Exploring soil layers and water tables with ground-penetrating radar

Ground-penetrating radar (GPR) has been used predominantly for environments with low electrical conductivity like freshwater aquifers, glaciers, or dry sandy soils. The objective of the present study was to explore its application for mapping in subsurface agricultural soils to a depth of several meters. For a loamy sand and a clayey site on the North China Plain, clay inclusions in the sand were detected; the thickness, inclination, and continuity of the confining clay and silt layers was assessed; and a local water table was mapped. Direct sampling (soil coring and profiling) in the top meter and independent measurement of the water table were utilized to confirm the findings. Also, effective estimates of the dielectric number for the site with the dielectric number of moist clayey soils depending strongly on frequency were obtained. Thus, important properties of soils, like the arrangement and type of layers and in particular their continuity and inclination, could be explored with moderate efforts for rather large areas to help find optimal locations for the time-consuming and expensive measurements which would be necessary to detail a model of the subsurface.     

Ecotoxicological assessment of nickel pollution of soil and water environments adjacent to soddy–podzolic soil

The indicators of functioning of soil microorganisms in soddy–podzolic soil contaminated with Ni compounds show different ranges of soil ecotoxicity. A halving of soil microorganisms' nitrogen-fixing activity has been shown in slightly acidic soddy–podzolic cultivated soil with a Ni concentration of 150 mg/kg and for noncultivated acidic soils with a Ni concentration 100 mg/kg. The reduction of denitrification activity in cultivated soil has been observed with a Ni concentration of 500 mg/kg, and in uncultivated soil it has been observed at a Ni dose of 100 mg/kg. The inhibition of soil respiration in slightly acidic soil occurred only at the highest dose of Ni, 1000 mg/kg, while in the acidic soil it took place at 300 mg/kg. Biotesting based on bacterial luminescence can be used for determination of soil pollution with heavy metals such as Ni, as well as for the assessment of the toxicity of aqueous environments in contact with contaminated soils.     

Inversion of soil properties in rare earth mining areas (southern Jiangxi,China) based on visible–near-infrared spectroscopy

Journal of Soils and Sediments - Traditional measurement for soil properties is time-consuming and costly, while visible–near-infrared spectroscopy enables the rapid prediction of soil...     

Improved soil–plant water dynamics and economic water use efficiency in a maize field under locally water stress

Soil–plant water dynamics is a major driving factor on crop yield which could be improved under optimal irrigation strategy. The soil water dynamics under partial root-zone drying (PRD) and its consequent effects on maize economics returns were investigated in a two-year field study in the research field of Sari Agricultural Sciences and Natural Resources University. Irrigation treatments included full irrigation (FI) and two PRD treatments including PRD₁ and PRD₂, receiving 100%, 75% and 55% of crop water demand at each irrigation event, respectively. TDRs were used for measuring soil water contents on a daily basis. Economic analysis was done based on net present value (NPV), benefit-to-cost ratio (B/C) and internal rate of return (INRR) indices. Applying PRD₁ treatment increased soil wetting front advance by 110–330% compared those for other treatments which caused 50% increase in root water uptake. Improved soil water dynamics under PRD1 prevented a significant reduction in maize grain yield, leading to 37.7%, 6.14% and 192% increase in NPV, B/C and INRR, respectively, under PRD₁ than those for FI treatment. Thus, PRD₁ was the most economic water-saving irrigation strategy under which 25% of irrigation water would be saved due to a better utilization of soil water supply.     

Variability of soil water content controlled by evapotranspiration and groundwater–root zone interaction

The central moments of soil water content (SWC) variability at the field scale are determined by soil texture, considering both smooth topography and groundwater table position. The characteristics of variability are governed by other soil factors like soil structure, micro relief, preferred water flow paths, root system characteristics, rock content, etc. This paper shows the integral effect of all these hardly quantifiable factors on SWC variability simulated by the processes of evapotranspiration and groundwater–root zone interaction using the HYDRUS ET model. SWC and soil hydraulic characteristics were spatially determined over a 4.5 ha field during two sampling campaigns under different atmospheric and groundwater conditions, and data distributions were compared to SWC distributions provided by mathematical modeling. The entire spring–summer period of 2003 was then examined for changes of SWC spatial variability. It was found that evapotranspiration influences SWC spatial variability only if SWC is under the critical value when wetter parts of the field evaporate more water than drier parts, resulting in smoothed SWC variability. Under wet conditions the spatial variability of SWC increases by drainage, as those parts of the soil with coarser texture drain faster than finer-textured parts.     

Transformation of soil and plant cover contaminated with oil and salt water in the middle Ob’ river basin

Changes in the soil and plant cover caused by contamination with oil and salt water in the middle Ob’ river region were estimated using geoinformatic and geostatistic approaches. The largest technogenically salinized areas include oligotrophic peat soils due to the extensive spill of highly saline waters on the flat bog surface and eutrophic soils located in lower topographic positions. The natural self-purification of salinized mineral forest soils proceeds within 1–2 years after the spill. The dominant species of secondary plant communities were detected. Correlations were revealed between the residual oil and chloride contents and the total projective plant cover.     

Effects of freeze–thaw cycles and the soil water content on carbon and nitrogen changes in different soil types of Heilongjiang Province,China

To reveal the influence of freeze–thaw cycles (FTCs) on soil carbon and nitrogen changes, six typical soils in Northeast China were selected as the research objects to conduct a FTC simulation test in an artificial climate chamber. Three soil volumetric water contents (10%, 20%, 30%) and eight FTCs (0, 2, 4, 6, 8, 10, 15, 20) were set. The results showed that the soil organic carbon (SOC) and microbial biomass carbon (MBC) contents of different soil types under the FTCs initially exhibited a downward and then an upward trend, while the dissolved organic carbon (DOC) content exhibited an upward and then a downward trend. Otherwise, the fourth and sixth FTCs were the key points of change. The SOC, MBC and DOC contents in paddy fields were higher than those in dry fields, showing upward and then downward trends spatially from northeast to southwest. The SOC and MBC contents in each soil type were the highest at the 20% water content, and the DOC content gradually increased with increasing water content. The ammonium nitrogen (NH₄⁺-N) content in different soil types at different water contents under the FTCs showed an upward trend first, then a downward trend and finally an upward trend. The NH₄⁺-N content in paddy fields was higher than that in dry fields. The nitrate nitrogen (NO₃^‒-N) content showed a downward trend first, then an upward trend and finally a downward trend. The NO₃^‒-N content in dry fields was higher than that in paddy fields. The NH₄⁺-N contents in the three soil types on the Sanjiang Plain were significantly higher than those on the Songnen Plain. The NH₄⁺-N and NO₃^‒-N contents showed upward trends with increasing water content, but the differences were not significant. The results have implications for the study of different types of soils and provide references for research on the mechanism of soil carbon and nitrogen transformation in typical farming areas in Northeast China.     

Microbial reduction of dinitrotoluene sulfonates in TNT red water–contaminated soil

Journal of Soils and Sediments - Large quantities of TNT red water which contained mainly dinitrotoluene sulfonates (DNTS) were produced during the production of TNT, threatening the surrounding...     

Amelioration of saline–sodic soil with gypsum can increase yield and nitrogen use efficiency in rice–wheat cropping system

A 2-year field experiment was conducted to determine crop yield and N use efficiency (NUE) from a saline–sodic soil (clay loam) with and without application of gypsum. Treatments included two N application rates (15% and 30%) higher than the recommended one to the normal soil, and gypsum added at 50% and 100% of soil gypsum requirement (SGR) to the saline–sodic soil, both cultivated with rice and wheat during 2011–2013. Results revealed a decrease in pH of saturated soil paste (pH_s), electrical conductivity of saturation extract (EC_e), sodium adsorption ratio (SAR) and exchangeable sodium percentage with N fertilizer along with gypsum application in saline–sodic soil. However, the effect was most prominent when gypsum was added at 50% of SGR. Crop yield and NUE remained significantly lower (p < 0.05) in saline–sodic-soils as compared to normal soil. However, gypsum application reduced this difference from 47% to 17% since both yield and NUE increased considerably. Crop yield and NUE remained higher for wheat than for rice. During first year, higher doses of N with gypsum application at 50% SGR proved most effective, whereas, in subsequent year, recommended N along with gypsum at 50% SGR became more profitable. All these results lead us to conclude that gypsum application can ameliorate saline–sodic soil thereby increasing crop yield and NUE.     

Radioecological description of the soil–plant cover and water objects within the impact zone of the Novovoronezh Nuclear Power Plant

The work considers the accumulation and redistribution of ¹³⁷Cs and ⁶⁰Co among the components of natural ecosystems (soils, bottom sediments, surface waters, and plants of different ecological groups (mesophytes, hygrophytes, hydrophytes, and hydathophytes)) within the impact zone of the Novovoronezh Nuclear Power Plant. It is shown that the current radioecological situation on this territory is satisfactory. Each of the studied parameters complies with the radiation safety standards.     

Effects of afforestation with four unmixed plant species on the soil–water interactions in a semiarid Mediterranean region (Sicily, Italy)

Purpose

An assessment of the effect of plant cover on the properties of four afforested soils in central Sicily was performed with the aim of discriminating among them after 60?years of afforestation.

Materials and methods

Chemical and biochemical soil analyses were coupled to fast field cycling (FFC) NMR relaxation investigations in order to monitor surface interactions of water in water-saturated soils.

Results and discussion

The traditional soil analyses revealed that the most stable soil properties such as soil texture and pH are not affected by 60?years of afforestation. Soils developed under eucalyptus trees showed larger amounts of hydrophilic organic matter as compared to the soils under pines and cypresses. FFC-NMR relaxometry data revealed that water, partitioned in clay-, loam-, and sand-type pores, showed longitudinal relaxation time values affected by the interactions with the soluble carbon content.

Conclusions

The results of the present study evidenced the potential of FFC-NMR relaxometry in differentiating the effect of diverse plant cover on chemical and hydrological properties of soils developed on the same parent material. In fact, in contrast with the traditional physicochemical and biochemical soil characterizations, which were unable to reveal differences among soils afforested with different plant species, FFC-NMR was capable of monitoring differences in water dynamics as affected by the presence of the most soluble soil organic material.     

Does the influence of earthworms on water infiltration, nitrogen leaching and soil respiration depend on the initial soil bulk density? A mesocosm experiment with the endogeic species Metaphire posthuma

Soil compaction has a negative impact on both earthworm abundance and diversity. Recent studies, however, suggest that earthworm cast properties are not influenced by the initial soil bulk density. With time, earthworms could therefore transform soils with different bulk densities into a soil with the same physical state and thus with a similar ecological functioning. This study aimed to test this hypothesis in two laboratory incubation experiments. First, we measured the influence of soil bulk density (1.1 or 1.4?g?cm^?3) on the production of cast by the endogeic earthworm species Metaphire posthuma. In a second experiment, we investigated the effect of M. posthuma on water infiltration, NH ₄ ⁺ , and NO ₃ ^? leaching and soil respiration at the same two soil bulk densities. Although initially higher, earthworm casting activity in soil at 1.4?g?cm^?3 decreased until it reached the same level of activity as earthworms in soil at 1.1?g?cm^?3. This behavioral plasticity led to a transformation of compacted and loose soils, with their own functioning, to a third and similar state with similar hydraulic conductivity, nitrogen leaching, and soil respiration. The consequences for soil organization and soil functioning are discussed.     

The use of comprehensive two-dimensional gas chromatography and structure–activity modeling for screening and preliminary risk assessment of organic contaminants in soil, sediment, and surface water

Purpose

This article aims to investigate the use and benefits of using comprehensive two-dimensional gas chromatography (GC?×?GC) and structure?Cactivity relationship modeling for screening and prioritization of organic contaminants in complex matrices. The benefit of applying comprehensive screening techniques to samples with high organic contaminant content is primarily that compounds with diverse physicochemical properties can be analyzed simultaneously. Here, a heavily contaminated industrial area was surveyed for organic pollutants by analyzing soil, sediment, and surface water samples. The hazard of the pollutants were ranked using SARs.

Material and methods

The water samples were liquid?Cliquid extracted using dichloromethane and directly analyzed by GC?× GC?Ctime-of-flight mass spectrometry (GC?×?GC?CTofMS). Soil and sediment samples were extracted with dichloromethane in an ultrasonic bath and subjected to gel permeation chromatography to eliminate lipids and humic matter. The low molecular weight fraction was then analyzed with GC?×?GC?CTofMS.

Results and discussion

More than 10,000 components were found in each sample, of which ca. 300 individual compounds were unambiguously identified using the National Institute of Standards and Technology mass spectra library and authentic reference standards. Alkanes, polycyclic aromatic hydrocarbons, and phthalates were generally the most abundant and were found in all matrices. In contrast, chlorinated compounds such as chlorophenols, biphenyls, and chlorinated pesticides were only detected in samples from a few hotspot regions. The toxicities of the most frequently detected compounds and of the compounds detected at the highest concentrations in samples from hotspot regions were estimated by ecological structure?Cactivity relationships. The ratio of the measured concentration to the predicted toxicity level was then calculated for each compound and used for an initial risk assessment in order to prioritize compounds for further transport and fate modeling, complementary measurements, and more advanced risk assessments.

Conclusions

The advantage of using of GC?×?GC?CTofMS for preliminary screenings of contaminated areas was evaluated at a polluted area in northern Sweden. The area was found to carry organic pollutants such as polyaromatic hydrocarbons, aliphatic hydrocarbons, polychlorinated biphenyls, phthalic compounds, and many chlorinated pesticides. Preliminary risk assessments indicate which compounds to use for subsequent remediation experiments based on their availability on the site or toxicity.     

Effects of coalbed methane‐produced water on sorghum‐sudangrass growth and soil chemical properties

Abstract

Production of methane gas from coal seams generates well water that is slightly to moderately saline. Since land application is a potential method of disposal for this water, a greenhouse study was conducted to evaluate plant response and changes in soil chemical properties resulting from irrigation with coalbed methane‐produced water. The soil was a Montevallo (Typic Dystrochrepts)‐Nauvoo (Typic Hapludults) association located in northern Alabama. Two irrigation methods used in the initial greenhouse test were 1) continuous, irrigation 24 h d^‐1 and 2) intermittent, irrigation for 12 h and off for 24 h. In a second greenhouse test, three irrigation methods were used: 1) continuous, irrigation for 24 h d^‐1, 2) intermittent, irrigation for 12 h and off for 48 h, and 3) irrigation to maintain field capacity, by daily additions of the respective irrigation water. The flow rate for continuous and intermittent irrigation treatments was 3.75 mm h^‐1. In each greenhouse test, 5 levels of salinity were generated by mixing well‐produced water with deionized water to give solutions containing 0, 10, 20, 40, and 100% well‐produced water (specific conductance (second greenhouse test) of 0.2, 1.4, 2.2, 4.4, and 9.3 dS m^‐1, respectively). Corresponding sodium adsorption ratios were 0.1, 27, 36, 55, and 81, respectively. Sorghum‐sudangrass [Sorghum bicolor (L.) Monech] was harvested for forage yields and chemical analysis at 14–30 days after initiation of irrigation treatments. Results from these preliminary short term, greenhouse studies show that coalbed methane produced water that is typical for Alabama (total dissolved solids ≤2000 mg L^‐1) can be applied to highly weathered soils. The results indicate that plant growth of summer annual grasses will be optimized if an irrigation system is used to apply produced water at a rate to maintain soil moisture at or near field capacity.     

Coupled effects of biochar use and farming practice on physical properties of a salt-affected soil with wheat–maize rotation

Purpose

Being carbon-rich and porous, biochar has the potential to improve soil physical properties, so does conventional farming practice. Here, a field trial was conducted to investigate the combined effects of biochar use and farming practice on the physical properties of a salt-affected compact soil for wheat–maize rotation in the Yellow River Delta region.

Materials and methods

Salix fragilis L. was used as feedstock to produce biochar in the field via aerobic carbonization at an average temperature of 502 °C, terminated by a water mist spray, for use as a soil amendment at 0, 1, 2, and 4 g kg^?1 doses (CK, T1, T2, and T3, respectively). Farming practices included rotary tillage/straw returning for wheat sowing, spring irrigation, no-tillage seeding of maize, and autumn irrigation. Both cutting ring and composite samples of the soil were collected at four stages of wheat–maize rotation (22, 238, 321, and 382 d after the benchmark date of land preparation for wheat sowing) for the determination of soil properties by established methods.

Results and discussion

Rotary tillage/straw returning reduced soil bulk density (BD) from 1.48 to 1.27 g cm^?3 (CK) and 1.14 g cm^?3 (T3) and increased saturated hydraulic conductivity (Ks) from 0.05?×?10^?5 to 0.75?× 10^?5 cm s^?1 (CK) and 1.25?× 10^?5 cm s^?1 (T3). This tillage effect on BD and Ks gradually disappeared due to the disturbance from the subsequent farming practice. Biochar use lessened the disturbance. At maize harvest, BD was 1.47 (CK) vs. 1.34 g cm^?3 (T3), and Ks was 0.06?×?10^?5 (CK) vs. 0.28?×?10^?5 cm s^?1(T3); in comparison with CK, T3 increased Na⁺ leaching by 65%, Cl^? leaching by 98%, organic carbon content by 40.3%, and water-stable aggregates (0.25–2 mm) by 38%, indicating an improvement in soil properties.

Conclusions

Biochar use and rotary tillage improved soil physical properties (BD, Ks) and favored soil aeration, water filtration, and salt leaching, which further helped the accumulation of soil organic carbon, the formation of water-stable aggregates, and the amelioration of salt-affected compact soil.