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Freshwater Environment

BIOLOGICAL AND CHEMICAL MONITORING OF FRESHWATERS

Environmental Analysis

The biological and chemical monitoring of freshwaters is undertaken by the Loughs Agency every year to assist in determining the concentration of harmful pollutants in the aquatic environment.  This pollution monitoring has several key objectives:

  1. to identify potential threats to fish health and aquatic ecosystems;
  2. to inform the public about the quality of the aquatic environment and to raise public awareness of environmental issues;
  3. to provide inputs into policy-making decisions;
  4. to assess the efficacy of pollution control measures;
  5. to identify trends in pollution and to identify future problems.

 

 Introduction to Sampling Programme

Over 100 sites have been selected for the annual biological and chemical sampling of rivers within the Foyle and Carlingford hydrological catchments.  The period of sampling normally runs from June to September.  The sampling sites are distributed throughout six zones as shown below:

Foyle Sampling Sites

Foyle Sample Sites

Carlingford Sampling Sites

Carlingford Sampling Sites

Frequency of Sampling – Chemical

Each of the sites is sampled to assess chemical quality once every month during the field season.  This results in 4 chemical samples per site across the catchments.  There is a two-stage process involved in gathering the chemical water quality data.  The first stage involves obtaining the sample from the site and deploying an electronic probe for recording supplementary data.  The second stage involves the laboratory analysis of each sample.

 

Site Sampling Procedure

Sampling Officers deploy a Hach HQ30d Rugged Multi-probe into a bucket of water obtained from the watercourse.  After the recommended time, the following parameters are recorded onto the handheld device’s memory for downloading later.

  • Dissolved Oxygen (% saturation)
  • Dissolved Oxygen (mg/l)
  • Conductivity (mS/cm)
  • Temperature (°C)
  • pH

In addition, the Sampling Officers obtain a sample of water using the recognised procedure for laboratory analysis.  These samples are stored correctly in the appropriate bottle.  The bottles of sample water are then stored in a cool box and transported to the Agency laboratory on the same day of collection.  On arrival at the laboratory, the Sampling Officer ensures that the Environmental Officer or Assistant Scientific Officer receives and signs for the sample batch.

  

Quantitative Analysis of Chemical Parameters

The following chemical parameters are analysed in the Loughs Agency laboratory:

  • Ammonia (NH3)
  • Total Phosphorus (PO4)
  • Suspended Solids (SS)
  • Biochemical Oxygen Demand (BOD)

 

Quality Assurance

As part of the biological and chemical monitoring of freshwaters, it is necessary to undertake a quality assurance programme.  This essentially involves 2 main stages:

  • Quality assurance in field data gathering techniques
  • Quality assurance in laboratory analysis

Quality assurance in field data gathering techniques:

This involves a random assessment of field data gathering techniques across the catchments.  This allows for standardisation across the Agency and assists in minimising any inaccuracies.

Quality assurance in laboratory analysis:

A 5% sample is sent to three outside laboratories for verification of results.  Samples are chosen at random during the entire field season.  The Sampling Officer will be notified in advance that the site is to return additional samples for verification at the above-mentioned laboratories.  This will mean a triplicate sample being obtained from the watercourse and delivered to the relevant laboratories.

 

 Frequency of Sampling - Biological

 

Each of the sampling sites are sampled to assess for biological indicators using the 3 minute kick sampling method, once during the field season.  A sample is obtained from the watercourse and stored in a plastic container for subsequent laboratory analysis.  Staff at the laboratory then undertake detailed macro invertebrate identification and record the results for subsequent determination of a BMWP score to indicate the level of water quality. 

During any electro-fishing surveys, a biological assessment will also be undertaken using the quicker Rapid Field Assessment method.  This allows for quick macro invertebrate identification in the river with no need to bring a sample back to the laboratory.