Nitrification Inhibitors: Chitosan Hydrogel Study
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Questions and Answers

What are the two fractions of DCD identified in the beads?

  • Organic DCD and inorganic DCD
  • Soluble DCD and insoluble DCD
  • Available DCD and locked DCD (correct)
  • Free DCD and complexed DCD

Which technique was used for bead morphology and surface analyses?

  • Atomic force microscopy (AFM)
  • Transmission electron microscopy (TEM)
  • Scanning electron microscopy (SEM) (correct)
  • X-ray diffraction (XRD)

What was the retention time of the second compound detected in beads incubated in water?

  • 4.0 min
  • 5.2 min
  • 6.3 min
  • 4.6 min (correct)

What mode of analysis was used to quantify the DCD content in samples?

<p>High-performance liquid chromatography (HPLC) (A)</p> Signup and view all the answers

What was the effect of acidification on the release of the glyoxal derivative?

<p>It released about twice as much glyoxal derivative (B)</p> Signup and view all the answers

What statistical method was employed to investigate the effects of independent variables?

<p>ANOVA (A)</p> Signup and view all the answers

What did the results indicate about the glyoxal-DCD adduct's hydrolysis?

<p>It is stable under acid conditions (A)</p> Signup and view all the answers

How much more glyoxal-DCD adduct did CG beads release compared to C beads?

<p>54% (A)</p> Signup and view all the answers

What is the main component of chitosan that results from its deacetylation?

<p>Chitin (A)</p> Signup and view all the answers

What was the percentage increase in the initial dry weight of CG beads compared to C beads?

<p>46% (A)</p> Signup and view all the answers

What property of chitosan allows for a high rate of wetting?

<p>It is highly porous (A)</p> Signup and view all the answers

What reaction can glyoxal undergo upon loss of water?

<p>Oligomerisation (D)</p> Signup and view all the answers

How can DCD be extracted from chitosan xerogel beads?

<p>Immersing in deionised or acidified water (A)</p> Signup and view all the answers

What kind of adducts might glyoxal form with the guanidine group of DCD?

<p>Schiff base glyoxal-DCD adducts (A)</p> Signup and view all the answers

What was the significant difference in DCD content between C beads and CG beads?

<p>C beads contained about 0.2 mg DCD per bead (B)</p> Signup and view all the answers

How did acidification affect DCD extraction from CG beads?

<p>It increased the amount of DCD extracted (B)</p> Signup and view all the answers

What was one example of an agrochemical delivered using chitosan-derived systems?

<p>Neem seed oil (B)</p> Signup and view all the answers

What was the method used to extract DCD from the beads?

<p>Incubating uncrushed beads in acidified water (D)</p> Signup and view all the answers

What analysis method was used to measure the quantity of DCD extracted from the beads?

<p>HPLC analysis (C)</p> Signup and view all the answers

What hypothesis can be made regarding glyoxal-DCD adducts under acidic conditions?

<p>They may hydrolyze to reform DCD (D)</p> Signup and view all the answers

What was the total DCD content per bead for C beads during the experiments?

<p>0.219 mg DCD (C)</p> Signup and view all the answers

What factor caused the swelling of the beads during acidification?

<p>The presence of glyoxal (D)</p> Signup and view all the answers

What was the main purpose of investigating DCD release kinetics from the beads?

<p>To assess the encapsulation efficiency of DCD (D)</p> Signup and view all the answers

What effect did the incubation of DCD solutions have under similar conditions to the bead study?

<p>It confirmed DCD stability under incubation conditions (B)</p> Signup and view all the answers

What role does chitosan play in the release of dicyandiamide (DCD)?

<p>It controls the release of DCD. (B)</p> Signup and view all the answers

What is one of the main benefits of using nitrification inhibitors like DCD in agricultural systems?

<p>Improves nitrogen use efficiency. (B)</p> Signup and view all the answers

How does glyoxal polymerisation affect the DCD encapsulation in chitosan beads?

<p>Higher polymerisation decreases the encapsulation of DCD. (C)</p> Signup and view all the answers

What happens to the DCD release profile when excess glyoxal is partly removed?

<p>DCD is released more slowly compared to dried beads. (A)</p> Signup and view all the answers

What was the primary investigation focus of the study regarding DCD?

<p>To sustain DCD persistence by slow release. (C)</p> Signup and view all the answers

What type of release characteristics do the chitosan beads impart to DCD?

<p>A two-fraction release, one quick and one delayed. (A)</p> Signup and view all the answers

Which of the following statements about the hydrogel used in the study is correct?

<p>It is biodegradable and derived from chitosan. (B)</p> Signup and view all the answers

What environmental impact does the use of nitrification inhibitors aim to address?

<p>Decreased emissions of nitrate and nitrous oxide. (C)</p> Signup and view all the answers

What percentage of DCD content was lost by C beads after 9 hours in deionised water?

<p>84% (D)</p> Signup and view all the answers

Which type of bead retained a larger proportion of DCD content over 14 days?

<p>C beads (A)</p> Signup and view all the answers

What was the percentage of DCD content released by CG beads after 14 days?

<p>23% (B)</p> Signup and view all the answers

What does the glyoxal-crosslinked chitosan indicate about its ability to hold DCD content?

<p>It retains a substantial proportion over time. (B)</p> Signup and view all the answers

After 14 days, what was the total fraction of DCD content released by C beads?

<p>87% (A)</p> Signup and view all the answers

What does the data suggest about the locked DCD fractions in C beads?

<p>They represent 16% of total DCD content. (A)</p> Signup and view all the answers

Which beads showed a rapid release of DCD before reaching a plateau?

<p>Both C and CG beads (D)</p> Signup and view all the answers

What was the DCD content release percentage of CG beads after 9 hours?

<p>19% (B)</p> Signup and view all the answers

What is the primary reason CG beads are heavier than C beads?

<p>CG beads have a higher glyoxal content. (D)</p> Signup and view all the answers

What happens to the locked fraction of DCD after acidification?

<p>It is completely released. (C)</p> Signup and view all the answers

What role does glyoxal play in the structure of chitosan beads?

<p>It functions as a covalent cross-linker. (C)</p> Signup and view all the answers

What implication does glyoxal's ability to polymerize have on DCD release?

<p>It hinders the release of DCD. (A)</p> Signup and view all the answers

What could be inferred about glyoxal derivatives in the beads?

<p>They can trap locked fractions of DCD. (C)</p> Signup and view all the answers

What aspect of glyoxal in chitosan has not been reported?

<p>Its polymerization within chitosan beads. (C)</p> Signup and view all the answers

What does the study suggest about the interaction of glyoxal with chitosan?

<p>Glyoxal modifies the physical properties of chitosan. (D)</p> Signup and view all the answers

Why is it significant to understand the polymerization of glyoxal in chitosan beads?

<p>It may influence the release of other species. (B)</p> Signup and view all the answers

Flashcards

Nitrification inhibitor

A chemical that slows down a process in soil called nitrification

Dicyandiamide (DCD)

A specific nitrification inhibitor used in agriculture

Chitosan hydrogel

A biodegradable material that releases DCD slowly over time

Glyoxal crosslinking

A process that creates a more durable chitosan hydrogel matrix

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Controlled DCD release

Slow delivery of DCD in soil, enhancing effectiveness

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DCD encapsulation

Trapping DCD inside the chitosan hydrogel beads

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Chitosan beads

Chitosan material formed into small, controlled-release structures

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Soil nitrification

Process in soil where ammonia changes to nitrite and nitrate

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Chitin

A natural polymer found in the exoskeletons of crustaceans, it's a key component of chitosan.

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Chitosan

A biodegradable material derived from chitin, it's highly porous and good at absorbing water.

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Hydrogel

A water-absorbing material like chitosan, it can trap and release substances slowly.

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Crosslinking

Connecting molecules in a material to form a stronger, more stable structure.

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Glyoxal

A chemical used to crosslink chitosan, it strengthens the material and can react with DCD.

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DCD Release Mechanism

The way DCD is slowly released from chitosan beads, controlled by the crosslinking density and pore size.

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Schiff Base

A chemical bond formed between glyoxal and DCD, potentially affecting DCD release.

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Advantages of Chitosan DCD

Chitosan beads offer slow DCD release, reducing frequent soil applications and enhancing its effectiveness.

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DCD Fraction

DCD within chitosan beads exists in two forms: 'available DCD' that releases easily and 'locked DCD' that remains trapped.

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DCD Release Rate

The speed at which DCD is released from chitosan beads depends on factors like rainfall and bead type.

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Glyoxal-DCD Adduct

A compound formed when glyoxal reacts with DCD inside chitosan beads. It's more stable and releases less DCD.

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Acidification Effect

Breaking down beads with acid releases more glyoxal-DCD adduct, but not DCD.

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CG Bead Release

CG beads release more glyoxal-DCD adduct than C beads when acidified, showing they hold more of the adduct compound.

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HPLC Retention Time

DCD and glyoxal-DCD adduct have different retention times on HPLC, allowing us to separate and quantify them.

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Bead Morphology

The shape and structure of chitosan beads influence DCD release. SEM helps visualize this.

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DCD Quantification

The amount of DCD in samples (water, soil) is measured using HPLC analysis.

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What is DCD?

Dicyandiamide (DCD) is a chemical that slows down the process of nitrification in soil, which is the conversion of ammonia to nitrates.

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What is the main difference between C and CG beads?

C beads are chitosan beads crosslinked with glyoxal and washed with DCD solution. CG beads are similar but washed with water, so they contain less DCD.

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How does acidification affect DCD release?

Acidification of the surrounding water causes a significant increase in DCD release from both C and CG beads.

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Why is the amount of DCD extracted reliable?

Incubating uncrushed beads in acidified water for 2 weeks provides a reliable measure of the total DCD encapsulated within the beads.

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What is the role of swelling in DCD release?

When the beads swell, the pores become larger and more DCD can escape from the beads into the surrounding water.

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What is the significance of DCD stability?

The stability of DCD in the solutions used for extraction ensures that the measured DCD truly reflects the amount initially encapsulated in the beads.

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How does DCD release from beads relate to soil?

DCD release from beads is investigated to understand how the beads will deliver DCD to the soil and slow down nitrification.

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How is DCD release from beads assessed in soil?

DCD release from beads is assessed by simulating different rainfall conditions and observing how DCD is released from the beads into the soil.

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Crosslinking Density

How densely the glyoxal molecules connect the chitosan chains, determining the rigidity and pore size of the material.

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Chitosan/Glyoxal Beads

Chitosan beads modified with glyoxal, creating a more resistant structure that controls DCD release.

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Why Glyoxal?

Glyoxal is used to crosslink chitosan because it forms a stable, durable structure and can interact with DCD, influencing its release.

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DCD Release in Water

When chitosan beads are placed in water, they release DCD over time, but the rate of release depends on the type of beads and the water conditions.

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C Beads vs. CG Beads

C beads release DCD more quickly than CG beads. This is because C beads are less crosslinked, allowing DCD to escape more easily.

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DCD Fraction Released

After a certain time in water, a portion of the total DCD present within the beads is released. This is called the 'DCD fraction released'.

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Glyoxal Crosslinking Effect

Glyoxal crosslinking strengthens the chitosan beads, slowing down DCD release because it creates a tighter structure.

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Locked DCD Fraction

The portion of total DCD within the beads that remains unreleased after a long time is called the 'locked DCD fraction.'

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Chitosan's DCD Holding Power

Glyoxal crosslinked chitosan can hold onto a significant portion of its DCD content for extended periods.

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DCD Release Plateau

After an initial rapid release of DCD, the rate of release slows down and reaches a plateau, meaning little additional DCD is released.

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Benefits of Slow DCD Release

The slow, controlled release of DCD from chitosan beads can enhance its effectiveness in the soil by reducing the need for frequent applications.

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Study Notes

Nitrification Inhibitor Delivery Using Chitosan Hydrogel

  • Dicyandiamide (DCD) encapsulated in glyoxal-crosslinked chitosan hydrogel beads to control release in water and soil.
  • Chitosan hydrogel delays DCD release, controlled by glyoxal crosslinking.
  • Higher glyoxal polymerization leads to slower DCD release, but also lower encapsulation.
  • DCD release in water is controlled by quasi-Fickian diffusion.
  • Release in water is primarily governed by bead erosion and leaching of glyoxal derivatives (primarily a glyoxal-DCD adduct).
  • Chitosan/glyoxal composite beads show promise for slow-release of agrochemicals, like DCD in soil.

DCD Encapsulation and Release

  • DCD encapsulated in chitosan beads with varying glyoxal crosslinking (C beads vs CG beads).
  • C beads (partially removed excess glyoxal) released higher DCD amounts (84% in 9h water/ 74-98% in 7d soil).
  • CG beads (dried with excess glyoxal) released much lower DCD amounts (19% in 9h water/ 33% in 7d soil with high rainfall).
  • Release is a two-stage process: quick release of available DCD, followed by slower release of locked DCD.
  • Release controlled by bead erosion and leaching of glyoxal-DCD adducts.

DCD Release in Soil

  • DCD release in soil is prolonged, especially in high rainfall conditions.
  • Release is initially slow, then increases over time (low, medium, high rainfall rates).
  • Rainfall/soil moisture affects release rate.
  • C beads release substantially more DCD than CG beads, especially under high-rainfall conditions.

Chitosan Hydrogel Properties

  • Chitosan is a biodegradable polymer extracted from crustacean shells.
  • Highly porous and hydrophilic, allowing for fast wetting.
  • Controlled release of encapsulated compounds based on cross-linking density and pore size.
  • Used for controlled drug delivery and other applications.

Overall Findings

  • Chitosan hydrogel provides a slow-release system for nitrification inhibitors, potentially reducing environmental impact and need for repeated applications.
  • The glyoxal content in the hydrogel plays a key role in controlling DCD release rates.
  • Soil moisture and rainfall affect the release profile significantly.

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Related Documents

Slow Delivery of a Nitrification Inhibitor to Soil Using Chitosan Hydrogel PDF

Description

This quiz explores the application of chitosan hydrogel as a delivery system for nitrification inhibitors like dicyandiamide (DCD). It covers the dynamics of DCD release in water and soil based on glyoxal crosslinking and the effects of polymerization on encapsulation efficiency. Test your knowledge on agrochemical delivery methods and their environmental impact.

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