High Nitrate Solutions Research Articles

Stability constant determinations for technetium (IV) complexation with selected amino carboxylate ligands in high nitrate solutions

Abstract The stability constants for Tc(IV) complexation with the ligands IDA, NTA, HEDTA, and DTPA were determined in varied nitrate concentrations using liquid-liquid extraction methods. The determined log β101 stability constants at 0.5 M NaNO3 were found to be 9.2±0.3, 10.3±0.3, and 15.3±0.3 for IDA, NTA, and HEDTA, respectively. The log β111 stability constant for DTPA was determined to be 22.0±0.6. These determined stability constants show a slight decrease in magnitude as a function of increasing NaNO3 concentration. These stability constants were used to model the total dissolution of Tc(IV) in acidic aqueous solutions in the presence of each ligand. The results of these predictive models indicate that amino carboxylic ligands have a high potential for increasing the aqueous dissolution of Tc(IV); at pH 2.3, 0.01 M ligand yield dissolved Tc(IV) concentrations of 1.42·10−5 M, 1.33·10−5 M, 6.07·10−6 M, 9.65·10−7 M, for DTPA, HEDTA, NTA, and IDA, respectively.

Nitric oxide is involved in nitrate-induced inhibition of root elongation in Zea mays.

Root growth and development are closely dependent upon nitrate supply in the growth medium. To unravel the mechanism underlying dependence of root growth on nitrate, an examination was made of whether endogenous nitric oxide (NO) is involved in nitrate-dependent growth of primary roots in maize. Maize seedlings grown in varying concentrations of nitrate for 7 d were used to evaluate the effects on root elongation of a nitric oxide (NO) donor (sodium nitroprusside, SNP), a NO scavenger (methylene blue, MB), a nitric oxide synthase inhibitor (N(omega)-nitro-L-arginine, L-NNA), H(2)O(2), indole-3-acetic acid (IAA) and a nitric reducatse inhibitor (tungstate). The effects of these treatments on endogenous NO levels in maize root apical cells were investigated using a NO-specific fluorescent probe, 4, 5-diaminofluorescein diacetate (DAF-2DA) in association with a confocal microscopy. Elongation of primary roots was negatively dependent on external concentrations of nitrate, and inhibition by high external nitrate was diminished when roots were treated with SNP and IAA. MB and L-NNA inhibited root elongation of plants grown in low-nitrate solution, but they had no effect on elongation of roots grown in high-nitrate solution. Tungstate inhibited root elongation grown in both low- and high-nitrate solutions. Endogenous NO levels in root apices grown in high-nitrate solution were lower than those grown in low-nitrate solution. IAA and SNP markedly enhanced endogenous NO levels in root apices grown in high nitrate, but they had no effect on endogenous NO levels in root apical cells grown in low-nitrate solution. Tungstate induced a greater increase in the endogenous NO levels in root apical cells grown in low-nitrate solution than those grown in high-nitrate solution. Inhibition of root elongation in maize by high external nitrate is likely to result from a reduction of nitric oxide synthase-dependent endogenous NO levels in maize root apical cells.

Nitrate-induced ethylene biosynthesis and the control of nodulation in alfalfa

We previously reported that inhibition of ethylene biosynthesis with aminoethoxyvinylglycine (AVG) eliminated the inhibitory effect of NO3– on nodulation of alfalfa (Medicago sativa L. cv. Aragon) plants grown aeroponically. In this work, the effect of Ag+, as an inhibitor of ethylene action, has been studied in plants growing aeroponically or in darkened tubes with vermiculite, and low-nitrate or high-nitrate solution. Vermiculite-grown plants developed up to 3 times as many nodules as did those growing aeroponically. Nodule formation was mirrored by dry-matter accumulation. High (10 mol m–3) NO3– applied from planting inhibited nodulation to an equal extent (c. 50%) in the two growth conditions. In contrast, Ag+ treatment increased nodule formation at all NO3– concentrations assayed under the two growth conditions, with the stimulation being higher in plants grown aeroponically. Finally, no effect of Ag+ (10 mmol m–3) on plant growth was observed in either of the growth conditions. The effectiveness of NO3– as a nodulation inhibitor and enhancer of ethylene biosynthesis in roots of alfalfa was also studied. Within 24 h after inoculation, 10 mol m–3 NO3– exerted most of its inhibitory effect on nodulation. At the same time, both 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase activity and ethylene evolution rates markedly increased in inoculated and uninoculated alfalfa roots treated with NO3–. Support for a role of endogenous ethylene in the control of nodule formation in legumes is discussed.

Simple Method for Technetium Removal from Aqueous Solutions

Because of an increasing need for {sup 99}Tc removal from treatment solutions during waste processing and environmental cleanups, several inexpensive sorbents were investigated. Here, Packed-column experiments with iron dust of 40 to 60 mesh (Fisher I-57) showed an excellent uptake of pertechnetate ions from alkaline (pH {approximately} 8.5) high-nitrate (100 to 250 g/l) solutions at flow rates measured in bed volumes (BVs) of between 0.05 and 0.15 BV/min. The columns worked well until they became plugged by rusting after several hundred bed volumes of solution were flowed through (330 to 900 BV). Similar tests using organic ion-exchange resins, such as Dowex SRB-OH and Reillex HP and Reillex HPQ, and the same alkaline high-nitrate solutions showed breakthroughs after 20 to 50 BV were passed.

The effects of nitrogen fixation, soil nitrate, and defoliation on the growth, alkaloids, and nitrogen levels of Lupinus succulentus (Fabaceae).

We examined the effects of nitrogen nutrition and defoliation on the alkaloids, nitrogen levels, and growth of Lupinus succulentus by growing plants under five nitrogen/defoliation treatments: 1) fertilization with a high-nitrate nutrient solution, 2) fertilization with a low-nitrate solution, 3) inoculation with N-fixing bacteria but without available soil nitrogen, 4) high-nitrate solution plus periodic partial defoliation, and 5) low-nitrate plus defoliation. In the absence of defoliation, plants from both the N-fixing and high-N treatments had higher concentrations of alkaloids and nitrogen, and higher growth rates than the low-N plants. Periodic defoliation had little effect on the high-N plants, but defoliated N-fixing plants were severely stunted and had lower alkaloid and nitrogen levels. The experimental treatments also affected the relative concentrations of the alkaloids. Our results indicate that 1) alkaloid composition and concentration in L. succulentus are determined by both nitrogen availability and developmental state, 2) plants relying solely on N-fixation respond quite differently to defoliation than those with adequate soil nitrogen, and 3) the food value of the plant tissue can be affected by an interaction between the effects of defoliation and nitrogen status.

Nitrate reduction in the roots and shoots of wheat seedlings

Intact wheat seedlings cultured in high nitrate solutions (high-NO 3 (-) cultures) reduced NO 3 (-) when placed for 24 hr in dilute CaSO4 solutions although they leaked NO 3 (-) back to solution during this period. Most of the reduction seemed to occur in shoots since in parallel experiments detached shoots reduced nearly as much of the previously absorbed NO 3 (-) as intact cultures. Detached roots leaked greater quantities of NO 3 (-) back to solution than did intact cultures, and failed to reduce any of their previously absorbed NO 3 (-) during the experimental period. Seedlings of identical age cultured without a nitrogen source and rich in carbohydrate reserves (low-N cultures) rapidly absorbed NO 3 (-) from dilute Ca(NO3)2 solutions and reduced 80% of that absorbed. Detached low-N roots also absorbed NO 3 (-) and reduced 40% of that absorbed. Total NO 3 (-) reduction by intact low-N cultures over the 24-hr period was comparable to that of high-NO 3 (-) cultures in spite of the fact that in vitro nitrate reductase activity of the former did not reach the levels found initially or at the end of the period in the latter, and that the total NO 3 (-) absorbed by low-N cultures was less than that initially present in high-NO 3 (-) cultures.

Soil aldehydes: A scientific study of a new class of soil constituents unfavorable to crops, their occurrence, properties and elimination in practical agriculture

The experimental results show that aldehydes are harmful to plant growth in aqueous culture solutions, in nutrient solutions, in soil in pots, and in soil in the field. The effects of six aldehydes—namely, salicylic aldehyde, vanillin, benzaldehyde, heliotropine, formaldehyde, and paraformaldehyde—were studied in nutrient-culture solutions and each proved to be detrimental to plant growth. The effect of the compounds varied according to the composition of the nutrient solutions. Salicylic aldehyde was least harmful in solutions composed of a high percentage of phosphates. Vanillin was least harmful in solutions with a high percentage of nitrates. Benzaldehyde was about equally harmful in all the nutrient solutions. It was slightly more harmful, however, in the high nitrate solutions than in the mainly phosphatic or potassic cultures. Paraformaldehyde was also least harmful in the phosphate culture, but formaldehyde and heliotropine showed harmful effects to an equal degree in almost all cultures, regardless of their composition. Salicylic aldehyde and vanillin were found to occur in soils quite frequently, especially in soils of low productivity. The isolated substance from the soils was harmful to plants when dissolved in aqueous solution. The two aldehydes were harmful in some soils and not in others. The field studies show that the added aldehydes disappeared in some soils and not in others. There was no harmful action where the aldehydes were destroyed. The soils in which the aldehydes were destroyed have strong biological activities, good oxidation powers, and are fertile. The results of the experimental work presented in this paper further show that unfertile soils, where due to the presence of harmful aldehydes, can be made productive by good drainage and by the use of lime and certain fertilizers. This is demonstrated, first, by the growth of plants in nutrient solutions, where it is shown that phosphates partially overcome the bad effects of salicylic aldehyde, and that nitrates ameliorate the harmfulness of another aldehyde, vanillin. Second, by the more normal absorption of phosphates by plants growing in solutions containing salicylic aldehyde. Third, by the growth of plants in soil in pots, which shows that the harmful action of salicylic aldehyde is partially overcome by lime and phosphates and the effects of vanillin by lime and nitrate fertilizers. Fourth, by the growth of plants in field soils to which aldehydes were added, which again shows that lime and phosphates lessen the harmfulness of salicylic aldehyde and lime and nitrates alter the effects of vanillin. Fifth, by chemical tests in which it was shown that salicylic aldehyde, when added to a soil, was destroyed where lime and phosphates were added, and vanillin was destroyed where lime and nitrates were added. Sixth, by the improved productivity from the addition of lime and phosphates to a soil in which salicylic aldehyde was naturally formed and persisted for a period of years.

Soil aldehydes: A scientific study of a new class of soil constituents unfavorable to crops, their occurrence, properties and elimination in practical agriculture

Abstract The experimental results show that aldehydes are harmful to plant growth in aqueous culture solutions, in nutrient solutions, in soil in pots, and in soil in the field. The effects of six aldehydes—namely, salicylic aldehyde, vanillin, benzaldehyde, heliotropine, formaldehyde, and paraformaldehyde—were studied in nutrient-culture solutions and each proved to be detrimental to plant growth. The effect of the compounds varied according to the composition of the nutrient solutions. Salicylic aldehyde was least harmful in solutions composed of a high percentage of phosphates. Vanillin was least harmful in solutions with a high percentage of nitrates. Benzaldehyde was about equally harmful in all the nutrient solutions. It was slightly more harmful, however, in the high nitrate solutions than in the mainly phosphatic or potassic cultures. Paraformaldehyde was also least harmful in the phosphate culture, but formaldehyde and heliotropine showed harmful effects to an equal degree in almost all cultures, regardless of their composition. Salicylic aldehyde and vanillin were found to occur in soils quite frequently, especially in soils of low productivity. The isolated substance from the soils was harmful to plants when dissolved in aqueous solution. The two aldehydes were harmful in some soils and not in others. The field studies show that the added aldehydes disappeared in some soils and not in others. There was no harmful action where the aldehydes were destroyed. The soils in which the aldehydes were destroyed have strong biological activities, good oxidation powers, and are fertile. The results of the experimental work presented in this paper further show that unfertile soils, where due to the presence of harmful aldehydes, can be made productive by good drainage and by the use of lime and certain fertilizers. This is demonstrated, first , by the growth of plants in nutrient solutions, where it is shown that phosphates partially overcome the bad effects of salicylic aldehyde, and that nitrates ameliorate the harmfulness of another aldehyde, vanillin. Second , by the more normal absorption of phosphates by plants growing in solutions containing salicylic aldehyde. Third , by the growth of plants in soil in pots, which shows that the harmful action of salicylic aldehyde is partially overcome by lime and phosphates and the effects of vanillin by lime and nitrate fertilizers. Fourth , by the growth of plants in field soils to which aldehydes were added, which again shows that lime and phosphates lessen the harmfulness of salicylic aldehyde and lime and nitrates alter the effects of vanillin. Fifth , by chemical tests in which it was shown that salicylic aldehyde, when added to a soil, was destroyed where lime and phosphates were added, and vanillin was destroyed where lime and nitrates were added. Sixth , by the improved productivity from the addition of lime and phosphates to a soil in which salicylic aldehyde was naturally formed and persisted for a period of years.