Post on 27-Aug-2018
transcript
Approaches to Water Quality Monitoring
Deborah Chapman,
UNEP GEMS/Water Capacity Development Centre,
University College Cork, Ireland
Overview: Approaches to Water Quality Monitoring
• Aim: to stimulate discussion around three themes occurring in the
workshop:
• monitoring ambient water quality from national to global scales;
• monitoring and managing the freshwater ecosystem;
• monitoring in relation to guidelines or targets
• What we understand by “water quality” and “monitoring”
• Overview of physical, chemical and biological monitoring approaches
• Choosing the right water quality monitoring approach
What do we mean by water quality?
• Water quality is defined by the characteristics or properties
of the water
• The characteristics of water govern its suitability for
different uses
• “Uses” include: drinking water, irrigation, assimilating
wastewaters, natural fisheries/aquaculture, aquatic
ecosystem, etc.
What do we mean by water quality?
Each use has its own set of water quality requirements in order to
reduce the levels of treatment needed, e.g.:
• drinking water should have low levels of pathogens and toxins
• irrigation water should be low in salts
• water for some industrial processes should be low in suspended
materials
Water quality can be determined and classified in different ways using
the physical, chemical and biological characteristics of the water
What do we mean by monitoring?
Water quality is characterised through scientific
studies and monitoring
Monitoring is the systematic collection of data over temporal or spatial scales in order to define:
• Current environmental conditions
• Past environmental conditions (historical monitoring)
• Repeated collection of data over long time scales can
indicate trends
Years
1960 1970 1980 1990 2000
P tota
l (µ
g/L
)
0
20
40
60
80
100
Mean Ptot concentration
Management objective
Start of phosphateremoval in STP
Ban of P in textilewashing products(CH)
Possible media for sampling or analysis in water quality programmes
• Water (filtered or unfiltered)
• Particulate matter (suspended or sedimented)
• Biota (filter feeder, predator, sedentary, mobile)
Choosing what to monitor
• Basic parameters
• Characterise the geological and climatological influences on the water body – provides a
baseline
• Ecosystem-related parameters
• Demonstrate potential human influence on the whole aquatic ecosystem
• Contaminants
• Demonstrate specific waste emissions, potential for ecosystem damage, potential risk for
human uses
Some naturally occurring elements/substances can be damaging to water bodies
if their levels are elevated substantially by human activities
Basic measures of water quality
Temperature
• Required because it affects processes within the water body, such as biological respiration, chemical reactions, etc.
Dissolved oxygen
• Fundamental for life in the aquatic ecosystem, including decomposition processes
pH
• May be influenced by chemical inputs but can also affect chemical and biological processes in the water
Major ions
• Depend on biogeochemical conditions; very variable in natural waters
Suspended solids
• Affects the transparency of the water, which in turn in can affect primary productivity and the aquatic ecosytem
Other physical/chemical measures of water quality
Conductivity
• Sensitive to dissolved solids, mainly mineral salts
• Indicates changes in water quality but does not identify cause
Total Organic Carbon (TOC)
• Convenient, non-specific measure of general water quality,
particularly organic contamination
Biochemical Oxygen Demand (BOD)
• Measure of the biochemically degradable organic matter
present in the water
Chemical Oxygen Demand (COD)
• Widely used as an indicator of the presence of sewage or
industrial effluents
Ecosystem-related parameters
Nutrients
Principally nitrogen and phosphorus compounds
• Essential for living organisms but excess can cause major changes
in aquatic ecosystems (eutrophication)
• Run-off/discharge from land sources: fertiliser use, manure and
sewage
Chlorophyll concentrations
• Photosynthetic pigment in plants and algae
• Provides an indirect measure of algal biomass and productivity
Ecological characteristics
• Presence or absence of specific species or combinations of species
that have preferred environmental characteristics, such as high
oxygen concentrations
Biological characteristics: Macro- to Micro Scale
• Ecosystem monitoring – e.g. remote sensing
• Community monitoring – e.g. species diversity
and abundance
• Species monitoring – bioindicators, biomonitors
http://www7333.nrlssc.navy.mil/images/projects/Ruhul_Lake_Erie.png
Biological community structure monitoring
Based on species numbers (diversity) and abundance
• Generates a numerical value (index)
• Can measure stress in the environment, e.g. Simpsons
Index, Shannon Weaver index
• Unstressed environments: Large numbers of species
and no single species highly dominant
• Maximum diversity: large number of species in relatively low
numbers
• Stressed environments: sensitive species disappear
and more tolerant species thrive
• Minimum diversity: community richness reduced, few
species but in large numbers
Bioindicator species
Presence or absence of indicator species
within the environment
Organisms, populations or assemblages
• Used for qualitative (non-specific) indication
of anthropogenic impacts
• Developed and used extensively in the
aquatic environment, especially rivers
Indicator organisms: Example for temperate rivers
• Chironomus sp.
• Asellus sp.
• Gammarus sp.
• Baetis rhodani
• Ephemera danica
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Status and trends using ecological data only
National rivers survey – Northern Ireland
• Based on benthic invertebrates
• Presents clear information to non-experts
http://www.doeni.gov.uk/niea/water-home/quality/rivers/rivers_historical_monitoring_results/gqabiolexpln.htm
Complex biological indicators
Index of Biological Integrity (IBI)
A synthesis of diverse biological information which numerically depicts associations between human influence and biological attributes
Requires extensive knowledge of aquatic communities and their responses to human impacts Reference wetlands Impaired wetlands
Invertebrate groups
http://water.epa.gov/type/wetlands/assessment/fact2.cfm
Species and community monitoring: Points to be considered
• What exactly are the organisms
responding to?
• Can the species integrate all impacts on the water body?
• Are they sensitive enough to changes in the water body?
• Geographical applicability: local, regional, global
• Need for trained biologists/taxonomists
• Relative cost compared with chemical measurements
Microbiological monitoring
• Microbiological indicators used where people will
come into contact with the water (e.g. drinking, personal hygiene, food preparation, recreational use)
• Can indicate faecal contamination of a water body by animals and/or humans
• The faecal coliform bacterium Escherichia coli is one of several used as indicators of the presence of potentially pathogenic micro-organisms
• Thermotolerant coliforms (faecal coliforms including E. coli) can also be used
Contaminants - Trace elements and organic compounds
• Usually of interest where human impacts are
suspected
• Require specific analytical facilities
• Can be expensive and difficult to measure at
low concentrations
• The range of new compounds with potential
impacts on aquatic ecosystems and/or human
health is growing rapidly – which ones should
be included?
Monitoring for contaminants: selecting a chemical or biological approach
• Is the toxic substance known?
• Expected concentration range and type of toxic substance
governs methods available
• Are effects on the environment important?
• Is there a risk that the toxic substance may bioaccumulate?
• Is there a risk to human health?
• Would sediment or biota samples be more appropriate?
Sediment Monitoring: Total mercury in surface sediments
Total mercury concentrations (ppm) in surficial sediments of the Great lakes (1997–2000). Reprinted from Environmental Pollution, Vol. 129,
Marvin et al. Spatial and temporal trends in surface water and sediment contamination in the Laurentian Great Lakes, 131–144,
Choosing what to monitor
Selecting what to include in a water quality monitoring programme depends on the
objectives of the monitoring programme, i.e. what do you need to know?
• Wastewater dilution and assimilation
• e.g. chemical measurements, oxygen depletion
• Inorganic pollutants and possible risk to human health
• e.g. filter feeding organisms, fish
• Pollutant impacts on aquatic ecosystem and recovery over time
• e.g. communities of aquatic species
• Accumulation of contaminants in a water body over time
• e.g. sedimented particles
Choosing the best approach for ambient
water quality
What do you want to know and how will
the information be used?
Should the needs of the ecosystem be
considered?
Classifying water quality: guidelines, standards and targets
Targets can be:
• precise values/standards
• a range of values, or
• a water quality classification
Water quality classifications can be used for biological and chemical
characteristics
• High, Good, Moderate, Poor, Bad
• Excellent, Good, Fair, Marginal, Poor
Classifications can be used to indicate whether water is suitable for
particular uses
Key Question: What gives the best indication of impacts on ambient water quality?
• Baseline or background conditions are needed
for reference (pristine conditions hardly likely to
occur anywhere in present day)
• Basic parameters indicate natural influences
• Physical and chemical parameters may indicate
human influence
• Biological indicators integrate all possible
influences on water quality but are usually non-
specific
• Select according to the monitoring programme
objectives
Water quality indicators
Biological and chemical parameters can be compiled to produce water
quality indicators
Indicators can be used to:
• Provide information to decision makers and the public on the state of
the environment
• Support policy development and priority setting, by identifying the
key factors causing pressure on the aquatic environment
• Monitor the extent and effects of these policies
• Provide a means of linking environmental impacts to socio-economic
activities and give an early warning of environmental problems
Water quality indicators: advantages and disadvantages
Composite indicators enable:
• Simplification
• Quantification
• Communication
Limitations of composite indicators:
• Require high quality data
• Data must be updated regularly
P.J.T.M. van Puijenbroeka et al., 2014
Netherlands
Ireland EPA
Status and trends combining ecological and basic chemical analysis
• Chemical status is assessed against Environmental Quality Standards (target values)
• Combined with status according to biological monitoring classes
Generating large amounts of data - getting citizens involved
Large amounts of data, but limited accuracy
Example - The Great Secchi Dip-in
Since July, 1994, more that 10,000 volunteers have
provided more than 41,000 transparency records on
more than 7,000 waterbodies in North America
The volunteers belong to 394 programmes, both
volunteer and professional, in:
50 USA states,
9 Canadian provinces, and
6 other countries
http://dipin.kent.edu/
Summary
Water quality can be monitored in different
ways using physical, chemical and
biological approaches
The most suitable approach depends on:
• What you need to know
• Resources available
• The target audience of the data
generated
Thank you for listening
We are interested in your opinions
Please feel free to ask questions