Levels Of Humic Acid Research Articles

EFFECT OF HUMIC ACID APPLICATION ON CADMIUM ACCUMULATION BY LETTUCE LEAVES

Humic acid (HA) is a plant growth stimulator compound that may also reduce cadmium (Cd) concentration in plant tissues. The aim of the present study was to investigate the effect of adding humic acid (HA) to the growth medium on Cd concentration in lettuce leaves. In a soilless experiment, seedlings of lettuce (Lactuca sativa L.) were exposed to three levels of Cd [0, 2 and 4 mg L−1 in the form of cadmium chloride (CdCl2)] and three levels of HA (0, 100 and 1000 mg L−1). Application of HA increased significantly the shoot fresh weight of lettuce while it had no effect on the photosynthetic rate and concentrations of chlorophyll, proline, and phosphorus (P) in lettuce leaves. In contrast, increasing Cd concentration was associated with decreases in the photosynthetic rate, shoot fresh weight, and leaf chlorophyll concentration. A significant reduction in leaf Cd concentration was found by addition of HA to the growth media. It seems that application of HA could be successful for improving plant growth and reducing accumulation of Cd in edible parts of lettuce.

The interactive effects humic acid application and several of nitrogen fertilizer on remobilization star wheat

In order to study the effect of the application of Humic acid and different levels of nitrogen on remobilization, production, and yield of star wheat a field experiment was carried out in the region of Viss in the form of split plot and randomized complete block design with four replications in crop year of 2011-2012. Main plots included various levels of nitrogen fertilizer (N0=50, N1=100, and N3=150 kgNha-1) and subplots included the application of Humic acid (H0= lack of Humic acid, H1=foliar spraying at stem elongation stage, H2=foliar spraying at reproductive stage).Results indicated that the effect of nitrogen and Humic acid on leaf area index, grain yield, rate of remobilization, share of remobilization, rate of photosynthesis and share of photosynthesis was significant. The highest amounts of leaf area index, grain yield, remobilization rate, current photosynthesis rate and share were obtained in treatment of 150 kgNha-1. The highest leaf area index, grain yield, remobilization rate, current photosynthesis rate and share were obtained at foliar spraying at reproductive stage. In examining the interactive effect of nitrogen and humic acid on leaf area index, remobilization rate, remobilization rate and share, the difference was significant. Also, at level of 150kgNha-1 the difference was significant for grain yield and current photosynthesis share at foliar spraying at reproductive stage but the difference was not significant at level of 100 kgNha -1 at foliar spraying at stem elongation stage. Therefore, for economical benefits, the application of 100 kgNha-1 along with humic acid foliar spraying at stem elongation stem is recommended.

EFFECT OF HUMIC ACID AND MICRONUTRIENTS FOLIAR FERTILIZATION ON YIELD, YIELD COMPONENTS AND NUTRIENTS UPTAKE OF MAIZE IN CALCAREOUS SOILS

Two field trials were conducted in calcareous soils at Nubaria Agriculture Research Station in 2011 and 2012 summer seasons. The objectives of this investigation was aimed to study the response of maize plants to humic acid and micronutrient foliar fertilization. This study was implemented in newly reclaimed lands at Nubaria region representing calcareous soils under surface irrigation system.Treatments were two humic acid levels (0 and 1000 ppm) and five micronutrient elements (Fe, Zn, Mn and mixture of Fe+Zn+Mn and control). Experimental design was split-plot with four replications. Humic acid was randomly assigned to the main plots, while micronutrients were arranged at random in sub-plots. Results showed that humic acid application resulted in significant decrease in days to 50% tasseling and silking but did not affect plant height and ear height. Spraying of FZM significantly increased weight of 100-kernel and grain yield. Macro- and micro-nutrients concentration in maize leaves and grains and also grain nutrients uptake were affected significantly by spraying humic acid and/or micronutrients comparing with control treatments. Spraying FZM recorded the highest nutrients concentrations and uptake in leaves. Interaction effects between humic acid and MN indicated that treatments of humic acid and micronutrients were superior to excluding humic acid. Nearly all prominent increases were obtained when a mixture of micronutrients and humic acid was used followed by humic acid, Fe, and Zn in the both growing seasons. Regression relation between grain yield (GY) and 18 independnt varibles showed that there is a highly significant relation between grain yield and twelve of the independnt varibles. The regressing between GY and the most effective parameters indicated that there were a statistical model contains all the eighteen independnt varibles explain 78% of grain yield differences at the same time there were four varibles explained 72% of yield variations including (Puptake leaf fe content Nuptake and grain Mn concentration ) under the experiment conditions.

Effects of different levels of humic acid on seedling growth and macro and micronutrient contents of tomato and eggplant

As opposed to direct sowing, production of seedlings of vegetable crops for transplanting is commonly practiced by vegetable growers. This study was undertaken to determine the effects of humic acid on the growth and the macro and micro nutrients contents in tomato (<i>Lycopersicon esculentum</i>) and eggplant (<i>Solanum melongena</i> var. <i>esculentum</i>) seedlings under greenhouse conditions. Different levels of humic acid (50, 100, 150, 200 ml l<sup>-1</sup>) were applied to growing media (peat) after transplanting of examined seedlings of the species every ten days by the time of planting. The highest growth rate for leaf stem and root growth were obtained at 50 and 100 ml l<sup>-1</sup> HA and 50, 100, 150 ml l<sup>-1</sup> HA for tomato and eggplant seedlings., respectively as compared to the control. The highest content of macro and micronu trient contents were obtained at 100 ml l<sup>-1</sup> HA and 200 ml l<sup>-1</sup> HA for tomato and egg plant seedlings, respectively as compared to the control.

Nitrogenous and phosphorus excretions in juvenile silver catfish (Rhamdia quelen) exposed to different water hardness, humic acid, and pH levels

This study examined ammonia, urea, creatinine, protein, nitrite, nitrate, and phosphorus (P) excretion at different water hardness, humic acid, or pH levels in silver catfish (Rhamdia quelen) juveniles. The fish were exposed to different levels of water hardness (4, 24, 50, or 100 mg L(-1) CaCO3), humic acid (0, 2.5, or 5.0 mg L(-1)), or pH (5.0, 6.0, 7.0, 8.0, or 9.0) for 10 days. The overall measured nitrogen excretions were 88.1% (244-423 μmol kg(-1 )h(-1)) for ammonia, 10.9% (30-52 μmol kg(-1 )h(-1)) for creatinine, 0.02% (0.05-0.08 μmol kg(-1 )h(-1)) for protein, 0.001 % (0.002-0.004 μmol kg(-1 )h(-1)) for urea, 0.5% (0.64-3.6 μmol kg(-1 )h(-1)) for nitrite, and 0.5% (0.0-6.9 μmol kg(-1 )h(-1)) for nitrate, and these proportions were not affected by water hardness or humic acid levels. The overall P excretion in R. quelen was 0.14-2.97 μmol kg(-1) h(-1). Ammonia excretion in R. quelen usually was significantly higher in the first 12 h after feeding, and no clear effect of water hardness, humic acid levels, and pH on this daily pattern of ammonia excretion could be observed. Water hardness only affected the ammonia and P excretion of R. quelen juveniles in the initial and fifth days after transfer, respectively. The exposure of this species to humic acid increased ammonia excretion after 10 days of exposure but did not affect P excretion. An increase in pH decreased ammonia and increased creatinine excretion but did not change P excretion in R. quelen. Therefore, when there is any change on humic acid levels or pH in the culture of this species, nitrogenous compounds must be monitored because their excretion rates are variable. On the other hand, P excretion rates determined in the present study are applicable to a wide range of fish culture conditions.

Sorption of nonpolar neutral organic compounds to low-surface-area metal (hydr)oxide- and humic acid- coated model aquifer sands

The roles of mineral-bound humic acid (HA) and mineral surfaces in the sorption of six nonpolar neutral organic compounds with relatively high aqueous solubility, Sw , (1,2,4-trichlorobenzene, 1,4-dichlorobenzene, chlorobenzene, m-xylene, toluene, and benzene) to low-surface-area (i.e., ≤ 1.2 m2/g) metal (hydr)oxide- and HA-coated sands with low organic carbon fractions (i.e., 0.006% ≤ foc ≤ 0.044%) were investigated using well-characterized mineral surfaces [i.e., α-FeO(OH)- or Al2O3- coated sands], terrestrial HA, and solutions with relatively constant pH and ionic strength. Sorption isotherms of all six compounds to low-surface-area metal (hydr)oxide-and HA-coated sands were practically linear (i.e., 0.898 ≤ n ≤ 1.06), and resulted from a combination of sorption to both mineral-bound HA and mineral surfaces, with the dominance of either contribution depending on the properties of the sorbents (e.g., foc ) and organic compounds (e.g., Sw and Kow ). Compared to HA-associated high-surface-area, pure metal (hydr)oxides or clay minerals illustrating that loading levels of HA significantly impacted sorption affinity (i.e., Koc ) and linearity (i.e., n) for particularly hydrophobic compounds (i.e., phenanthrene, anthracene and pyrene) due to the changes in fractionation, and structural and chemical properties of mineral-bound HA, the subsequent changes of sorption affinity and linearity appeared to be insignificant for the sorption of organic compounds with relatively high Sw to low-surface-area metal (hydr)oxide- and HA-coated sands with low foc values. Thus, the predictive models for the sorption of organic compounds with relatively high Sw to low-surface-area metal (hydr)oxide- and HA-coated sands may not be remarkably improved by incorporating the complex changes of sorption affinity and linearity caused by the changes in fractionation, and structural and chemical properties of mineral-bound HA, although the mineral surfaces apparently caused physical and chemical changes of HA, and vice versa during adsorption onto mineral surfaces.

Photosynthetic Activity and N Metabolism of Lettuce as Affected by Humic Acid

The mechanism by which humic substances stimulate plant biological activities is not clear. To study effects of humic acid on N metabolism and growth of lettuce (Lactuca sativa L.) a hydroponic experiment was conducted under greenhouse conditions. Humic acid (HA) at 0, 100, or 1000 mg·L−1 was added with a nutrient solution to plants. HA accelerated uptake of N and NO3 and accelerated N metabolism by enhancing nitrate reductase activity, which resulted in production of protein. HA did not affect P absorption and proline content of leaves. The photosynthetic activity of lettuce increased with all levels of HA due to enhancement of chlorophyll content and mesophyll conductance. HA can stimulate N metabolism and photosynthesis activity of lettuce to improve yield.

An Environmental Fate Study of Methoxychlor Using Water-Sediment Model System

Agricultural waste water containing pesticides can reach the sea via rivers and estuaries, including brackish lakes. We studied the metabolic fate of methoxychlor [MXC; 1,1,1-trichloro-2,2-bis(4-methoxyphenyl)ethane] in a model system consisting of sediment and associated water collected from two sampling sites: a brackish lake and a freshwater river. MXC degraded rapidly and was finally mineralized in both sediment systems. The first step of degradation was dechlorination to yield 1,1-dichloro-2,2-bis(4-methoxyphenyl)ethane [de-Cl-MXC] or CN-replacement to yield 2,2-bis(4-methoxyphenyl)acetonitrile [MXC-CN], followed by O-demethylation. Although the metabolites were common to the two sediments, the dynamics of the metabolites over time were clearly distinct. In the brackish lake sediment, de-Cl-MXC accumulated transiently, whereas in the river sediment, it was rapidly converted to its demethylated metabolite. We also found that dechlorination and CN-replacement proceeded in autoclave-sterilized river sediment. In the river sediment, the abiotic reaction mediated by abundant humic acid and low oxygen level also appeared to contribute to the overall MXC metabolism.

Influence of different levels of humic acid and esterified glucomannan on growth performance and intestinal morphology of broiler chickens

A study was under taken to investigate the effect of dietary supplementations of humic acid and esterified glucomannan) on broiler performance and the morphological measurements of small intestine. Two hundred and ten day old broiler chicks were weighed and randomly assigned to seven treatment groups in triplicate. The dietary treatments included T1) control (basal diet without any additives), T2) basal diets supplemented with 0.1% humic acid, T3) basal diets supplemented with 0.2% humic acid, T4) basal diets supplemented with 0.3% humic acid, T5) basal diets supplemented with 0.1% esterified glucomannan, T6) basal diets supplemented with 0.2% esterified glucomannan and T7) basal diets supplemented with 0.3% esterified glucomannan. Different parameters including body weight gain (BWG), feed intake (FI), feed conversion ratio (FCR) and morphology of small intestine were evaluated during six weeks of experimental period. According to the results, at the end of experimental period, the highest average BWG were recorded in T4 group (fed with 0.3% humic acid), compared to control (T1) and other experimental groups (p < 0.05). Where as, the highest body weight gain were observed during starter period in treatment 7 (fed with 0.3% esterified glucomannan) as compare to other experimental groups (p < 0.05). Statistically, feed intake remained unaffected during the experimental period in all the treatment groups. However, the lowest and the highest feed intake were observed numerically within treatments T4 and T1 with 4229.70 g and 4362.30 g, respectively. Addition of dietary supplements used in the study appeared to have significant effect on the morphology of the small intestine (jejunum mucosal development) of the broilers in different treatment groups. Compared to control group, the inclusion of either humic acid or esterified glucomannon decreased (p < 0.01) the crypt depth and increased villus height respectively (p < 0.05). More ever, the diet supplements with humic acid 0.3% (T4) decreased crypt depth compared to esterified glucomannan and control. The dietary supplementations resulted in an increase in the villus height of intestinal mucosa of broilers. The increase in the villus height was associated with improvement of growth performance for both humic acid and esterified glucomannan. Based on our results it appeared that humic acid and esterified glucomannan can be used as a growth promoter in broiler diets and they can improve the gut health too.

Pharmacokinetic modelling of multi-decadal luminescence time series in coral skeletons

As corals grow, they incorporate chemical indicators of seawater conditions into their aragonite skeleton after they have traversed an outer living tissue layer. Long-lived, massive coral skeletons can record decade- and century-long time series of seawater status. One such environmental clue is luminescence intensity which can correspond to river flow patterns and has been attributed to humic acid incorporation. Seawater humic acid levels are linked to river flow as rainfall extracts them from catchment soils to then flow into rivers and coastal seas. However, discrepancies exist when validating coral luminescence records against river flow data with intense luminescence sometimes occurring in the absence of increased flows. This contributes to uncertainty when reconstructing pre-instrumental river flows and rainfall from coral luminescence. Here we demonstrate that a major portion of coral core luminescence time series can be explained using a single-compartment, pharmacokinetic model that incorporates river flow measurements as the equivalent of drug dose. The model was robust for luminescence series in corals from near-shore reefs regularly influenced by river flow. The model implies that after floods, a proportion of subsequent luminescence peaks can be derived from the initial flood. This explains why some luminescence peaks after floods often do not correspond to additional significant river flows. This provides the first mechanism-based explanation for temporal changes in coral skeleton luminescence that incorporates a mathematical link between two independent time series making this proxy even more robust for reconstructing river flow and rainfall.

Effect of amending urea with humic acids and acid sulphate on biomass production of Masmadu (Zea mays L.) and selected soil chemical properties.

Excessive use of fertilizers especially nitrogenous fertilizers with low management in relation to food safety and environmental pollution has in recent times become a subject of concern. This greenhouse study compared the effect of three different urea-humic acid-acid sulphate soil mixtures on maize biomass production, soil pH, ammonium and nitrate contents, and urea use efficiency compared with urea-N without additives (urea alone). Humic acid (HA), acid sulfate soil and soil used in the greenhouse study were analyzed for selected soil physio-chemical properties. The fertilizer mixtures and ammonia loss determination were carried out using standard methods. The treatments were evaluated in a completely randomized block design with 3 replications. The data obtained at the end of the study on biomass production, soil pH, exchangeable ammonium and available nitrate were analyzed using analysis of variance and the means were compared using Duncan’s test using statistical analysis systerm (SAS) version 9.2. The soil used to test treatments was a sandy clay loam Typic Tualemkuts (Nyalau Series). Urea amended with different levels of HA alone significantly improved soil exchangeable ammonium compared to urea alone. All the mixtures significantly improved soil pH compared with urea alone. However, all the mixtures did not significantly affect biomass production and content of available nitrate compared with urea alone. Amending urea with HA and acid sulphate soil did not significantly affect biomass production of Masmadu (test crop) but it significantly improved soil pH and retention of exchangeable ammonium. Key words: Humic acid, acid sulphate soil, urea, ammonium, nitrate, Zea mays, biomass production.

Kinetics of oxidation of dimethyl trisulfide by potassium permanganate in drinking water

Metabolites of algae such as geosmin, 2-methylisoborneol etc. are reported to induce pungent odors into drinking water and attract additional scientific attention. Recently, in China, taste and odor outbreaks in drinking water supply have become increasingly common. In source water affected by eutrophication, dimethyl trisulfide, speculated to be produced by decayed algae, was found to be the source of taste and odor issues and can be removed effectively by usual oxidation agents. In this experimental study, batch scale tests were carried out focusing on the removal of dimethyl trisulfide. Reaction kinetics of dimethyl trisulfide oxidized by potassium permanganate in water had been studied; influence factors such as pH, organic substrate, other existed taste, and odor contaminant in equivalent concentration were also discussed. Results showed that dimethyl trisulfide can be removed by potassium permanganate efficiently; the ratio can reach more than 70% with oxidant dosage of 4 mg·L−1 and contact time prolonged to 120 min. The dimethyl trisulfide decomposition followed a second-order kinetics pattern with a rate constant k = 0.00213 L·(min·mg)−1. Typically, the degradation rate of dimethyl trisulfide was increased with the increasing KMnO4 dosage, but dramatically dropped with the increasing levels of humic acid (1.8–4.5 mg·L−1) and other odor-causing compounds (e.g. β-cyclocitral, 0−1886.0 μg·L−1). Solution pH (5.2–9.0) and initial dimethyl trisulfide concentration did not significantly affected the degradation. This study demonstrates that KMnO4 oxidation is an effective option to remove dimethyl trisulfide from water.

Lignite-Derived Humic Acid Effect on Growth of Wheat Plants in Different Soils

Humic acid (HA), a fairly stable product of decomposed organic matter that consequently accumulates in ecological systems, enhances plant growth by chelating unavailable nutrients and buffering pH. We examined the effect of HA derived from lignite on growth and macronutrient uptake of wheat ( Triticum aestivum L.) grown in earthen pots under greenhouse conditions. The soils used in the pot experiment were a calcareous Haplustalf and a non-calcareous Haplustalf collected from Raisalpur and Guliana, respectively, in Punjab Province, Pakistan. The experiment consisted of four treatments with HA levels of 0 (control without HA), 30, 60, and 90 mg kg −1 soil designated as HA 0, HA 1, HA 2, and HA 3, respectively. In the treatment without HA (HA 0), nitrogen (N), phosphorus (P), and potassium (K) were applied at 200, 100, and 125 mg kg −1 soil, respectively. Significant differences among HA levels were recorded for wheat growth (plant height and shoot weight) and N uptake. On an average of both soils, the largest increases in plant height and shoot fresh and dry weights were found with HA 2 (60 mg kg −1 soil), being 10%, 25%, and 18%, respectively, as compared to the control without HA (HA 0). Both soils responded positively towards HA application. The wheat growth and N uptake in the non-calcareous soil were higher than those of the calcareous soil. The HA application significantly improved K concentration of the non-calcareous soil and P and NO 3-N of the calcareous soil. The highest rate of HA (90 mg kg −1 soil) had a negative effect on growth and nutrient uptake of wheat as well as nutrient accumulation in soil, whereas the medium dose of HA (60 mg kg −1 soil) was more efficient in promoting wheat growth.

Effects of potassium and humic acid on emergence, growth and nutrient contents of okra (Abelmoschus esculentus L.) seedling under saline soil conditions.

The effects of potassium and humic acid (HA) on emergence, growth and nutrient contents of okra (Abelmoschus esculentus L cv. Sultani) seedlings in saline soil conditions were evaluated. Different levels of humic acid (0, 500, 1000 and 1500 mg kg-1) and potassium (0, 75, 150 and 300 mg kg-1) were applied on growing media treated with 50 mg NaCl kg-1 before seed sowing. The experiment was designed as randomized completely factorial block and each parcel had ten pots without drainage. Two okra seeds were sown in each pot having 300 cc volumes of growth media. The seedlings were thinned to one after emergence. The seedlings were irrigated with distilled water. Seed emergence, root and shoot size, leaf number, 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 seedlings were also determined. All data were subjected to a one-way analysis of variance and separated by Duncan’s multiple range test which was performed using the Costat statistical software. There were statistical differences in terms of effects of potassium and HA on the okra seedling performances. The effects of K, Ca, Na, Cu, Fe, Mn, Zn and HA applications on plant mineral (N, P, K, Ca, Cu, Fe, and Mn) contents were significant at p < 0.005. Key words: Okra (Abelmoschus esculentus L.), potassium, humic acid, nutrient content, seedling growth.

Clinical efficacy of potassium humate in the treatment of allergic rhinitis: double-blind placebo-controlled trial

The anti-inflammatory properties of products that contain high levels of humic acid, such as peat, sapropeles, and mumie, are well described. The aim of this study was to establish the clinical efficacy of brown coal-derived potassium humate, as in vivo animal models had suggested similar efficacy of humate to prednisolone. In this double-blind, placebo-controlled study, atopic volunteers were recruited and randomized to placebo or 1.8 g potassium humate/day (three divided dosages) when they presented with hay fever. The efficacy parameters used were skin-prick tests for wheal and flare reactions, nasal smears for inflammatory cell accumulation, and cytokine levels. Patients also filled out daily symptom score cards to determine efficacy against symptoms of hay fever. Potassium humate resulted in a significant decrease in wheal and flare reactions as well as nasal eosinophil counts. These findings were supported by similar changes (not significant) in cytokine levels. Changes in symptom scores did not reach significance. This proof of concept study clearly demonstrated the potential of potassium humate in the treatment of inflammatoryconditions such as hay fever. Drug Dev Res 71:358-363, 2010. C!J 2010Wiley-Liss, Inc.

Effect of Humic Acid on Plant Growth, Nutrient Uptake, and Postharvest Life of Gerbera

ABSTRACT Humic acid (HA) might benefit plant growth by improving nutrient uptake and hormonal effects. The effect of HA on growth, macro—and micronutrient contents, and postharvest life of gerbera (Gerbera jamesonii L.) cv. ‘Malibu’ were examined. Different levels of humic acid (0, 100, 500, and 1000 mg/L) were applied to nutrient solution. Root growth increased at 1000 mg/L HA incorporated into the solution. Macro- and micronutrient contents of leaves and scapes including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), and zinc (Zn) were significantly enhanced by HA. However, high levels of HA decreased some nutrient contents. Five-hundred mg/L HA increased the number of harvested flowers per plant (52%). Higher HA levels extended the vase life of harvested flowers by 2—3.66 days and could prevent and delay bent neck incidence. These postharvest responses were most probably due to Ca accumulation in scapes and hormone-like activity of HA.

Evaluation of Enhanced Panicum amarum Establishment through Fragment Plantings and Humic Acid Amendment

The ability of the dune grass Panicum amarum to resprout from vegetative fragments as well as the response of this species to a commercially available soil conditioner (humic acid) were evaluated using a factorial design in a greenhouse setting. A general trend of greater P. amarum biomass production with humic acid amendment was noted. Panicum amarum growth did not demonstrate either an asymptote or decline with the highest level of humic acid addition, indicating that its growth may potentially be further enhanced by humic acid levels greater than those used in this study. The survivorship of P. amarum fragments (belowground fragment material only and aboveground material fragment only) were comparable with whole-plant planting success with high survivorship noted for all three planting approaches. As anticipated, the whole-plant planting treatments resulted in the greatest total biomass, followed by the belowground-only plantings, which had greater biomass production than the aboveground-only plantings. Overall, the addition of commercial humic acid to the soil during the planting of P. amarum appears to have the potential for enhancing establishment and growth. Importantly, this research demonstrates that the use of P. amarum fragments may be a successful alternative approach in projects where it may be desirable to double planting densities or in situations where whole plant transportation is logistically difficult. Further evaluations of these restoration methods under more realistic field scenarios with longer monitoring of effects are required to determine fully the benefits of these techniques.

Effect of nitrogen, potassium and humic acid on 134 Cs transfer factors to wheat from tropical soils in Neubauer growth units

A Neubauer plantlet experiment was carried out using Inceptisol (Typic Haplustept) and Vertisol (Typic Chromustert) soils contaminated with 134Cs at 74 kBq kg(-1) soil to study the transfer factor to wheat crop (Triticum aestivum) as influenced by four levels of humic acid (100, 200, 300, 400 mg HA kg(-1) soil), potassium and NH4-N (36.4, 54.5, 72.7 and 90.9 mg K or NH4 kg(-1) soil) under tropical climate. The biomass yield and K uptake by wheat were significantly improved in Vertisol with NH4-N and K application. The potassium application significantly increased the potassium concentration in wheat plants. The increase in the levels of each of the treatments dramatically improved the yield, K content and K uptake parameters, irrespective of the soils. The 134Cs transfer factors, irrespective of the treatments were observed to be higher in Vertisols as compared to Inceptisols. Among the treatments, the effect of HA was significantly greater than that of K and NH4-N application in Inceptisol, however, in Vertisols both HA and NH4-N were observed to be superior as compared to K application. With each increment in the levels of the treatments, a significantly lowered TF value was found, higher in Inceptisols (56.3%) than Vertisols (48.5%). Comparison of treatments indicates that in general higher potassium concentration in plant drastically lowered radiocesium transfer to wheat. Neubauer plant culture study, a rapid laboratory experimental model based on simple soil-plant system was quite clearly brought out the potential effectiveness of N, K and HA on soil-to-wheat transfer of radiocesium. Such screening technique needs to be extended to cover wider crop species, different climatic conditions and factors governing/modifying the mobility of radiocesium in soil and its absorption by crop plants.

Humic Acid Interferes with Species Recognition in Zebrafish (Danio rerio)

Few studies have addressed how chemosensation may be impaired by chemical alterations of the environment and anthropogenic disturbance. Humic acid (HA) is a pervasive, naturally occurring organic derivative found in aquatic and terrestrial environments; human activity, however, can lead to elevated levels of HA. Recent studies suggest that environments that contain high levels of HA may hinder chemical communication. We tested the ability of adult zebrafish (Danio rerio) to discriminate between conspecific and heterospecific urinary chemical cues found in the presence and absence of HA. We show that high humic acid levels (200 mg/l) can impair the ability to differentiate conspecifics from heterospecifics. We also found that zebrafish prefer untreated water over HA-treated water. These findings suggest that, in addition to human-produced synthetic compounds, changes in the abundance of naturally occurring substances may also negatively impact natural behaviors in aquatic species by disturbing the sensory environment.

Predicting Bioavailability and Accumulation of Organochlorine Pesticides by Japanese Medaka in the Presence of Humic Acid and Natural Organic Matter Using Passive Sampling Membranes

Adsorption to dissolved organic matter (DOM) may significantly decrease the freely dissolved concentration of many hydrophobic organic compounds and, hence, result in reduced bioavailability to aquatic organisms. Here, the suitability of using triolein-embedded cellulose acetate membrane (TECAM) as a biomimetic surrogate to assess the bioavailability of organochlorine pesticides (OCPs) in water in the presence of DOM was explored. The accumulation of OCPs was measured in TECAM and pelagic Japanese medaka (Oryzias latipes) in the laboratory after 12 h exposure to water containing different levels of Aldrich humic acid. Further, OCP uptake by TECAM and medaka in real aqueous environments was evaluated after 30 d exposures in two sites. Laboratory results showed that OCP uptake by medaka consistently decreased with increasing levels of humic acid in the range of 0-15 mg C/L in sample solutions. This tendency was closely mimicked by OCP accumulation in TECAM under the same conditions. Field results showed that TECAM accumulated similar OCP patterns as medaka (r2 = 0.92 for site 1 and r2 = 0.94 for site 2), although comparison of the in-field eight OCP concentrations in TECAM to those in medaka yielded approximately a factor of 3 (on a wet weight basis). These results suggest that the TECAM method can be used as a simple and useful tool to predict the bioavailability and bioaccumulation potential of poorly biotransformed organic compounds in pelagic fish in aqueous environment.