting mineralization the soil population shows many of the characteristics of recognised emergent systems such as ant colonies and slime moulds. In particular, the whole is more than the sum of the parts, and the system shows clear evidence of bottom-up organization. Furthermore, the ‘quorum sensing’ recently discovered in soil and other bacteria strongly suggests that chemical signalling plays a part among the soil population, as it does in other biological emergent systems. Emergent behaviour has consequences for measuring and modelling mineralization. The idea that the whole is more than the sum of the parts suggests that measurements must be made at a scale that includes all the parts, while the bottom-up organization implies that there is no controlling parameter on which a model can be centred. Other emergent systems have been simulated using simple sets of rules for organisms that correspond to the local information they use in practice, and this approach could be tried with mineralization. Candidate rules are suggested.     

Distribution and Accumulation of Copper and Cadmium in Soil–Rice System as Affected by Soil Amendments

The effects of seven amendments on the distribution and accumulation of copper and cadmium in a soil–rice system were investigated using a pot experiment. Results showed that application of limestone, calcium magnesium phosphate (Ca–Mg–P fertilizer), calcium silicate (silicon fertilizer), Chinese milk vetch, pig manure, and peat significantly decreased the concentrations of Cu and Cd in rice roots by 24.8–75.3% and 9.7–49.9%, respectively. However, no significant difference was observed between zinc sulfate (zinc fertilizer) and the control treatment. The concentrations of Cu and Cd in different parts of rice followed the order: root > straw > grain, and all amendments restrained the transfer of Cu and Cd from rice root to stem. Copper and Cd concentrations in rice stems at the tillering stage were the highest, and then decreased from the tillering stage to the heading stage. However, they increased again at the ripening stage. The results also showed that application of amendments changed Cu and Cd solubility in soil and decreased their bioavailability, which resulted in the reduction of Cu and Cd uptake by rice. Significant correlations between the concentrations of Cu and Cd in soil solutions and in rice stems were found. The result demonstrated that limestone has the best efficiency among all the amendments used in reducing Cu and Cd contamination to rice production.     

Stretching Soil Sampling to Watershed: Evaluation of Soil‐Test Parameters in a Semi‐arid Tropical Watershed

Soil sampling is an integral component of fertility evaluation and nutrient recommendation for efficient use of nutrients in crop production. Little attention has been devoted to evaluating methodology for sampling watersheds under dryland agriculture. A stratified random sampling methodology for sampling the Appayapally watershed in Mahabubnagar district of Andhra Pradesh state in the semi‐arid tropical region of India was adopted and evaluated. The watershed has an area of about 500 ha, with gentle sloping lands (<1% slope), and 217 farmers own land in the watershed. The soils are Alfisols. A total of 114 soil samples were collected from the top 15‐cm layer to represent the entire watershed. Each sample was a composite of 7–8 cores, randomly collected from the area represented by a crop and group of farmers. The soil samples were air dried, ground, and analyzed for pH, electrical conductivity (EC), organic carbon (C), total nitrogen (N), and extractable phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), sulfur (S), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), and boron (B). Statistical analysis of the results on soil fertility parameters showed that the mean‐ or median‐based results of soil tests performed in the study did not differ significantly when the sample set size varied from 5 to 114 (100% of the population). Our results indicate that farmers' fields in the Appayapally watershed are uniform in the chemical fertility parameters studied, and even a small sample set size can represent the whole population. However, such a sampling strategy may be applicable only to watersheds that are very gently sloping and where fertilizer use is very low, resulting in an overall low fertility in the whole watershed.     

Release of Soil Nonexchangeable K by Organic Acids

The amounts of soil nonexchangeable K extracted with 0.01mL/L oxalic acid and citric acid solutions and that with boiling 1mL/L HNO3 for ten minutes were remarkably significantly correlated with each other,and the amount extracted with the oxalic acid solution was higher than that with the citric acid solution.The soil nonexchangeable K release was comprised of two first-order kinetic processes.The faster one was ascribed to the interlayer K in outer sphere,while the slower one to that in inner sphere.The rate constants of the soil nonexchageable K were significantly correlated with the amounts of nonexchangeable K ex tracted with boiling 1mL/L HNO3 for ten minutes.Study on the fitness of different kinetic equations indicated that the first-order,parabolic diffusion and zero-order equations could all describe the release of soil nonexchangeable K well,but Elovich equation was not suitable to describe it.     

Leaching and Transformation of Nitrogen Fertilizers in Soil After Application of N with Irrigation： A Soil Column Method

A soil column method was used to compare the effect of drip fertigation （the application of fertilizer through drip irrigation systems, DFI） on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation （SFI）, and to study the leaching loss and transformation of three kinds of nitrogen fertilizers （nitrate fertilizer, ammonium fertilizer, and urea fertilizer） in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N （NH4^＋-N ＋ NO3^--N） in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control （without urea addition）, on the first day when soils were fertigated with urea, there were increases in NH4^＋-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH4^＋-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH4^＋-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH4^＋-N fixation or volatilization in the soil during the fertigation process.     

Titratable Acidity and Alkalinity of Red Soil Surfaces

The surfaces of red soils have an apparent amphotenc character, carrying titratable acidity and titratable alkalinity simultaneously. The titratable acidity arises from deprotonation of hydroxyl groups of hydrous oxide-type surfaces and dissociation of weak-acid functional groups of soil organic matter, while the titratable alkalinity is derived from release of hydroxyl groups of hydrous oxide-type surfaces. The titratable acidity and titratable alkalinity mainly depended on the composition and content of iron and aluminum oxides in the soils. The results showed that the titratable acidity and titratable alkalinity were in significantly positive correlation not only with the content of amorphous aluminum oxide(Alo) and iron oxide(Feo) extracted with acid ammonium oxalate solution, free iron ox-ide(Fed) extracted with sodium dithionite-citrate-bicarbonate (DCB) and clays, but also with the zero point of charge (ZPC) of the samples. Organic matter made an important contribution to the titratable acidity.     

Soil： An Extreme Habitat for Microorganisms？

The question is asked whether soils can be regarded as extreme environments with respect to microorganisms. Afterdefining some extreme environments in a general sense, special properties of extreme environments are compared to soilhabitats, with special emphasis laid on time frame and localities. In relation to water availability, nutrients and otherproperties, such places as aggregates can show properties of extreme habitats. These features, which can act at differentlevels of the system from the community level down to the cellular level, are summarized as stress factors. The latter,where many switches are located leading to different strategies of survival, is described as the most important one. Thisraises the question of how organisms have adapted to such conditions. The soil system demands a broad spectrum ofadaptations and/or adjustments for a highly variable environment. The soil microorganisms‘ adaptation can thus be seenas the highest kind of flexibility and is more useful than any other special adaptation.     

Effect of Incorporation of Wheat Straw and Urea into Soil on Biomass Nitrogen and Nitrogen-Supplying Characteristics of Paddy Soil

Pot experiments were carried out to study the effect of incorporation of wheat straw and/ or urea into soil on biomass nitrogen and mineral nitrogen and its relation to the growth and yield of rice.The combined appliation of wheat straw and urea increased much more biomass nitrogen in soil than the application of wheat straw or urea alone and consequently increased the immobilization of urea nitrogen added and reduced the loss of urea nitrogen.An adequate nitrogen-supplying process to rice plant could be obtained if C/ N ratio of the material added was about 20.The three yield components of rice were affected significantly by the status of nitrogen supplying.More than 30mg N/ kg soil of mineral nitrogen at effective tillering stage,panicle initiation stage and filling stage should be maintained in order to get high rice yield,though the criteria varied with the different experimental conditions.