Effects of zinc-smelter emissions on forest soil microflora

Within 2 km of a zinc (Zn) smelter in Palmerton, Pennsylvania, near the Lehigh Water Gap, up to 13.5% Zn by weight has been measured in the O2 horizon of the soil, and up to 8% Zn in the A1 horizon. The total numbers of bacteria, actinomycetes, and fungi (measured by dilution plate counts) were greatly reduced in the most severely Zn-contaminated soils compared with control soils. The reduction of microbial populations may be a partial cause of the decreased rate of litter decomposition at Lehigh Gap.Growth of most bacteria from control sites was reduced by 100 to 200 μM Zn, most actinomycetes by 100 μM Zn, and most fungi by 100 to 1000 μM Zn in thin-Pablum extract agar (TPab). All the tested actinomycetes and non-spore-forming bacteria isolated from Zn-contaminated Lehigh Gap soils were Zn-tolerant, growing normally in media containing 600-2000 μM Zn. Most fungi, regardless of source, were capable of at least 50% of normal growth at 700 μM Zn. Zinc-tolerant bacteria, actinomycetes, and fungi were readily isolated from low-Zn soils, suggesting that selection for Zn tolerance may proceed rapidly.Acidophilic Mortierella species have been selectively eliminated near the smelter, apparently because of elevated soil pH. Peyronellaea glomerata (Corda) Goidanich and Coniothyrium spp. were found only in the high-Zn soils.

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Fractionation of Heavy Metals in Multi-Contaminated Soil Treated with Biochar Using the Sequential Extraction Procedure

Biomolecules ◽

10.3390/biom11030448 ◽

2021 ◽

Vol 11 (3) ◽

pp. 448

Author(s):

Mahrous Awad ◽

Zhongzhen Liu ◽

Milan Skalicky ◽

Eldessoky S. Dessoky ◽

Marian Brestic ◽

...

Keyword(s):

Heavy Metals ◽

Organic Matter ◽

Soil Organic Matter ◽

Soil Ph ◽

Contaminated Soil ◽

Contaminated Soils ◽

Extraction Procedure ◽

Sequential Fractionation ◽

Relationship Of ◽

The Relationship

Heavy metals (HMs) toxicity represents a global problem depending on the soil environment’s geochemical forms. Biochar addition safely reduces HMs mobile forms, thus, reducing their toxicity to plants. While several studies have shown that biochar could significantly stabilize HMs in contaminated soils, the study of the relationship of soil properties to potential mechanisms still needs further clarification; hence the importance of assessing a naturally contaminated soil amended, in this case with Paulownia biochar (PB) and Bamboo biochar (BB) to fractionate Pb, Cd, Zn, and Cu using short sequential fractionation plans. The relationship of soil pH and organic matter and its effect on the redistribution of these metals were estimated. The results indicated that the acid-soluble metals decreased while the fraction bound to organic matter increased compared to untreated pots. The increase in the organic matter metal-bound was mostly at the expense of the decrease in the acid extractable and Fe/Mn bound ones. The highest application of PB increased the organically bound fraction of Pb, Cd, Zn, and Cu (62, 61, 34, and 61%, respectively), while the BB increased them (61, 49, 42, and 22%, respectively) over the control. Meanwhile, Fe/Mn oxides bound represents the large portion associated with zinc and copper. Concerning soil organic matter (SOM) and soil pH, as potential tools to reduce the risk of the target metals, a significant positive correlation was observed with acid-soluble extractable metal, while a negative correlation was obtained with organic matter-bound metal. The principal component analysis (PCA) shows that the total variance represents 89.7% for the TCPL-extractable and HMs forms and their relation to pH and SOM, which confirms the positive effect of the pH and SOM under PB and BB treatments on reducing the risk of the studied metals. The mobility and bioavailability of these metals and their geochemical forms widely varied according to pH, soil organic matter, biochar types, and application rates. As an environmentally friendly and economical material, biochar emphasizes its importance as a tool that makes the soil more suitable for safe cultivation in the short term and its long-term sustainability. This study proves that it reduces the mobility of HMs, their environmental risks and contributes to food safety. It also confirms that performing more controlled experiments, such as a pot, is a disciplined and effective way to assess the suitability of different types of biochar as soil modifications to restore HMs contaminated soil via controlling the mobilization of these minerals.

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Reduction of Microorganisms on Citrus Fruit Surfaces during Packinghouse Processing

Journal of Food Protection ◽

10.4315/0362-028x-61.7.903 ◽

1998 ◽

Vol 61 (7) ◽

pp. 903-906 ◽

Cited By ~ 39

Author(s):

STEVEN PAO ◽

G. ELDON BROWN

Keyword(s):

Test Organism ◽

Citrus Fruit ◽

Microbial Populations ◽

Most Probable Number ◽

Probable Number ◽

E Coli ◽

Plate Counts ◽

High Level ◽

Inoculation Study ◽

Fruit Surface

Citrus fruit surface microbial populations were evaluated following various packingline processes of seven Florida commercial packinghouses. At each packinghouse, six fruits (oranges or tangerines) were collected at each of four sampling points. The sampling was conducted in duplicate; thus, 336 fruit were evaluated during this survey. Average aerobic plate counts and yeast and mold counts on fruit surfaces before washing were about 4.0 log CFU/cm2 and 3.3 log CFU/cm2, respectively, and were reduced to 2.1 log CFU/cm2 and 1.3 log CFU/cm2, respectively, by packinghouse processing. Waxing alone reduced the average fruit surface aerobic plate counts and coliform counts from 3.7 log CFU/cm2 and 35.2 most probable number (MPN)/cm2, respectively, to 2.6 log CFU/cm2 and 1.4 MPN/cm2. No Escherichia coli was recovered from fruit at the end of packinghouse processing, and no salmonellae were found on fruit during the entire processing. In an inoculation study to test the effect of packinghouse processes, test organism E. coli was applied to fruit to achieve a high level (4.8 log CFU/cm2) of contamination. The average E. coli count was reduced about 2.4 log cycles by washing and rinsing with potable water (40 psi, 25 °C) for about 30 s. The combination of washing and waxing significantly reduced the inoculated level of E. coli from 4.8 to 1.4 log CFU/cm2.

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Effects of potassium azide on soil microbial populations and soil enzymatic activities

Canadian Journal of Microbiology ◽

10.1139/m75-079 ◽

1975 ◽

Vol 21 (4) ◽

pp. 565-570 ◽

Cited By ~ 16

Author(s):

W. D. Kelley ◽

R. Rodriguez-Kabana

Keyword(s):

Soil Enzyme ◽

Soil Microflora ◽

Microbial Populations ◽

Bacterial Populations ◽

Soil Microbial ◽

Fungal Populations ◽

Potassium Azide ◽

Time Changes ◽

Bacteria And Fungi ◽

Microbial Numbers

Preplant applications of potassium azide (KN3) to pine nursery beds were evaluated for effect on the soil microflora and on soil enzyme activity where either plastic-sealing or water-sealing techniques were used. Two weeks after incorporation of azide (0–224 kg/ha), soil samplings revealed reduced populations of bacteria and fungi and a corresponding decline in invertase and amylase activities. These effects were proportionate to the amount of azide used and were more pronounced in plastic-sealed plots. Phosphatase activity was little affected. Five weeks after azide application, bacterial populations were higher in treated plots than in controls. Greater numbers of bacteria were recorded from plastic-sealed plots and highest populations coincided with plots receiving the highest rates of azide, regardless of the sealing technique. Fungal populations at this sampling were generally less in treated plots than in the controls, but were higher under plastic seal. At this time, changes in invertase and amylase activities did not correspond to increased microbial numbers. Sixteen weeks after applications of KN3, bacterial populations in treated plots did not differ significantly from controls, but remained higher in plastic-sealed than water-sealed plots. Fungal populations under plastic seal had changed little and remained significantly lower in treated water-sealed plots than in controls. The earlier recorded reduction in invertase and amylase activities was still evident at the final sampling.

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IMMOBILIZATION OF EXCHANGEABLE CROMIUM IN A CONTAMINATED SOIL USING NATURAL ZEOLITE AS AN EFFECTIVE ADSORBENT

Vietnam Journal of Science and Technology ◽

10.15625/2525-2518/58/5a/15155 ◽

2020 ◽

Vol 58 (5A) ◽

pp. 10

Author(s):

Van Minh Dang ◽

Huu Tap Van ◽

Thi Bich Hanh Nguyen ◽

Dinh Vinh Nguyen ◽

Thị Tuyet Nguyen ◽

...

Keyword(s):

Soil Ph ◽

Contaminated Soil ◽

Contaminated Soils ◽

Natural Zeolite ◽

Organic Matters ◽

Amended Soils ◽

Mn Oxide ◽

Content Ratio ◽

Incubation Experiments ◽

Exchangeable Fraction

This work investigated the effects of soil pH and the content ratio of natural zeolite on Cr contaminated soil. The immobilization experiments of the exchangeable Cr in contaminated soils were conducted using the batch method. The incubation experiments were carried out over 30 days in plastic bottles to determine five fraction of Cr existence (exchangeable fraction (F1), Fe/Mn/Oxide (F2), carbonate bound (F3), organic matters (F4) and residual (F5)) in amended soils after incubation. Results showed that the content and proportion of the exchangeable Cr decreased with an increase in soil pH from 5 to 9. At soil pH 5, the exchangeable Cr in soil reduced from 44.80±0.772 mg/kg (initial soil) to 17.72±0.300 mg/kg after 30 days of incubation with natural Zeolite 3%. Meanwhile, the exchangeable Cr of soil also decreased with increasing the content ratio of natural zeolite from 1% to 5% in soil. The ratio of 3% was suitable for incubation of the exchangeable Cr in contaminated soil with natural zeolite. The exchangeable Cr in contaminated soil decreased from 80.34% at un-amended soil treatment to 25.06% after incubation of 30 days. The forms of carbonate bound (F3) and organic matters (F4) in amended soils increased to 36.54% and 28% compared with 4.26% and 6.90% in un-amended contaminated soil. Ion exchange, precipitation and adsorption on the surface of natural zeolite might be the potential mechanisms of immobilization of the exchangeable Cr. The results indicated that natural zeolite can be used as the effective adsorbent for immobilizing the exchangeable Cr in contaminated soils and leading to a decrease in the environmental risk from Cr toxicity.

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Agrichemicals boost the effects of antibiotics on antibiotic resistance evolution

10.7287/peerj.preprints.26925 ◽

2018 ◽

Author(s):

Brigitta Kurenbach ◽

Amy M Hill ◽

William Godsoe ◽

Sophie van Hamelsveld ◽

Jack A Heinemann

Keyword(s):

Antibiotic Resistance ◽

Acquired Resistance ◽

Genotypic Diversity ◽

Microbial Populations ◽

Phenotypic Variance ◽

Short Term ◽

Resistance Evolution ◽

Term Evolution ◽

Comprehensive Test ◽

Selection For

Antibiotic resistance is medicine’s climate change: caused by human activity, and resulting in more extreme outcomes. Resistance emerges in microbial populations when antibiotics act on phenotypic variance within the population. This can arise from either genotypic diversity (resulting from a mutation or horizontal gene transfer), or from ‘adaptive’ differences in gene expression due to environmental variation. Adaptive changes can increase fitness allowing bacteria to survive at higher concentrations of the antibiotic. They can also decrease fitness, potentially leading to selection for antibiotic resistance at lower concentrations. There are opportunities for other environmental stressors to promote antibiotic resistance in ways that are hard to predict using conventional assays. Exploiting our observation that commonly used herbicides can increase or decrease the minimum inhibitory concentration (MIC) of different antibiotics, we provide the first comprehensive test of the hypothesis that the rate of antibiotic resistance evolution under specified conditions can increase, regardless of whether a herbicide increases or decreases the antibiotic MIC. Short term evolution experiments were used for various herbicide and antibiotic combinations. We found conditions where acquired resistance arises more frequently regardless of whether the exogenous non-antibiotic agent increased or decreased antibiotic effectiveness. This “damned if you do/damned if you don’t” outcome suggests that the emergence of antibiotic resistance is exacerbated by additional environmental factors that influence competition between bacteria. Our work demonstrates that bacteria may acquire antibiotic resistance in the environment at rates substantially faster than predicted from laboratory conditions.

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Pollen̵1Pistil Interactions in Eucalyptus calophylla Provide No Evidence of a Selection Mechanism for Aluminium Tolerance

Australian Journal of Botany ◽

10.1071/bt9930541 ◽

1993 ◽

Vol 41 (5) ◽

pp. 541 ◽

Cited By ~ 3

Author(s):

LM Egerton-Warbuton ◽

BJ Griffin ◽

BB Lamont

Keyword(s):

Pollen Tube ◽

Soil Ph ◽

Aluminium Tolerance ◽

Forest Site ◽

Al Tolerance ◽

Mine Site ◽

Reproductive Tissues ◽

Forest Sites ◽

Significant Difference ◽

Selection For

Selection for aluminium (Al) tolerance was assessed by studying pollen-pistil interactions in Eucalyptus calophylla trees colonising a 30-year-old abandoned coal mine-site (soil pH 4.3) compared with E. calophylla trees on an adjacent forest-site (soil pH 5.3). Energy-dispersive X-ray micro-analysis of reproductive tissues demonstrated that low levels of Al occurred in the stigma, lower style and unfertilised ovules of forest-site flowers. In contrast, significantly higher levels of Al were detected in all reproductive tissues of mine-site flowers. Al concentrations were higher at the base of the style than in the stigma. Al was also detected in stigmatic exudates of mine-site flowers. Selection for Al tolerance occurred in the anther of mine-site flowers as pollen from mine-site flowers germinated six-fold (15.6%) compared with forest-site pollen (2.6%) at the highest concentration of Al (22 ppm) used. However, the rate of pollen tube growth was not significantly different between mine- and forest-sites at any Al concentration. Tolerance of Al by the mine-site pollen was not shared by the progeny as there was no increase in the survival or growth of mine-site seedlings in mine soils over forest-site seedlings. Controlled pollinations between mine-/forest-site pollen and mine-site pistils demonstrated that there was no significant difference in the number of mine- or forest-site pollen tubes at any level in the style in mine-site pistils. Pollen tube abnormalities principally occurred in mine-site pistils. We concluded that there is no evidence yet for a genetically-based tolerance of Al in E. calophylla on coal mining soils.

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Rhizosphere microbial populations in contaminated soils

Water Air & Soil Pollution ◽

10.1007/bf02406163 ◽

1997 ◽

Vol 95 (1-4) ◽

pp. 165-178 ◽

Cited By ~ 67

Author(s):

T. D. Nichols ◽

D. C. Wolf ◽

H. B. Rogers ◽

C. A. Beyrouty ◽

C. M. Reynolds

Keyword(s):

Contaminated Soils ◽

Microbial Populations

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The response of swede varieties and their hybrids to soil pH

The Journal of Agricultural Science ◽

10.1017/s0021859600062262 ◽

1975 ◽

Vol 85 (3) ◽

pp. 395-401 ◽

Cited By ~ 4

Author(s):

O. A. Denton ◽

W. J. Whittington

Keyword(s):

Regression Analysis ◽

Soil Ph ◽

Low Ph ◽

Average Yield ◽

Inheritance Patterns ◽

High Ph ◽

Number Of Leaves ◽

Selection For ◽

Marked Resistance

SUMMARYFour swede varieties and their six F1 hybrids were grown for 2 years in plots varying in pH from 4·2 to 8·4. Yields were highest at intermediate pH's and the average yield of the hybrids was greater than that of the parents. The plants on the low pH plots (4·2, 4·6, 4·7) were less infected with mildew than those at high pH (6·7, 7·7, 8·4). There was no marked resistance to mildew amongst the varieties. The response by the parents and hybrids was assessed by regression analysis and showed that the variety Reform was most reactive and Harvester most stable. Stability patterns appeared to be inherited. Inheritance patterns for yield and number of leaves were determined. It was concluded that selection for better swedes should be carried out in environments other than those to which the crop is currently restricted.

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