Assimilative capacity is the ability for
pollutant
A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like oi ...
s to be absorbed by an environment without detrimental effects to the environment or those who use of it.
Natural absorption into an environment is achieved through
dilution
Dilution may refer to:
* Reducing the concentration of a chemical
* Serial dilution, a common way of going about this reduction of concentration
* Homeopathic dilution
* Dilution (equation), an equation to calculate the rate a gas dilutes
*Tradema ...
,
dispersion
Dispersion may refer to:
Economics and finance
*Dispersion (finance), a measure for the statistical distribution of portfolio returns
*Price dispersion, a variation in prices across sellers of the same item
*Wage dispersion, the amount of variatio ...
and removal through chemical or
biological process
Biological processes are those processes that are vital for an organism to live, and that shape its capacities for interacting with its environment. Biological processes are made of many chemical reactions or other events that are involved in the ...
es.
The term assimilative capacity has been used interchangeably with environmental capacity, receiving capacity and absorptive capacity.
It is used as a measurement perimeter in
hydrology
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...
,
meteorology
Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not ...
and
pedology
Pedology (from Greek: πέδον, ''pedon'', "soil"; and λόγος, ''logos'', "study") is a discipline within soil science which focuses on understanding and characterizing soil formation, evolution, and the theoretical frameworks for modeling ...
for a variety of environments examples consist of: lakes, rivers,
oceans
The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the worl ...
, cities and soils. Assimilative capacity is a subjective measurement that is quantified by governments and institutions such as
Environmental Protection Agency
A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
(EPA) of environments into guidelines.
Using assimilative capacity as a guideline can help the allocation of resources while reducing the impact on organisms in an environment. This concept is paired with
carrying capacity
The carrying capacity of an environment is the maximum population size of a biological species that can be sustained by that specific environment, given the food, habitat, water, and other resources available. The carrying capacity is defined as t ...
in order to facilitate
sustainable development
Sustainable development is an organizing principle for meeting human development goals while also sustaining the ability of natural systems to provide the natural resources and ecosystem services on which the economy and society depend. The des ...
of city regions.
Assimilative capacity has been critiqued as to its effectiveness due to ambiguity in its definition that can confuses readers and false assumptions that a small amount of pollutants has no harmful effect on an environment.
Hydrosphere
![Waves in pacifica 1](https://upload.wikimedia.org/wikipedia/commons/4/45/Waves_in_pacifica_1.jpg)
Assimilative capacity in
hydrology
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...
is defined as the maximum amount of
contaminating pollutants that a
body of water
A body of water or waterbody (often spelled water body) is any significant accumulation of water on the surface of Earth or another planet. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as p ...
can naturally absorb without exceeding the water quality guidelines and criteria. This determines the
concentration
In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', ''molar concentration'', ''number concentration'', an ...
of pollutants that can cause detrimental effects on aquatic life and humans that use it.
Self-
purification and dilution are the main factors effecting the total amount of assimilative capacity a body of water has.
Estimations of breaches of assimilative capacity focus on the health of aquatic organisms in order to predict an excess of pollutants in a body of water. Dilution is the main way that bodies of water reduce the concentration of contaminants to levels under their assimilative capacity.
This means that body of water that move rapidly or have a large volume of water will have larger assimilative capacities then a slow-moving stream.
Coastal and Marine
Coast
The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. The Earth has around of coastline. Coasts are important zones in n ...
al and
Marine environment
Marine habitats are habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea (the term ''marine'' comes from the Latin ''mare'', meaning sea or ocean). A habitat is an ecological or environmental ...
s will have much greater assimilative capacity due to the large volumes of water creating a much greater
dilution factor. Contaminants added into areas would be needed in much greater volumes in order to exceed the assimilative capacity and create harmful negative effects on aquatic life. However, oceans often are the end point for many pollutants resulting in large accumulation of pollutants. It is estimated that “270 tonnes of
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
enter the sea annually” in Western Australia.
Rivers
River
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...
s have a large focus on being monitored as they are the primary place for
runoff
Runoff, run-off or RUNOFF may refer to:
* RUNOFF, the first computer text-formatting program
* Runoff or run-off, another name for bleed, printing that lies beyond the edges to which a printed sheet is trimmed
* Runoff or run-off, a stock market ...
from
agricultural
Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilization, whereby farming of Domestication, domesticated species created food ...
industries. This results in there being large changes in their original conditions. Agricultural runoff is high in contaminants including
Phosphorus
Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
and
Nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
. When phosphorus is added to a river
eutrophication
Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...
occurs a rapid production of algae that’s production was previously limited by the amount of phosphorus in the water. These algae have a high
biochemical oxygen demand
Biochemical oxygen demand (BOD) is the amount of dissolved oxygen (DO) needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at a certain temperature over a specific time period. T ...
and reduce the available oxygen for other
aquatic organisms. Close monitoring of the assimilative capacity or rivers is needed in order to stop eutrophication which can result in the loss of many aquatic organism.
Atmosphere
![Top_of_Atmosphere](https://upload.wikimedia.org/wikipedia/commons/b/be/Top_of_Atmosphere.jpg)
Assimilative capacity of the
atmosphere
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
is defined as the maximum load of pollutants that can be added without compromise of its resources.
Meteorologist
A meteorologist is a scientist who studies and works in the field of meteorology aiming to understand or predict Earth's atmospheric phenomena including the weather. Those who study meteorological phenomena are meteorologists in research, while t ...
s calculate assimilative capacity through the atmosphere using
ventilation coefficient or through the
pollution potential.
The ventilation coefficient is calculated by multiply the
mixing height (the height at which vigorous mixing of gasses occur) with the average
wind speed
In meteorology, wind speed, or wind flow speed, is a fundamental atmospheric quantity caused by air moving from high to low pressure, usually due to changes in temperature. Wind speed is now commonly measured with an anemometer.
Wind speed ...
.
Atmospheric concentrations change rapidly as gasses move due to winds,
convection
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...
current and dispersion of gasses. The pollution potential is determined by calculating the concentration of pollutants and comparing that to the acceptable limits.
This way of calculating takes into consideration the current level of pollutants and assesses how much more can be added in order to reach the assimilative capacity.
Sulphur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
(SO
2),
Nitrogen monoxide
Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its c ...
(NO) and
Nitrogen dioxide
Nitrogen dioxide is a chemical compound with the formula . It is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use primarily in the producti ...
(NO
2) and
suspended particulate matter (SPM) are important pollutants to measure. High concentrations sulphur dioxide can cause
acid rain
Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but acid ...
which damages structures and increases acidity of soils and bodies of water. High concentrations nitrogen monoxide and nitrogen dioxide can cause photochemical smog which has adverse effects on those with compromised lungs. High concentrations of suspended particulate matter can be absorbed by the lungs into the bloodstream can cause
pneumonia
Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...
.
Uses to determine management of environments
Assimilative capacity is used as a
monitoring
Monitoring may refer to:
Science and technology Biology and healthcare
* Monitoring (medicine), the observation of a disease, condition or one or several medical parameters over time
* Baby monitoring
* Biomonitoring, of toxic chemical compounds, ...
guideline for
sustainable growth
Sustainable development is an organizing principle for meeting human development goals while also sustaining the ability of natural systems to provide the natural resources and ecosystem services on which the economy and society depend. The desir ...
of city regions. Assimilative capacity allows governments to understand how much pressure a region is under. Working within the assimilative capacity means that regions will be constructed with future stability in mind. “An assimilative capacity study develops specific scientific modelling to support and assist municipalities and other legislative authorities in predicting the impacts of land use”.
United States
In the United States legislation on assimilative capacity as a guideline for the maximum amount of pollutants to be added to bodies of water comes from each individual state and from the environmental protection agency. Assimilative capacity is a quantitatively useful concept codified in the
Clean Water Act
The Clean Water Act (CWA) is the primary federal law in the United States governing water pollution. Its objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters; recognizing the responsibiliti ...
and other laws and regulations that is unrelated to the perception of an
environmental crisis
An ecological or environmental crises occurs when changes to the environment of a species or population destabilizes its continued survival. Some of the important causes include:
* Degradation of an abiotic ecological factor (for example, incr ...
. Assimilative capacity specifically refers to the capacity for a body of water to absorb constituents without exceeding a specific concentration, such as a
water quality
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...
objective. Water quality objectives are set and periodically revised by regulatory agencies, such as the
Environmental Protection Agency
A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
(EPA), to define the limits of water quality for different uses, which include human health, but also other ecologically important functions,
wildlife
Wildlife refers to domestication, undomesticated animal species (biology), species, but has come to include all organisms that grow or live wilderness, wild in an area without being species, introduced by humans. Wildlife was also synonymous ...
habitat,
irrigated
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been devel ...
agriculture, etc. For example, if the irrigation water quality objective for salt is 450 mg/L of total dissolved solids, the assimilative capacity of a body of water would be the amount of salt that could be added to the water such that its concentration would not exceed 450 mg/L.
India
India uses assimilative capacity in management of land, water and air.
Though each have largely varying assimilative capacities due to variations in type of pollutants and the difference in dilution dispersion and chemical and biological breakdown in differing environments.
Comparison to accommodative capacity
Assimilative capacity has been critiqued as to the value it adds as a tool for creating guidelines in hydrology. There is a large amount of
ambiguity
Ambiguity is the type of meaning in which a phrase, statement or resolution is not explicitly defined, making several interpretations plausible. A common aspect of ambiguity is uncertainty. It is thus an attribute of any idea or statement ...
in the definition as it is subjective. It has been questioned as to what exactly statements such as whether harmful to aquatic organism means “death of individual organisms, elimination of food chains, or a change in energy flow patterns”.
Inconsistency in assimilative capacity has led to the term to be restricted by the
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...
(NOAA) and
Environmental Protection Agency
A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
(EPA).
Accommodative capacity is used to mean “the rate at which waste material can be added to a body of water in such a way that the ambient concentration of contaminants is maintained below levels that produce unacceptable biological impact”.
Accommodative capacity has been suggested to remove ambiguity as uses of it have been more greatly defined in quantitative numbers.
See also
*
Water pollution
Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water ...
*
Sewage
Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residenc ...
References
{{Authority control
Environmental science
Ecology
Hydrology
Atmosphere
Environmental management schemes