Clean Soil Research Articles

Avoidance tests with the oribatid mite Oppia nitens (Acari: Oribatida) in cadmium-spiked natural soils

Avoidance behavior can be a useful parameter for assessing the ability of organisms to escape from pollutants in their environment. For soil evaluation, a variety of invertebrates is used including the oribatid mite Oppia nitens. Here, we tested the avoidance behavior of O. nitens using a two-chamber test and an escape test with exposures to different cadmium concentrations of up to 800mg kg-1 dry LUFA 2.2 soil for 2, 4, and6 days, and up to 7 weeks. With the two-chamber method, the oribatid mites had the choice between clean and polluted soils, whereas they were allowed to escape from a box with polluted soil to clean containers without soil with the escape method. Avoidance of cadmium was observed after 2 days in both tests and the net response of the mites in the two-chamber test increased with increasing cadmium exposure concentrations. Mite responses varied through time, especially with the escape method; with the avoidance behavior becoming more variable and overall non-significant with longer test durations. This is the first study investigating the escape test simultaneously with long-term avoidance of cadmium by O. nitens. This mite species is a promising species for avoidance testing in soil ecotoxicology, but more experiments are needed to evaluate the factors that influence its responses in laboratory tests and the consequences for its distribution in contaminated ecosystems.

. In vitro propagation of the new orchid Dendrobium trankimianum T. Yukawa

Dendrobium trankimianum T. Yukawa is a beautiful, endemic orchid of Vietnam, a new species with a first - published description in 2004. It is very rare and expected to be added to the IUCN Red List status - CR. In vitro studies of orchid D. trankimianum T. Yukawa were conducted in order to conserve and increase the genetic pool of this precious wild orchid species. The results showed that full-strength MS medium supplemented with 2.0 mg/L BA and 0.5 mg/L NAA (10.24 PLBs/explant; 90.11% explants formed PLBs) or full-strength MS medium supplemented with 1.5 mg/L TDZ and 0.5 mg/L NAA (14.11 PLBs/explant; 92.06% explants formed PLBs) were the most suitable for protocorm formation. For subculture, suitable growth of shoots were obtained on full-strength MS medium supplemented 1.5 mg/L BA (22.35 shoots/explant; shoots length of 1.96 cm) and full-strength MS medium supplemented with 60 g ripe banana per liter (25.11 shoots/explant; shoots length of 2.12 cm). The shoots in vitro were transferred to half-strength MS supplemented with different concentrations of IAA, IBA and NAA to investigate root formation. The best rooting occurred at 0,5 mg/L NAA (7.91 roots/shoot; root length of 4.01 cm; 98.51% root formation). The plantlets with uniform growth were planted on different substrate: Eco clean soil, Coconut fiber, Fern fiber, 50% Rice husk in combination with 50% Eco clean soil for research the most suitable substrate. After 60 days of transplantion and acclimatization, the result showed that Fern fiber was suitable substrate for plantlet growth in a nursery garden (8.0 roots/ explant; root length of 5.5 cm; survival rate of 93.29%).

Masthead: Clean Soil Air Water. 7–8/2020

Masthead: Clean Soil Air Water. 7–8/2020

Cover Picture: Clean Soil Air Water. 7–8/2020

Cover Picture: Clean Soil Air Water. 7–8/2020

Characterization and Partitioning Behavior of Creosote in Different Matrices: Soil, Water, and Air

Creosote is a multicomponent oil classified as a dense non-aqueous phase liquid (DNAPL) produced from coal tar distillation. The concept of phase distribution is critical in decision-making to remediate contaminated sites. The creosote mass transfer between sorbed, aqueous, vapor, and DNAPL phases is controlled by physicochemical characteristics, geology of the site, and environment conditions. This study evaluated phase distribution of the main polycyclic aromatic hydrocarbons (PAHs) of creosote in a sandy soil with low organic matter content. The creosote was collected from a contaminated site in Sao Paulo, Brazil, and was characterized by gas chromatography–mass spectrometry (GC-MS). Clean soil was collected upgradient from the same area. Initially, the soil was artificially contaminated with creosote. After, the contaminated soil was put in contact with clean water in sealed vials for 72 h. Samples of the soil, vapor, and liquid phases were collected and analyzed by GC-MS. In total, 50 compounds were identified in the creosote, and 9 PAHs were selected to be studied, which represented around 30% of total creosote mass. The major contaminant concentration was detected in the sorbed phase. For instance, naphthalene mass was distributed in sorbed (33.0%), DNAPL (1.5%), aqueous (3.4%), and vapor (0.2%) phases. The results provided an understanding of the contaminant species partitioning that occurs in a real contaminated site.

Impact of Silica Fume on the Strength Characterizes of Contaminated Soil

In this paper a silica fume (SF) utilized as an admixture for improving the strength characterizes of contaminated soil and create new useful soils. Compaction test and direct shear test are used to evaluate the strength properties of clean and contaminated soil. Mixing SF with contaminated soil by crude oil is a rare study carried out. The strength characterizes of clean and polluted soil with crude oil was investigated. Three amount of light crude oil is combined with soils artificially in the percentage of 3%, 6%, and 9% by dry weight. However, three portions of SFs are used in the experimental work, which are 0%, 12%, and 18%. In the compaction test, results show that optimum moisture content (OMC) decreases with increasing degree of contamination, inversely while adding SF, OMC is increased. Maximum dry density dramatically decreased with an increasing amount of SF and crude oil. The shear strength properties enhance by utilizing SF where observed that the cohesion in clean soil is increased from 25.3 to 40.3 kPa and in contaminated soil by 9% crude oil is raised from 12.3 to 18.6 kPa so that SF can be rate as a successful material to enhance the soil properties.

Modelling the cleaning of viscoplastic layers by impinging coherent turbulent water jets

Impinging liquid jets are widely used to clean unwanted soil layers from the walls of structures and vessels. When the soil is a thin layer of an immiscible viscoplastic material, removal involves the growth of a cleared area (which is circular for a jet impinging normally) bounded by a berm of displaced material. Glover et al. [1] presented a semi-empirical model relating the rate of removal to the momentum flow rate in the liquid film. We present a first-order model for cleaning thin layers of these materials based on the rate of viscous dissipation in a shallow wedge of material at the cleaning front. This yields a result of the form of the model in [1], with expressions linking the kinetic parameters to measurable quantities including the rheology of the soil. The fully coupled problem is not solved: the wedge angle and residual layer thickness need to be specified and were obtained here by fitting to the data. The model is compared with experimental results obtained for three soft solids – two petroleum jellies and a soft paraffin – which exhibited Bingham plastic behaviour and creep, for jet Reynolds numbers between 10,000-37,000, and 0.1<h¯/δo<1.5, where h¯ is the average film depth and δo the layer thickness. The data show reasonable agreement with the model.

An Emerging Frontier: Metal(loid) Soil Pollution Threat Under Global Climate Change.

An Emerging Frontier: Metal(loid) Soil Pollution Threat Under Global Climate Change.

PECULIARITIES OF HEAVY METAL ACCUMULATION IN SOILS IN URBANIZED LANDSCAPES OF BROVARY TOWN

The regularities of heavy metals distribution in technogenically polluted soils of urbanized territories on the example of the town of Brovary of Kyiv region were analyzed. Physical and chemical properties of conditionally clean and technogenically polluted soils were determined. Regularities of the geochemical distribution of heavy metals in the soil cover of the town under the influence of industrial enterprises were studied. Due to the influence of the Brovary enterprises, heavy metals content is significantly increased in comparison with conditionally clean soils. Using geochemical criteria the technogenic associations of heavy metals in soils were determined. Technogenic associations of heavy metals in soils are represented by the following elements: copper > plumbum > zinc > cobalt > chrome > vanadium > molybdenum > manganese > nickel. The total content level of chemical elements compounds in soils of different zones of the town is heterogeneous. The maximum of the man-caused load was recorded in urban areas of the transport infrastructure zone and the zone of production and communal-warehouse facilities. Copper and plumbum are the main pollutants according to the indices of heavy metals content in soils of anthropogenic zones of the city. Mobile forms of zinc and nickel are the most dangerous soil pollutants at all functional zones of the Brovary. The ecological and geochemical estimation of the total pollution index using Yu.Ye. Saet methodology is performed. The value of this indicator of the soil surface layer in Brovary town (0-10 cm) ranges from 30 to 106, the average value is 65, which corresponds to the dangerous level of contamination of the soil cover. The zones of transport infrastructure and the zones of production and communal-warehouse facilities have high levels of pollution, and the permissible pollution level dominates in the residential zone. According to the concentration ratio of technogenic pollution, the Brovary town belongs to the dangerous category of soil pollution. The investigated soils of the town are characterized by lead geochemical specialization. High levels of zinc, manganese, cobalt and chromium were established. The main factors that influence the concentration levels and heavy metals migration in the town soils were analysed. The dependence of heavy metals content and industrial production objects (factors of anthropogenic load on the natural components of the urban environment) in Brovary was established.

An investigation into whether effect of tree species on soil microbial community is related with deciduous property or leaf shape

This study was performed to investigate whether visible properties of trees species (leaf shape and deciduous property) exhibit strong effects on soil microbial community (SMC). Herein, forest soil and leaves were collected from six pure planted forests of City Forestry Demonstration Base at Harbin, northeast China. These forest stands included Pinus tabuliformis Carr. var. mukdensis Uyeki, P. sylvestris L. var. mongolica Litv, Larix gmelinii (Rupr.) Kuzen, Betula platyphylla Suk, Quercus mongolica Fisch. ex Ledeb, and Fraxinus mandschurica Rupr. The clean soil samples combined with the leaves were incubated in vitro to simulate the degradation of leaves. Analysis of soil fungal microbial community (SFC) and soil bacterial community (SBC) structures by soil fungal internal transcribed spacer (ITS) and bacterial 16S ribosomal RNA gene sequencing resulted that tree species could shape the microbial relative abundance, dominant microbial operational taxonomic unit (OTU), and even SMC structure. Further, analysis on SMCs was performed to test our hypothesis that SFC and SBC structures were correlated with leaf shape (needle or broad) and deciduous property (evergreen or deciduous). Our findings accepted the partial hypothesis that dominant fungal OTUs were sensitive to leaf shape and deciduous property, but could not alter the SFC structure (p > 0.05). A dominant bacterial OTU and not significantly different SBC structure was shared by the leaf shape groups (r = 0.1694, p = 0.0250); while deciduous property determined the dominant bacterial OTU and SBC structure (r = 0.4743, p = 0.0030). The present study provides an insight into the effects of visible properties of tree species on SMC structures.

Preliminary study on Cd accumulation characteristics in Sansevieria trifasciata Prain

Phytoremediation techniques to clean heavy metal pollution soil depend on identifying plant species that can act as phytoremediators. One important approach to screening potential phytoremediators is to evaluate characteristics of heavy metal accumulation. In this study, we performed firsthand analysis of Cd tolerance and accumulation characteristics of three Sansevieria trifasciata cultivars by pot experiment. Plant growth results showed that all three S. trifasciata cultivars can tolerate 50 mg kg−1 soil Cd concentration. After growth under 50 mg kg−1 soil Cd concentration for 4 months, the Cd bioconcentration factors in the shoots of S. ‘Trifasciata’, S. trifasciata ‘Laurentii’, and S. trifasciata ‘Silver Hahnii’ were 1.26, 1.30, and 1.19, while those in the roots were 12.53, 11.43, and 5.45, respectively. This result reveals the considerably low translocation factors of 0.10, 0.12, and 0.22 for S. ‘Trifasciata’, S. trifasciata ‘Laurentii’, and S. trifasciata ‘Silver Hahnii’, respectively. These results suggest that all three S. trifasciata cultivars had high Cd absorption capacities but low Cd translocation capacities. In combination with total Cd accumulation distribution and plant growth characteristics, S. trifasciata can be designed as a phytostabilizer in Cd-contaminated soils in its cultivation regions. Meanwhile, the mechanism of high Cd tolerance and accumulation characteristics in the roots of S. trifasciata should be explored. This study provides new resources for dealing with Cd-contaminated soils and exploring Cd tolerance and accumulation mechanisms in plants.

Masthead: Clean Soil Air Water. 5–6/2020

Masthead: Clean Soil Air Water. 5–6/2020

Cover Picture: Clean Soil Air Water. 5–6/2020

Cover Picture: Clean Soil Air Water. 5–6/2020

Bioremediation of PAH-Contaminated Soils: Process Enhancement through Composting/Compost

Bioremediation of contaminated soils has gained increasing interest in recent years as a low-cost and environmentally friendly technology to clean soils polluted with anthropogenic contaminants. However, some organic pollutants in soil have a low biodegradability or are not bioavailable, which hampers the use of bioremediation for their removal. This is the case of polycyclic aromatic hydrocarbons (PAHs), which normally are stable and hydrophobic chemical structures. In this review, several approaches for the decontamination of PAH-polluted soil are presented and discussed in detail. The use of compost as biostimulation- and bioaugmentation-coupled technologies are described in detail, and some parameters, such as the stability of compost, deserve special attention to obtain better results. Composting as an ex situ technology, with the use of some specific products like surfactants, is also discussed. In summary, the use of compost and composting are promising technologies (in all the approaches presented) for the bioremediation of PAH-contaminated soils.

Remediation of hexavalent chromium in contaminated soil using amorphous iron pyrite: Effect on leachability, bioaccessibility, phytotoxicity and long-term stability

A large amounts of arable land is facing a high risk of hexavalent chromium (Cr(VI)) pollution, which requires remediation using a low toxic agent. In this study, the remediation effect of amorphous iron pyrite (FeS2(am)) on Cr(VI) in Cr(VI)-contaminated soil was evaluated by systematically analyzing the variation of the leachability, bioaccessibility, phytotoxicity, and long-term stability of the remediated soil. The effectiveness of FeS2(am) on the leachability was assessed by alkaline digestion and the toxicity characteristic leaching procedure (TCLP); the effect on the bioaccessibility was evaluated via the physiologically based extraction test (PBET) and the Tessier sequential extraction; the effect on the phytotoxicity was assessed via phytotoxicity bioassay (seed germination experiments) based on rape (Brassica napus L.) and cucumber (Cucumis Sativus L.), and the long-term stability of the Cr(VI)-remediated soil was appraised using column tests with groundwater and acid rain as the influents. The results show that FeS2(am), with a stoichiometry of 4× exhibited a high efficiency in the remediation of Cr(VI) and decreased its leachability and bioaccessibility during the 30-day remediation period. In addition, seed germination rate, accumulation and translocation of Cr, and root and shoot elongation of rape and cucumber of remediated soil are not significantly different from those of clean soil, illustrating that FeS2(am) is suitable for remediating Cr(VI) contaminated arable soil. The stabilization of Cr(VI) in contaminated soil using FeS2(am) was maintained for 1575 days. The long-term effectiveness was further confirmed by the increasing amount of free Fe and Mn in the effluent and the decreasing redox potential. In summary, FeS2(am) has an excellent efficiency for the remediation of Cr(VI), demonstrating it is a very promising alternative for use in the contaminated arable soil.

Evaluation of the Biotechnological Potential of New Bacterial Strains Capable of Phenol Degradation

A number of bacteria, including rhizospheric bacteria, capable of transforming aliphatic and aromatic compounds to varying degrees were isolated from clean soils and soils contaminated with polycyclic aromatic hydrocarbons. Seven bacteria capable of decomposing phenol at a concentration of at least 500 mg/L were selected. Identification by the 16S rRNA gene showed that they belong to the genera Rhodococcus, Pseudomonas, Stenotrophomonas, Lysinibacillus, and Isoptericola. Determination of the activity of phenol destruction enzymes in these cultures showed the absence of a meta-pathway of catechol cleavage during phenol degradation. The activity of catechol 1,2-dioxygenase and protocatechuate 3,4-dioxygenase was detected in cell-free extracts. The activity of the latter enzyme was 15 times higher than the catechol 1,2‑dioxygenase, that was described for the first time for members of the genus Isoptericola. Strains isolated from the rhizosphere of plants growing in contaminated soil were capable of destroying up to 15 individual pollutants, such as aliphatic hydrocarbons, chlorophenols, 2,4,5-trichlorophenoxyacetic acid, and caprolactam. The presence of enzymes, such as β-galactosidase and lysine-decarboxylase, was shown with the use of biochemical test systems for representatives of the genera Stenotrophomonas and Isoptericola. The isolated bacteria can be used both to create biopreparations for bioremediation and to create producer strains for the target enzymes.

Multigenerational Exposure to WCCo Nanomaterials-Epigenetics in the Soil Invertebrate Enchytraeus crypticus.

It has become clear how important it is to assess longer term effects of (nano) materials in the environment given the current evidence showing how epigenetics drives response mechanisms. Here we studied global DNA methylation in standard soil invertebrate Enchytraeus crypticus over 224 days when exposed to nanostructured tungsten carbide cobalt (WCCo nanomaterials (NMs)) and to cobalt (CoCl2) in a multigenerational experiment. In order to assess the transgenerational effect, we used a multigenerational (MG) test design consisting of four generations in spiked soil followed by two generations in clean soil. Results showed that MG exposure to WCCo NMs caused global DNA methylation to increase, which continued in unexposed generations and was associated with an increase in reproduction (phenotypic effect). In general, WCCo NMs caused more (and more consistent) methylation than CoCl2.

Effects of sewage sludge supplementation on heavy metal accumulation and the expression of ABC transporters in Sinapis alba L. during assisted phytoremediation of contaminated sites.

ATP binding cassette (ABC) transporters, types C, G, and B were monitored via qPCR in order to investigate the influence of heavy metal (HM) contamination of post-industrial and post-agricultural soils and the effects of its supplementation with sewage sludge, on Sinapis alba plants. Five house-keeping genes were selected and validated to ensure the best reference points. The relative expression of ABC types C and G genes was profoundly affected by experimental conditions and included their upregulation after plants exposure to heavy metals and downregulation after supplementation with sewage sludge. However, ABC type C was more responsive then type G. The experimental conditions altered the expression of ABC type C gene faster than ABC type G and thus, the expression of ABC type C can therefore potentially be used as a bioindicator during assisted phytoremediation of degraded sites. In clean soil, supplementation with sewage sludge with a slight content of heavy metals still caused an upregulation in the expression of ABC types C and G, which showed that proper toxicity assessments are necessary to ensure safe application of sewage sludge into soils. Results showed that the analysed genes take a significant part in plants metal detoxification and that their expression is regulated at transcriptional level after exposure to soil contaminated with heavy metals by both, industrial activities and by sewage sludge supplementation. Thus, their expression can potentially be used as an early-warning biomarker when soil supplementation with sewage sludge is incorporated into the soil-management process.

Cover Picture: Clean Soil Air Water. 4/2020

Cover Picture: Clean Soil Air Water. 4/2020

Masthead: Clean Soil Air Water. 4/2020

Masthead: Clean Soil Air Water. 4/2020