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PubMed2002

Separation and identification of aromatic acids in soil and the Everglades sediment samples using solid-phase microextraction followed by capillary zone electrophoresis.

The separation and identification of aromatic acids in soil and the Everglades sediment samples was carried out using solid-phase microextraction (SPME) followed by capillary zone electrophoresis (CZE). The soil and sediment samples were subject to a series of sample treatments including oxidative hydrolysis with molecular oxygen in a sodium hydroxide solution, acidification and filtration. The aromatic acids in the sample filtrate were extracted using SPME with a polyacrylate-coated fiber. The acids adsorbed on the fiber were subsequently desorbed in methanol. The desorbed acids were then separated by CZE. Several aromatic acids (e.g.. salicylic acid, p-coumaric acid, ferulic acid and vanillic acid) in both soil and sediment samples were separated, identified and quantified. The results of this study show that the combination of SPME with CZE is promising for environmental analysis.

Acids↗
PubMed2001

Enhanced degradation of phenoxyacetic acid in soil by horizontal transfer of the tfdA gene encoding a 2,4-dichlorophenoxyacetic acid dioxygenase.

Few studies have investigated the possible impact of in situ gene transfer on the degradation of xenobiotic compounds in natural environments. In this work we showed that horizontal transfer of the tfdA gene, carried on plasmid pRO103, to phenol degrading recipient strains significantly increased the degradation rate of phenoxyacetic acid in sterile and non-sterile soil microcosms. The tfdA gene encodes a 2,4-dichlorophenoxyacetic acid/2-oxoglutarate dioxygenase and by complementation with the phenol degradation pathway an expanded catabolic substrate range, now including phenoxyacetic acid, is evolved. Presence of selective pressure had a positive effect on the emergence of transconjugants. However, even in the absence of phenoxyacetic acid transconjugant populations were detected and were kept at a constant level throughout the experimental period. The residuesphere (interface between decaying plant material and soil matrix) of dry leaves of barley was shown to be a hot-spot for gene transfer and presence of barley straw increased the conjugation frequencies in soil microcosms to the same extent as presence of organic nutrients. The results of this study indicate that dissemination of catabolic plasmids is a possible mechanism of genetic adaptation to degradation of xenobiotic compounds in natural environments, and that complementation of catabolic pathways possibly plays an important role in the evolution of new degradative capabilities. The application of horizontal gene transfer as a possible tool in bioremediation of contaminated sites is discussed.

Journal Article↗
PubMed2004

Interactions between variable-charge soils and acidic solutions containing fluoride: an investigation using repetitive extractions.

The reaction between two variable-charge soils and acidic solutions containing F was investigated with a repetitive extraction method. When added F concentration was 10(-4) mol/L, F did not markedly enhance solution pH in the whole prolonged extractions, in comparison with F-free acidic solution extractions. Most of the added F was adsorbed on soil surfaces and Al-F complexes were the dominant F species in solution. With increasing extractions, the fraction of Al-F slightly increased, arising from dissolution and/or desorption of Al. In comparison with F-free acidic solution extractions, F-induced Al dissolution did not significantly increase Al release, probably because of the modest reactivity of metal-F surface complexes at terminal sites at low F loading. The gradual decrease in Al release in the following extractions was due to the gradual depletion of readily reactive Al-containing mineral phases. In contrast to the low F loading, at an F concentration of 10(-3) mol/L, the pH was enhanced dramatically in the initial extraction and a high pH was maintained in the following extractions. In the initial extraction, the increase in negative surface charges and solution pH seemingly depressed proton-induced Al dissolution and enhanced readsorption of some positively charged Al-F complexes, resulting in low amounts of Al and F in solution. In the following several extractions, F-induced Al dissolution and desorption of Al-F complexes substantially enhanced the amounts of Al and F, and the fraction of Al-F complexes in solution. Several interconnected mechanisms such as ligand exchange, the release of OH(-) ions from soluble hydroxylated Al groups, desorption of Al as Al-F complexes, and F-induced breakdown of soil minerals were responsible for the alteration in pH, Al release, and the fraction of Al-F complexes in the later extractions. A molecular-level interpretation is needed in order to address the different impacts of varying F concentration levels on soil chemistry and environments.

Journal Article↗
PubMed2006

Interrelationships between p-coumaric acid, evapotranspiration, soil water content, and leaf expansion.

Increasing concentrations of p-coumaric acid applied to (cucumber seedling)-[Cecil A( p ) soil-sand mixture (or soil)] systems inhibited evapotranspiration (primarily transpiration) and leaf area expansion of cucumber seedlings and increased soil moisture. Higher soil moisture resulting from the inhibition of evapotranspiration lowered soil solution concentrations of p-coumaric acid by 14-40% but did not significantly influence the inhibitory effects of p-coumaric acid on seedlings. Inhibition of evapotranspiration and total leaf area and increases in lowest daily soil water were observed 1-3 d after the first p-coumaric acid treatment, whereas inhibition of absolute and relative rates of leaf expansion was observed within a 24-hr period. Development of the maximum effects of p-coumaric acid required several additional days. Recovery from effects, i.e., return to control levels, after p-coumaric acid depletion from soil solution was a gradual process requiring days for evapotranspiration, lowest daily soil water, and total leaf area, but was slightly faster for leaf area expansion. It appears, at least for short-term studies, that the initial input or treatment concentrations of p-coumaric acid represented a reasonable estimate of dose despite the dynamic nature of soil solution concentrations, and that the lowering of available p-coumaric acid concentrations, associated with the elevation of soil moisture, did not result in a concurrent detectable seedling response. However, increased soil moisture associated with p-coumaric acid treatments of sensitive species suggests a means by which the magnitude of some allelopathic interactions may be modified and resource competition and allelopathy could interact.

Coumaric Acids↗
PubMed2003

Determination of low molecular weight organic acids in soil, plants, and water by capillary zone electrophoresis.

Determination of low molecular weight organic acids in soils and plants by capillary zone electrophoresis was accomplished using a phthalate buffer and indirect UV detection mode. The influence of some crucial parameters, such as pH, buffer concentration and surfactant were investigated. A good separation of seven organic acids was achieved within 5 min using an electrolyte containing 15 mmol L(-1) potassium hydrogen phthalate, 0.5 mmol L(-1) myristyltrimethylammonium bromide (MTAB), and 5% methanol (MeOH) (v/v) at pH 5.60, separation voltage -20 kV, and temperature 25 degrees C. The relative standard deviation (n=5) of the method was found to be in range 0.18-0.56% for migration time and 3.2-4.8% for peak area. The limit of detection ranged between 0.5 micro mol L(-1) to 6 micro mol L(-1) at a signal-to-noise ratio of 3. The recovery of standard organic acids added to real samples ranged from 87 to 119%. This method was simple, rapid and reproducible, and could be applied to the simultaneous determination of organic acids in environmental samples.

Electrolytes↗
PubMed2006

Aluminium mobilization from acidic forest soils in Leigongshan area, Southwestern China: Laboratory and field study.

Aluminium mobilization from acidic forest soils in the remote Leigongshan area in southwestern China was investigated in the field and by a laboratory batch experiment using sequential extractions with HCl solutions with pH of approximately 3.4. Experimental data showed that strongly organically bound aluminium (Alp-Alcu) decreased significantly after sequential extraction, whereas exchangeable aluminium (Alex) increased in all three horizons. In the A-horizon with higher base saturation (BS), dissolved aluminium exchanged with base cations (BCs) on soil complex, causing lower aluminium release but significant leaching of BCs. In AB- and B-horizon with lower BS, more dissolved aluminium remained in solution. Al3+ activities in both experimental soil extracts and field soil waters strongly deviated from those predicted by the gibbsite model (i.e., pAl = pKsp + 3.0 pH) despite a significant increase in Al3+ with a decrease in pH. The soil organic-bound aluminium model, using Alcu and Alp to account for differences in the size of available Al pools in the soil, gave considerably better fits to both experimental and field data. SOM-Al model, approved by using Alex instead of organically bound aluminium (i.e., Alp and Alcu), could depict the changes in Al activities most successfully. We have concluded that Alp-Alcu is the main source of aqueous aluminium, whereas Alex plays an important role in regulating aluminium solubility during soil acidification.

Aluminum↗
PubMed2006

[Distribution characters and affecting factors of Al(i)/(Ca + Mg) molar ratio in acid forest soils].

By using principle component analysis (PCA) and partial least square (PLS) regression, this paper studied the distribution characters and their affecting factors of Al(i)/(Ca + Mg) molar ratio in acid forest soils in southern and southwestern China. The monitoring data from 2000 to 2002 showed that in most cases, the Al(i)/(Ca + Mg) molar ratio in soil moisture was lower than assumed critical value 1.0, indicating that significant aluminum toxicity to vegetation was not occurred in the study regions. PLS regression suggested that soil aluminum saturation (AlS) was the dominant factor affecting the Al(i)/(Ca + Mg) molar ratio in soil A horizon. Higher AlS led to a higher Al(i)/ (Ca + Mg) molar ratio in soil moisture. Despite of its lower acid deposition, Liuxihe basin had a higher Al(i)/(Ca + Mg) molar ratio in soil A horizon than other catchments, mainly due to its higher AIS. In deeper soil horizons (B1, B2 and BC), the inorganic aluminum (Al(i)) in soil moisture was the main factor affecting Al(i)/(Ca + Mg) molar ratio. Higher inorganic aluminum concentration resulted in higher Al(i)/(Ca + Mg) molar ratio. In each of study catchments, the vertical distribution of Al(i)/(Ca + Mg) molar ratio was basically identical with the distribution of inorganic aluminum (Al(i)) through soil profile. It was concluded that soil aluminum saturation was the main factor controlling the regional variation of Al(i)/(Ca + Mg) molar ratio in soil moisture, and the vertical distribution of soil Al(i)/(Ca + Mg) molar ratio in each site was mainly due to the vertical change of inorganic aluminum in soil moisture.

Acids↗
PubMed2005

Effect of some anions on the mobility of amino acids in soils by thin layer chromatography.

The mobility rate of some cyclic and aliphatic amino acids in terms of Rf values by using soil-thin layer chromatography shows the following order: glutamic acid > histidine > valine > leucine > serine > alanine. After conducting the studies to determine the effect of some anions, viz. MoO4(2-), B4O7(2-), C2O4(2-),CO3(2-), HCO3- and H2PO4- on the mobility of those amino acids, the mobility of the amino acids was found to increase with the increasing concentration of these anions up to a certain limit and thereafter the mobility rate declined except in case of glutamic acid which shows a fall in its movement throughout the entire range of their application in all cases. The results have been explained on the basis of a reaction mechanism involved in the interaction of these anionic species with soil colloids and amino acids in soil solution.

Amino Acids↗
PubMed2002

Effects of pig slurry application on soils and soil humic acids.

The effect of three annually consecutive additions of pig slurry at two rates (90 and 150 m3 x ha(-1) x year(-1) on soils and soil humic acids (HAs) was investigated in a field experiment under semiarid conditions. Soils and pig slurries were analyzed by standard methods. The HAs were isolated from soils and pig slurry by a conventional procedure based on alkaline extraction, acidic precipitation to pH 1, purification by repeated alkaline dissolutions and acidic precipitations, water washing, dialysis, and final freeze-drying. The HAs obtained were analyzed for elemental (C, H, N, S, and O) and acidic functional group (carboxylic and phenolic) composition, and by UV-vis, FT-IR, fluorescence, and ESR spectroscopies. With respect to the control soil, the pig slurry amended soils had greater pH and electrical conductivity, slightly larger total N content, and smaller values of C/N ratio. A decrease of total organic C was observed only in soils amended for 2 and 3 years at the higher slurry rate. With respect to control soil HA, pig slurry HA was characterized by larger contents of S- and N-containing groups, smaller acidic functional group and organic free radical contents, a prevalent aliphatic character, extended molecular heterogeneity, and smaller aromatic polycondensation and humification degrees. Amendment with pig slurry HA determines a number of modifications in soil HAs, including increase of C, S, and COOH contents, C/N ratios, and aliphaticity and decrease of extraction yields and N, O, phenolic OH, and organic free radical contents. These effects are generally more evident after the first year of slurry application and tend to disappear with increasing number of treatments. Most probably, over the years the slightly humified slurry HA is mineralized through extended microbial oxidation, whereas only the most recalcitrant components, such as S-containing, phenolic, and aliphatic structures, are partially accumulated by incorporation into soil HA.

Animals↗
PubMed2002

Influence of poultry manure on phosphorus availability and the standard phosphate requirement of crop estimated from quantity-intensity relationships in different soils.

Twelve samples comprising of non-calcareous, calcareous and acidic soils were used to study P availability parameters and standard phosphate requirement (SPR) in the presence and absence of poultry manure (PM). Adsorption of P and phosphate potential decreased while Olsen extractable P increased by PM addition, the extent varying with the type of soil. The calculated SPR to attain soil solution concentration of 0.2 microg P ml(-1) was invariably higher in fine textured soils. Acid and calcareous soils registered higher SPR compared to non-calcareous soils. PM addition lowered the SPR in all the soils. The observed P supplementation through PM ranged from 11.6% to 100% signifying no fertilizer P need in the latter. Calibration curves were drawn for calculating the SPR for a given soil solution P concentration without and with the addition of PM.

Animals↗
PubMed2004

[Transformation characteristics of sulfur forms in acid sulfate soils under different soil water conditions].

Aimed to detect the quantitative impact of soil water condition on the transformation of sulfur forms in acid sulfate soils (ASS), a simulation test was made with 8 treatments. The results indicated that water was an important factor affecting the transformation processes. Wet but not inundated or over dried condition was benefit to the oxidation of pyrite S and the formation of water soluble S (WS-S) and exchangeable S (Ex-S) in ASS. In the three treatments with different inundated and drained off cycles, soil pyrite S content averagely decreased 1.29-3.20 g x kg(-1) during a single drained off period, while soil WS-S and Ex-S contents averagely increased 0.90-1.63 and 0.58-1.47 g x kg(-1), respectively. During inundated period, soil pyrite S content was relatively stable, but soil WS-S and Ex-S contents were decreased significantly due to the dilution of water. It was suggested that the total S (mainly WS-S) of ASS was discharged in drainage process, and the accumulative amount of the discharge and the transformation of the S forms were associated with the length of the inundated and drained off cycles. The dynamics of Jarosite S, organic S and element S in all treatments were also discussed here.

Iron↗
PubMed1990

Trace elements in soil and biota in confined disposal facilities for dredged material.

We studied the relation of trace element concentrations in soil to those in house mice (Mus musculus), common reed (Phragmites australis) and ladybugs (Coccinella septempunctata at five disposal facilities for dredged material. The sites had a wide range of soil trace element concentrations, acid soils and a depauperate fauna. They were very poor wildlife habitat because they were dominated by the common reed. Bioassay earthworms exposed to surface soils from three of the five sites died, whereas those exposed to four of five soils collected a meter deep survived, presumably because the deeper, unoxidized soil, was not as acid. Concentrations of Ni and Cr in the biota from each of the sites did not seem to be related to the concentrations of the same elements in soil. Although Pb, Zn and Cu concentrations in biota were correlated with those in soil, the range of concentrations in the biota was quite small compared to that in soil. The concentrations of Pb detected in mice were about as high as the concentrations previously reported in control mice from other studies. Mice from the most contaminated site (530 ppm Pb in soil) contained only slightly more Pb (8 ppm dry wt) than did mice (2-6 ppm dry wt) from sites containing much less Pb (22-92 ppm in soil). Despite the acid soil conditions, very little Cd was incorporated into food chains. Rather, Cd was leaching from the surface soil. We concluded that even the relatively high concentrations of trace elements in the acid dredged material studied did not cause high concentrations of trace elements in the biota.

Journal Article↗
PubMed2006

Reduced inorganic sulfur speciation in drain sediments from acid sulfate soil landscapes.

We examined processes regulating reduced inorganic sulfur (RIS) speciation in drain sediments from coastal acid sulfate soil (ASS) landscapes. Pore water sulfide was undetectable or present at low levels (0.6-18.8 microM), consistent with FeS(s) precipitation in the presence of high concentrations of Fe2+ (generally >2 mM). Acid-volatile sulfide (AVS), with concentrations up to 1019 micromol g(-1), comprised a major proportion of RIS. The AVS to pyrite-S ratios were up to 2.6 in sediment profiles containing abundant reactive Fe (up to approximately 4000 micromol g(-1)). Such high AVS:pyrite-S ratios are indicative of inefficient conversion of FeS(s) to pyrite. This may be due to low pore water sulfide levels causing slow rates of pyrite formation via the polysulfide and H2S oxidation pathways. Overall, RIS speciation in ASS-associated drain sediments is unique and is largely regulated by abundant reactive Fe.

Chemical Precipitation↗
PubMed2006

Reduced adsorption of ametryn in clay, humic acid, and soil by interaction with ferric ion under Fenton treatment conditions.

Previous work in our laboratory indicated a weak interaction between ferric ion and several triazine/triazinone herbicides during a Fenton treatment process, and the intensity of the interaction was calculated. To further support the existence of this weak interaction, the adsorption of ametryn, a triazine herbicide, was investigated in kaolinite clay, humic acid, and soil under pseudo-Fenton conditions. At a low addition rate of ferric ion, the adsorption of ametryn in clay, humic acid, and soil was enhanced due to the decreased pH resulting from the hydrolysis of ferric ion. But the pH effect was totally neutralized and the adsorption of ametryn was significantly reduced by further addition of ferric ion, demonstrating the existence of the weak interaction between ametryn and ferric acid. Further study showed that the adsorption-reduction effect of ferric ion existed not only with ametryn but also with several other triazine/triazinone herbicides. This weak interaction may accelerate the desorption process during the remediation of triazine/triazinone herbicide-contaminated soil using a Fenton/Fenton-like treatment, but it may also impede the degradation of these herbicides.

Adsorption↗
PubMed2006

Supercritical fluid extraction of bioavailable amino acids from soils and their liquid chromatographic determination with fluorometric detection.

A new procedure with supercritical CO2 modified with 0.5 mL of water and 0.75 mL of 0.1 M HCl in situ and 0.75 mL of water on-line at 15 MPa and 50 degrees C for 45 min was applied for the extraction of bioavailable amino acids from soil samples. Total extraction time was 60 min, but more favorable conditions are even possible for selected groups of amino acids. All analytes were trapped into 20 mL of methanol with satisfactory recovery (94-104%) and determined using high-performance liquid chromatography with fluorometric detection on a Zorbax Eclipse column (4.6 x 75 mm, 3.5 microm) with Na2HPO4 and acetonitrile/methanol/water as a mobile phase. Linear calibration curves were obtained (r > 0.999 except 0.99823 for Ile) with lower limits of detection (S/N = 3) in the range from 1.54 pg (Gly) to 13.5 pg (Cy2) or from 18.6 fmol (Ser) to 64.8 fmol (Lys). Validation and repeatability data are also given. Comparable results were obtained with a robust, commonly used extraction method (0.5 M ammonium acetate, 60 min in shaker, followed by filtration and lyophilization). Limiting values of artificial release of amino acids were also determined for each soil sample to eliminate any false results to ensure that all extracted amino acids originate from soil solution and exchangeable bound positions of soil samples.

Acetates↗
PubMedDate not supplied

Sorption of apolar aromatic compounds to soil humic acid particles affected by aluminum(III) ion Cross-Linking.

Sorption of hydrophobic compounds in soils often shows nonlinearity, competition, and hysteresis. Since such behaviors have been associated with organic polymers in glassy state, it has been postulated that some forms of soil humic substances are glassy. The glassy state is favored by properties that decrease the flexibility of macromolecules, such as cross-linking, presence of unsaturated bonds, and high molecular weight. Polyvalent metal ions, which are abundant in soils, may cross-link humic substances by coordinating to multiple functional groups on different strands. Accordingly, we prepared an Al(3+)-cross-linked humic acid (Al-HA) from the H(+) form (H-HA) of a soil humic acid by a flocculation technique that leaves Al ions bound to organic groups. Sorption of naphthalene and 1,2,4-trichlorobenzene (TCB) on H-HA was nonlinear, competitive, and slightly hysteretic, in agreement with previous studies showing glass transition temperatures of humic acids that lie above room temperature. Nonlinearity, competition, and hysteresis were all enhanced in Al-HA, validating the hypothesis that metal ion cross-linking enhances nonideal sorption. Application of a glassy polymer sorption model reveals that cross-linking increases the affinity of solutes for the hole domain relative to the dissolution domain. The results (i) indicate that isolated, purified soil humic acid behaves like a glassy solid, (ii) indicate that metal-ion cross-linking creates a more rigid-chain structure and supports a link between nonideal sorption and the glassy character of soil organic matter, and (iii) underscore the importance of metal ions on humic structure in relation to sorption of hydrophobic organic compounds.

Adsorption↗
PubMed2001

Effect of applying Hong Kong biosolids and lime on nutrient availability and plant growth in an acidic loamy soil.

A greenhouse experiment was conducted to evaluate the growth of Brassica chinensis L. in an acidic loamy soil amended with municipal biosolids with or without lime treatment (750 mg kg(-1)). The soil was amended with one of two municipal biosolids from Tai Po (TP) or Yuen Long (YL) wastewater treatment plants at application rates of 0, 5, 10, 25 and 50% (v/v). Initial NH(+)4-N and PO(3-)4-P concentrations in the amended soil increased with an increase in municipal biosolids loading rates and those with biosolids from TP had a greater increase in nutrients than those from YL. However, initial NO(-)3-N contents in both municipal biosolids amended soils decreased with an increase in biosolids loading rates, particularly for the soil amended with YL. Soluble K, Mg, Na and Ca concentrations in the soil increased with application rates. Municipal biosolids amended soil without lime treatment had higher NH(+)4-N, NO(-)3-N and major cation contents than those with lime. Addition of Tai Po municipal biosolids and lime significantly increased the dry weight yields of B. chinensis L., while YL municipal biosolids increased yields only at the 5% rate with lime amendment. The maximum growth was obtained at municipal biosolids application rates of 5 and 10% for TP and 5% for YL for limed soil. Addition of municipal biosolids increased the total N, P, Zn, Cr and major cation concentrations in the shoot tissue, while lime treatment reduced Zn and Cr contents. The high salt and metal concentrations would likely be factors inhibiting plant growth at high application rates, especially for YL biosolids. Further studies to determine the long-term effects of biosolid application on soil and crop quality are warranted.

Brassica↗