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PubMed2006

Seasonal variation of microbial ecology in hemlock soil of Tatachia Mountain, Taiwan.

BACKGROUND AND PURPOSE: Forest soil microorganisms and fauna decompose the organic materials, and thus strongly influence the nutrient cycling of the ecosystem. Soil microorganisms also contribute to soil structure and soil fertility. In Taiwan, the microbial distributions of soils have only been determined in acidic soil, inorganic acidic soil, upland soil, alkaline soil and power plant areas. There are few data on the microbial populations of forest soils. Tatachia Mountain is located in the central part of Taiwan and is a typical high altitude protected ecosystem area, designated as a National Park. This study investigated the role of microorganisms in the ecology and nutrient transformation of forest soil in Taiwan. METHODS: As part of long-term ecological research in Taiwan, the environmental conditions, seasons, microbial populations, biomass and organic acid contents of hemlock soil were investigated. We also studied the effect of depth on microbial populations and biomass. RESULTS: The soil temperatures were between 5.5 and 15.6 degrees C and the soil pH ranged from 3.3 to 4.4. Total organic carbon and total nitrogen contents ranged from 2.3 to 37.1% and from 0.3 to 1.7%, respectively. The carbon/nitrogen ratio was between 8.2 and 24.4. In topsoil, each gram of soil contained 10(5)-10(7) colony-forming units (CFU) culturable bacteria, 10(2)-10(5) CFU actinomycetes, 10(3)-10(5) CFU fungi, 10(4)-10(6) CFU cellulolytic microbes, 10(4)-10(6) CFU phosphate-solubilizing microbes, and 10(3)-10(6) CFU nitrogen-fixing microbes. Microbial populations were higher in topsoil compared with subsoil, but lower in topsoil than in organic layer. Microbial populations also decreased with the depth of soil. Microbial populations at 1E horizon were 0.6% to 9.4% of those at O horizon. The microbial biomass evaluated contained carbon 391-1013 mug, nitrogen 51-146 mug, malic acid 76-557 nM and succinic acid 37-527 nM per gram of soil. Summer season had higher microbial populations, biomass and organic content than winter season, but the differences were not significant. CONCLUSION: Heavy coverage of organic matter was found in hemlock and spruce soils and was associated with acidic pH. Microbial populations decreased with increasing soil depth. Microbes play a very important role in organic matter decomposition and nutrition transformation in hemlock soil.

Actinobacteria↗
PubMed2004

Key role of the low molecular size fraction of soil humic acids for fluorescence and photoinductive activity.

The IHSS soil humic acid (HA) standard and two HAs from soils of very different origin (Chernozem and Ranker) were fractionated by tandem size-exclusion chromatography-polyacrylamide gel electrophoresis. From each HA, three fractions with different molecular sizes (MSs) and electrophoretic mobilities were obtained and investigated for their fluorescence properties and abilityto photoinduce the transformation of 2,4,6-trimethylphenol and herbicide fenuron. Regardless of the source of the HA, the two high MS fractions were found to be very weakly fluorescent. They photoinduced the degradations of fenuron and 2,4,6-trimethylphenol less efficiently than the bulk HA (10-50-fold and 1.4-5.3-fold, respectively). In contrast, the low MS fraction was proved to be fluorescent and to photoinduce the transformation of probes as least as efficiently than the bulk HA. These results show that (i) most of fluorophores and a great part of photoinductive chromophores are located in the low MS fractions of soil HAs and (ii) this distribution of photochemically active constituents may be characteristic across broad soil types.

Chromatography, Gel↗
PubMed2000

An improved analytical procedure for determination of total actual acidity (TAA) in acid sulfate soils

An improved analytical procedure is proposed for the determination of total actual acidity (TAA) in acid sulfate soils. The proposed method involves the use of a superior extracting solution, 0.5 M BaCl2, instead of the 1 M NaCl used by Konsten et al. (Konsten CJM, Brinkman R, Andriesse W. A field laboratory method to determine total potential and actual acidity in acid sulfate soils. In: Dost H, editor. Selected papers of the Dakar Symposium on Acid Sulfate Soils. Wageningen: ILRI Publication 44, 1988:106-134.) and improved experimental design to obtain correction factors for calculating TAA. The introduction of a multi-choice procedure also enables increased accuracy of analytical results to be obtained if more accurate TAA estimation is required.

Journal Article↗
PubMed1997

Toxicity of acid-sulfate soil leachate and aluminum to embryos of the Sydney Rock oyster.

The toxicity of leachate water from acid-sulfate soil to the early embryonic development of the Sydney Rock oyster, Saccostrea commercialis, was assessed. Concentrations of acid-sulfate soil leachate water as low as 3.3% in seawater were found to decrease the normal development of oyster embryos after 48 hr exposure, and this effect could not be attributed to any significant change in pH or salinity. An EC50 value for the acid-sulfate soil leachate water of 2.5 to 2.9% in seawater was obtained, and the no observed effect concentration was determined at a concentration of 2% in seawater. In tests conducted with aluminum added to seawater, a significant decrease in the percentage of embryos developed to the D-veliger stage occurred at concentrations of 150 micrograms/liter and greater, with no effects at 100 micrograms/liter. An EC50 of 225 micrograms/liter for the effect of added aluminum on embryo survival was obtained and all embryos showed developmental abnormalities at concentrations of 400 micrograms/liter and greater. A significant decrease in the embryonic development occurred when the fertilized eggs were incubated in pH-adjusted seawater at pH values < or = 6.75, but no significant effects were found at pH 7.0 or above. Since aluminum was present in high concentrations in the acid-sulfate soil leachate water, it was concluded that aluminum was the main toxicant in the acid-sulfate water that disrupted the oyster embryonic development.

Aluminum↗
PubMed1984

Chlorination of ozonated soil fulvic acid: mutagenicity studies in Salmonella.

Samples of soil fulvic acid (SFA) were ozonated and subsequently chlorinated under acidic or slightly basic conditions. The residues were tested for His+ reversion in a fluctuation assay, using Salmonella typhimurium TA100 as the tester strain. The ozonated/chlorinated samples were mutagenic, but activity was dependent on the amount of ozone utilized and the pH of the reaction medium. Although increases in cell concentrations were also induced by some mutagenic samples, this alone did not account for the mutagenicity observed. Unchlorinated samples displayed insignificant activity.

Benzopyrans↗
PubMed2003

3-D structural modeling of humic acids through experimental characterization, computer assisted structure elucidation and atomistic simulations. 1. Chelsea soil humic acid.

This paper describes an integrated experimental and computational framework for developing 3-D structural models for humic acids (HAs). This approach combines experimental characterization, computer assisted structure elucidation (CASE), and atomistic simulations to generate all 3-D structural models or a representative sample of these models consistent with the analytical data and bulk thermodynamic/structural properties of HAs. To illustrate this methodology, structural data derived from elemental analysis, diffuse reflectance FT-IR spectroscopy, 1-D/2-D 1H and 13C solution NMR spectroscopy, and electrospray ionization quadrupole time-of-flight mass spectrometry (ESI QqTOF MS) are employed as input to the CASE program SIGNATURE to generate all 3-D structural models for Chelsea soil humic acid (HA). These models are subsequently used as starting 3-D structures to carry out constant temperature-constant pressure molecular dynamics simulations to estimate their bulk densities and Hildebrand solubility parameters. Surprisingly, only a few model isomers are found to exhibit molecular compositions and bulk thermodynamic properties consistent with the experimental data. The simulated 13C NMR spectrum of an equimolar mixture of these model isomers compares favorably with the measured spectrum of Chelsea soil HA.

Humic Substances↗
PubMed1999

Acid sulfate soils in intertidal mosquito breeding habitats and implications for habitat modification.

Public concern about the use of chemicals for mosquito control in coastal Australia has lead to the development of physical habitat modification methods that aim to reduce mosquito populations to acceptable levels. Habitat modification methods include runnels (depth < 0.30 m) and ditches (depth > 0.50 m). During excavation for habitat modification, a risk of exposure of acid sulfate soils may exist. Acid sulfate soils are soils that contain iron sulfides, in particular pyrite (FeS2), and produce sulfuric acid when exposed to air. These soils occur predominantly in coastal lowland areas that are also prime mosquito breeding habitats. The paper discusses the problem and illustrates the application of survey methods that facilitate wise decision making and management of intertidal wetlands.

Australia↗
PubMed2003

Effect of fly ash, organic wastes and chemical fertilizers on yield, nutrient uptake, heavy metal content and residual fertility in a rice-mustard cropping sequence under acid lateritic soils.

A field experiment was conducted for two years in sandy loam acid lateritic soil to study the direct effect of fly ash, organic wastes and chemical fertilizers on rice (Oryza sativa) and their residual effect on mustard (Brassica napus var glauca) grown in sequence. Rice yields were higher when fly ash, organic wastes and chemical fertilizers were used in an integrated manner as compared to sole application of chemical fertilizers. Yields of mustard were also higher under the residual effect of the former rather than the latter. However, this beneficial residual effect under integrated nutrient sources was inadequate for the mustard crop in the low fertility test soil. Hence, direct application of fertilizers was needed, in addition to residual fertility. The effect of fly ash on mean rice equivalent yield of the rice-mustard cropping sequence was highest (up to 14%) when it was used in combination with organic wastes and chemical fertilizers. While the yield increase was 10% when it was used in combination with only chemical fertilizers. The minimum yield advantage, 3%, occurred when fly ash was applied alone. The equivalent yield of the rice-mustard cropping sequence was equally influenced by either of the organic wastes. Cadmium and Ni content in rice grain and straw were less under the direct effect of fly ash. The residual effect on mustard was similar for Ni content in seed and stover; however, Cd content was increased. Beneficial residual soil chemical properties in terms of pH, organic carbon and available N, P and K were noted for integrated nutrient treatments involved fly ash, organic wastes and chemical fertilizers as compared to continuous use of only chemical fertilizers. Application of fly ash alone was effective in raising soil available P. Thus, integrated use of fly ash, organic wastes and chemical fertilizers was beneficial in improving crop yield, soil pH, organic carbon and available N, P and K in sandy loam acid lateritic soil.

Agriculture↗
PubMed1997

Toxicity of acid-sulphate soil leachate and aluminium to the embryos and larvae of Australian bass (Macquaria novemaculeata) in estuarine water.

The toxicity of leachate water from acid-sulphate soil to the early life stages of Australian bass, Macquaria novemaculeata, incubated in seawater was evaluated. Acid-sulphate soil leachate water (pH> or =6.8) delayed the hatching of fertilised eggs, but after 48 h the per cent hatching was normal. In comparison, acidic saline water (25 per thousand salinity) at pH 4.0 or less prevented embryos from hatching. The survival of yolk-sac larvae exposed to acid-sulphate soil leachate water at a concentration of 32% in seawater and an initial pH of 7.2, was significantly different to controls after 96 hours. In corresponding tests with only acidified saline water (20 per thousand salinity), pH levels equal to or below 5.0 killed yolk-sac larvae after 96 h exposure. Aluminum showed a pH dependent toxicity to yolk-sac larvae, with added aluminium as low as 200 microg litre(-1) having a significant effect on larval survival at pH 5.5, and concentrations of 600-800 microg litre(-1) having a significant effect on larval survival at an initial pH range of 6.0 < pH < 6.8. It was concluded that significant mortality of the early life stages of Australian bass would occur if they are exposed to acid-sulphate soil leachate that results in a pH in the receiving estuarine water below 5.5, or when the pH is below 6.8 and aluminium is present at a total concentration of 800 microg litre(-1) or greater.

Journal Article↗
PubMed2003

Distribution of rare earth elements in anionic, cationic and particulate fractions in boreal humus-rich streams affected by acid sulphate soils.

The abundance, fractionation and physicochemical forms of rare earth elements (REEs) were determined in five boreal humus-rich streams (dissolved organic carbon, DOC = 14-40 mg/l) affected by acid sulphate soils. The sampling was carried out during high-water flow in autumn when the acid sulphate soils are extensively flushed. The analytical procedures included ion-exchange experiments in field and ICP-MS determination. There was a general decrease in pH (range 4.5-6.2) and increase in the REE concentrations (La range 0.82-23 microg/l) as the proportion of the catchment cover of acid sulphate soils increased, explained by high amounts of REEs in the acidic runoff from such soils. In each stream, four different REE fractions were identified: (1) A cationic fraction, which is dominant in the REE-rich runoff from the acid sulphate soils and which is depleted in HREEs due to hydrochemical and/or geochemical processes, (2) an anionic fraction identified as humus-REE complexes, which in general is more abundant the higher the DOC concentrations and which also becomes increasingly abundant across the lanthanide series, (3) a fraction having a well-developed MREE enrichment, presumably consisting of colloidal REEs, and (4) a minor uncharacterised particle-associated fraction. The REE pool in the streams thus consists of several coexisting and contrasting REE species. The identification and quantification of such species is a prerequisite for the precise and accurate characterisation of the REE hydrochemistry of the streams.

Carbon↗
PubMed2003

Chemical species of Al reacting with soil humic acids.

The formation and presence of aluminum tridecamer (Al(13), [AlO(4)Al(12)(OH)(24)(H(2)O)(12)](7+)) in solution was strongly inhibited by soil humic acids (HA), as shown by liquid-state 27Al-nuclear magnetic resonance (NMR) analyses. It was also observed that Al(13) coprecipitated with HA in the form of Al(13)-HA complexes, as shown by solid-state magic angle spinning (MAS) 27Al-NMR analyses. Tetrahedral Al in the Al(13)-HA complexes was gradually converted to octahedral Al, indicating that Al(13) in Al(13)-HA complexes was decomposed into Al-HA complexes with reaction time. When HA was present in the acidic Al solution before the partial neutralization, the precipitates formed after the partial neutralization did not contain any tetrahedral Al, indicating the absence of Al(13) and that HA is a strong inhibitor of Al(13) formation. These results indicate that Al(13) is not formed from Al complexed with soil HA after partial neutralization. If Al(13) was added to soils, it would preferentially form precipitates of non-phytotoxic Al(13)-HA complex in the presence of excess HA (i.e. a COOH/Al(13) molar ratio of more than 9) and gradually be converted to an octahedral Al-HA complex. Therefore, Al(13) is not a major plant-growth inhibitor in humus-rich acidic soils.

Aluminum Compounds↗
PubMed2006

Use of DNA marker to select well-adapted Phaseolus-symbionts strains under acid conditions and high temperature.

Soil acidity and high temperature contribute to the failure of nodulation in the common bean. It is therefore urgent to select strains with a high competitive ability under these stress conditions. Two Egyptian Rhizobium etli strains, EBRI 2 and EBRI 26, were examined against Rhizobium tropici CIAT 899G labeled with the gus (beta-glucuronidase) reporter gene. EBRI 2 and EBRI 26 were less competitive than CIAT 899G under acid conditions with both the Egyptian cultivar Giza 3 and the Colombian cultivar Rab 39. However, EBRI 2 and EBRI 26 gave higher nodule occupancy (78% and 62.5, respectively) than the nodule occupancy (18.5% and 35%) obtained by CIAT 899G at 35 degrees C with cultivar Giza 3. Soil acidity (pH 5.8) was less detrimental to the nodule occupancy of EBRI 2 than EBRI 26 when they tested in competition with CIAT 899G.

DNA, Plant↗
PubMed2004

Alkaline biosolids and EDTA for phytoremediation of an acidic loamy soil spiked with cadmium.

A greenhouse experiment was conducted to investigate the growth of Brassica juncea and Cd phytoextraction in a mimicked Cd contaminated acidic loamy soil amended with alkaline biosolids, prepared from sewage sludge and coal fly ash, in the presence and absence of EDTA at 2 mmol kg(-1). The acidic loamy soil was spiked with 0, 5, 20, 50 and 100 mg Cd kg(-1) in the form of CdCO(3) and then amended with 4% alkaline biosolids (w/w). Alkaline biosolids and 0.12% CaCO(3) amendments resulted in a higher biomass than unamended soil spiked with 20 mg kg(-1) Cd where plants did not survive and of the two amendments, alkaline biosolids amendment had higher plant dry weight yield and phytoextraction of Cd. Adding 2 mmol kg(-1) EDTA to alkaline biosolids amended soil significantly increased the solubility of Cd ions by 9- to 29-fold, but plant Cd accumulation decreased by a factor of 24-48%. The results indicate that alkaline biosolids amendment is an effective approach for assisting growth of B. juncea and phytoextraction of Cd from the contaminated acidic loamy soil, but further application of chelating agents did not enhance the phytoextraction efficiency of Cd.

Biodegradation, Environmental↗
PubMed2001

Overexpression of malate dehydrogenase in transgenic alfalfa enhances organic acid synthesis and confers tolerance to aluminum.

Al toxicity is a severe impediment to production of many crops in acid soil. Toxicity can be reduced through lime application to raise soil pH, however this amendment does not remedy subsoil acidity, and liming may not always be practical or cost-effective. Addition of organic acids to plant nutrient solutions alleviates phytotoxic Al effects, presumably by chelating Al and rendering it less toxic. In an effort to increase organic acid secretion and thereby enhance Al tolerance in alfalfa (Medicago sativa), we produced transgenic plants using nodule-enhanced forms of malate dehydrogenase and phosphoenolpyruvate carboxylase cDNAs under the control of the constitutive cauliflower mosaic virus 35S promoter. We report that a 1.6-fold increase in malate dehydrogenase enzyme specific activity in root tips of selected transgenic alfalfa led to a 4.2-fold increase in root concentration as well as a 7.1-fold increase in root exudation of citrate, oxalate, malate, succinate, and acetate compared with untransformed control alfalfa plants. Overexpression of phosphoenolpyruvate carboxylase enzyme specific activity in transgenic alfalfa did not result in increased root exudation of organic acids. The degree of Al tolerance by transformed plants in hydroponic solutions and in naturally acid soil corresponded with their patterns of organic acid exudation and supports the concept that enhancing organic acid synthesis in plants may be an effective strategy to cope with soil acidity and Al toxicity.

Adaptation, Physiological↗
PubMed1996

Immunological determination of triazine pesticides bound to soil humic acids (bound residues).

An immunological method for the determination of triazine herbicides covalently bound to soil humic acids has been developed. A sandwich-immunoassay has been performed, based on both polyclonal humic acid-antibodies and monoclonal triazineantibodies. A peroxidase-labelled third antibody has been used for the photometric detection. A triazine-humic acid conjugate served as calibration standard. The coupling density for this conjugate has been determined by measuring the difference of free amino groups both with ninhydrin and with the trinitrobenzene sulfonic acid method. In addition, the coupling density has been confirmed by scintillation counting using a (14)C-atrazine derivative. Due to nonspecific interactions between antibody proteins and humic acids, different blocking steps had to be performed. Finally, the assay has been applied to a triazine contaminated soil sample. Humic acids (including bound residues) have been extracted by diluted sodium carbonate solution. Concentrations of bound atrazine residues have been found in the range of 2 mg/kg soil on fields where triazine herbicides has been applied over a period of 21 years. These results are comparable to both the applied amount and the nonextractable fraction.

Journal Article↗
PubMed2000

[Continuous cropping obstacle and rhizospheric microecology. III. Soil phenolic acids and their biological effect].

The contents of phenolic acids in the extracts of soil and roots of continuously cropped for five years and normally cropped soybean in Heilongjiang province and their biological effects were studied with HPLC method. The result showed that the contents of p-hydroxy benzoic acid, vanillic acid(extracted by 1 mol.L-1 NaOH) in continuous cropping soil were significant higher than that in normal cropping soil, and the content of vanillin had no significant difference in these soils. The contents of p-hydroxybenzoic acid, vanillic acid, vanillin, ferulic acids, and coumarin of aqueous extracts of soyhean roots were higher in continuous cropping than in normal cropping soil. The activity of polyphenol oxidase in continuous cropping soil was higher than in normal cropping soil. Under conditions of water culture and adding exogenous p-hydroxybenzoic acid, the aqueous extract of soybean roots inhibited the growth of soybean seedlings. After a week of exogenous phenolic acids addition, the residual rates of p-hydroxybenzoic acid, vanillic acid, vanillin, benzoic acid, ferulic acids, and coumarin were 10.4%, 15.3%, 4.1%, 2.3%, 5.2%, 17.5%, respectively. There was a very significant exponential relationship between the addition amount of exogenous phenolic acids and the fungi population in soil.

Agriculture↗