Clean Soil Research Articles

Improvement in humus synthesis by the humus precursors derived from nitrobenzene degradation during co-composting of nitrobenzene-polluted soil and cow manure

Nitrobenzene (NB) mineralization problem exists during co-composting of NB-polluted soil and cow manure (CM). Regulating the conversion of NB degradation into humus (HS) synthesis offers a new way to circumvent the aforementioned problem. To explore the influence of the presence of NB on humification process during co-composting, co-composting of NB-polluted soil and cow manure was conducted with composting of clean soil and CM, serving as the control. Results showed that a 54.66% of NB-degradation rate was achieved after 47 d of composting. Simultaneously, compared to CK, not only HS content increased by 18.75%, but also the proportion of fluorescent component with the highest complexity of humic and fulvic acid increased by 21.92% and 44.44%, respectively. NB intermediate metabolites substantially contributed to HS formation. Meanwhile, a markedly strong interaction between bacteria and environmental factors may be crucial for enhancing the humification process in the NB group. It was verified that the addition of NB increased the content of polyphenols (λ = 0.912, p＜0.001) and further improved the synthesis of humic acid (λ = 0.420, p＜0.05) by strengthening the Maillard reaction. Simultaneously, the inhibitory effects of NB and polyphenols on bacterial growth prevented excessive depletion of ammonia nitrogen, favoring humic acid synthesis. These results illustrated that NB intermediate metabolites promoted HS synthesis, which was the prerequisite for subsequent establishment of targeted regulation technology of NB degradation-HS synthesis during co-composting.

Issue Information: Clean Soil Air Water. 5/2024

Issue Information: Clean Soil Air Water. 5/2024

Feasibility of constructed soils for tree planting – A pilot study in New York City

Constructed soils are soils that are created with a mixture of various materials. An innovative soil exchange program - the Clean Soil Bank (CSB) in New York City allows recycling of clean glacial outwash sediments excavated from depth at construction sites. One previous study showed that soils constructed from CSB sediment and compost can effectively support crop growth in community gardens, but no research has been conducted on its potential usage as a medium for tree growth. Moreover, biochar has been used to improve soil quality, but its efficacy for street trees incorporated into constructed soils has largely not been quantified in the field. The objective of this project was to evaluate the feasibility of using soils constructed from the CSB and compost for tree planting and to investigate the impact of biochar on tree performance. Thirty-six trees of two species (Maackia amurensis and Zelkova serrata) were planted in 2019, on the sidewalks of a residential-business neighborhood in Bronx, New York. Each tree pit contains one of three soil types: type A - existing and purchased topsoil mixed with 33% compost and biochar, type B - CSB sediment mixed with 33% compost, and type C - CSB sediment mixed with 33% compost and biochar. Soil samples were collected in 2019 (before planting) and in 2021. Tree health assessments were conducted in September 2020 and July 2021 using a protocol developed by the USDA Forest Service. Other tree health parameters collected include diameter at breast height (DBH), crown diameter, tree height, photosynthetic capacity, and foliar chemistry. Significant differences in bulk density, water holding capacity, and K, Fe, and Zn concentrations were found among the three soil types. However, comparison of tree performance and foliar chemistry showed no systematic differences among the three soil types. The results indicate that CSB sediment mixed with compost can be an effective replacement for purchased topsoil for tree growth. No evidence was found that biochar provides additional benefits to street tree performance. Considering the abundant availability of glacial outwash sediment at low cost to the city, as well as access to locally produced compost, constructed soils can be a reliable source of material for urban forestry programs.

Consideration of Vadose Zone Moisture Dynamics in Remediation of PFAS‐Impacted Soils

AbstractOilfield brines are soluble, non‐volatile, and recalcitrant contaminants that are vulnerable to capillary effects and evapoconcentration and have been known to recontaminate clean fill soils emplaced after excavations. This problem may also occur for some poly‐ and perfluoroalkyl substances (PFAS) at PFAS sites. In this paper, we consider the soil moisture characteristic curve, wetting front dynamics, and the moisture redistribution cycle to understand the potential behavior of different PFAS in the vadose zone. Drawing on experience with remediation of soils impacted by brine spills, we provide recommendations on the design and implementation of soil excavation and cover remedies such as capillary barriers to prevent recontamination.

Cover Picture: Clean Soil Air Water. 4/2024

Cover Picture: Clean Soil Air Water. 4/2024

Clean and accurate soil quality monitoring in mining areas under environmental rehabilitation in the Eastern Brazilian Amazon.

Soil quality monitoring in mining rehabilitation areas is a crucial step to validate the effectiveness of the adopted recovery strategy, especially in critical areas for environmental conservation, such as the Brazilian Amazon. The use of portable X-ray fluorescence (pXRF) spectrometry allows a rapid quantification of several soil chemical elements, with low cost and without residue generation, being an alternative for clean and accurate environmental monitoring. Thus, this work aimed to assess soil quality in mining areas with different stages of environmental rehabilitation based on predictions of soil fertility properties through pXRF along with four machine learning algorithms (projection pursuit regression, PPR; support vector machine, SVM; cubist regression, CR; and random forest, RF) in the Eastern Brazilian Amazon. Sandstone and iron mines in different chronological stages of rehabilitation (initial, intermediate, and advanced) were evaluated, in addition to non-rehabilitated and native forest areas. A total of 81 soil samples (26 from sandstone mine and 55 from iron mine) were analyzed by both traditional wet-chemistry methods and pXRF. The available/exchangeable contents of K, Ca, B, Fe, and Al, in addition to H+Al, cation exchange capacity at pH = 7, Al saturation, soil organic matter, pH, sum of bases, base saturation, clay, and sand were accurately predicted (R2 > 0.70) using pXRF data, with emphasis on the prediction of Fe (R2 = 0.93), clay content (R2 = 0.81), H+Al (R2 = 0.81), and K+ (R2 = 0.85). The best predictive models were developed by RF and CR (86%) and when considering pXRF data + mining area + stage of rehabilitation (73%). The results highlight the potential of pXRF to accurately assess soil properties in environmental rehabilitation areas in the Amazon region (yet scarcely evaluated under this approach), promoting a more agile and cheaper preliminary diagnosis compared to traditional methods.

Cover Picture: Clean Soil Air Water. 3/2024

Cover Picture: Clean Soil Air Water. 3/2024

Construction of an effective method combining in situ capping with electric field-enhanced biodegradation for treating PAH-contaminated soil at abandoned coking sites

The simultaneous application of in situ capping and electro-enhanced biodegradation may be a suitable method for ensuring the feasibility and safety of reusing abandoned coking sites. However, the capping layer type and applied electric field pattern may affect the efficiency of sequestering and removing pollutants. This study investigated changes in electric current, soil moisture content and pH, polycyclic aromatic hydrocarbon (PAH) concentration, bacterial number, and microbial community structure and metabolic function during soil remediation at abandoned coking plant sites under different applied electric field patterns and barrier types. The results indicated that polarity-reversal electric field was more conducive to maintaining electric current, soil properties, resulting in higher microbial number, community diversity, and functional gene abundance. At 21d, the mean PAH concentrations in contaminated soil, the capping layer's clean soil and barrier were 78.79, 7.56, and 1.57 mg kg−1 lower than those with a unidirectional electric field, respectively. The mean degradation rate of PAHs in the bio-barrier was 10.12 % higher than that in the C-Fe barrier. In the experiment combining a polarity-reversal electric field and a bio-barrier, the mean PAH concentrations in contaminated soil and the capping layer were 706.68 and 27.15 mg kg−1 lower than those in other experiments, respectively, and no PAHs were detected in the clean soil, demonstrating that the combination of the polarity-reversal electric field and the bio-barrier was effective in treating soil at abandoned coking plant sites. The established method of combining in situ capping with electro-enhanced biodegradation will provide technical support for the treatment and reuse of heavily PAH-contaminated soil at abandoned coking plant sites.

Behavior of Potential of Half-Cell AISI 1018 and GS in Concrete Buried in Sand in the Presence of MgSO4

This project, in the area of reinforced concrete corrosion, evaluated the potential of half-cell AISI 1018 CS (Carbon Steel) and GS Steel (Steel with galvanized coating); 15 cm long bars were used as reinforcement in specimens of concrete buried in a Type SP Sand (contaminated with 0% and 3% MgSO4). The experimental arrangement of this research represents the case of the elements of the foundations of concrete structures that are planted near marine areas where this type of soil exists with the presence of high contents of depassivating ions such as sulfates. The study specimens were made with two concrete mixtures with a water/cement ratio 0.45 but with different types of cement (Portland Cement and Sulfate Resistant Cement). For monitoring the half-cell potential according to ASTM C 876-15, the specimens were buried in the clean SP soil and in the same soil but contaminated with MgSO4. After more than 270 days of exposure to uncontaminated SP sand contaminated with MgSO4, the behavior of the half-cell potentials or corrosion potentials show that the specimen made with the sulfate-resistant cement and reinforced with GS Steel (Steel with galvanized coating) presents the highest resistance to corrosion by MgSO4 at a concentration of 3%.

The Release and Migration of Cr in the Soil under Alternating Wet-Dry Conditions.

In recent decades, chromium contamination in soil has emerged as a serious environmental issue, demanding an exploration of chromium's behavioral patterns in different soil conditions. This study aims to simulate the release, migration, and environmental impact of chromium (Cr) in contaminated soils under natural rainfall conditions (wet-dry cycles). Clean soils sourced from Panzhihua were used to cultivate chromium-containing soils. Simulated rainfall, prepared in the laboratory, was applied to the cultivated chromium-containing soils in indoor simulated leaching experiments. The experiments simulated three years of rainfall in Panzhihua. The results indicate that soils with higher initial Cr contents result in higher Cr concentrations in the leachate, but all soils exhibit a low cumulative Cr release. The leachate shows similar patterns in total organic carbon (TOC), pH, electrical conductivity, and Cr content changes. An analysis of the speciation of Cr in the soil after leaching reveals a significant decrease in the exchangeable fraction for each Cr species, while the residual and oxidizable Cr fractions exhibit notable increases. The wet-dry cycle has the following effects on the soil: it induces internal reduction reactions in the soil, leading to the reduction of Cr(VI) to Cr(III); it alters the binding of Cr ions to the soil, affecting the migration of chromium; and it involves microorganisms in chemical processes that consume organic matter in the soil. After three years of rainwater leaching, chromium-containing soils released a relatively low cumulative amount of total chromium, resulting in a reduced potential risk of groundwater system contamination. Most of the chromium in the chromium-containing soil is fixed within the soil, leading to less biotoxicity.

Multigenerational exposure of Ag materials (nano and salt) in soil - environmental hazards in Enchytraeus crypticus (Oligochaeta).

Because of its properties, silver is among the most used metals both as salt and as nanomaterials (NMs), hence reaching the environment. Multigenerational (MG) exposure testing is scarce, and especially so for NMs and soil invertebrates. In this study the MG effects of Ag NMs (Ag NM300K) and Ag salt (AgNO3) were assessed, using Enchytraeus crypticus in LUFA 2.2 soil. Survival, reproduction and internal Ag concentration in the animals were measured throughout 7 generations (5 generations (F0-F4) in spiked soil plus 2 (F5-F6) in clean soil) exposed to sublethal concentrations corresponding to the reproduction EC10 and EC50 obtained in standard toxicity tests (45 and 60 mg Ag per kg soil DW for AgNO3; 20 and 60 mg Ag per kg soil DW for Ag NM300K). MG exposure caused a dose-related decrease in reproduction for both Ag forms. Ag uptake peaked in the F1 (64 days) for AgNO3 and F2 (96 days) for Ag NM300K, after which it decreased. In agreement with toxicokinetic studies, a maximum body Ag concentration was reached (20 mg Ag per kg body DW (AgNO3) and 70 mg Ag per kg body DW (Ag NM300K)) and after which detoxification mechanisms seem to be activated with elimination of Ag accompanied by a decrease in reproduction. Transfer to clean soil allowed Ag to be (fully) eliminated from the animals. This MG study confirmed the effects determined in standard reproduction toxicity tests but further allowed to monitor the dynamics between exposure and effects of the Ag materials, and how the animals seem to cope with Ag for 7 generations by compensating between detoxification and reproductive output.

Анализ уровня экологической компетентности учителей биологии Северо-Казахстанской области

The article presents an analysis of the level of environmental competence of biology teachers in the North Kazakhstan region. The relevance of the research is due to the need to form the environmental competence of teachers in order to achieve sustainable development of society and the economy in education and the transfer of environmental knowledge. The method used was a sociological survey using an Internet resource on the Google platform. As a result of the study, data were obtained that most teachers need to improve their knowledge, skills and abilities in the field of ecology, since this integrative indicator characterizing teachers is considered as a separate component of their professional activity. In turn, it influences the transfer of acquired environmental competencies to students through the implementation of educational activities during biology training. Environmental education should become a universal part of education, first of all, so that every teacher has environmental competence in the face of growing demand for natural resources, taking into account the careful attitude and transfer of clean air, genetic biodiversity and soil fertility to future generations.

Features of the functioning of microbiocenoses of cultivated soddy-podzolic soil under conditions of oil pollution

The study goal was to explore the characteristics of the functioning of microbiocenoses of well-cultivated soddy-podzolic soil, contaminated with doses of oil under the conditions of a field experiment. The level of initial pollution with petroleum products was in percentage: 0, 0.5, 1.0, 1.5 and 3.0. Sampling for laboratory research was carried out 14 days, 6 and 18 months after the oil spill. To assess the activity of the microbiota under conditions of soil self-purification from oil pollution, integral indicators were chosen. 1. The amount of carbon dioxide released from the soil, the so-called basal respiration, corresponds to the complete destruction of oil (to CO2 and H2O) by soil microorganisms. 2. The medium-regulating (regulatory) microorganisms’ activity, which is defined as the biological response of the soil to a disruption of chemical balance, was assessed by the quantity of CO2 release after 1% glucose addition. The oil products content was defined in real time mode. Soil microbiocenoses were highly perseverant to the inhibitory effects of oil pollution. Disturbances in the normal functioning of the microbiota as a result of oil pollution were non-critical and reversible. Half-year after the oil spill, at all levels of pollution, there was a sharp increase in basal respiration. Its level exceeded the respiration rate of clean soil several-fold. This indicated the high biochemical activity of hydrocarbon-oxidizing resident microbiota and as a result an active self-cleaning of soil from oil pollution. The negative dynamics of the petroleum products content proved the microbial character of the oil destruction processes in the soil.

Cover Picture: Clean Soil Air Water. 1/2024

Cover Picture: Clean Soil Air Water. 1/2024

Experimental validation of Monte Carlo NaI(Tl) detector efficiency responses with surrogate 137Cs environmental contamination source term

Radiological site remediation is a resource intensive process requiring extensive field sampling to demonstrate regulatory compliance. Specifically, the application of Monte Carlo (MC) simulations and automated hybrid radiation transport methods has garnered interest in streamlining the remediation process by simulating detector responses for a plurality of contaminated media, contamination depths and profiles, and source-detector orientations. In this study, experimental validation of gamma-ray detector efficiency responses was conducted for simulations of radiological site-specific and idealized external contamination conditions. Measurements were performed with a cylindrical 2′′ × 2″ sodium iodide thallium-doped (NaI(Tl)) scintillator detector suspended above a 217.8 kBq, 50 cm × 50 cm 137Cs contamination source located on the surface of or buried within environmental soil. New area correction factors (ACFs) and gamma shielding factors (GSFs) were also derived to modify the simulated idealized detector efficiency responses, accounting for reductions in source area and clean soil covering layers, respectively, that may be encountered when performing in-situ gamma spectrometry in the field. The study concluded that simulated total detection efficiency from energy deposition in the active volume of the detector crystal can be adopted for radionuclide screening purposes. Furthermore, pragmatic implementation of environmental surveying using gamma-spectrometry requires site-specific information.

BIOTESTING OF SOIL CONDITIONS AT THE TERRITORIES ADJACENT TO AIRPORTS

The development of civil aviation is accompanied by a constant increase in man-made load on the environment. The application of methods of bioindication and biotesting of anthropogenic and technogenic influences on the ecosystem components is one of the possible options for monitoring the state of the environment at territories subject to technogenic stress due to the activities of environmentally hazardous enterprises. To study the level of man-made impact of airport activities on the state of the soil (namely, phytotoxicity), at the territory adjacent to the airport "Kyiv" named after I. Sikorskyi International Airport from the upper and lower levels at different distances from the airport runway (from 5 m to 2 km) soil samples were taken using the envelope method. As a control (conditionally clean soil), a soil sample collected at the territory of Holosiiv Park (soil type: dark gray forest soils) was used. In total, six soil samples were analyzed. On the third day of germination the growth characteristics of Allium cepa seedlings were determined. Test parameters that were used to determine the phytotoxic effect: the percentage of seed germination, namely the energy of its germination, the length of the root and the length of the stem. The analysis of the obtained data on the germination of Allium cepa seeds showed that the lowest germination was recorded for the soil samples that were taken at a distance of 5 and 1500 m from the runway, which indicates an increased level of phytotoxic impact due to the activities of the airport.
 The greatest phytotoxic effect for the stem of Allium cepa seedlings was observed for the soil sample located at a distance of 5 m from the ZPS. For soil samples taken at a distance of 5 m to 1000 m, i.e. with distance from the runway of the airport, a decrease in the level of phytotoxicity of the soil is observed. Only when approaching the highway (at a distance of 1,000 m to 2,000 m) there was observed an increase in phytotoxicity of the soil again.
 Among the investigated samples of meristem tissues, the presence of mitotic activity of cells was observed in the meristems of root tip samples of onion seedlings germinated on soil samples that were taken at a distance of 5 m, 1500 m and 2000 m from the airport. The determined mitotic indices (MI) for these soil samples are as following: for a soil sample taken at a distance of 5 m, it was 2.9 %; for a soil sample taken at a distance of 1500 m was 2.6 %; for a soil sample taken at a distance of 2000 m was 2.6 %. The research results confirm the need for constant monitoring of the soil condition at these technogenically loaded territories, in order to increase the level of environmental safety of these territories.

Cover Picture: Clean Soil Air Water. 12/2023

Cover Picture: Clean Soil Air Water. 12/2023

Phyto- and bio-management of metal(loid)-contaminated soil by inoculating resistant bacteria: evaluating tolerance of treated rice plant and soil with its efficiency.

Anthropogenic activities are increasing the amount of heavy metals and metalloids in the environment on a global scale, harming all living things and necessitating the employment of bioremediation procedures. Metal-resistant bacteria were used to clean polluted soil and promote plant growth; this approach has gained attention in recent years for bioremediation of heavy metal-contaminated systems. We studied the effects of chromium and lithium in Oryza sativa under controlled conditions. In the present study, lithium concentration was applied 50ppm to 200ppm according to the dose tolerance level, while the concentration of chromium was 10ppm throughout the experimental setup due to its concentration observed up to 10ppm in the targeted soil, which is present in Kasur area Punjab, Pakistan, for rice crop production in future perspective. The results reflect that plants with high lithium concentration have shown decreased plant growth and development, but due to bacterial presence, they thrived until harvesting stage. Due to increase in stress concentration up to 200ppm, decline in plant growth was observed, but after bacterial inoculation, better growth was seen (chlorophyll content increased to 40, and panicle numbers were more than 13). Our findings reveal that lithium and chromium have a direct negative impact on Oryza sativa, which can be minimized by utilizing halophilic microbes (Klebsiella pneumonia and Enterobacter cloacae) through soil-plant system.

Cover Picture: Clean Soil Air Water. 11/2023

Cover Picture: Clean Soil Air Water. 11/2023

Cover Picture: Clean Soil Air Water. 10/2023

Cover Picture: Clean Soil Air Water. 10/2023