Pristine Soil Research Articles

Distribution patterns of Acidobacteriota in different fynbos soils.

The Acidobacteriota is ubiquitous and is considered as one of the major bacterial phyla in soils. The current taxonomic classifications of this phylum are divided into 15 class-level subdivisions (SDs), with only 5 of these SDs containing cultured and fully described species. Within the fynbos biome, the Acidobacteriota has been reported as one of the dominant bacterial phyla, with relative abundances ranging between 4-26%. However, none of these studies reported on the specific distribution and diversity of the Acidobacteriota within these soils. Therefore, in this study we aimed to first determine the relative abundance and diversity of the Acidobacteriota in three pristine fynbos nature reserve soils, and secondly, whether differences in the acidobacterial composition can be attributed to environmental factors, such as soil abiotic properties. A total of 27 soil samples were collected at three nature reserves, namely Jonkershoek, Hottentots Holland, and Kogelberg. The variable V4-V5 region of the 16S rRNA gene was sequenced using the Ion Torrent S5 platform. The mean relative abundance of the Acidobacteriota were 9.02% for Jonkershoek, 14.91% for Kogelberg, and most significantly (p<0.05), 18.42% for Hottentots Holland. A total of 33 acidobacterial operational taxonomic units (OTUs) were identified. The dominant subdivisions identified in all samples included SDs 1, 2, and 3. Significant differences were observed in the distribution and composition of these OTUs between nature reserves. The SD1 were negatively correlated to soil pH, hydrogen (H+), potassium (K+) and carbon (C). In contrast, SD2, was positively correlated to soil pH, phosphorus (P), and K+, and unclassified members of SD3 was positively correlated to H+, K, and C. This study is the first to report on the specific acidobacterial distribution in pristine fynbos soils in South Africa.

Impact of N-fertilization and peanut shell biochar on soil microbial community structure and enzyme activities in a Typic Haplustoll under different management practices

The application of biochar with N-fertilizer is one of the most attractive practices for increasing soil quality and fertility. However, few studies have examined the combined effects of peanut biochar and urea on soil microbial community structure and function. Phospholipid fatty acid (PLFA) analysis and various enzyme activities were used to monitor microbial community structure and function in a 20-week incubation experiment. Different rates of biochar (0, 1, and 3% dry wt. soil) and N-fertilizers (with or without urea addition at 0.2 g kg−1) were applied to a Typic Haplustoll under conventional (CV) and conservation (CS) land management practices. A pristine forest soil (CK) was also included as control. Overall, the lowest microbial activity and abundance of microbial PLFA bioindicators were recorded under CV, confirming that conservation management may improve soil quality. Our study also indicated that the effect of biochar and management practices on the microbial community structure was more significant than that of urea. Particularly under both CS and CK, biochar tended to increase glucosidase, glucuronidase, and phosphomonoesterase activities, being on average 65%, 43%, and 85% significantly higher in biochar 3% than in the control treatment, respectively. Thus, we found a strong correlation between soil macronutrients and enzymes such as glucosidase and urease. Although total PLFA content was poorly affected, biochar addition increased some individual PLFA biomarkers, suggesting that both the biochar rates (1% and 3%) may increase Gram-negative bacteria and fungal populations. Regardless of biochar addition, urea application significantly increased urease activity. We also found a positive correlation between fungal PLFAs (VAM and total fungi) and urease activity, indicating that biochar tended to increase fungal biomass. The combined application of biochar and urea to soil under appropriate management may thus be a feasible and effective strategy for improving soil microbial quality.

Geochemical signatures and natural background values of rare earth elements in soils of Brazilian Amazon.

Rare earth elements (REEs) are generally defined as a homogenous group of elements with similar physical-chemical properties, encompassing Y and Sc and the lanthanides elements series. Natural REEs contents in soils depend on the parent material, the soil genesis processes and can be gradually added to the soil by anthropogenic activities. The REEs have been considered emerging pollutants in several countries, so the establishment of regulatory guidelines is necessary to avoid environmental contamination. In Brazil, REE soils data are restricted to some regions, and knowledge about them in the Amazon soils is scarce, although this biome covers more than 40% of the Brazilian territory. Thus, the objectives of this study were to determine the REE content in soils of two hydrographic basins (Solimões and Rio Negro) of the Amazon biome, establish their Quality Reference Values (QRV) and to investigate the existence of enrichment of REEs in urban soils. The ΣREE(Y+Sc) content of Solimões surface samples was 109.28mgkg-1 and the ΣREE(Y+Sc) content in the subsurface samples was 94.11mgkg-1. In soils of Rio Negro basin, the ΣREE(Y+Sc) was 43.95 15mgkg-1 surface samples and 38.40mgkg-1 in subsurface samples. The ΣREE(Y+Sc) in urban topsoils samples was 38.62mgkg-1. The REEs contents pattern in three studied areas are influenced in different amplitude by natural soil properties. The REEs content in urban topsoils were slightly higher than the Rio Negro pristine soils, but the ecological risk was low. QRVs recommend for Solimões soils ranged from 0.01 (Lu) to 145.6mgkg-1 (Ce) and for Rio Negro soils ranged from 0.05 (Lu) to 15.8mgkg-1 (Ce).

Environmental Magnetic Properties of Lateritic Soils from Southwestern India

Soil formation is influenced mainly by lithology, climate, organic matter, vegetation, topography, and time. Soil-forming processes have been well studied in temperate regions. However, there is little data on such processes in the tropics. In this work, we have studied the environmental magnetic properties of lateritic soils developed on gneiss and charnockite. We sampled surficial soils from different environmental settings (urban, agricultural, pristine, and gleyed) to determine the processes involved in their formation. A range of environmental magnetic parameters and inter-parametric ratios were investigated to determine the magnetic concentration, grain-size and mineralogy of the soil samples. Redness rating (RR) index was also calculated to estimate the reddening of tropical soils and to examine its relationship with magnetic properties. The pristine soils exhibit the highest average value for χlf and a higher value of χfd%, indicating a greater amount of ultra-fine magnetic minerals. The gleyed and agricultural soils are weakly magnetic, probably be due to waterlogging, and are characterized by a coarser magnetic grain size. A high proportion of “soft” ferrimagnetic minerals like magnetite and titanomagnetite is present in the samples (average S-ratio ~ 0.90). Hematite content is the highest in unburnt soils and the least in gleyed soils (unburnt > burnt > pristine > urban > agricultural > gleyed). The high concentration of hematite in these soils could be due to transformation of maghemite, resulting from low-temperature oxidation of magnetite. We documented a distinction between the magnetic properties of burnt and unburnt soil types as fire can significantly enhance the magnetic values of unburnt soils. The concentration of hematite (indicated by HIRM) and redness rating (RR) index are fairly well correlated for all the sample types with the exception of urban (r = 0.51; p = 0.11; n = 11) and unburnt soils (r = 0.60; p = 0.28; n = 5), which show a strong correlation. Therefore, RR index can be effectively used as an indicator of reddening of tropical soils due to pedogenesis. This study demonstrates that environmental magnetism can aid in differentiating the diverse environments of soils even though they developed on a similar rock type and under similar climatic conditions.

Effect of the intensification of cropping sequences on soil organic carbon and its stratification ratio in contrasting environments

In environments where continuous agriculture leads to soil organic carbon (SOC) depletion, intensification practices (i.e. polyculture, cover crops (CC), and crop fertilization) have been suggested as strategies to improve crop residue inputs which, in turn, can increase SOC storage. However, SOC dynamics are regulated by a complex interplay of climatic and soil conditions. The objective of our study was to assess how intensification practices affect SOC, particulate organic carbon (POC) and SOC stratification ratio (SRSOC) as compared to soybean [Glycine max (L.) Merr.] monoculture, in soils with contrasting soil properties and climate. The experiment was carried out in four long term experiments (>10 yr) located in areas with contrasting environments. The surface soil textures ranged from sandy-loam to silty-clay and clay-loam, initial SOC (0–20 cm) from 34.5 to 67.8 Mg ha−1, mean air temperature: 14.0–18.9 °C, annual precipitation: 719.8–886.1 mm. Five treatments were evaluated: soybean monoculture (SB), soybean monoculture fertilized with phosphorus (P) and sulfur (S) (SBPS), CC/PS-fertilized soybean (SBPS/CC), nitrogen (N)-fertilized CC/PS-fertilized soybean (SBPS/CCN) and NPS-fertilized crop rotation (ROTNPS). Intensification of crop sequences (SBPS/CC, SBPS/CCN and/or ROTNPS) increased SOC and POC at 0–5 cm and in SRSOC in most sites as compared to SB. All treatments showed SOC depletion as compared to the beginning of the experiment. However, the magnitude of SOC lost during 10 years was 26–65% lower when intensified crop sequences were applied as compared with SB. Carbon input and environment characteristics influenced the impact of intensification practices on the analyzed variables. However, this effect was mostly associated with the ratio between SOC at the beginning of the experiment and the SOC of pristine soil (degradation status). The intensification practices evaluated were not sufficient to reverse the tendency of agricultural soils to lose SOC, but they slowed the rate of this degradation process.

Distribution and bioaccessibility of polycyclic aromatic hydrocarbons in industrially contaminated site soils as affected by thermal treatment

Thermal treatment can not only efficiently remove volatile pollutants but also distinctly alter the speciation of organic carbon (C) and the behaviors of residual pollutants in contaminated soils. Here we examined the distribution and bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in industrially contaminated site soils affected by thermal treatment (temperature ranging of 105–650 ℃) using synchrotron-based infrared microspectroscopy and n-butanol extraction (a mild solvent extractant). In the pristine soils, the sequestration and distribution of PAHs were simultaneously controlled by aromatic C, aliphatic C and clay minerals. Desorption efficiency of PAHs was substantially increased with increasing temperature, whereas the residual PAHs were strongly immobilized within their binding sites evidenced by their dramatically decreased bioaccessibility. Aliphatic and carboxylic C were gradually decomposed and/or carbonized with increasing temperature. In contrast, aromatic C remained relatively recalcitrant during the thermal treatment and was the key controlling factor for the desorption of residual PAHs in the soils with either thermal treatment or n-butanol extraction. This study is the first to visualize the changes in the binding sites and bioaccessibility of PAHs induced by thermal treatment, which have important implications for understanding the sequestration mechanisms of organic pollutants in soil and optimizing the remediation technique.

Archaeological cereals as an isotope record of long-term soil health and anthropogenic amendment in southern Scandinavia

Maintaining soil health is integral to agricultural production, and the archaeological record contains multiple lines of palaeoclimatic and palaeoenvironmental proxy evidence that can contribute to the understanding and analysis of long-term trajectories of change that are key for contextualizing 21st century global environmental challenges. Soil is a capital resource and its nutrient balance is modified by agricultural activities, making it necessary to ensure soil productivity is maintained and managed through human choices and actions. Since prehistory this has always been the case; soil is a non-renewable resource within a human lifetime. Here, we present and interpret carbon and nitrogen isotope analysis of charred cereals from southern Scandinavia. Anthropogenic effects on soils are evident from the initiation of farming 6000 years ago, as is amendment to counteract its effects. The earliest cereals were planted on pristine soils, and by the late Neolithic, agriculture extensified. By the Iron Age it was necessary to significantly amend depleted soils to maintain crop yields. We propose that these data provide a record of soil water retention, net precipitation and amendment. From the start of the Neolithic there is a concurrent decrease in both Δ13C and δ15N, mitigated only by the replacement of soil organic content in the form of manure in the Iron Age. The cereal isotopes provide a record of trajectories of agricultural sustainability and anthropogenic adaptation for nearly the entire history of farming in the region.

Assessing the faecal source sensitivity and specificity of ruminant and human genetic microbial source tracking markers in the central Ethiopian highlands

This study tested genetic microbial source tracking (MST) methods for identifying ruminant‐ (BacR) and human‐associated (HF183/BacR287, BacHum) bacterial faecal contaminants in Ethiopia in a newly created regional faecal sample bank (n = 173). BacR performed well, and its marker abundance was high (100% sensitivity (Sens), 95% specificity (Spec), median log10 8·1 marker equivalents (ME) g−1 ruminant faeces). Human‐associated markers tested were less abundant in individual human samples (median: log10 5·4 and 4·2 (ME + 1) g−1) and were not continuously detected (81% Sens, 91% Spec for BacHum; 77% Sens, 91% Spec for HF183/BacR287). Furthermore, the pig‐associated Pig2Bac assay was included and performed excellent (100% Sens, 100% Spec). To evaluate the presence of MST targets in the soil microbiome, representative soil samples were tested during a whole seasonal cycle (n = 60). Only BacR could be detected, but was limited to the dry season and to sites of higher anthropogenic influence (log10 3·0 to 4·9 (ME + 1) g−1 soil). In conclusion, the large differences in marker abundances between target and non‐target faecal samples (median distances between distributions ≥log10 3 to ≥log10 7) and their absence in pristine soil indicate that all tested assays are suitable candidates for diverse MST applications in the Ethiopian area.

A comparative study on the adsorption behavior of pesticides by pristine and aged microplastics from agricultural polyethylene soil films

Compared with pristine agricultural polyethylene (PE) soil films microplastics (MPs), aged agricultural polyethylene (APE) soil films MPs have a rougher surface, more cracks and have some oxygen-containing functional groups that makes them adsorb organic pollutants, such as pesticides more easily. This may be more harmful to human beings than marine MPs as the agricultural soil films are closer to our living environment. But few works focused on the adsorption of pesticides on pristine or aged agricultural polyethylene soil films MPs. In order to promote the risk assessment of co-exposure of pesticides and agricultural polyethylene soil films MPs, a comparative study on the adsorption behavior and mechanism of four pesticides (carbendazim, diflubenzuron, malathion, difenoconazole) by pristine PE MPs and APE MPs were carried out in this paper. The results showed microcracks and surface oxidation observed on APE MPs. The adsorption kinetics and isotherm models indicated that the adsorption capacity of APE MPs was higher than that of PE MPs, which attribute to the larger surface area of APE MPs. The adsorption capacities of pesticides on APE MPs were positively correlated with LogKow (Water octanol partition coefficient) values of these four pesticides, showed the hydrophobic partitioning played the most important part in the adsorption, but also some H-bonding between secondary amines in the molecular of diflubenzuron and polar O-containing functional groups on APE MPs may be formed. And electrostatic forces or interactions are not the determining factor for these pesticides adsorption behavior of PE MPs, and the effect of pH is mainly driven by changes in sorbate properties rather than changes in surface properties of MPs. The results presented herein show the APE MPs can be a better vector of most hydrophobic pesticides than pristine MPs in the agricultural field, and more attention should be paid to the problem of films and pesticides residue in farmland soil.

DBP biodegradation kinetics by Acinetobacter sp.33F in pristine agricultural soil

Dibutyl phthalate (DBP) is one of the most widely used plasticizers used in various applications. Due to its toxic effects on the organisms, it has been classified as the highest priority pollutant. It has been observed that DBP can leach out from the landfill and other related sites. This plasticizer ultimately reaches the soil, entering the food chain. Although phthalate esters biodegradation have been reported for different bacteria. But bacteria from the genus Acinetobacter have various advantages as compared to others. They are much more efficient in removal of organic pollutants from the contaminated environments. Therefore, Acinetobacter sp.33F have been selected in the study. This study is focused on DBP biodegradation kinetics by Acinetobacter sp.33F in pristine agricultural soils. The study also compared the results with DBP biodegradation kinetics in minimal media. Biodegradation kinetics studies were performed at 100–2000 mg/L. To model DBP biodegradation kinetics, non-linear models were used. Monod paradigm was used to explain DBP degradation kinetics in minimal medium. The observed values for μ max and K s were 0.0083 (mg/L/h) and 30.57 mg/L. Non-linear Haldane inhibition model was used to explain DBP degradation kinetics in the agricultural soils. μ max , K s , and K i were 0.02008 ± 0.002 (mg/L/h), 176.5 ± 2.3 mg/L and 433.7 ± 3.0 mg/L. This study also demonstrated that Acinetobacter sp.33F could utilize diethyl phthalate (DEP), mono-butyl phthalate (MBP), benzyl butyl phthalate (BBP), di-octyl phthalate (DIOP), and di-decyl phthalate (DIDP) as sole carbon source. The above properties make Acinetobacter sp. 33F a promising candidate for phthalate esters removal from the contaminated agricultural sites. • DBP degradation kinetics demonstrated in minimal media at 100–2000 mg/L. • DBP has inhibitory effect on Acinetobacter sp.33F in the agricultural soil. • Michaelis–Menten paradigm was used to explain kinetics in minimal medium. • Non-linear Haldane inhibition model was used to explain kinetics in the agricultural soil. • Acinetobacter sp.33F can grow on DBP derivatives DEP, MBP, BBP, DIOP, DIDP and PC.

Large-scale biogeographical patterns of antibiotic resistome in the forest soils across China

Soil is a reservoir of environmental resistomes. Information about their distribution, profiles, and driving forces in undisturbed environments is essential for understanding and managing modern antibiotic resistance genes (ARGs) in human disturbed environments. However, knowledge about the resistomes in pristine soils is limited, particularly at national scale. Here, we conducted a national-scale investigation of soil resistomes in pristine forests across China. Although the antibiotics content was low and ranged from below limit of detection (LOD) to 0.290 μg/kg, numerous detected ARGs conferring resistance to major classes of modern antibiotics were identified and indicated forest soils as a potential source of resistance traits. ARGs ranged from 6.20 × 10−7 to 2.52 × 10−3 copies/16S-rRNA and were predominated by those resisting aminoglycoside and encoding deactivation mechanisms. Low abundance of mobile genetic elements (MGEs) and its scarcely positive connections with ARGs suggest the low potential of horizontal gene transfer. The geographic patterns of ARGs and ARG-hosts in pristine forest soils were mainly driven by soil physiochemical variables and followed a distance–decay relationship. This work focusing on pristine soils can provide valuably new information for our understanding of the ARGs in human disturbed environments.

Ecological impact of organochlorine pesticides consortium on autochthonous microbial community in agricultural soil

Organochlorine pesticides (OCPs) used in agricultural practices are of global concern due to their toxicological hazards on biomes of the impacted soil. Geochemistry and microbiome of OCPs-impacted (OW) soil was determined and compared with those of pristine (L1) soils. Microbiome of OW was based on sequencing total 16S rRNA genes of prokaryotes and Internal Transcribed Spacer (ITS2) regions between 5.8S and 28S rRNA genes of eukaryotes using Illumina MiSeq platform for bacterial and fungal communities, respectively. Geochemical properties of OW were assessed for ecological risks of OCPs on biota via risk quotient (RQ) and maximum cumulative ratio (MCR). It was established OW was polluted with 15 OCPs, along with consequential nitrate and phosphorous deficiencies. Ten of the 15 OCPs exerted severe ecological risk (RQ > 1: 4–992), of which endosulfan contributed 76% of the ecotoxicity (MCR = 1.3) on OW. The key players in OW were observed to be Enterobacteriaceae and Mortierellaceae represented by Escherichia and Mortierella taxa, respectively. Low abundance of Nitrospirae species and extinction of Glomeromycota in OW connoted serious toxicological consequences of the OCPs. Taxon XOR (Taxon Exclusive Or) analysis revealed 38,212 and 63,474 counts of bacterial and fungal species, respectively, were exclusively found in the impacted OW and possibly contributed to natural attenuation of the OCPs in the impacted agricultural soil. Conversely, 61,005 (bacteria) and 33,397 (fungi) species counts that were missing in OCPs-impacted OW, but present in pristine L1, opined the species as bio-indicators of OCPs ecotoxicity in agricultural soils. While the species tagged as bio-indicators would be valuable in monitoring OCPs pollution, those suggested to be players in self-recovery process will be invaluable to designing bioremediation strategies for OCPs-impacted agricultural soil.

Abundance, diversity and mobility potential of antibiotic resistance genes in pristine Tibetan Plateau soil as revealed by soil metagenomics.

Widespread occurrence of antibiotic resistance genes (ARGs) has become an important clinical issue. Studying ARGs in pristine soil environments can help to better understand the intrinsic soil resistome. In this study, 10 soil samples were collected from a high elevation and relatively pristine Tibetan area, and metagenomic sequencing and bioinformatic analyses were conducted to investigate the microbial diversity, the abundance and diversity of ARGs and the mobility potential of ARGs as indicated by different mobile genetic elements (MGEs). A total of 48 ARG types with a relative abundance of 0.05-0.28 copies of ARG/copy of 16S rRNA genes were detected in Tibetan soil samples. The observed ARGs were mainly associated with antibiotics that included glycopeptide and rifamycin; the most abundant ARGs were vanRO and vanSO. Low abundance of MGEs and potentially plasmid-related ARGs indicated a low horizontal gene transfer risk of ARGs in the pristine soil. Pearson correlation and redundancy analyses showed that temperature and total organic carbon were the major environmental factors controlling both microbial diversity and ARG abundance and diversity.

Combined application of Bacillus sp. MN-54 and phosphorus improved growth and reduced lead uptake by maize in the lead-contaminated soil.

Lead (Pb) is considered an important environmental contaminant due to its considerable toxicity to living organisms. It can enter and accumulate in plant tissues and become part of the food chain. In the present study, individual and combined effects of Bacillus sp. MN-54 and phosphorus (P) on maize growth and physiology were evaluated in Pb-contaminated soil. A pristine soil was artificially contaminated with two levels of Pb (i.e., 250 and 500mgkg-1 dry soil) and was transferred to plastic pots. Bacillus sp. MN-54 treated and untreated maize (DK-6714) seeds were planted in pots. Recommended doses of nutrients (N and K) were applied in each pot while P was applied in selective pots. Results showed that Pb stress hampered the maize growth and physiological attributes in a concentration-dependent manner, and significant reductions in seedling emergence, shoot and root lengths, fresh and dry biomasses, leaf area, chlorophyll content, rate of photosynthesis, and stomatal conductance were recorded compared with control. Application of Bacillus sp. MN-54 or P particularly in combination significantly reduced the toxic effects of Pb on maize. At higher Pb level (500mgkg-1), the combined application effectively reduced Pb uptake up to 42.4% and 50% by shoots, 30.8% and 33.9% by roots, and 18.4% and 26.2% in available Pb content in soil after 45days and 90days, respectively compared with that of control. Moreover, the use of Bacillus sp. MN-54 significantly improved the P uptake by maize plants by 44.4% as compared with that of control. Our findings suggest that the combined use of Bacillus sp. MN-54 and P could be effective and helpful in improving plant growth and Pb immobilization in Pb-contaminated soil.

COMPARATIVE DISSIPATION OF ANTHRACENE AND PHENANTHRENE IN A PRISTINE TYPIC HAPLUDOLL SOIL

Polycyclic aromatic hydrocarbons (PAHs) are of great environmental concern due to their widespread occurrence and persistence. Anthracene and phenanthrene (C14H10) are two priority pollutants that are found in high concentrations in PAHs-contaminated surface soils. The objective of this study was to analyze the capability of endogenous soil microorganisms of a pristine soil of the Pampas region, Argentina, to dissipate two isomers: anthracene and phenanthrene. Nutrient availability and the effects of ryegrass (Lolium perenne L.) on these PAHs´ dissipation were also evaluated. After 100 days, both contaminants were significantly degraded in root-free soils by autochthonous microorganisms. L. perenne significantly enhanced microbial degradation. The dissipation of both pollutants in the rhizosphere was accompanied by higher values of total bacteria counts at the end of the experimental period. No biostimulation effect was observed. In all cases, the dissipation of phenanthrene was significantly higher than anthracene. These results point to the important role of indigenous PAH degrading microorganisms, even present in a non-polluted soil.

ACID RESIDUES REMEDIATION FROM MINES USING BIOCHAR, MONOPOTASSIUM PHOSPHATE AND LIME

The Zimapan mining district in the state of Hidalgo (Mexico) generates residues with high content of Cu, Pb and Zn which have been disposed for decades on sites that could cause toxicity to the surrounding area. Simultaneously, district’s water dams have been affected by an invasive plant called water hyacinth ( Eichhornia crassipes ), both of problems require attention and remediation treatments. The objectives of this research were: a) to evaluate biochar derived from water hyacinth (H) in mining acid residues; and b) to compare its performance vs monopotassium phosphate (F), lime (L) and the phosphates mixtures with biochar (FH) or with lime (FL) by a bioassay of barley root growth, soluble metal and pH. In this investigation four substrates was used to emulate pollution gradients: 100 %-neutral pristine soil (M1); 100 %-acid mine residues (M4); and two mixtures soil: residues (w/w) of 65:35 (M2) and 35:65 (M3). The substrates were treated with the amendment (dose w/w): H (10 %-substrate), L (3.4 %-residues), F (0.06 %-soil + 0.6 %-residues), FH (0.06 %-soil + 0.6 %-residues + 10 %-substrate) y FL (0.06 %-soil + 0.6 %-residues + 3.4 %-residues) (22 total-treatments, blanks-included). This study shows that water hyacinth could be utilized as an acid mine residues treatment by converting it to biochar. It caused the increase of root length, pH and reduce the soluble Cu and Zn as with the others amendments when the residues were present. Although the reduction of soluble Pb with biochar was considerably lower than with lime in the residues-substrates.

Phosphorus binding to soil organic matter via ternary complexes with calcium

Soil organic matter (SOM) is known to exert a major control on the mobility and bioavailability of cationic nutrients. However, the role of SOM in the fate of anionic nutrients, especially phosphorus (P), is less well characterized. The objectives of this study were to (1) compare the formation of binary complexes of calcium (Ca) with humic acids (HA) extracted from two contrasting soils, and (2) determine if binary HA-Ca complexes could incorporate P by forming ternary HA-Ca-P complexes. The Ca binding capacities of the HA extracted from an agricultural organic soil (AOS) and a pristine riparian soil (RS) were measured via potentiometric titrations; the formation of ternary complexes was analyzed by size fractionation using MWCO tubes. Proton and Ca binding capacities of RS-HA were higher than AOS-HA, and pH had a weaker effect on Ca binding to RS-HA. These differences are consistent with lower proportions of aromatic groups, and a higher proportion of alkyl groups derived from 13C NMR spectroscopy. Together, the NMR, titration and MWCO data indicate that Ca binds to RS-HA through monodentate complexes and electrostatic attraction that are capable of binding P producing ternary complexes. In contrast, at pH 8.5 Ca forms bidentate complexes with AOS-HA, which do not provide bridging positions to incorporate P. Overall, our results imply that the formation of HA-Ca and HA-Ca-P complexes depend on the structure of the HA, and that complexation to HA may play an important role in the fate of P in terrestrial and aquatic environments.

Characterization of Novel Broad-Host-Range Bacteriophage DLP3 Specific to Stenotrophomonas maltophilia as a Potential Therapeutic Agent.

A novel Siphoviridae phage specific to the bacterial species Stenotrophomonas maltophilia was isolated from a pristine soil sample and characterized as a second member of the newly established Delepquintavirus genus. Phage DLP3 possesses one of the broadest host ranges of any S. maltophilia phage yet characterized, infecting 22 of 29 S. maltophilia strains. DLP3 has a genome size of 96,852 bp and a G+C content of 58.4%, which is significantly lower than S. maltophilia host strain D1571 (G+C content of 66.9%). The DLP3 genome encodes 153 coding domain sequences covering 95% of the genome, including five tRNA genes with different specificities. The DLP3 lysogen exhibits a growth rate increase during the exponential phase of growth as compared to the wild type strain. DLP3 also encodes a functional erythromycin resistance protein, causing lysogenic conversion of the host D1571 strain. Although a temperate phage, DLP3 demonstrates excellent therapeutic potential because it exhibits a broad host range, infects host cells through the S. maltophilia type IV pilus, and exhibits lytic activity in vivo. Undesirable traits, such as its temperate lifecycle, can be eliminated using genetic techniques to produce a modified phage useful in the treatment of S. maltophilia bacterial infections.

Impact of Hospital Waste from the University of Port Harcourt Teaching on the Environment

The aim of this study is to determine the impact of hospital wastes indiscriminately dumped at exposed dumpsites within the University of Port Harcourt Teaching Hospital. Ten random samples (100g each) were withdrawn from a depth of 0–15 cm from each sampling site for soil analysis and settling plate technique was used for microbial air quality assessment. The Microbiological assessment of the dumpsites revealed an array of microorganisms viz; Baccilus sp., Staphylococcus sp., Pseudomonas sp., Salmonella sp., Proteus sp. Escherichia coli, Trichophyton sp., Scopulariopsis sp. Candida albicans, Fusarium sp., Mucor sp. and Cladosporium sp. and the microbial population dynamics reveals that the bacterial and fungal counts where more abundant on hospital dumpsites when compared to a pristine soil, as was the heavy metals levels. The air quality assessment of the dump site area reveals that most of the isolated pathogens from the soil analysis could also be airborne. This study has shown that improper dumping of hospital waste impacts deleteriously on the environment and measures must be put in place for proper management to avert any adverse health impact.

Changes in soil microbial respiration and physicochemical properties following bonny light crude oil contamination of sandy loam soil

This study was undertaken to investigate the effects of Bonny light crude oil contamination of sandy loam soil on aspects of microbial metabolism and physicochemical properties of the soil. Bonny light crude oil (specific gravity = 0.81) was used at eight different levels (0.5%, 1.0%, 2.0%, 2.5%, 5.0%, 10.0%, 15.0% or 20.0% v/w of soil) for the controlled pollution of pristine soil samples, each weighing 1 kg. The experiment lasted for eightweeks. Results of the effects of crude oil on the physicochemical properties of the soil showed that high levels of the oil significantly (p&lt; 0.05) increased soil organic matter but had no significant effect on the pH and moisture content. With the exception of organic carbon, the levels of bioavailable nitrogen, sodium, potassium, calcium, magnesium, sulphur and phosphorus in the test samples with higher levels of crude oil (5.0%, 10.0%, 15.0% and 20.0%) were significantly reduced when compared to their levels in the controls. Similarly, higher levels of the oil significantly (p&lt;0.05) reduced soil microbial phospholipid synthesis and CO emission. 2 Correlation analysis using the Pearson's correlation model showed a positive correlation between soil CO and 2 phospholipid (r = 0.74).&#x0D; Keywords: Contamination, Crude oil, Microbial respiration, Physicochemical properties.