Levels Of Humic Acid Research Articles

Induced plant uptake and transport of mercury in the presence of sulphur‐containing ligands and humic acid

The induced accumulation of mercury (Hg) by plants was investigated for the species Phaseolus vulgaris (Bush bean), Brassica juncea (Indian mustard), and Vicia villosa (Hairy vetch). All plants were grown in modified Hg-contaminated mine tailings and were treated with sulphur-containing ligands to induce Hg accumulation. The effects of varied substrate Hg concentration and humic acid (HA) level on the induced plant-Hg accumulation for B. juncea were examined. Thiosulphate salts (ammonium and sodium) mobilised Hg in the substrates and caused an increase in the Hg concentration of roots and shoots of all tested plant species. Root Hg accumulation was positively correlated to extractable Hg for (NH4)2S2O3-treated B. juncea plants grown in HA-amended substrates. However, shoot Hg translocation for this species was inhibited at 1.25 g HA kg(-1) of substrate. Mercury-thiosulphate complexes could be translocated and accumulated in the upper parts of the plants up to 25 times the Hg concentration in the substrate. We conclude that shoot Hg accumulation in the presence of thiosulphate salts is dependent upon plant species characteristics (e.g. root surface area) and humic acid content.

Steady-state humic-acid-containing blanket in upflow suspended bed

We investigated the effects of turbidity and concentration of humic acid on the steady-state behavior of the blanket, which was coagulated using polyaluminum chloride (PACl) as coagulant. The three-dimensional solid-flux plot was constructed. Based on fixed PACl dosage, the iso-humic-acid solid-flux surfaces stacked that enveloped the feasible regime for the blanket bed. The steady-state point moved toward low solid flux and low solid fraction regime with decreasing initial raw water turbidity and/or increasing humic-acid concentration. Low water turbidity and high humic-acid concentration yielded a bulky blanket, with the former producing clean, and the latter turbid effluent. The presence of humic acid was thereby harmful to blanket strength, except for the case of low raw water turbidity. An optimal range of humic acid for blanket strength and clarification efficiency existed at 1 mg l(-1). Low level of humic acid is beneficial to blanket development with low-turbidity raw water.

Calcium and humic acid affect seed germination, growth, and nutrient content of tomato (Lycopersicon esculentum L.) seedlings under saline soil conditions

The effects of calcium and humic acid on seed germination, growth and macro- and micro-nutrient contents of tomato (Lycopersicon esculentum L.) seedlings in saline soil conditions were evaluated. Different levels of humic acid (0, 500, 1000 and 2000 mg kg−1) and calcium (0, 100, 200 and 400 mg kg−1) were applied to growth media treated with 50 mg NaCl kg−1 before sowing seeds. Seed germination, hypocotyl length, cotyledon width and length, root size, shoot length, leaf number, shoot and root fresh weights, and shoot and root dry weights of the plant seedlings were determined. Macro- and micro-nutrient (N, P, K, Ca, Mg, S, Cu, Fe, Mn and Zn) contents of shoot and root of seedlings were also measured. Humic acid applied to the plant growth medium at 1000 mg kg−1 concentration increased seedling growth and nutrient contents of plants. Humic acid not only increased macro-nutrient contents, but also enhanced micro-nutrient contents of plant organs. However, high levels of humic acid arrested plant growth or decreased nutrient contents. Levels of 100 and 200 mg kg−1 Ca2+ application significantly increased N, Ca and S contents of shoot, and N and K contents of root.

Highly Stable Voltammetric Detection of Nitroaromatic Explosives in the Presence of Organic Surfactants at a Polyphenol‐Coated Carbon Electrode

AbstractA polyphenol‐coated screen‐printed carbon electrode is used for highly sensitive voltammetric measurements of the 2,4,6‐trinitrotoluene (TNT) explosive in the presence of surface‐active substances. The permselective/protective polyphenol coating offers excellent resistance to surfactant fouling, while allowing facile transport of the target TNT. High levels of gelatin, humic acid and sodium dodecyl sulfate (SDS) (up to 50 mg/L) have negligible effects upon the square‐wave voltammetric TNT response. The TNT peak current and potential remain nearly the same in the presence of these organic macromolecules, as compared to substantial peak suppressions and shifts at the bare electrode. Control of the electropolymerization time was used for achieving the desired exclusion of interfering surface‐active macromolecules while allowing transport of the target TNT. The response for ppm levels of TNT is highly linear and stable for prolonged operations in the presence of surface‐active substances. By meeting the high sensitivity, selectivity, stability, portability and low‐cost demands, such voltammetric sensing holds great promise for field‐based voltammetric monitoring of nitroaromatic explosive compounds.

Effect of fertiliser and humic acid on rhizosphere microorganisms and soil enzymes at an early stage of sugarcane growth

The influence of humic acid and fertilisers on microbial population and rhizosphere enzymes in sugarcane rhizosphere was studied. Among the microbial population, bacteria were found to dominate, varied from 26.3 x 105 to 38.3 x 105 cfu g-1 at different levels of fertiliser and humic acid. Application of 100 per cent NPK with 20 kg HA ha-1 recorded higher bacterial population of 35.8 x 105 cfu g-1 while 100 per cent NPK and 30 kg HA ha-1 recounted maximum of fungi and actinomycetes (14.0 x 103 cfu g-1 and 15.3 x 104 cfu g-1) population. Application of 100 per cent NPK recorded the maximum amount of soil enzymes. Humic acid at 20 kg HA ha-1 were found to enhance the catalase activity (164.9 mg of KMnO4 oxidised g-1 20 min-1) and alkaline phosphatase activity of 65.3 m mol p-intro phenol g-1 hr-1. Humic acid application at 30 kg ha-1 significantly influenced the dehydrogenase activity of 115.9 ig of TPF formed g-1 24 hr-1. The increase in population might be due to the presence of humic acid in the root zone, which favours the microbial growth in the rhizosphere.

Magnetic bead hybridization to detect enterotoxigenicEscherichia colistrains associated with cattle in environmental water sources

A magnetic capture hybridization - polymerase chain reaction (MCH-PCR) method was used to increase the detection sensitivity of the enterotoxin gene LTIIa, used as a biomarker for waste in environmental samples. The samples were collected from cow lagoons of different farms and from environmental waters. Total DNA was extracted from colonies grown on mTEC medium or directly from environmental samples. The cow-specific Escherichia coli LTIIa gene was used as a DNA marker. A LTIIa-specific oligonucleotide probe was designed to capture the LTIIa marker during the MCH, followed by PCR. Varying levels of humic acid were added to the DNA extracts to evaluate the sensitivity and effectiveness of MCH-PCR. The minimal detection limit of MCH-PCR for the LTIIa gene was 2.5 ag/muL DNA. In the presence of humic acid, MCH-PCR was able to increase the detection sensitivity 10 000-fold over that of conventional PCR. The MCH-PCR could also detect one cell with the LTIIa DNA marker in a 1-L seeded environmental water sample. Results in this study indicate that MCH-PCR is more sensitive than nested PCR in testing environmental samples.

The effect of humic acids on nitrobenzene oxidation by ozonation and O 3/UV processes

Three types of commercially available humic acids from different sources were used to simulate natural organic matter in water for the investigation of nitrobenzene oxidation by ozonation and O 3/UV. Despite the structural differences among the Fluka, Aldrich and Suwanee River humic acids as reflected by the UV absorptivity, their effects on nitrobenzene removal rate was observed to be similar for the two processes. Removal rate of nitrobenzene was hindered by the addition of humic acids in ozonation as well as in O 3/UV processes. However, the hindrance by the humic acids was more pronounced in O 3/UV as compared to the ozonation process. The effect of humic acid in O 3/UV was primarily a UV light screening. Addition of humic acids above a certain concentration did not cause any further retardation on nitrobenzene removal rate by ozonation and O 3/UV. Accumulation of hydrogen peroxide as well as probable formation of peroxy radicals in the solutions might induce chain promoting reactions to produce hydroxyl radical during the nitrobenzene oxidation. For waters containing high levels of humic acid, ozonation alone might be as effective as O 3/UV process for the removal of nitrobenzene.

EFFECT OF DIFFERENT LEVELS OF LIGNITIC COAL DERIVED HUMIC ACID ON GROWTH OF MAIZE PLANTS

In view of the high cost of chemical fertilizers, use of natural fertilizer sources for increasing crop production on a sustainable basis has become imperative. A pot experiment was conducted in silty clay loam, mixed, hyperthermic typic calciustepts, and Tarnab soil series to study the effect of different levels of humic acid (HA) derived from lignitic coal on the growth of maize (Zea maysL. Kissan). HA was sprayed on soil at the rate of 0, 50, 100, 150, 200, 250, and 300 mg kg−1 soil along with uniform dose of nitrogen–phosphorus–potassium (NPK) (120–90–60 kg ha−1). The addition of 50 and 100 mg kg−1 HA caused significant increase of 20 and 23% in shoot and 39 and 32% in root dry weight of maize plants as compared to control. The increasing levels of HA above 50 and 100 mg kg−1 produced no significant effect on maize yield. Soil organic matter content was improved slightly (7 to 14%) and pH values were decreased by 0.2 to 0.3 unit by the HA treatments. Addition of HA increased soil N concentration and plant N accumulation significantly over control with no significant differences within the treatments of different levels of HA applied. Soil P concentration improved significantly by the addition of 200 mg kg−1 HA whereas plant P accumulation was not significantly affected by the application of different levels of HA. Micronutrients [zinc (Zn), iron (Fe), manganese (Mn), and copper (Cu)] concentrations of soil and their accumulations by maize plants increased nonsignificantly over control by the application of HA. Laboratory incubation experiment conducted to study the effect of HA on soil biological and physicochemical properties showed that the addition of 0.5 and 1.0 kg ha−1 HA promoted CO2 evolution, increased bacterial population by 355% to 476%, fungi 610 to 716%, and cation exchange capacity of the soil by 13.8 to 28.9%. Results suggest that increases in growth of maize due to HA addition may be associated with the improved biochemical environment of the soil.

Uptake of chlorination disinfection by-products; a review and a discussion of its implications for exposure assessment in epidemiological studies.

We have reviewed the relevant issues in the exposure assessment of disinfection by-products (DBPs) of chlorination for epidemiological and health risk assessment. Various DBPs can be detected in drinking water and swimming pools, and the reported levels show a considerable range, but were generally below the current health standard for total trihalomethanes (TTHMs) (100 microg/l). Relatively little information is available on the correlation between the various DBPs in drinking water and in swimming pools. Chloroform was generally, but not always, the most predominant DBP. In epidemiological studies, TTHM levels have been used as an indicator for total DBP load, even though TTHM levels do not always correlate well with individual DPBs. Factors such as residence time, temperature, pH, organic content, including humic and fulvic acid and bromide levels affect the composition and levels of DBPs. Although there are biomarkers of DBPs, mainly for chloroform and more recently for the other volatile trihalomethanes (THMs) and the nonvolatile haloacetic acids (HAAs) such as trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA), they have not been used in epidemiological studies. The THMs have been measured in exhaled breath and serum, while the HAAs have been measured in urine. These biomarkers have been useful to estimate the actual uptake of the DBPs and the relative contribution of various exposure routes. Physiologically based pharmacokinetic (PBPK) models exist for, e.g. chloroform, but their main target organs are the kidney and liver and they have not been used in epidemiological studies. Tap water ingestion, showering, bathing, swimming, boiling water and dishwashing are all activities that have been associated with the uptake of DBPs, and considerable variation in these activities has been observed between people. No studies have reported on the correlation between human uptake of DBPs and water-zone mean estimates, but various studies found a good correlation between THM concentrations in exhaled breath and THM concentrations in water during showering and swimming. In general exposure assessment in epidemiological studies has been limited which complicates the interpretation. These findings have implications for epidemiological studies, particularly with reference to Berkson and classical error type models, study power, attenuation and precision of health-risk estimates and study efficiency. Recommendations are made for further areas of study.

The characterisation and behaviour of carbonaceous material in a refractory gold bearing ore

Sulfide ore and a flotation concentrate from Fosterville contained 0.76% carbonate carbon, 0.18% native carbon and 0.20% organic carbon of which 4.5 ppm were n-alkane hydrocarbons. The concentrate yielded 0.99% native carbon, 0.28% carbonate carbon and 0.11 % organic carbon of which 19.7 ppm was n-alkane hydrocarbons. IR spectroscopy of the fulvic acid fraction of the flotation concentrate showed it to be similar to humic acid. The addition of representative levels of n-alkane hydrocarbons, carbonate carbon and humic acid to the oxidised ore indicated that these components had negligible effect on gold recovery. The addition of 0.2% native carbon decreased gold recoveries from 84.4% to 68.8% while 0.2% activated carbon reduced recovery to 3.1%. Native carbon when acidified, mimicking the environment of bacterial oxidation, resulted in recovery dropping from 84.4% to 61.0%. Gold recovery for a standard sulfide float was 92.5%. Sodium naphthalene sulfonate (SNS) was the only depressant to lower native carbon levels in the concentrates without reducing gold recovery. 275 g/t SNS depressed 45% of the native carbon and gold recovery was unchanged. Nitric acid oxidation and subsequent cyanidation of the SNS concentrates lead to overall gold recovery improving from 88.3% for a standard sulfide float to 92.0%.

Humic‐Acid Transformation during Composting of Municipal Solid Waste

AbstractComposting of municipal solid waste (MSW) was studied in an attempt to characterize concomitant transformations of humic acid (HA). Humic acid and Core‐HA were extracted from MSW at various stages during composting using the following methods: (i) The common IHSS method (HA); and (ii) performing organic solvent and sulfuric acid extractions prior to the alkaline extraction (Core‐HA). Mass balance was calculated for each compost sample during composting, and cross polarization magic angle spinning (CPMAS) 13C‐NMR and fourier transform infrared (FTIR) spectroscopy measurements were employed on the purified HAs and Core‐HAs. The absolute level of HA decreased during composting by 50% whereas the level of Core‐HA was steady throughout the process. The 13C‐NMR and FTIR spectra of the HAs indicated a high rate of change in structure during composting. The aromatic and phenolic C‐containing groups increased by 23 and 16%, respectively. In contrast, the Core‐HA spectra were stable, with only minor changes recorded during composting. The “coating” materials (polysaccharides, peptides, and lipids) bonding to the “core” HA structure degraded during composting, resulting in HA structures of higher aromaticity. The FTIR spectra of both HA and Core‐HA exhibited minor peaks in the carboxyl C, and the high rate of aliphatic C‐containing groups recorded from the 13C‐NMR spectra resembled “young” (type III) humified materials from soils. The mass‐balance data, together with the spectroscopic analyses indicate that one of the major HA transformation processes occurring events during the process is the degradation of the coating materials, yielding the core HA structure.

Potential Effects of Surface Water Components on Actinide Determinations Conducted by Ion Chromatography

An elution program for separating actinides (thorium, uranium, neptunium, plutonium, americium, and curium) on low hydrophobicity ion exchange columns was evaluated for solutions spiked with actinides and common surface water components. Potential interferences from dissolved ions (Na+, K+, Ca2+, Cl-, and SO(4)2-), humic acid, and radium were investigated. Sulfate levels greater than 0.25 mumol interfered with separation of americium, curium, and plutonium. Humic acid levels above 100 micrograms produced distinct widening of actinide peaks and reduced actinide recoveries. These interferences limit the range of useful sample volumes and create a need for sample pretreatment procedures. No interferences were produced by 0.025 to 2.5 mumol Ca2+, 0.045 to 4.5 mumol Na+, 0.015 to 1.5 mumol K+, and 0.025 to 4.5 mumol Cl-. In the absence of interferences, the program effectively separated radium from the actinides.

Effect of different levels of humic acid on the growth and nutrient uptake of teak seedlings

Abstract A greenhouse experiment to study the effect of humic acid (HA) on the growth and nutrient uptake of Teak (Tectona grandis L.f.), a tropical hardwood, was conducted in Ibadan, Nigeria. The plants were grown for four months in top soils (0–30 cm) collected from an Alfisol (high organic matter) and an Oxisol (low organic matter) in Southern Nigeria. Three levels of HA, viz:, 50, 500, and 1000 mg/kg were added to the two soils. The results indicated that HA was beneficial to the growth and nutrient uptake of teak seedlings. Plant monthly growth rates, and height and total dry matter yield increased significantly (p = 0.05) over the controls in the two soils at the three HA application levels. Effects of adding 500 mg/kg and more of HA to the Alfisol were less beneficial while plant parameters and nutrient uptake tended to increase with increasing amounts of HA in the Oxisol. A significant positive correlation was established between rate of HA application and plant height (r = 0.57), stem diameter (r...

The toxicity of cadmium to barley plants as affected by complex formation with humic acid

An ‘alternating solution’ culture method was used to study the effects of chloride ions and humic acid (HA) on the uptake of cadmium by barley plants. The plants were transferred periodically between a nutrient solution and a test solution containing one of four levels of HA (0, 190, 569 or 1710 μg cm−3) and one of five levels of Cd (0, 0.5, 1.0, 2.5 or 5.0 μg cm−3) in either a 0.006M NaNO3 or 0.006M NaCl medium. Harvest and analysis of shoots and roots was after nineteen days. The distribution of Cd in the test solutions between Cd2+, CdCl+ and HA-Cd was determined in a separate experiment by dialysis equilibrium.

Formation of mutagens following chlorination of humic acid A model for mutagen formation during drinking water treatment

Aqueous chlorination of humic acids results in the formation of compounds with direct-acting mutagenic activity in the Ames/Salmonella plate assay for tester strains TA98, TA100, TA1535, TA1537 and TA1538. The addition of a rat-liver microsomal fraction (S9) plus cofactors causes a substantial decrease of activity, the extent of which is tester strain dependent. The non-chlorinated humic acids are not mutagenic either in the presence or absence of S9. Formation of mutagenic activity and of total organic halogen (TOX) is linearly related to humic concentration in the range of 0.2–1.6 mg/ml total organic carbon (TOC), and to chlorine concentration in the range of 0.1–1.0 chlorine equivalents per mole of carbon. The mutagenic activity is due predominantly to non-volatile compounds. Mutagenic activity is also detectable, after sample concentration by lyophilization, upon chlorination at a humic acid level of 0.02 mg/ml TOC. The specific mutagenic activities (per mg TOX), and also the degree of chlorine incorporation into humic acid, at 0.02 mg/ml TOC are similar to those present after chlorination at 1 mg/ml TOC. Production of mutagens is greatly dependent on the chlorination pH, with a pattern of decreasing mutagenic activity with increasing pH. This order of activity can be at least partially explained by the alkali lability of the compounds. Chlorination of commercial humic acids is proposed as a model for examination of mutagen formation during water chlorination.

The distribution of organic material and trace metals in sediments from the River Liffey Estuary, Dublin

Sediments of the River Liffey Estuary have been analysed for organic carbon, Kjeldahl nitrogen, humic acid and crude fibre contents. Several trace metals were also analysed. The hydrographic conditions which control the transport of this material were also studied over a tidal cycle. Results indicate that the upper reaches of the estuary are isolated from the incoming seawater and that trace metal enrichment is localized. This metal enrichment is accompanied by an increase in the organic carbon, nitrogen, and humic acid levels.

Caloric and Micronutrient Content of Nuphar polysepalum

Caloric equivalents are cited for eight vegetative and reproductive tissue types of Nuphar polysepalum; leaf blade tissue was highest (4499 cal/g ash-free dry weight) and rhizome tissue lowest (3976 cal/g ash-free dry weight). In addition, the concentration of Fe, Mn, Cu, and Zn was determined for each tissue type; leaf blade tissue was consistently highest for each micronutrient while seed tissue was consistently lowest. N. polysepalum is nearly always restricted to Colorado semidrainage mountain lakes; lakes whose waters have consistently high levels of total Fe, N03-N, and humic acid (color). Energy and micronutrient content of aquatic macrophytes is becoming increasingly important economically and ecologically. Westlake (1965) emphasized the need for data concerning the caloric and chemical composition of aquatic vascular plants, particularly as they relate to our study and understanding of energy flow in aquatic ecosystems. Caloric values for about 35 species of aquatic angiosperms have been cataloged (Cummins and Wuycheck 1971). In nearly all cases either the entire plant was used or conspicuous (above ground) vegetative and reproductive parts were combined before analysis. The primary objective of this paper is to present caloric equivalents for eight vegetative and reproductive parts of the yellow pond-lily Nuphar polysepalum Engelm. 1865 (-Nuphar luteum subsp. polysepalum). A second objective is the presentation of micronurient (Cu, Fe, Mn, and Zn) content within these eight tissue types. A final and tertiary objective is to document a unique set of limnological conditions of a Colorado semidrainage mountain lake (Red Rock Lake) for which Nuphar polysepalum is an indicator species of lake type in Colorado and is the predominant hydrophyte and photoautotroph. METHODS AND MATERIALS. Selected structural parts of Nuphar polysepalum, a perennial herb common to the unique semidrainage lakes of western North America (Pennak 1969), were collected from Red Rock Lake, Colorado, (Fig. 1) during the period June-September 1968 and 1969. Red Rock Lake is a 1Contribution No. 1 from the Water Resources Research Laboratory, The University of Southern Colorado.

Stimulation of Plant Growth by Humic Substances

AbstractHumic substances prepared by different techniques of extraction and from different sources of organic materials were tested for their effects on growth of corn seedlings and algae. Stimulating effects were confirmed with optimum concentrations about 5 ppm C as Na‐humate for corn and 60 ppm for algae. With corn, the increase was 30 to 50% in nutrient solution or low organic matter soil; with algae, about 100%. Variation of effects among humic acids derived from different organic materials was not great.The concentrations of elements in corn seedlings did not show any correlation with yield or humic acid level except for P and Fe. Phosphorus concentration was increased with increasing levels of humic acid regardless of the yield response. Higher Fe concentration in the plant tops and lower in roots was observed in the treatments with humic acid.The application of humic acid to a soil low in organic matter or to nutrient solution gave the greatest growth response. Application to a high organic matter soil gave little growth response, or even a slightly negative response, indicating that the natural soil, without extraction, supplied optimum amount of humic substances to the plants. It is suggested that a test be developed to predict whether a given soil can furnish an optimum level of humic substances.Different humic substances showed different degrees of stimulation of algal growth, with the most stimulation from a mixture of humic and fulvic acids. Humic substances in paddy soils may affect the growth of beneficial algae and of the rice (Oryza sativa L.) itself. As pollutants, humic substances may stimulate undesirable algal growth in bodies of water.