Communities caring for catchments
Module 4 - physical and chemical parameters
Waterwatch Australia Steering Committee
Environment Australia, July 2002
ISBN 0 6425 4856 0
This section contains information and tips that you need to know before you go into the field or laboratory. It discusses sampling methods and equipment in a general sense, how to select sampling sites, how to record information about samples and how to make sure you get good results. It also discusses important safety considerations as well as reagents and waste disposal.
Please read this section before you proceed with the second section and before you go into the field or laboratory.
One way that Waterwatchers can assess the health of catchments and waterways is by examining the water's quality. We do this by measuring various physical and chemical characteristics (or parameters) of the water, such as temperature, salinity and turbidity.
This module outlines the water quality characteristics and how they behave in a range of conditions. It describes methods of measuring them and gives hints to help interpret the measurements. The module also describes how to collect, store and analyse a water sample. It gives reminders about safety when sampling, and lists the nationally-adopted methods and equipment.
Details on how to use the equipment commonly used by Waterwatch groups can be obtained from your Waterwatch State facilitator or regional coordinator. A field for each of the parameters described in this module has been included in the Waterwatch Database program (see module 5, Data… Information… Action!).
Water has some remarkable features:
The properties of water vary naturally depending on the surrounding environment, so data collected about water quality must be interpreted in the context of the waterbody's particular environment and position in the catchment.
With our existing knowledge no-one can list 'normal' temperature, turbidity, salinity and so on for every part of every waterbody in Australia. The 'normal' characteristics of a waterbody can best be discovered by measuring them over a period of time that is long enough to encompass a range of normal situations.
Ideally, each group that cares about a waterbody will make regular measurements of its characteristics to determine patterns that are usual for that waterbody in wet, dry and 'normal' years.
By measuring the physical and chemical characteristics of our local waterbodies we can determine the health of our water and therefore its ability to sustain life. Several of the physical and chemical characteristics of a waterway or waterbody can be measured by more than one method. Methods can range from simple to complex. Some are accessible to primary school children; others require greater skill, and a few methods have to be used in analytical laboratories on samples that Waterwatchers have collected.
The results of the measurements can also range considerably in usefulness, depending on how much attention is given to detail during the measuring. Results may merely indicate the condition of the waterbody, or they may give very accurate data that can be used to identify matters significant for the waterbody's ecology and health.
In all methods, quality control is important so the measurements are as credible and meaningful as possible. The greater the quality control, the more useful are the data.
To choose a method, first check your group's monitoring plan (see module 2) to identify why you are monitoring. Is it to:
The quality and quantity of data you collect will depend on your reason for monitoring and on who will be using your data. For example, the data may be of value to teachers, students, the general public, land-owners, natural resource managers, government agencies, and catchment and rivercare groups. For some of these groups, only the highest quality data will do, while others will be satisfied with intermediate or low data confidence. Your choice of method may also be affected by the accessibility of your selected sampling sites and your frequency of monitoring.
How often your group monitors will depend on the questions you want to answer. For example, baseline monitoring should take place regularly during baseflow conditions (weekly to monthly); contamination effect monitoring should take place at the time of discharge or the time of use of the waterway (e.g. for swimming).
Monitoring consists of more than just taking measurements or samples on the spot. It also entails recording the results (including date and time and weather conditions) in a standard format and storing them in the Waterwatch database or forwarding them to the regional coordinator for storage.
If your observations show that a contamination incident has occurred, it is important to report it immediately to the Waterwatch coordinator, for advice on appropriate action.
The way in which you choose a site will depend on the type of waterbody and your reasons for monitoring it (see also module 2).
The way you collect and treat your samples can have a huge effect on your results. For accuracy and precision you should aim always to sample:
Your choices of methods for collecting samples should be guided by the purpose of your monitoring program and the quality of data you need.
Generally sample:
Avoid sampling surface water or stagnant water, non-flowing water near the stream edge or surface, or water near the stream bottom, unless you specifically intend to examine these situations.
Some natural variation in water quality within a waterbody is to be expected. The effect that this variation can have on the data can be quite large. Different sample types — grab or composite — can be used to account for this variability. Grab samples are collected in separate bottles and kept as single entities throughout the measurement stage. Composite samples are taken separately and then bulked with others before the measurement stage.
Grab samples are the type commonly used by Waterwatch groups, as they are simple. The type of sample you take is not as important as ensuring consistency in the time you monitor and the way in which you monitor.
For a large waterbody you may need a boat. Alternatively, an extension (long-handled) sampling pole enables you to collect water from wide or deep streams or pools. Rubber boots or waders will give you access to small and shallow streams or pools (but, for safety, don't wear waders in a boat).
You will also need:
And so on. The list will depend on your objective and methods.
For most basic water quality tests a plastic or glass bottle will suffice. The most important consideration is to make sure your container is clean. It used to be said that household detergents should never be used for washing sample bottles, because phosphate molecules that used to occur in detergents have a tendency to attach (adsorb) to the inside surfaces of sample containers and bottles, contaminating the samples you take. Nowadays, however, detergents are all, or almost all, phosphate-free (read the label). If a phosphate-free detergent is not available, your containers must be acid-washed in a laboratory, to remove possible adsorbed phosphate before they are used in the field.
The bottles you use must be able to withstand repeated contact with hydrochloric acid. Plastic bottles — high-density polyethylene or polypropylene — are preferable to glass because they will better withstand breakage. If factory-sealed disposable Whirl-pak® bags are used for sampling, no preparation is needed. If other containers are to be used they will need to be prepared for sampling. If you are collecting water samples or sediments for pesticides, heavy metals or bacterial analysis by a laboratory, ask the laboratory to provide the required containers.
To prepare your own containers for sampling, follow the instructions for cleaning containers in this section.
All sample containers and glassware, whether new or reused, must be clean.
There are a few things to remember when you are collecting water samples:
Using an extension pole to hold a sample bottle
When you extend the handle, leave 10 cm unextended, for strength.
Have a coworker hold on to you when you are using the extended pole.
When retrieving the bottle and water sample, hold the pole slightly downwards pointing away from you to avoid being wetted by water from inside the long arm.
Do not lift or carry the pole above your head in case it touches power lines - the metal arm would conduct electricity to you and electrocute you.
| Parameter | Preservation method | Maximum holding time | Comments |
|---|---|---|---|
| pH | Refrigeration | 24 hours | Fill sample bottle completely to exclude air. Preferably tested in the field. |
| Conductivity | None required | 24 hours |
Fill sample bottle completely to exclude air. |
| Refrigeration | 1 month | ||
|
Turbidity Suspended solids |
None required | 24 hours | Preferably tested in the field. |
| Refrigerate | 24 hours | ||
| Nitrate | Refrigeration | 24 hours | Unfiltered sample. |
| Filter on site and freeze | 1 month | ||
| Phosphate, dissolved | Filter on site and refrigerate | 24 hours | |
| Filter on site and freeze | 1 month | ||
| Phosphate, total | Refrigerate |
24 hours |
|
| Freeze | 1 month | ||
| Dissolved oxygen | None required Fix oxygen in the field and store in the dark |
24 hours | Determine on site. Avoid excessive turbulence to sample. Fix as described in chosen method. |
| Temperature | Not applicable | Not applicable | Must be analysed on site. |
| Pesticides, heavy metals, faecal coliforms | Contact analytical lab for details |
* Source: Water quality - Sampling. Part 1. AS/NZS 5667.2: 1998. Australian/New Zealand Standard.
Every time you collect and label a sample, you should also record its details on the water quality result sheet (see pages 51-52). These details will be useful when you analyse your results.
The physical and chemical characteristics of a water sample can change during transport and storage. Careful packaging can prevent damage to the containers and loss of the sample. Preservation methods only slow chemical and biological changes that inevitably occur after collecting your sample. Some parameters change more quickly than others, and so need to be analysed on site. In general, the shorter the time between collection and analysis, the more reliable your results will be. Table 4.1 outlines recommended standard holding times and preservation techniques for ensuring high quality data.
To maintain your equipment in good working order and get high quality results, you should regularly inspect and calibrate each piece of test equipment, and record the calibration results in a table; see the Waterwatch equipment maintenance and calibration record sheet on page 48.
A field replicate is a sample taken at the same time and place as another and treated identically, or a measurement made immediately after another at the same spot and in the same way.
Mystery solutions, available from Waterwatch coordinators, are solutions that have been analysed by experienced analysts. Test these solutions yourself, and then compare your own test results with the original analysis. This will help you assess the accuracy of your techniques and of your equipment.
For external checks, send 10% of your samples to a separate laboratory elsewhere to be analysed, and then compare their results with your own for the same samples.
You can increase the quality of your data with your current equipment simply by always using the hints and checks above. If the extra results obtained by internal and external checks do not exactly agree with your own results, calculate by how much the results differ. This can be expressed as a percentage. For example, if an external result reports a turbidity reading of 100 units and your result is 110, you can record an 'error' or variation of +10% for all your turbidity meter results (but not for results of other parameters, such as pH - they must be tested separately).
The smaller the percentage variation between your results and the external ones, the more confidently you and others can use your results to help solve the problems in your waterway.
In general, if proper safety precautions are followed, the tests in this module do not present significant health or safety risks. There are, however, some basic precautions you should take to ensure your own safety and that of those working with you.
Material safety data sheets are fact sheets the manufacturer includes with each chemical used for water quality tests.
They are to ensure all water quality monitors know about the hazards of chemicals produced or used. The data sheets contain usage, storage, first aid and disposal information for hazardous products.
Do not allow children to test in the field without adult supervision - students must be fully supervised by their teacher in accordance with Education Department guidelines.
A reagent is a substance which, on account of the reactions it causes, is used in chemical analysis. For accurate results, reagents need to be kept in good condition and used before their expiry date.
Many reagents in test kits can become contaminated and degrade quickly under field conditions. The inevitable result is inaccurate measurements of water quality, extra expense and a lot of wasted time. By checking the condition of the reagents and taking a few simple precautions, you can avoid these problems.
Check the appearance of reagents and look for any changes such as colour, cloudiness and formation of solids. If in doubt over the condition of reagents, test a water sample with reagents and compare your result from a test carried out with another kit, or with fresh reagents, or with a meter. Replace any reagents that have been degraded.
Reagents degrade more quickly at high temperatures, so store and transport them away from heat and sunlight.
Many reagents react with oxygen or carbon dioxide in the air so keep bottles tightly capped when not in use.
Contamination of reagents with foreign matter or other chemicals will cause degradation. Use dedicated spoons and droppers for each reagent to avoid cross contamination.
Replacing reagents is a major ongoing expense for Waterwatch groups. However, avoiding expired reagents is important for all groups particularly where data quality is important.
Reagents have a limited life span from the date of manufacture, e.g. sodium thiosulfate (1 year) and starch indicator (1.5 years), and it makes little sense to continue using them after expiry. The manufacturer will tell you the life span of each reagent.
You should record the date of manufacture and write the date of expiry on the label of each reagent bottle. To do this, look for a series of numbers usually at the bottom left corner of any reagent label. The first two digits indicate the week of manufacture and the third digit indicates the year. For example, a sodium thiosulfate reagent bottle with the numbers 0382341 would have been made in week 3 (January) of 1998. Since sodium thiosulfate has a one-year life-span, the expiry date is week 3 of January 1999.
Leave the site cleaner and tidier than you found it - pick up and transport out all rubbish you generate as well as other people's rubbish, if possible.
Place all used gloves, used paper towels, empty reagent packaging and any other rubbish from testing into an intact and secure plastic garbage bag and take it with you when you leave.
Be very careful if you are testing nitrate with the cadmium reduction method. Cadmium is present in the reagent powder and drops to the bottom of the test tube at the end of the test. Waste from this test should not be poured down the drain but stored separately in a hazardous waste jar labelled 'toxic waste'. This jar must be disposed of as 'special waste', along with other such wastes from your organisation or school.
Hold all test bottles over a wide-mouthed liquid waste bottle while adding the liquid and powder reagents from the following tests: pH, dissolved oxygen, phosphate and nitrate.
After each piece of used equipment has been rinsed with distilled water, pour the rinse water into the liquid waste bottle.
Do not put solid waste into the liquid waste bottle.
Consult your Waterwatch coordinator about disposing of the liquid waste.