Sandy Topsoil Research Articles

Effects of root-derived organic acids on sorption of pharmaceutically active compounds in sandy topsoil

The presence and fate of pharmaceutically active compounds (PhACs) in agricultural fields are rarely investigated. The present study highlights that root-derived low-molecular-weight organic acids (LMWOAs) affect the mobility of PhACs in cultivated humic Arenosol. Sorption experiments are conducted using three PhACs characterised by different physicochemical properties: carbamazepine (CBZ), 17α-ethinylestradiol (EE2), and diclofenac-sodium (DFC). The results suggest that the adsorption of EE2 is more intense than the other two PhACs, whereas DFC and CBZ are primarily dominated by desorption. LMWOAs mainly provide additional low-energy adsorption sites for the PhACs, and slight pH changes do not significantly affect the sorption mechanism. During competitive adsorption, the high-energy sites of the adsorbents are initially occupied by EE2 owing to its high adsorption energy (∼15 kJ/mol). The new low-energy binding sites enhance the adsorption of DFC (from 8.5 % to 72.0 %) and CBZ (from 31.0 % to 70.0 %) during multicomponent adsorption. LMWOAs not only affect adsorption by modifying the pH but also provide additional binding sites that allow the PhACs to remain in the root environment for a longer period. As the concentration of LMWOAs temporarily changes, so does the availability of PhACs in the root zone. Environmental changes in the humic horizon enhance the mobility of the adsorbed PhACs, which renders them continuously available for uptake by plants, thus increasing the possibility of PhACs entering the human food chain.

Clay and organic compost as quality conditioners of a sandy soil in the brazilian semiarid

Due to natural and anthropic pressures of semiarid regions, like sandy texture, organic matter (OM) deficiency, water scarcity and inadequate management, we carried out an experiment under greenhouse conditions, to evaluate the effects of clay and OM addition on the quality of a sandy soil of the Brazilian semiarid. The experiment lasted 75 days, testing four clay contents (10 and 31% natural soils, 15% by clay addition to a sandy soil and 26% by mixing clay subsoil to a sandy topsoil) in the absence and presence of organic compost (7.5g.kg-1). For biological parameters, sorghum plants were used for biometric and mineral composition analysis, in addition to assessing microbial activity (BSR, MBC, and qCO2). The results showed significant differences in soil microporosity and total porosity; the field capacity and permanent wilting point correlated linearly with clay content and OM addition; potencial and exchangeable soil acidity decreased significantly in the presence of compost. Sorghum plants showed higher values of biometric attributes and lower levels of nutrients in the presence of compost. The microbial activity did not show significant differences in terms of clay content or compost addition. The cluster analysis correlated the mixed soils (26%) to the lowest clay content soil (10%), and the clay addition (15%) to the highest clay content soil (31%), showing potential as soil conditioner in association with compost, as it might promote changes in the soil quality properties of semiarid regions.

Priming is frequently overestimated in studies using 14C-labelled substrates due to underestimation of 14CO2 activity

The priming effect defined as an increased turnover of soil organic matter (SOM) upon organic substrate addition to soils has been investigated for decades, but its underlying mechanisms remain elusive. It has been shown that 14CO2 trapped in NaOH can be rapidly released from the solution when mixing small volume, low molar or highly CO2-saturated NaOH samples with scintillation cocktails. Therefore, liquid scintillation counting can substantially underestimate the 14C-activity of such samples. In this study, we explore the implications of this methodological shortcoming for priming studies.In a literature review, we look at priming studies that use 14C-labelling to differentiate CO2 evolved from substrates and SOM published in 1993–2021. Out of 65 studies in total, 34 use scintillation cocktails that we had previously tested for outgassing of 14CO2. Out of the 21 studies that provide information about the relevant scintillation counting parameters that determine stability of the measurement, 33–43% use scintillation counting parameters that can be expected to underestimate 14C-activity. In an exemplary priming study, we examine a potential magnitude of error resulting from such incorrect measurements for priming determination and a method to correct the results even when the samples are no longer available to be re-measured. A sandy topsoil and subsoil were incubated with and without added nutrients and 500 (μg C) g−114C-labelled sucrose for 33 days, evolving CO2 was trapped in 0.35 M NaOH and scintillation counted with Ultima GoldXR. By repeatedly re-measuring similarly prepared calibration vials of known 14C-activity, we correct the measurements based on the time passed between preparation and measurement of the vial. We find that with these experimental parameters, 14C-activity is underestimated by 10–30% and consequently, priming is overestimated by 53–66 (μg C) g−1 soil. After correction of the data, we find 16–40 (μg C) g−1 primed carbon. Mass balancing reveals that 10.5–12.8% of 14C-activity of the substrate were recovered by the scintillation correction while 7.3–10.2% remain unaccounted for.These findings suggest that if the 14CO2 activity is underestimated during scintillation counting, then priming can be overestimated by a multiple of the true value and priming can even be found where there isn't any. This issue should not be ignored when discussing priming, considering the prevalence of this method in priming studies, the lack of reporting of relevant experimental parameters and the number of reported flawed experimental parameters found in the literature.

Fertility capability classification for agricultural land use planning in the beach sands area of Akwa Ibom State, Nigeria

Soil survey and fertility capability classification (FCC) were carried out in an area mostly underlain by the beach ridge sands (BRS) parent material in Akwa Ibom State, Nigeria. The study applied the FCC in agricultural land use planning for efficient land management and optimal agricultural productivity of the beach soils. Field and laboratory data were obtained from 40 pedons located across eight Local Government Areas on the BRS parent material. From the results of field and laboratory studies, 11 FCC units were identified in the area. Based on similarities in certain soil profile characteristics, the 11 FCC units were grouped into four agro-ecological units (AEUs): (i) poorly drained FCC units with sandy topsoil over sandy subsoil, grouped to form AEU-A, covered 65.00% of study area; (ii) well drained FCC units with sandy topsoil over sandy subsoil, formed AEU-B and covered 22.50% of study area; (iii) poorly drained FCC units with sandy topsoil over loamy subsoil or loamy top- and sub- soils, formed AEU-C and covered 7.50% of study area; (iv) well drained FCC units with sandy topsoil over loamy subsoil, which formed AEU-D, occupied 5.00% of study area. The result of this study has shown that FCC can be employed as a simple but efficient tool in agricultural land use planning. Major soil profile characteristics used to differentiate land units within the beach sands area of Akwa Ibom State are drainage and texture.

Integrated geophysical characterization of saltwater intrusion in Lagos State, Eastern Dahomey Basin, Southwestern Nigeria

Integrated geophysical methods of Electrical resistivity tomography (ERT), Induced Polarization (IP), and Well Logging were employed in this study to delineate the lateral and depth extent of saline water intrusion in Oniru area of Lagos State, South-western Nigeria due to reported saltwater contamination of some wells at relatively shallow depths. Ergo, improving the scientific understanding of fresh and saline waters occurrence in the coastal areas of Lagos State.Five traverses, each of variant lengths (100 to 200 m) were established for both ERT and IP as space permitted. For each profile level, Wenner electrode configuration was adopted with a minimum electrode spacing of 3 m and maximum electrode spacing of 50 m. Ten levels were achieved for profiles 1, 2, 4, and 5 while eight levels were accomplished for profile 3. The ERT and IP data were processed using RES2DINV 2-D resistivity data processing software. The well log data utilized were acquired from two existing lithological logs within the study area to validate the results of the ERT and IP.The unconsolidated sandy formation was characterized by high resistivity with corresponding low to medium chargeability while the clay units were characterized by low resistivity with equivalent high chargeability. The sandy formation saturated by saltwater was characterized by very low resistivity with corresponding low chargeability while that of freshwater was characterized by medium to high resistivity with corresponding low chargeability. The integrated geophysical methods of ERT, IP and borehole logging in the study area identified three lithological sequences. The first layer corresponded to high resistivity values of unconsolidated sandy topsoil, mostly less than 5 m. However, in profiles 3 and 4, it occurred as saturated marshy topsoil. The top layer was underlain by sand/clayey sand formation, which was observed to have pockets of saline water intrusion as evinced from the results of the ERT and IP data. The saline water-bearing zones were observed to intermingle with the freshwater-bearing sand units. The freshwater-saline water transition tends to be conspicuous especially in profiles 3 and 5. The base of profiles 1 and 2 was occupied by clay units which were evident from the results of the borehole log, the ERT, and the IP sections.The integrated geophysical method was able to successfully delineate the fresh and saline water interface and extent of saltwater intrusion within the study area and thus would provide a reliable database for future groundwater development and management within the study area.

Role of porosity and water holding capacity of soil in nmdc dantewada of Chhattisgarh

An examination was done to concentrate on the physical and substance properties of soils and their relationship with water-holding limits along the altitudinal slope for developed soils of South Bastar Dantewada. The geography Dantewada is located at 18.9000°N 81.3500°E. [1] It has an average elevation of 351 meters (1154 feet). Dantewada city is situated on the river banks of the Shankani and Dankini rivers. The soil surface went from sandy topsoil to earth with somewhat acidic (7.6) to profoundly acidic (5.2) in response. The natural carbon content fluctuated from 1.22 to 3.45 % with a mean worth of 2.31 %. The mass thickness, molecule thickness, porosity, volume extension and water in air-dry soils went from 1.08 to 1.54 gm/cc, 2.05 to 2.77 gm/cc, 42.44 to 61.73 per cent, 2.95 to 11.9 % and 0.68 to 4.32 %, individually. The water-holding limit (WHC) went from 33 to 73.86 % with a mean worth of 54.18 %. The outcomes uncovered that20% of the soil tests have medium to high WHC while just 80% are of low class.

Effect of Phosphorus and Zinc Nutrition on Fodder Yield and economics of Cowpea (Vigna unguiculata L. walp)

The area test becomes done for the length of Zaid 2021 at Crop concentrates on Farm, part of Agronomy, SHUATS, Prayagraj, (U.P). On the surface, the test plot's dirt was sandy topsoil, almost impartial in soil response (pH 7.2), low in natural carbon (0.536%), accessible N (163.42 Kilograms per hectare), to be had P (21. 96 Kilograms per hectare), to be had k (256. 48 Kilograms per hectare). The treatments incorporate three phases of phosphorus (50 Kilograms per ha, 60 Kilograms per ha, and 70 Kilograms per ha) and zinc (15 Kilograms per hectare, 20 Kilograms per hectare, and 25 Kilograms per hectare). The test becomes spread out in a Randomized Block format that incorporates nine treatments and is repeated threefold. The impacts found that the greatest green fodder yield (365.13 q per ha) and dry matter yield (74. 14 q per ha) were recorded with a product of 70 Kilograms per ha P2O5 + 25 Kilograms per ha ZnSO4. be that as it may, the most over the high gross returns (91282.07 INR per ha), net returns (61277.50 INR per ha), and benefit cost ratio (2.04) were gotten highest inside the treatment mix of 70 Kilograms per ha P2O5 + 25 Kilograms per ha ZnSO4.

Studies on the Thermal Unit and Heat Use Efficiency Requirement of the Mustard Crop (Brassica juncea L.) under Different Ambient Temperatures and Cultivars

A field experiment was directed during the rabi period of 2020-21 in the sandy topsoil of A.N.D. University of Agriculture and Technology, Kumarganj, Ayodhya (U.P.). The investigation was directed in Split Plot Design (S.P.D.), comprising of three growing environments/ambient temperature viz. 31st October (22.6°C), 10th November(21.2°C), 20th November(19.4°C) and three cultivars i.e. NDR-8501 (V1), Kranti (V2) and Varuna (V3). The experiment was replicated four times. Results revealed that the highest thermal unit (1667.2 days) and thermal use efficiency (0.61 g/m²/ºdays) was recorded at developing climate/encompassing temperature of 31st October (T1) (22.6°C)while least gathered hotness units from planting to development (1468.9ºC days) was seen under the developing climate/surrounding temperature of twentieth November. The late-planted mustard crop recorded the least GDD prerequisite at every one of the stages. The least Thermal use proficiency from planting to development 0.435g/m²/ºdays was seen under developing climate/encompassing temperature (tenth November)(21.2°C). Late planted cultivars recorded the least warm use effectiveness necessity at all stages.

The potential of fragipans in sustaining pearl millet during drought periods in north-central Namibia

Abstract. Sandy soils with fragipans are usually considered poorly suited for agriculture. However, these soils are cultivated in Namibia as they can secure a minimum harvest during droughts. In order to understand the hydrological influence of fragipans in these soils, Ehenge, their soil moisture content was measured for 4 months. These data were then compared to a deep soil without fragipan, Omutunda, which is more productive during normal years but less productive during droughts. The results illustrate that the combination of sandy topsoil and shallow fragipan has beneficial effects on plant-available water during dry periods. Three reasons can be determined: (i) high infiltration rate in the sandy topsoil, (ii) prevention of deep drainage by the fragipan, and (iii) limitation of evaporation losses through the sand. Consequently, transferring these findings to other dry, sandy areas with fragipans, with respective consequences on farming practices, crop productivity, and food security, should be possible.

Evaluation of soils on a toposequence formed from the coastal plain sands of the Imo river basin, Southeastern Niger

Due to the increasing land degradation in southeastern Nigeria – with particular reference to the ubiquitous gully network in the region – selected soils formed from the Coastal Plain Sands of the Imo River Basin were evaluated and characterized to determine their potentials and capabilities. , Three profile pits were consequently dug on the upper slope (Umuariam), -mid-slope (Umulogho), and foot slope (Umungwa) of three towns on the Imo River Basin underlain by the coastal plain sands. The soil color ranged from greyish brown (5 YR 5/2) to dull brown (7.5 YR 5/3) in the topsoil and from dull orange (5 YR 6/4) to orange (5 YR 6/7) in the subsoil. The soils had sandy topsoil and relatively more clayey subsoil. The pH (in KCl) ranged from very strongly acidic (4.5 – 5.0) to moderately acidic (5.1 – 6.0). They had low organic matter, low total nitrogen, low ECEC, low Al saturation, and moderate base saturation. The soils of Umuariam (Upper Slope) and Umulogho (Mid Slope) were classified as Typic Hapludults (Chromic Acrisols), while that of Umungwa (Foot Slope) was classified as Typic Udipsamments (Rubic Arenosols). Umuariam had a USDA land capability class of IIes and a USBR land capability class of 2v/C. Umulogho and Umungwa both had a USDA and USBR capability class of IVs and 3v/C respectively. Though moderately to marginally irrigable, the soils can still produce increased and sustainable agricultural yield if the appropriate land use and husbandry practices are adopted, with particular reference to erosion control, organic manure, lime, and fertilizer application.

Investigation of groundwater potential using integrated geophysical methods in Moloko-Asipa, Ogun State, Nigeria

Water is essential for livelihood, development, and industrial growth. Its exploration in sufficient quantity is required where it does not freely occur on the surface. This research was aimed to delineate aquifer regions and provide information on the subsurface lithology of Moloko-Asipa Southwestern Nigeria. A combination of eight traverses investigated with very low frequency electromagnetic (VLF-EM) method at 5 m constant sampling interval and ten vertical electrical sounding (VES) were carried out in the survey. Measurements from the VLF-EM survey were processed with Karous and Hjelt filtering to give the resistivity contrast across the selected profiles. The VES data processing involved an automatic approximation of the initial resistivity and thickness of the geoelectric layers with IPI2Win and further filtering by WinResist iteration. Estimation of Dar-Zarrouk parameters was also employed to investigate the aquifer protective capacity of the area. The processed VLF-EM results showed the geology of the area to an average depth of 25 m. The geoelectric section of the VES data revealed minimum of 3 layers from sandy top soil to weathered layer and fresh basement with an average resistivity values of 1,816, 926 and 17,503 Ωm, respectively. The integration of VLF-EM and VES in the investigation revealed that the potential for groundwater exploration in the study area is poor due to the thin nature of the weathered layer and its shallow depth to basement. The aquifer protective capacity of the area was likewise inferred to be poor.

Struvite recovery from human urine in inverse fluidized bed reactor and evaluation of its fertilizing potential on the growth of Arachis hypogaea

Nutrients, nitrogen and phosphorus, present in wastewater need to be removed to protect water bodies from the consequences of eutrophication. Among the many possibilities, recovering the nutrients as struvite has become attractive, particularly from the isolated sources of urine stream considering its potential use as a fertilizer akin to Diammonium phosphate (DAP). The present paper deals with studies on the production of struvite from synthetic human urine using an inverse fluidized bed reactor (IFBR) based on the batch process results. Unlike the 85% recovery of struvite for the optimized molar ratios of magnesium, ammonium and phosphate at pH 9.5, the IFBR experiments yielded approximately 95% recovery at optimal operating parameters with respect to condition, size of low density polypropylene particles (6 mm) with density (963 kg/m3) and bed height (45 cm). The purity and microstructure were examined using XRD, SEM / EDS, and Raman spectroscopy. The fertilization efficiency was assessed with struvite application and integrated with nitrogen-fixing Azospirullum rhizobium and phosphate-solubilizing Bacillus megaterium on the growth of Arachis hypogaea plants in the field. Studies conducted along with commonly used DAP on sandy topsoil indicated efficient absorption of struvite by microbes and providing the most encouraging number of seed/pod (capsule) and straw yields (g/plant) comparable to conventional superphosphate DAP. The nutrient availability in the soil was confirmed based on the soil properties before and after harvest. Extensive tests of the plant properties proved the positive agronomic results of struvite fertilization.

Coal Exploration using Electrical Resistivity Method in Some Parts of Benue Trough, Nigeria

Geoelectrical resistivity sounding technique was used to delineate the occurrence and extents of coal seam. Fifteen points were sounded with Schlumberger configuration in the suspected coal deposit site bounded by longitudes 7.344° E and 7.366° E, and latitudes 7.318° N and 7.33° N. The vertical electrical sounding (VES) data were analyzed and the corresponding geo-electric parameters at various depths were modeled. The earth model within the study area was correlated with available lithology of a nearby mine site. The sounding signatures are KQHK and KHK curve types which revealed five to six distinct geo-electrical equivalent layers. The wet to dry sandy topsoil has resistivity range of 300–1000 Ωm and average thickness of 1.5 m. Next is a layer with higher resistivity range (1000–20000 Ωm). This layer, which extends to 14 m depth, is considered probably to be laterite, patched with sand in some places. Underlain this is a shale formation that laterally sandwiched the coal seam. The thickness and resistivity range of the coal seam is 1.5–3.4 m and 778–103000 Ωm, respectively, while the shale domain has resistivity range of 99–898 Ωm. Therefore, it could be concluded that the coal seam occurrence take shale as host rock in the area and the largest deposit appeared at the Eastern part of the area.
 Keywords: Benue trough; Resistivity; Electrical sounding; Coal seam; Overburden

Greenhouse gas emissions of rice straw return varies with return depth and soil type in paddy systems of Northeast China

ABSTRACT A two-year field experiment was performed to investigate greenhouse gas emissions from rice straw return to different return depths and soil types. The experiment comprised of six treatments: without straw return (silty clay loam, SC; sandy loam, SL); straw return to topsoil (SCT, SLT); and straw return to subsoil (SCS, SLS). SCT and SLT released 2402.18 and 2494.01 kg ha−1 more CO2 than SC and SL in total, respectively. Straw return to topsoil and subsoil in both soil textures significantly increased CH4 emissions. Compared to the total cumulative CH4 fluxes in SC and SL, those of SCT and SLT increased by 239.62 and 131.34 kg ha−1, and those of SCS and SLS increased by 125.07 and 89.93 kg ha−1, respectively. SCT and SCS emitted 389.06 and 168.94 g ha−1 less N2O than SC in total, respectively. SL released 146.28 and 72.06 g ha−1 more N2O than SLT and SLS in total, respectively. The variations in the ratio of the total cumulative fluxes of CO2 and CH4, indicate that rice straw return to silty clay loam and subsoil tend to release more carbon in the form of CH4 compared to sandy loam and topsoil, respectively.

Thermal imaging of a hydrophobic soil’s response to surfactant application at the Avon River Catchment Critical Zone Observatory

The hydrology of water repellent soil is poorly understood, in part because measuring hydrophobicity often interferes with subsequent water flow. Since soil surface temperatures provide information on near surface water content, thermography offers the potential to indirectly monitor this hydrology non-invasively. Using a near-infrared thermal camera, 15 plots, each 1 m2, of a hydrophobic sandy topsoil were recorded continuously for three weeks in the field. Treatments included plots with surfactant applied in bands from 16 cm to 100 cm width and a control (no surfactant). Soil sampling and continuous monitoring of soil moisture, soil temperature and weather conditions supplemented surface temperature measurements. Surface temperature and surface soil moisture were shown to be negatively correlated during the day and positively at night. Soil moisture probes indicated that water from three 10 mm irrigation events was largely restricted to depths less than 10 cm throughout the experiment. Dynamics of the semi-variance for treated plots were different to that of the control. Empirical orthogonal functionals (EOF) initially showed the dominant variability in spatial pattern reflected the surfactant application. During the course of the experiment, changes in the EOFs revealed the gradual re-emergence of background soil heterogeneity related to prior seeding rows. The monitoring did not reveal any lateral expansion of wetted areas from the edges of surfactant treated strips. Thermography was able to inform the dynamics of soil moisture related to spatial and temporal variability in hydrophobicity under field conditions. The approach offers the potential to non-invasively image dynamic soil hydraulic properties and to evaluate water repellence amelioration methods.

Preliminary Investigations for Landfill Siting in Lafia, Nasarawa State of Central Nigeria

Waste management has taken the front purview in recent years due to the evident and attendant effects of indiscriminate disposal of wastes to the environment. This led to the preliminary investigations for the proposed siting of a landfill facility in Lafia and environs of Nasarawa State in Central Nigeria, with the aim of providing valuable information on the suitability for location for the disposal of Municipal Solid Waste (MSW). The combined use of geo-resistivity, geological and hydrogeological investigations were carried out for the study. Ten Vertical Electrical Soundings (VES) of the Schlumberger array was used to investigate the properties of the subsurface lithologies to determine their properties especially, clay, for siting a landfill. Clay, an attenuating material, is significant for siting a landfill facility because it tends to isolate potentially toxic wastes from the environment by slowing down the movement of leachates into groundwater and the environmental. Quantitative interpretation of data of the VES survey using the IPI2win computer software revealed the presence of four to five geologic layers comprising of sandy top soil (247 – 1964Ωm), silty sand (98 – 3488Ωm), clayey-shally/sand (68 – 3922Ωm), saturated clayey sand (31 – 3226Ωm) and loose sand (478Ωm). Clay was found to be abundant in the area and found at depths ranging from 30m to infinity. Geologically, structures like lineaments abound and were analysed; they show a dominant trend in the NW – SE direction from the Rosette Diagram. Lineaments are useful for studies because they are possible conduits where decomposed wastes in liquid form, such as leachates, get transported to pollute groundwater. Hydrogeological studies surveyed Static Water Levels (SWL) measurement from 51 hand dug wells in the study area. The SWL ranges between 5.8m and 37.1m. The data from the SWL was used to construct the absolute water level map in a 3D form to show the flow direction of the groundwater. The study revealed the presence of impermeable clays at VES 1, 2, 3, 9 and 10. This is significant for selection for landfill due to its pollution-prevention properties of groundwater pollution. The investigations carried out in this study show that Shabu, a town located about 8km from Lafia, is likely suitable for siting a landfill facility; because of the abundance of clay at a shallow depth of 30m and with limited preponderance of lineaments.

Environmental behaviour of radioactive particles from chernobyl

Long-term environmental behaviour of radioactive particles released during the Chernobyl accident and deposited in sandy topsoil in Ivankiv district of Kyiv Region (Ukraine), in radioactive trench waste materials from the Red forest, and in bottom sediments from the Cooling pond has been assessed. The efficiency of the models describing the dissolution/weathering rates of U fuel particles developed 15–20 years ago was tested, and their predictions for the dynamics of remobilization, mobility and plants uptake of 90Sr were confirmed.It was found that at present in the topsoil and in radioactive trench waste material, total dissolution of fuel particles of low chemical stability (UO2+x) has occurred and about half of the non-oxidized chemically stable fuel particles (UO2) has also dissolved, indicating radiological stabilization of the environment and that the mobile fraction of radionuclides would be reduced in the future. The biological availability of 90Sr in topsoil due to fuel particles dissolution has reached maximum values and further decrease is expected.The presence of chemically extra-stable fuel particles (U-Zry-Ox) in environments should be taken into account when the total radionuclides activity concentrations are assessed during radioactive materials management.It was shown that nearly half of the 90Sr activity remained as part of the non-dissolved UO2 fuel particles at the time of the study. Taking into consideration that 31 ± 4% of the radionuclide activities were still associated with non-dissolved chemically extra-stable particles (U-Zry-Ox) in radioactive trench waste materials from the Red forest, increased dissolution should not be expected in the near future.The physico-chemical form of radionuclides in air exposed sediments from the Cooling pond were determined, and results showed that about 70–80% of total 90Sr, 241Am and plutonium isotopes activity were associated with U fuel particles. The low dissolution rate of radionuclides from the pond sediments is attributed to prolonged slightly alkaline pH in the medium due to zebra mussel residues.According to new data, the emission value of 238Pu associated with fuel particles released during the Chernobyl accident amounted to 1.8 × 1013Bq (1.2% of the activity in the reactor) and 90Sr amounted to 2.6 × 1015Bq (1.5% of the activity in the reactor).

The effect of four calcium‐based amendments on soil aggregate stability of two sandy topsoils

AbstractThe structural stability of soil is a physical characteristic that affects soil degradation processes. Calcium‐based amendments, such as calcium carbonate, calcium sulfate, and calcium oxide/hydroxide, have been shown to improve the stability of soil aggregates. This study seeks to determine which calcium‐based soil amendments, and at what concentration, are the most efficient in improving aggregate stability of sandy topsoils derived from granitic and metamorphic parent materials, and to analyze the mechanisms involved. In the pot experiment, soils amended with CaCO3, CaCl2, and CaSO4 did not present significant differences in aggregate stability compared to the control or among each other. In contrast, Ca(OH)2 soil amendment brought the greatest stability to the soil aggregates. A dose of 1% Ca(OH)2 significantly increased the stability of soil aggregates. This effect is due to the reaction of Ca(OH)2 with atmospheric CO2 which leads to the formation of CaCO3, a delayed reaction not showed by the other soil amendments tested. Likewise, the greater solubility of Ca(OH)2 compared to CaCO3 exerts a greater aggregation effect on soil. Thus, the mechanism of action of Ca(OH)2 is related to cementation, rather than flocculation. Future studies should be carried out to demonstrate the effectiveness of Ca(OH)2 under field conditions.

Effect of urbanization on soil methane and nitrous oxide fluxes in subtropical Australia

Increasing population densities and urban sprawl are causing rapid land use change from natural and agricultural ecosystems into smaller, urban residential properties. However, there is still great uncertainty about the effect that urbanization will have on biogeochemical C and N cycles and associated greenhouse gas (GHG) budgets. We aimed to evaluate how typical urbanization related land use change in subtropical Australia affects soil GHG exchange (N2 O and CH4 ) and the associated global warming potential (GWP). Fluxes were measured from three land uses: native forest, a long-term pasture, and a turf grass lawn continuously over two years using a high-resolution automated chamber system. The fertilized turf grass had the highest N2 O emissions, dominated by high fluxes >100gN2 O-Nday-1 immediately following establishment though decreased to just 0.6kgN2 O-Nha-1 in the second year. Only minor fluxes occurred in the forest and pasture, with the high aeration of the sandy topsoil limiting N2 O emissions while promoting substantial CH4 uptake. Native forest was consistently the strongest CH4 sink (-2.9kgCH4 -Cha-1 year-1 ), while the pasture became a short-term CH4 source after heavy rainfall when the soil reached saturation. On a two-year average, land use change from native forest to turf grass increased the non-CO2 GWP from a net annual GHG sink of -83CO2 -e ha-1 year-1 to a source of 245kgCO2 -eha-1 year-1 . This study highlights that urbanization can substantially alter soil GHG exchange by altering plant soil water use and by increasing bulk density and inorganic N availability. However, on well-drained subtropical soils, the impact of urbanization on inter-annual non-CO2 GWP of turf grass was low compared to urbanized ecosystems in temperate climates.

Enhancing tailings revegetation using shallow cover systems in arid environments: Hydrogeochemical, nutritional, and ecophysiological constraints

AbstractMineral tailings impoundments represent a rapidly growing land area requiring revegetation and a major challenge to restoring biodiversity in postmined environments. Topsoil covers are essential for revegetation, to mitigate the physical and hydrogeochemical obstacles presented by tailings. However, mines in arid and semiarid regions are often large scale and geographically isolated from resources and suffer a scarcity of suitable topsoil, stimulating interest in cost‐effective shallow cover systems incorporating minimal volumes of local material. Using a mine in arid Western Australia as a case‐study, we address challenges pertinent to using 200‐mm‐deep sandy topsoil directly overlying mildly reactive, circum‐neutral copper ore tailings. We combined detailed hydrogeochemical, ecophysiological, and nutritional data from a year‐long glasshouse experiment, to evaluate responses of native species to the model system. The model system enhanced emergence, growth, and root development by providing a physical and hydrogeochemical buffer, increasing the volume of profile with conditions favourable to water and nutrient acquisition. Plants scarcely utilised saline water from the underlying tailings, limiting growth between irrigation events, although the tailings did support minimal functional activity over timescales in the order of weeks. We identified relatively high tailings pore‐water salinity, the limited volume of geochemically benign topsoil providing storage release of uncontaminated meteoric water, and the geochemically evolving nature of the tailings cover system, as key challenges to overcome. The findings encourage further studies incorporating optimised designs and demonstrate the benefits of combining detailed, temporally resolved hydrogeochemical and ecophysiological data to adequately capture the plant–water relations existing within candidate cover systems.