Unpolluted Soil Research Articles

Zn concentration decline and apical endpoints recovery of earthworms (E. andrei) after removal from an acidic soil spiked with coated ZnO nanoparticles

ZnO nanoparticles (ZnO-NPs) can reach soil in both deliberate and non-deliberate ways, which leads to contamination. Notwithstanding knowledge about ZnO-NPs impacts on earthworms inhabiting these soils is limited and gaps appear in the recovery of damaged functions after their migration to unpolluted environments. To estimate these impacts, earthworms (Eisenia andrei) were exposed to different concentrations of coated ZnO-NPs (20, 250, 500, 1000 mgZnkg−1) in an acidic agricultural soil (pH 5.4) for 28 days. Subsequently, earthworms were placed in the same unpolluted soil to study the depletion of Zn accumulated and the recovery potential of the affected functions for another 28-day period.In the exposure phase, ecotoxicological responses were dose-dependent. Mortality and growth were affected at 500 and 1000 mg kg− 1, and the reproduction was impaired from 250 mgZnkg− 1 compared to control (54% fecundity and 80% fertility reduction). Zn uptake increased with coated ZnO-NPs in soil but it did not exceed 163 mgZnkg− 1 earthworm. During the recovery period, the Zn in earthworms were similar to the control regardless of the initially Zn accumulated. Reproduction parameters returned to the control values in the animals pre-exposed to 250 mgZnkg− 1 as coated ZnO-NP. In the earthworms preexposed to the two highest doses, growth and fertility were stimulated compared to the control when placed in clean soil, but not fecundity. However, the total hatchlings number did not reach the control figures after 28 days, but probably would for in longer times, which would be key for maintaining earthworm populations.

Response of bacterial and fungal communities to high petroleum pollution in different soils

Petroleum pollution of soils is a major environmental problem. Soil microorganisms can decompose a significant fraction of petroleum hydrocarbons in soil at low concentrations (1–5%). This characteristic can be used for soil remediation after oil pollution. Microbial community dynamics and functions are well studied in cases of moderate petroleum pollution, while cases with heavy soil pollution have received much less attention. We studied bacterial and fungal successions in three different soils with high petroleum contents (6 and 25%) in a laboratory experiment. The proportion of aliphatic and aromatic compounds decreased by 4–7% in samples with 6% pollution after 120 days of incubation but remained unchanged in samples with 25% hydrocarbons. The composition of the microbial community changed significantly in all cases. Oil pollution led to an increase in the relative abundance of bacteria such as Actinobacteria and the candidate TM7 phylum (Saccaribacteria) and to a decrease in that of Bacteroidetes. The gene abundance (number of OTUs) of oil-degrading bacteria (Rhodococcus sp., candidate class TM7-3 representative) became dominant in all soil samples, irrespective of the petroleum pollution level and soil type. The fungal communities in unpolluted soil samples differed more significantly than the bacterial communities. Nonmetric multidimensional scaling revealed that in the polluted soil, successions of fungal communities differed between soils, in contrast to bacterial communities. However, these successions showed similar trends: fungi capable of lignin and cellulose decomposition, e.g., from the genera Fusarium and Mortierella, were dominant during the incubation period.

A fluorescent tool for sensing the battery-pollution event in soil samples based on Zn2+-triggering ratiometric signals

The leakage of hazardous substances from batteries leads amount of pollution events for their high toxicity and universal use all over the world. Herein, a fluorescent sensor based on triphenylamine (TPAI) was designed to monitor the battery pollution in the real soil examples. Because Zn2+composes a large part of primary and secondary batteries, TPAI was constructed for high affinity of Zn2+ within an efficient intramolecular charge transfer process that could output an obvious green-to-red (510–600 nm) signal to avoid interference from the background substances. In this way, TPAI showed a low detection limit (4.16 × 10−9 M) and high binding constants towards Zn2+ (2.82 × 1012 M−1). Moreover, TPAI exhibited excellent selectivity for Zn2+ over other metal ions and several common compounds in soil. The sensing mechanism indicated that the selectivity might need to be further optimized through adjusting the bulk of donor segment of TPAI. Then, TPAI was used to discriminate the polluted and unpolluted soil samples through a feasible on-line detection proposal under the self-made mobile platform. Combining with the fluorescent sensors and our mobile platform, we believe this work can provide a practical tool for monitoring the pollution events in diverse environmental examples.

Percentage Bioremediation Assessment of Spent Mushroom Substrate (SMS) and Mucor racemosus in Hydrocarbon Contaminated Soil

Aim: The aim of the study was to assess Percentage Bioremediation of Spent Mushroom Substrate (SMS) and Mucor racemosus in hydrocarbon contaminated soil
 Place and Duration of Study: A portion of Rivers State University demonstration farmland in Nkpolu-Oroworukwo, Mile 3 Diobu area of Port Harcourt, Rivers State was used for this study. The piece of land is situated at Longitude 4°48’18.50’’N and Latitude 6o58’39.12’’E measuring 5.4864 m x 5.1816 m with a total area of 28.4283 m2. Bioremediation monitoring lasted for 56 days, analysis carried out weekly (per 7 days’ interval).
 Methodology: Five (5) experimental plots employing the Randomized Block Design were used each having dimensions of 100 x 50 x 30 cm (Length x Breadth x Height) = 150,000cm3. Baseline study of the uncontaminated and the deliberately contaminated agricultural soil was investigated for its microbiota and physico-chemical properties. Two of these plots were designated as pristine (Unpolluted soil) (CTRL 1) and crude oil contaminated soil without nutrient organics and bioaugmenting microbes (CTRL 2); these two serve as controls. Each of the experimental plots, except the control (CTRL 1), was contaminated with 2500 cm3 (2122.25 g) of crude oil giving initial Total Petroleum Hydrocarbon (TPH) value of 8729.00 mg/kg. The crude oil polluted soil in Plot 3 was further treated with 750 ml of Mucor racemosus broth (CS+Muc), Plot 4 was treated with 3000 g of Spent Mushroom Substrate (CS+SMS) while plot 5 was treated with the combination of both (CS+Muc+SMS). The plots were left for 7 days to ensure even distribution and soil-oil bonding. Sampling was done at seven-day interval (Day 1, 7, 14, 21, 28, 35, 42, 49, 56). Physicochemical parameters monitored were pH, Temperature, Nitrogen, Phosphorus, Potassium, and Total Petroleum Hydrocarbon (TPH) throughout the experimental period. Microbial parameters monitored were Total Heterotrophic Bacteria (THB), Total Heterotrophic Fungi (THF), Hydrocarbon Utilizing Bacteria (HUB) and Hydrocarbon Utilizing Fungi (HUF). Percentage (%) Bioremediation was estimated from percentage (%) reduction of Total Petroleum Hydrocarbon (TPH) from day 1 to day 56 in relation to control plots. Net % Bioremediation were also assessed to ascertain the actual potential of treatment agents singly or combined.
 Results: Total Heterotrophic Bacteria (THB) (CFU/g) recorded on day 7 and day 56 of the bioremediation were; day 7; CTRL 1 – US (1.07 x109), CTRL- CS (5.4 x108), CS+Muc (3.0 x108), CS+SMS (4.6 x108) and CS+Muc+SMS (5.0 x108). On day 56, data obtained were CTRL 1 –US (9.4 x108), CTRL 2 –CS (7.2 x109), CS+Muc (3.7 x108), CS+SMS (8.1x108) and CS+Muc+SMS (6.8 x108). The increase in number in the treated plots is a depiction of an increase in activity of the organism and the stimulating effect of bio-organics SMS while the untreated plot CTRL 1-US showed decrease in population at day 56. Similar trend showed for Total Heterotrophic Fungi. Generally, it was observed that the highest growth/ count was recorded at the 7th and 8th week (day 42 or day 49), at the 9th week there was an observable decrease; probably due to depletion of nutrients and other factors such as rainfall and seepage. The Net Percentage Hydrocarbon Utilizing Bacteria and Fungi (Net %HUB and Net %HUF) were highest in Crude Oil contaminated plot treated with Spent Mushroom Substrate (SMS) singly; that is (CS+SMS) (11.02% and 12.07%) and lowest in the uncontaminated soil – Control (CTRL 1 –US) (5.41% and 9.26%) respectively. The trend in decreasing order of Net % Hydrocarbon Utilizing Bacteria were as follows: CS+SMS (11.02%) > CS+Muc+SMS (10.14%) > CS+Muc (9.43%) > CTRL 2 –CS (8.1%) > CTRL 1 –US (5.41%) while Net % Hydrocarbon Utilizing Fungi followed similar trend and were: CS+SMS (12.07%) > CS+Muc+SMS (11.76%) = CS+Muc (11.76%) > CTRL 2 –CS (11.05%) > CTRL 1 –US (9.26%). Evaluation of Amount of Crude Oil or Hydrocarbon remediated and Net %Bioremediation revealed Crude Oil contaminated plot augmented with Mucor racemosus broth singly (CS+Muc) as having the highest bioremediation potential while the least is the untreated soil. The trend is as follows: CS+Muc (8599.19 mg/kg; 33.93%) > CS+Muc+SMS (8298.95 mg/kg; 32.74%) > CS+SMS (8197.03 mg/kg; 32.34%) > CTRL 2 –CS (166.54 mg/kg; 0.66%) > CTRL 1 –US (85.48 mg/kg; 0.34%)
 Conclusion: This shows that a single nutrient substrate or augmenting microorganism applied appropriately may have a more positive result, that is; higher bioremediation potential than combined or multiple mixed treatments. It was further observed that microbial counts decreased with time in treatments with augmenting organisms alone but increased considerably in treatments supplement with organics having its peak on the 49th day. It is therefore recommended that bioremediation of crude oil-polluted soil using bio-augmenting microorganism should be applied appropriately noting the volume: area ratio and be supplemented with efficient nutrient organics after every 49-day interval.

ECOLOGICAL RISK ASSESSMENT AND POLLUTION LOAD OF HEAVY METALS IN SOILS WITHIN BORI URBAN, RIVERS STATE, NIGERIA.

The study assessed the ecological risk and polluting load of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in surface soils within Bori Urban. The composite soil samples collected from different locations were prepared and atomic absorption spectrophotometer (AAS) was used for the analysis of the heavy metals. From the results of the analysis, the mean concentrations (mg/kg) of the heavy metals decreased in the order Cu (37.42) > Ni (34.06) > Cr (28.66) > Zn (7.75) >Pb (2.03) > Cd (0.89). The mean concentrations of Cd, Cu, and Ni were above USEPA soil guidelines and world unpolluted soil average, while those of Pb and Zn were below. The mean concentrations of the heavy metals from the study locations were all above that of the control location. The findings indicated that the urban soils of the study were loaded with heavy metals due to anthropogenic activities. The anthropogenic percentage input was in the range of 63.92 - 89.13 above 50% indicating anthropogenic origin of the heavy metals in soils of the study area. The results of ecological risk index (Er) indicated that Cd with Er (467.40) contributed up to 94.51% to the potential ecological risk index (RI) while Zn (0.78) contributed 0.16%. The heavy metals under study posed highly strongly potential ecological risk with RI value of 494.56 to the Bori urban soil due to anthropogenic activities. The ANOVA result of FCal 6.42 > [F(5.30) = 2.53, P< 0.05)] revealed significant differences between the soil sample mean values due to different anthropogenic pollution sources with different loads of heavy metals as pollutants. The Omega Squared (w2) value of 0.52 > 0.14 showed very strong interactive relationship among the heavy metals to bring about high level of ecological potential risk of the urban soils in the study area. Based on the findings, the surface soils have elevated load of heavy metals thereby posing ecological potential risk to Bori urban soils. Therefore, there should be periodic monitoring and environmental audit by relevant authorities to ensure good soil quality of Bori urban soil. Keywords: Potential ecological risk, pollution load, Bori Urban, Anthropogenic Percentage input, contamination Factor.

Changes in soil chemistry and element uptake by Oak seedlings after application of soil amendment

ABSTRACT The purpose of this study is to investigate the effect of cellulosic wastes and nanoscale zero-valent iron (nZVI) on the soil properties and the nutrient uptake by Quercus castaneifolia C.A.Mey seedlings. The seedlings were planted in pots (unpolluted soil) and cadmium (Cd) was added to the pots in three concentrations (10, 20, 30 mg.kg−1). Cellulosic wastes were mixed with the soil (at the same time as the planting) in four levels (W: 0, 10, 20, 30 g.100g−1 soil). The reduction method was used to prepare nZVI, then the nanoparticles were injected into the polluted pots in four levels (N: 0, 1, 2, and 3 mg.kg−1). The lowest concentration of Cd in leaves, stems and roots and for all the contamination levels was observed in N3. All the cellulosic wastes and N3 significantly increased the soil pH at all the levels of contamination. An increasing trend of the soil carbon (C) content was observed by adding the cellulosic wastes. The highest pH and C content were observed in W3. The lowest bioavailable Cd contents for all the contamination levels was observed in N3. According to the results, nZVI and cellulosic wastes could help the plants establishing in heavy metal-polluted lands.

POLLUTION POTENTIAL AND CHEMICAL INTERACTION OF SOME PHYSICOCHEMICAL PARAMETERS OF SOIL CONTAMINATED WITH E-WASTE

The rapid increase in the amount of electronic waste in our environment is of great concern. This study investigated the contamination level, pollution potential and chemical interaction of cation exchange capacity (CEC), total nitrogen (TN), total phosphorus (TP), electrical conductivity (EC), total organic carbon (TOC), total organic matter (TOM) and pH, on soil contaminated with electronic waste and background soil (unpolluted soil). It was found that CEC has the highest pollution values, which range from 194,616.00(10-20 cm)- 221,024.760 mg/kg (0-10 cm) for the polluted soil, which show a remarkable variation from the background soil. The TN value range from 139.257 -185.654 mg/kg across depths. The values of EC on polluted soil ranged from 0.260 – 0.746 mg/kg across depths. While that of TOC and TOM, ranged from 4,250.00 – 5,800.000 mg/kg and 8,300.000 – 10,000.000 mg/kg across depths, the values of pH for the polluted soil also ranged from 6.2 – 7.1 across depths. The pollution potential also showed high values across depths, the TOM, which ranged from 48.473 – 61.450 and TOC are almost of the same ranged with the TOM. The TN and TP were very low and the EC exerted negative pollution potential in all the depths. The chemical interaction showed high values in TN which ranged from 12,776.708 - 9,419.512 across depths, followed by TP and CEC which also display high values, but lower than that of TN. The EC values were low, which ranged from 1.620 – 5.984 across depths. The TOC and TOM were very low when compared to the rest parameter in the chemical interaction. The high values obtained in some of the parameters compared with the standard values, call for need for strict monitoring of the disposal of e-waste in our environment.

Tolerance of Some Soil Fungi to the Content of Deep Cycle Battery and Their Bioremediation Potential

Aims: The purpose of this study was to isolate and screen soil fungi that are able to tolerate the contents of spent deep cycle battery (inverter), and to test for their bioremediation potential.
 Place and Duration of Study: Sample: Department of Microbiology, Rivers State University, between June 2019 and February 2020.
 Methodology: Soil samples were collected from a mechanic village while spent inverter batteries were obtained from a waste vendor. The battery was forced open to extract its contents of the battery. Using standard microbiological techniques, fungi were enumerated and characterized. Stock solution of the battery content was prepared by dissolving the inverter battery content in sterile deionized water. This stock solution was used to carry out the screening test on the fungal isolates to ascertain the fungi that can tolerate the contents of the spent battery.
 Results: Total heterotrophic fungal counts for the polluted and unpolluted soil were 6.0 x 103 cfu/g and 7.5 x 104cfu/g respectively. The fungal isolates identified from the polluted soil samples were members of the genera Rhizopus, Mucor, Aspergillus, Penicillium, and Candida, while, the isolates identified from the unpolluted soil sample includes: Candida sp, Aspergillus niger, Penicillium sp, Aspergillus fumigatus, Aspergillus flavus, Mucor sp, Yeast, Fusarium sp and Aspergillus sp. After the screening, total heterotrophic fungal counts for the soil ranged from 1.0 x 102cfu/g to 9.5 x 102cfu/g. Two fungi of the genera: Rhizopus and Mucor had the highest counts during 72 hours of incubation for the screening test. The results obtained from this study indicated that species of Aspergillus, Penicillium, and Candida were the most inhibited by the contents of the spent battery while Rhizopus and Mucor spp were more tolerant to the contents of the inverter. Rhizopus and Mucor spp were therefore, adopted in the bioremediation of soil contaminated with contents from the battery. It was observed that Rhizopus and Mucor spp in a consortium had the highest percentage of heavy metal removal (or uptake) in the following order: Cadmium (66.66%) > Lead (38.15%) > Zinc (26.83%) > Nickel (20.83).
 Conclusion: These organisms can be used in the bioremediation of soil polluted with metals from spent deep cycle batteries.

Influence of agricultural amendments on arsenic biogeochemistry and phytotoxicity in a soil polluted by the destruction of arsenic-containing shells

Agricultural soils can contain high arsenic (As) concentrations due to specific geological contexts or pollution. Fertilizer amendments could influence As speciation and mobility thus increasing its transfer to crops and its toxicity. In the present study, field-relevant amounts of fertilizers were applied to soils from a cultivated field that was a former ammunition-burning site. Potassium phosphate (KP), ammonium sulfate and organic matter (OM) were applied to these soils in laboratory experiments to assess their impact on As leaching, bioavailability to Lactuca sativa and microbial parameters. None of the fertilizers markedly influenced As speciation and mobility, although trends showed an increase of mobility with KP and a decrease of mobility with ammonium sulfate. Moreover, KP induced a small increase of As in Lactuca sativa, and the polluted soil amended with ammonium sulfate was significantly less phytotoxic than the un-amended soil. Most probable numbers of AsIII-oxidizing microbes and AsIII-oxidizing activity were strongly linked to As levels in water and soils. Ammonium sulfate negatively affected AsIII-oxidizing activity in the un-polluted soil. Whereas no significant effect on As speciation in water could be detected, amendments may have an impact in the long term.

Assessment of earthworm diversity and pesticide toxicity in Eudrilus Eugeniae

Pesticides have become an inseparable part of modern agricultural production and technology. Malathion pesticide more than 139,000 MT production capacity annually, with more than 219 technical grade and manufacturing units, and over 4000 formulation units in India. The earthworm survey was carried out in all the five sites at regular monthly intervals. In this present work, a total of six earthworms from five different species were collected from different vegetation such as garden, pond, paddy, edible tubers, and sugarcane field. The organophosphate pesticide malathion is selected as a target compound for toxicity study. The earthworm species Eudrilus eugeniae was used as a model organism. Contact toxicity was studied by filter paper method and to observe the mortality rate of different concentrations of pesticide for 24 and 48 h. The soil toxicity study was done by using artificial soil for 14 days. Surviving worms also had reduced body weight, and in some cases, morphological changes. Enzymatic activities of SOD, CAT, and protease were evaluated in the vermicast of pesticide-treated earthworm. This study refers to the earthworm population between pesticide-contaminated and unpolluted soil. This work will provide information to estimate the toxic level of Malathion against the earthworm.

The influence of environmental condition on the creation of organic compounds in Pinus sylvestris L. rhizosphere, roots and needles

Key messageStudied organic molecules in Pinus sylvestris L. seem to have acted as a safety net for metal transport, chelation and sequestration, allowing adaptation and growth under highly polluted conditions.Pinus sylvestris L. is known for its ability to survive in areas of highly elevated metal pollution, such as flotation tailings. The aim of the study was to estimate the content of selected organic molecules (including aliphatic low molecular weight organic acids (ALMWOAs), phenolic compounds and terpenes) and the physiological mechanisms underlying differences in metal/metalloid tolerance of P. sylvestris growing in unpolluted (soil) and polluted (flotation tailings) areas. The dominant ALMWOAs in rhizosphere soil extracts were citric acid followed by malic and oxalic acids, whereas in flotation tailings malic and oxalic acids. In roots and needles, the content of ALMOWAs was significantly higher in P. sylvestris L. tissue from flotation tailings in comparison to soil. Phenolic compounds were detected only in roots and needles, with a generally higher content of nearly all detected compounds from flotation tailings. The composition of roots did not contain all the compounds detected in needles. The profile of needles additionally contained four hydroxybenzoic, protocatechuic and salicylic acids. In pine needles, 24 volatile terpenes were identified in total. The content of these compounds in pine needles from the polluted area was markedly different from the unpolluted area. The dominant volatile monoterpenes in P. sylvestris L. needles from the unpolluted area was three carene, while in pine needles from the polluted area monoterpenes α-pinene was dominant.

BIO STIMULATORY INFLUENCE OF COMPOST AND INORGANIC FERTILIZER ON BACTERIAL DEGRADATION OF SPENT ENGINE OIL CONTAMINATED SOIL

The harmful effects of spent engine oil on aquatic and terrestrial ecosystems have been well established in literature. This study was conducted to assess the bio stimulatory influence of amendments; compost and inorganic fertilizer on bacterial degradation of spent engine oil contaminated soil. 500 g of unpolluted soil was collected and artificially contaminated with 5, 10 and 15% (v/w) spent engine oil. The experiment was laid out in a completely randomized design. Each amendment (50 g) was subsequently mixed thoroughly with the spent engine oil contaminated soil at varying levels except nine experimental bottles used as control. Incubation study was carried out and lasted for four weeks. Estimation of total petroleum hydrocarbon, pH, electrical conductivity, temperature and bacterial population density was done within two weeks interval during the incubation study. Results obtained indicate that compost significantly enhanced total petroleum hydrocarbon reduction by 87% while inorganic fertilizer facilitated 62% total petroleum hydrocarbon reduction on 5% spent engine oil contamination level respectively. Estimation of hydrocarbon utilizing bacteria on 5, 10 and 15% spent engine oil contaminated soil indicated that compost enhanced higher hydrocarbon utilizing bacteria thereby influencing bacterial degradation than those stimulated with inorganic fertilizer. pH remained in the range of alkalinity (7.8 and 8.06) for compost and 6.2 and 6.7 for inorganic fertilizer. The potential that compost recorded in influencing bacterial degradation of spent engine oil contaminated soil in this study has made it a good bio stimulant for the bioremediation of hydrocarbon polluted environments.

Fungal heavy metal adaptation through single nucleotide polymorphisms and copy-number variation.

Human-altered environments can shape the evolution of organisms. Fungi are no exception, although little is known about how they withstand anthropogenic pollution. Here, we document adaptation in the mycorrhizal fungus Suillus luteus driven by soil heavy metal contamination. Genome scans across individuals from recently polluted and nearby unpolluted soils in Belgium revealed low divergence across isolates and no evidence of population structure based on soil type. However, we detected single nucleotide polymorphism divergence and gene copy-number variation, with different genetic combinations potentially conferring the ability to persist in contaminated soils. Variants were shared across the population but found to be under selection in isolates exposed to pollution and located across the genome, including in genes involved in metal exclusion, storage, immobilization and reactive oxygen species detoxification. Together, our results point to S. luteus undergoing the initial steps of adaptive divergence and contribute to understanding the processes underlying local adaptation under strong environmental selection.

Using X-ray microtomography to characterize the burrowing behaviour of earthworms in heterogeneously polluted soils

Large amounts of chemicals are released into soil environments due to human activities, thereby harming organisms and their habitats. Earthworms are important bioindicators for chemical risk assessments of soil ecosystems, but the question remains of how they respond to different patterns of pollution. Laboratory experiments in soil mesocosms were carried out to observe changes in the burrowing behaviour of two earthworm species (Aporrectodea caliginosa and Lumbricus terrestris) with regard to different spatial distributions of benzo(a)pyrene, cadmium and copper, using X-ray computed microtomography (μCT). This is, to our knowledge, the first contribution of μCT to study earthworm behaviour in heterogeneously multi-polluted soils. Columns (14 × 30 cm) were filled with a silt loam soil and packed to represent two scenarios of heterogeneous pollution: a) ‘binary’, containing polluted soil in the low half part and unpolluted soil on top; and b) ‘patches’, containing small portions of polluted soil randomly placed into an unpolluted matrix. Earthworms were introduced individually in the columns and left in climatic chambers for 7 weeks. μCT images revealed that earthworms avoided the polluted zones differently (e.g. A. caliginosa>L. terrestris, ‘binary’ configuration). Individuals of L. terrestris that entered polluted areas showed a lower burrowing activity (volume and length of the burrow system) than those that did not enter. The presence of ‘patches’ of polluted soil did not cause a reduction of the burrowing activity such as that found in the ‘binary’ columns, although earthworms showed avoidance. Our results indicate that pollutants had a greater effect on earthworms’ burrowing behaviour in the presence of larger portions of contaminated soil compared with small random ones. The more evident avoidance behaviour of A. caliginosa pinpoints its usefulness in toxicity bioassays based on avoidance patterns, but questions its use in assays based on bioaccumulation of pollutants in tissues, for which L. terrestris may perform better.

The recruitment of bacterial communities by the plant root system changed by acid mine drainage pollution in soils.

This study aims to better understand the relationship between the response to acid mine drainage (AMD) stress of tolerant plants and changes in root-related bacterial communities. In this study, reed stems were planted in AMD-polluted and unpolluted soils, and high-throughput sequencing was conducted to analyze the bacterial community composition in the soil, rhizosphere, rhizoplane and endosphere. The results showed that the effect of AMD pollution on root-associated bacterial communities was greater than that of rhizo-compartments. Proteobacteria were dominant across the rhizo-compartments between treatments. The microbiomes of unpolluted treatments were enriched by Alphaproteobacteria and Betaproteobacteria and depleted in Gammaproteobacteria ranging from the rhizoplane into the endosphere. However, the opposite trend was observed in the AMD pollution treatment, namely, Gammaproteobacteria were enriched, and Alphaproteobacteria and Deltaproteobacteria were mostly depleted. In addition, endophytic microbiomes were dominated by Comamonadaceae and Rhodocyclaceae in the unpolluted treatment and by Enterobacteriaceae in the AMD-polluted soils. PICRUSt showed that functional categories associated with membrane transport, metabolism and cellular processes and signaling processes were overrepresented in the endosphere of the AMD-polluted treatment. In conclusion, our study reveals significant variation in bacterial communities colonizing rhizo-compartments in two soils, indicating that plants can recruit functional bacteria to the roots in response to AMD pollution.

Behavior of Cd Accumulation in Sinapis alba L. in the Presence of Essential Elements (Ca, Mg, Fe, Zn, Mn, Cu, Ni)

Heavy metal toxicity in plants is well known due to their severe phytotoxic effects and also because of their capability to accumulate in vegetables. The use of aromatic plants in remediation techniques has increased in the context of environmental pollution issues, including metal soil contamination. Cadmium is knowed as a toxic and bio accumulative element provided by natural or anthropic sources. In this context, the paper presents a laboratory experimental study aiming to evaluate the accumulating and transfer behavior of Cd in the plant organs of Sinapis alba L. (white mustard) and in the presence of essential elements (Ca, Mg, Fe, Zn, Mn, Cu, Ni). The study involves a comparison between white mustard cultivated in unpolluted soil and in two Cd polluted soils at values above the alert (2.8 mg/Kg), respectively intervention threshold for soils with sensitive use (5.6 mg/kg) according to the legislation in force in Romania. While Cd accumulated predominantly in roots (TC values 1.46 and 2.22), its transfer to the stem and leaves was observed too, the TF values for the aerial part of the plant being greater than 1. Moreover, the study showed that certain elements (Zn, Ca, Mg, Mn) were found in higher concentrations in plants subjected to Cd pollution than in the control sample indicating antagonistic effects and Cd toxicity limiting. Other essential metals, such as Cu, Fe and Ni were found in lower concentrations in intoxicated plants compared to control plants. Their translocation from soil in plant organs could be reduced by the Cd toxicity. Contrariwise, the mobility of these elements from roots to leaves could support the tolerance effect of plants to Cd stress. The study allows us to consider that Sinapis alba L. aromatic plants are suitable for soil phytoremediation technologies used in Cd decontamination.

Effects of Oil Pollution on Water Movement in Soils with Different Textures

Exploring water movement characteristics in oil-polluted soils could facilitate the understanding of soil stress resistance. The aim of the present study was to evaluate the effects of oil pollution on water movement in soils with different textures and explore the underlying mechanisms. A heavy loam (Earth-cumuli-Orthic Anthrosols, EOA), a light loam (Hapli-Ustic Cambosols, HUC), and a sandy loam (Usti-Sandic Primosols, USP) were spiked with different levels of crude oil (0, 0.5, 1, 2, and 4%, w/w). Soil water movement parameters, including saturated hydraulic conductivity, unsaturated hydraulic conductivity, and specific water capacity were measured. Soil water availability under different levels of oil pollution was also analyzed. According to the results, saturated hydraulic conductivity of all three soils decreased with an increase in the level of oil pollution, as did the unsaturated hydraulic conductivity of HUC and USP. Under 4% oil pollution, the saturated hydraulic conductivity of the EOA, HUC, and USP decreased by 52.8%, 81.7%, and 39.6%, compared with their respective unpolluted soils, while the unsaturated hydraulic conductivity of HUC and USP decreased by 78.0% and 39.9% at 20% soil water content. In addition, the unsaturated hydraulic conductivity of EOA decreased with an increase in oil pollution level when the soil water content was >25%; however, a reverse trend was observed at soil water content <25%. The specific water capacity of all soils increased first and then decreased with an increase in water suction, while it decreased with an increase in the level of oil pollution. The suction ranges corresponding to the available water content in the three soils were reduced by oil pollution, and the corresponding water-holding capacities were weakened. Oil pollution had major negative impacts on water movement in the soils with different textures, causing a decline in water infiltration and supply capacities, which could hamper soil drought resistance. However, the effects of soil texture on water movement were greater than the effects of oil pollution under the experimental conditions.

Lead Impact on the Earthworm Eisenia fetida and Earthworm Recovery after Exposure

This study investigates the effects of lead (Pb) on earthworm Eisenia fetida and its potential to recover from Pb exposure. Adult earthworms E. fetida were exposed for 4 weeks to lead (40–2500 mg Pb kg−1) in soil, and after the period of exposure, earthworms were transferred to clean unpolluted soil for 4 weeks to recover. Pb had no effect on the earthworm’s survival but inhibited earthworm growth; growth rate decreased with Pb concentration in the soil. During the recovery period, Pb pre-exposed earthworms did not manage to recover completely their growth. Lead had a highly significant effect on the malondialdehyde (MDA) concentration during both exposure and recovery periods. Pb showed concentration dependent toxicity relationships (weight, lipid peroxidation) for total earthworm Pb concentration. However, earthworm Pb bioconcentrations after recovery period could not explain the higher MDA concentration and lower earthworm fresh weight. Earthworms pre-exposed to low Pb levels have the potential to recover their growth and decrease Pb bioconcentrations, though more prolonged recovery period is needed to full recovery.

Microbial diversity changes and enrichment of potential petroleum hydrocarbon degraders in crude oil-, diesel-, and gasoline-contaminated soil.

This study investigated the impacts of crude oil, diesel, and gasoline on the diversity of indigenous microbial communities as well as culturable microorganisms in the studied soil. Oil contamination led to shifts in thediversityofthesoil'smicrobialcommunities, regardless of the contaminant applied. Unpolluted soils were more diverse and evenly distributed than contaminated samples. The domain Bacteria accounted for 65.15% of the whole microbial community. The bacterial phylum Proteobacteria dominated in all samples, followed by Actinobacteria and Acidobacteria. Pseudomonas with 28.15% of reads dominated in Proteobacteria, while Rhodococcus (3.07%) dominated in Actinobacteria, and Blastocatella (2.53%) dominated in Acidobacteria. The dominant fungal phyla across all samples were Ascomycota dominated by Penicillium (50.48% of sequences), and Zygomycota dominated by Mortierella (16.87%). Sequences similar to the archaeal phyla, Euryarchaeota and Thaumarchaeota, were also detected. The number of culturable microorganisms increased following the contamination and was higher in contaminated samples than in clean samples. Oil contamination also resulted in the enrichment of oil-degrading strains. Two bacteria, Serratia marcescens strain PL and Raoultella ornithinolytica PS, which were isolated from crude oil-contaminated soil, exhibited strong crude oil degradation ability. Strain PL was the most efficient strain and degraded 75.10% of crude oil, while strain PL degraded 65.48%, after 20days of incubation. However, the mixed culture of the two strains was more effective than single strain and could achieve up to 96.83% of crude oil degradation, with a complete abatement of straight-chain hydrocarbons (from C12 to C25), and more than 91% removal of highly branched hydrocarbons, phytane and pristane, which are known to be more recalcitrant to biodegradation. Strains PS and PL are two newly isolated crude oil degraders that are not among the most prominent crude oil-degrading strains referenced in the literature. Therefore, their high degradation capacity makes them perfect candidates for the bioremediation of petroleum hydrocarbon contaminated environments.

Content, Distribution, and Migration of 238U in Soils of Natural and Technogenic Landscapes of Southern Yakutia

The contents, distribution in the profile, and migration capacity of 238U in automorphic podburs (Entic Podzols) and hydromorphic alluvial (Fluvisols) soils of natural and human-transformed landscapes of southern Yakutia are analyzed. Human-transformed (technogenic) landscapes of southern Yakutia, including the Elkon uranium deposit area, in particular, are characterized by two distinct types of element migration in soils: the aero-technogenic and the hydro-technogenic migration. These types of element migration determine the level of 238U pollution of soils, the distribution pattern of 238U in the soil profiles, and the proportion between 238U compounds with different migration capacity. The soils subjected to the radioactive contamination are characterized by the increased mobility and migration capacity of 238U isotopes in comparison with the unpolluted soils of natural landscapes. Also, in contrast to automorphic podburs, hydromorphic alluvial soils are characterized by the increased level of radioactive pollution and higher concentrations of mobile uranium compounds.