A comparative study of carbofuran metabolism in treated and untreated soils

A method for isolating soil organic matter after the extraction of humic and fulvic acids

This study describes the removal of polycyclic aromatic hydrocarbons (PAHs) from creosote oil contaminated soil by modified Fenton's reaction in laboratory-scale column experiments and subsequent aerobic biodegradation of PAHs by indigenous bacteria during incubation of the soil. The effect of hydrogen peroxide addition for 4 and 10 days and saturation of soil with H(2)O(2) on was studied. In both experiments the H(2)O(2) dosage was 0.4 g H(2)O(2)/g soil. In completely H(2)O(2)-saturated soil the removal of PAHs (44% within 4 days) by modified Fenton reaction was uniform over the entire soil column. In non-uniformly saturated soil, PAH removal was higher in completely saturated soil (52% in 10 days) compared to partially saturated soil, with only 25% in 10 days. The effect of the modified Fenton's reaction on the microbial activity in the soil was assessed based on toxicity tests towards Vibrio fischeri, enumeration of viable and dead cells, microbial extracellular enzyme activity, and oxygen consumption and carbon dioxide production during soil incubation. During the laboratory-scale column experiments, the toxicity of column leachate towards Vibrio fischeri increased as a result of the modified Fenton's reaction. The activities of the microbial extracellular enzymes acetate- and acidic phosphomono-esterase were lower in the incubated modified Fenton's treated soil compared to extracellular enzyme activities in untreated soil. Abundance of viable cells was lower in incubated modified Fenton treated soil than in untreated soil. Incubation of soil in serum bottles at 20 degrees C resulted in consumption of oxygen and formation of carbon dioxide, indicating aerobic biodegradation of organic compounds. In untreated soil 20-30% of the PAHs were biodegraded during 2 months of incubation. Incubation of chemically treated soil slightly increased PAH-removal compared to PAH-removal in untreated soil.

Soil Organic Matter Black Box

Transformation of [ 14C] and [ 35S]labeled lignosulfonates during soil incubation

Since it is very difficult to investigate the chemical structure of coal itself by chemical means, studies of the regenerated humic acid which is the primary decomposition product of coal have been done.In this paper, the results of experiments carried out for preparing the regenerated humic acids from some kinds of coal by alkaline fusion method were reported. Sodium or potassium hydroxide was used as a reagent of the alkaline fusion, and the reaction temperature was arranged in the range from 175°C to 350°C. The carbon content of coals used in the experiment was between 70% and 80%.In the case of reaction of Ube Coal having carbon content of 70.0% with sodium hydroxide, the yield of humic acid was maximum, about 55%, at 250°C; and that of residual coal (the unreacted) was minium, about 17%, at 300°C.Reactivity of potassium hydroxide with coal was greater than sodium hydroxide at the same temperature.The following results depended on the degree of the carbon content of sample coals were obtained:(1) C>80%(a) The yield of humic acid was very low.(b) The carbon content of residual coal was similar to that of the original coal.(2) C=77-80%(a) The yield of humic acid was low with sodium hydroxide at 250°C, while very high with potassium hydroxide at 300°C.(b) Even in the case of the low yield of humic acid, the carbon content of residual coal was higher than that of the original coal.(3) C<76%(a) The yield of humic acid was high.(b) The carbon content of residual coal was higher than that of the original coal.It was remarkable that the carbon content of the regenerated humic acid obtained from coal by alkaline fusion method was more than 70%, and different from the humic acid obtained from the other ordinary oxidation methods.

A field experiment was carried out on a newly reclaimed land at the Agricultural Experimental Desert Station, Faculty of Agriculture, Cairo University, in Wady El-Natroon district, ElBeheira Governorate, Egypt, cultivated with tomato plants (Supper Strain B F1 cultivar) and irrigated with saline water (2500 ppm) during the summer growing seasons of 2013 and 2014 to study the potential benefit of some repellant salinity agents (Dinamic, Uni-sal and humic acid) for alleviating adverse effect of saline irrigation water on vegetative growth, yield and fruit quality of tomato. This experiment was designed in completely randomized block design with three replications. Seven soil treatments, namely, Dinamic, Uni-sal, humic acid and all possible combinations among them were compared with control (untreated soil). Each compound was used four times (at the transplanting and 15, 30 and 45 days after transplanting) through drip irrigation system at rate of 4 liter/feddan. The effects of these repellant salinity agents on plant length, number of branches, fresh, dry of shoot weight, nutrients content in leaves, total yield, fruit firmness, TSS, titratable acidity and vitamin C in fruits were studied. Results revealed that, all repellant salinity agents were effective in alleviating the adverse effect of salinity on vegetative growth and yield in compared to the control treatment. Using combination between Dinamic and Uni-sal with or without humic acid gave the highest value of vegetative growth, nutritional content, yield and fruit characters compared to other treatments.

The mobility of phenanthrene (PHE) in soils depends on its sorption and is influenced by either the existing soil humus or exogenous humic substances. Exogenous humic acids (HAs) were added to soil to enhance the amount of soil organic carbon (SOC) by 2.5, 5.0, and 10.0 g kg(-1). PHE desorption of the treated soils was determined at two pH levels (3.0 and 6.0) and temperatures (15 and 25 degrees C). Soil PHE adsorption was related to pH and the type and quantity of added HAs. Humic acid (HA) and fulvic acid (FA) derived from peat had different effects on adsorption of PHE. Adsorption increased at first and then decreased with increasing quantity of exogenous FA. When the soil solution pH (in 0.005 M CaCl(2)) was 4.5 or 3.0, the turning points were 2.5 g FA kg(-1) at pH 3.0 and 5 g FA kg(-1) at pH 4.5. When soil solution pH was 6, the amount of adsorbed PHE was enhanced with increasing exogenous HAs (HA or FA) and amount of adsorption by soil treated with FA was higher than with HA. Adsorption of PHE in the FA treatment at 10.0 g kg(-1) was lower than the controls (untreated soil or treatment with HAs at 0 g kg(-1)) when the soil solution pH was 3.0. This suggests that FA adsorbed by soil was desorbed at low pH and would then increase PHE solubility, and PHE then combined with FA. PHE adsorption was usually higher under lower pH and/or lower temperature conditions. PHE sorption fitted the Freundlich isotherm, indicating that exogenous humic substances influenced adsorption of phenanthrene, which in turn was affected by environmental conditions such as pH and temperature. Thus, exogenous humic substances can be used to control the mobility of soil PAHs under appropriate conditions to decrease PAH contamination.

The&nbsp;mobility of a pesticide in soil is determined by the extent and strength of sorption,&nbsp;which&nbsp;is influenced by either the existing soil humus or exogenous humic substances. Exogenous humic acids&nbsp;(HAs)&nbsp;were added to soil to enhance the amount of soil organic carbon&nbsp;(SOC)&nbsp;by 2.5, 5.0 and 10.0 g kg-1. Imidacloprid sorption of the treated soils was studied at three pH levels&nbsp;(4.5, 6.0 and 7.5)&nbsp;and two temperatures (15 and 25&deg;C). Soil imidacloprid adsorption was related to pH and the type and quantity of added HAs. Humic acid&nbsp;(HA)&nbsp;and fulvic acid&nbsp;(FA)&nbsp;derived from peat had different effects on adsorption of imidacloprid. When soil solution pH was 6, the amount of adsorbed imidacloprid was enhanced with increasing exogenous HA.&nbsp;On the contrary,&nbsp;the amount of adsorbed imidacloprid decreased with increasing quantity of exogenous FA. Adsorption of imidacloprid in the FA treatment at 5.0 and 10.0 g kg-1&nbsp;was lower than the controls&nbsp;(untreated soil or treatment with HAs at 0 g kg-1)&nbsp;when the soil solution pH was 6.0. However adsorption of imidacloprid in the HA treatment was higher than the controls. Imidacloprid adsorption was usually higher under lower pH and/or lower temperature at same condition. Imidacloprid sorption fitted the Freundlich isotherm, indicating that exogenous humic substances influenced adsorption of imidacloprid, which in turn was affected by environmental conditions such as pH and temperature. Thus, exogenous HA can be used to control the mobility of soil pesticide under appropriate conditions to decrease pesticide pollution diffusion and probably increase effectiveness of pesticides. &nbsp; Key words:&nbsp;Imidacloprid, soil adsorption, humic acid, fulvic acid.

Studies on arsenate (As(V)) sorption and desorption have been mainly limited to soil minerals and sorption and desorption reactions in whole soils are poorly understood. In this study the sorption of As(V) by and phosphate-induced desorption from a Chinese red soil were studied in the presence of oxalate and humic acid (HA). Arsenate was strongly sorbed mainly through ligand exchange reactions on the soil. Arsenate sorption decreased in the presence of oxalate or HA. Oxalate and HA influenced As(V) sorption mainly by competing for sorption sites and reducing sorption sites, and oxalate could also decrease sorption through dissolving clay minerals. Oxalate and HA could also facilitate As(V) desorption from the soil. Both sorption and desorption kinetics were two stage processes. Sorption kinetics conducted from 0.2–840 h showed that As(V) sorption increased with increasing residence time. Sorption equilibrium was retarded and the maximum sorption decreased in the presence of oxalate or HA. Phosphate-induced desorption kinetics conducted on the soil with 24 h and 840 h of sorption equilibrium time showed a significant effect of equilibrium time on As(V) desorption. The presence of oxalate or HA during the sorption process resulted in more As(V) desorption. Due to the degradation of oxalate, soil treated with oxalate and with a sorption equilibrium time of 840 h showed no significant difference in desorption kinetics from untreated soil.

In sustainable agriculture, seeking eco-friendly methods to promote plant growth and improve crop productivity is a priority. Humic acid (HA) and plant growth promoting rhizobacteria (PGPR) are among the most effective methods that utilize natural biologically-active substances. The aim of the present study was to analyze the effect of the presence of HA on potato (Solanum tuberosum L.) inoculation with PGPR (Bacillus megatorium and Bacillus subtilis) when compared to control and recommended doses of NPK. Seed tubers treated by humic acid (200, 400, and 600 kg ha−1) and PGPR, separately or in combination, and NPK (50% and 100%) were planted into soil and untreated soil. Treatments were assessed for plant growth, classified tuber yields, quality, and mineral contents of potato tubers. There were highly significant increases in potato growth, tuber yields, and quality in PGPR and HA inoculated crops. Tuber size, weight, specific gravity, dry matter, starch, protein, and mineral contents (except Cu) were improved with PGPR treatments and further increased when administered with humic acids. Inoculation with PGPR mixed culture and 400 kg ha−1 HA increased total potato tuber yield by about 140% while conventional single treatment of 100% NPK fertilizer only led to an increase in potato production of 111% when compared to the control. The results demonstrated that this integrated approach has the potential to accelerate the transformation from conventional to sustainable potato production.

In view of the problem of clogging of ultrafiltration membrane in ultrafiltration process, the contamination mechanism of humic acid solution on ultrafiltration membrane was studied in depth. Through the ultrafiltration test of different concentrations of humic acid solution, it was found that humic acid can cause pollution to the ultrafiltration membrane, and the higher the humic acid concentration, the more serious the membrane contamination. The introduction of calcium carbonate particles can delay the progress of ultrafiltration membrane fouling in the initial stage of ultrafiltration, but as the ultrafiltration time increases, the membrane fouling rate increases rapidly. The kaolin particles can aggravate the contamination of the ultrafiltration membrane by humic acid, and the contamination can be washed away by the aqueous sodium hydroxide solution. The introduction of calcium ions can significantly aggravate membrane fouling and polymerize humic acid molecular chains. Sodium hydroxide and sodium hypochlorite alkali solution can effectively remove the humic acid pollution on the ultrafiltration membrane, wherein the sodium hydroxide solution has better cleaning effect, and the calcium carbonate-containing pollutant can be washed with a citric acid solution.

The forms of phosphorus in humic and fulvic acids of a toposequence of alpine soils in the northern Caucasus

Problem statement: Fertilizer N use efficiency is reduced by ammonia volatilization. Under low soil CEC and high pH, N from soil solution is released to the atmosphere. Ammonia loss due to low worldwide N use efficiency (33%) has been implicated in global warming. Thus, the objectives of this laboratory study were to evaluate the effectiveness of liquid humic and fulvic acids, isolated from tropical peat soils in reducing N loss from urea fertilizer as well as to investigate the ability of these acids to retain NH4 + and NO3 ¯ or reduce soil pH. Approach: Formulated liquid N fertilizers consisting of urea and different types of humic molecules (HA or FA or mixture of both), solid and liquid urea were surface applied to 250 g of soil. A closed dynamic air flow system was used to trap NH3 loss in boric acid after which samples were titrated with 0.01 M HCl to estimate NH3 loss. After 30 days of incubation, the soil was air dried and analysed for pH, exchangeable NH4 + , available NO3 ¯ and exchangeable cations. The results were analysed using SAS and treatments means were compared using Duncan's New Multiple Range Test (DNMRT). Results: The use of humic molecules reduced NH3 loss and increased exchangeable NH4 + . The high CEC of Humic Acids (HA) made the LHA treatment the best in reducing N loss after surface application. The presence of HA and Fulvic Acids (FA) increased NH4 + recovery. Even though, the soil pH of all the treatments were high, significant reduction of N loss was observed for humic molecules treatments. Conclusion: The use of liquid organic N fertilizer has the ability to reduce NH3 volatilization in acid soil. The use of both humic and fulvic acids could be effective in promoting NH4 + retention. Thus, it can be concluding that, humic substances, in general, have great ability in controlling NH3 loss and retaining NH4 + in acid

Effects of dissolved and fixed humic acid on Eu(III)/Yb(III) adsorption on aluminum hydroxide: A batch and spectroscopic study

Materials and methods. 18 native humic acids (HAs) were received from nine representative types of peat of the Tomsk region. Two extraction methods were used: sodium hydroxide and sodium pyrophosphate. Molecular structure parameters were investigated by IR-spectroscopy. The assessement of qualitative and quantitative features of the IR-spectra of 18 different humic acids was made. When HAs with mouse macrophages were cultured their ability to influence the NO-stimulation was determined. Thus, the biological activity of HAs and its dependence on the parameters of the molecular structure were studied. Results. The results of infrared spectroscopy showed that the HAs of upland types of peat contain more carbonyl, carboxyl, and ester groups, and HAs of lowland types of peat contain more aromatic carbon, phenolic and alcoholic hydroxyl, ether and carbohydrate fragments. The results of biological activity showed that HAs from upland types of peat induce the formation of nitrogen oxide, wherein the cell activation decreases with HAs obtained by alkali. All types of HAs from lowland types of peat contain an admixture of endotoxin. Some HAs obtained by sodium pyrophosphate have higher immunotropic activity; the HAs can cause antigen-specific stimulation of cells. The activity of HAs does not depend on endotoxin admixture. The results of molecular spectroscopy showed that the most biologically active HAs have higher aromaticity and higher concentration of oxygen-containing functional groups. This result can be used as a marker factor in the standardization of HAs.