Description

Nitrate (NO₃⁻) is a naturally occurring ion that is a crucial component of the Nitrogen cycle in the environment. It is a highly soluble and mobile form of Nitrogen, essential for plant growth and often used in agricultural fertilisers. However, excessive concentrations of Nitrate in water can lead to significant environmental problems and pose health risks.

Why is Nitrate Monitoring Important?

Monitoring Nitrate levels in water is critical for public health, environmental sustainability, and effective resource management:

• Eutrophication: Along with Phosphorus, excess Nitrate is a primary contributor to eutrophication in rivers, lakes, and coastal marine waters. This leads to excessive growth of algae (algal blooms), which can deplete dissolved Oxygen when they decompose, creating “dead zones” that harm aquatic life and disrupt ecosystems.
• Pollution Indicator: Elevated Nitrate levels often indicate pollution from human activities, including runoff from agricultural fields (fertilisers, manure), discharge from wastewater treatment plants, and failing septic systems. Its high solubility means it readily leaches into groundwater and surface water.
• Agricultural Management: Monitoring Nitrate in soil and water helps farmers optimise fertiliser application, ensuring adequate nutrients for crops while minimising runoff and environmental pollution.
• Wastewater Treatment: In wastewater treatment, Nitrate monitoring is essential for controlling the nitrification and denitrification processes, which are biological steps designed to remove Nitrogen compounds before discharge to prevent environmental harm.
• Environmental Research: Tracking Nitrate concentrations helps environmental scientists understand pollutant transport, assess ecological impacts, and evaluate the effectiveness of mitigation strategies.

How the 2000-NIT Electrode Works

The 2000-NIT Electrode is an Ion Selective Electrode (ISE) designed to measure the concentration of charged Nitrate ions (NO₃⁻) in water. Like other ISEs, it operates by generating a voltage potential that is directly proportional to the activity (effective concentration) of the Nitrate ions in the solution.

Key aspects of its operation include:

1. Solid-State Design: Aquaread Nitrate sensors are solid-state, meaning they do not contain gel electrolytes that can dry out. This provides the advantage of a long storage shelf life when dry, as the sensor does not degrade from the point of manufacture, if stored correctly.
2. Ion Selectivity: The electrode contains a polymer membrane with organic ion exchangers that are selective to nitrate ions. When the membrane comes into contact with the sample, a potential difference is generated across it, which is then measured.
3. Nernstian Response: The measured voltage is related to the Nitrate ion concentration by the Nernst equation.
4. Temperature Dependency & Calibration: The measured concentration varies with temperature, and the sensor requires careful calibration. On initial use, a three-point calibration is typically performed, including a temperature compensation point (often a second calibration point at a significantly different temperature) to accurately characterise the sensor’s response across a temperature range. Subsequent calibrations can be simpler.
5. Interference: Like all ISEs, Nitrate electrodes can suffer from interference from other ions that are similar in size and charge to nitrate (e.g., Chloride, Bromide and Perchlorate). For this reason, these ISEs are generally not recommended for use in brackish or salt water due to the high level of interfering ions that can lead to inaccurate readings.

When to Monitor Nitrate

The AP-2000 Nitrate Electrode is a valuable tool for various water quality monitoring applications where nitrate levels are of concern:

• Agricultural Runoff: Monitoring drainage ditches, streams, and groundwater in agricultural areas to assess the impact of fertilisers and manure.
• Wastewater Effluent: Checking the effectiveness of biological nutrient removal processes in treatment plants and ensuring discharged water meets regulatory limits.
• Drinking Water Sources: Regularly testing raw water sources and treated drinking water to ensure Nitrate levels are below safe limits.
• Environmental Baseline and Pollution Tracing: Establishing natural Nitrate levels in ecosystems and tracking contamination plumes from pollution sources like landfills or leaky septic systems.
• Lake and River Health: Assessing nutrient loading to prevent or manage eutrophication and its negative impacts on aquatic life.
• Groundwater Protection: Monitoring aquifers, especially those used for drinking water, for Nitrate contamination from surface sources.
• Industrial Discharge: Checking effluents from industries that may contribute Nitrogen compounds to waterways.

2000-NIT Electrode Specifications

Each ISE is prone to interference from ions that are similar in nature to the target ion. The main interfering ions for the Fluoride electrode are Hydroxide (OH-). If the water under test contains interfering ions, the electrode will produce erroneous readings. Ion Selective Electrodes are not recommended for use in brackish or salt water due to the high level of interfering ions.

Each ISE can only operate within a specific pH and EC range. All ion selective electrodes work in conjunction with the pH electrode during measurement. For this reason, the main probe must have a working pH or pH/ORP electrode fitted and the conductivity (EC) of the water under test must be greater than 50μS/cm.