Soil pollution, health effect of the soilPresentation Transcript
Pollution of the soil What Is Soil Pollution?
Soil pollution results from the build up ofcontaminants, toxic compounds, radioactivematerials, salts, chemicals and cancer-causing agents. The most common soilpollutants are hydrocarbons, heavy metals(cadmium, lead, chromium, copper, zinc, mercury andarsenic), herbicides, pesticides, oils, tars, PCBs and dioxins.
Until the 1970s, there was little talk of soilpollution and its devastating effects. In the1980s, the U.S. Superfund was created to setguidelines for the handling of hazardousmaterial and soil contamination cleanup.Today there are more than 200,000 sitesawaiting EPA soil cleanup, which is veryexpensive and labor-intensive work. Even asmall cleanup project can cost $10,000, whilelarger areas require millions of dollars toclean it up for future use.
Following WWII and Vietnam, scientists discovered high incidences of mutation, miscarriage, mental defects, cancer and sickness in areas where nuclear warheads had been dropped. Food shortages also alerted officials that something was seriously wrong with the local soil. DDT and Dioxin were two of the worst pollutants from war aftermath. In some cases, agricultural processes cause soil pollution. High levels of radionuclides like nitrogen and phosphorus can be found surrounding farm centers containing high population densities of livestock. Pesticides applied to plants can also seep into the ground, leaving lasting effects. Heavy metals can arrive in the soil by using polluted water to wet crops and by using mineral fertilizers.
Industry is to blame for some of the biggest soil-pollution disasters. Heavy metals come fromiron, steel, power and chemical manufacturingplants that recklessly use the Earth as a dumpingground for their refuse. Plants that burn theirwaste on-site are guilty of releasing heavy metalsinto the atmosphere, which come to settle in thesoil, thus leaving behind lasting effects for yearsto come. Even companies that try to dispose oftheir waste properly contribute to the problemwhen faulty landfills and bursting undergroundbins leach undesirable toxins into the soil.
Mining leaves a tremendous impact on thesurrounding communities. The 2001 WestVirginia Geological and Economic Survey foundthat people living near mines have a 70 percenthigher risk of kidney disease, 64 percent higherrisk for chronic obstructive pulmonary diseaseand a 30 percent higher risk of high bloodpressure. "People in coal-mining communitiesneed better access to health care, cleaner air,cleaner water, and stricter enforcement ofenvironmental standards," concluded MichaelHendryx, Ph.D., associate director of the WVUInstitute for Health Policy Research
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Before purchasing land for development or inhabiting, itsimportant to have a soil test performed to ensure a soundinvestment. A soil test can reveal the presence ofnitrogen, phosphorus, potassium, sulphur, calcium, magnesium, iron, manganese, copper, zinc, boron, molybdenumand aluminum. It can also analyze soil acidity, electricalconductivity, organic matter, moisture content, andidentify dangerous soil contaminants likebenzene, petroleum hydrocarbons, xylene and toulene.Even if the soil is in fine condition for planting, landownerscan use their soil tests to make more informed decisionsregarding fertilizers and crop growing. Most people call ina local professional to do the job, although stores likeHome Depot and Lowes are now selling do-it-yourselfmail-in kits as well.
Love Canal is perhaps the most famous case study ofsoil pollution. In the snowy winter of 1976, chemicalwaste began to seep above ground in schoolplaygrounds and communities in Niagara Falls, NewYork. The area suffered high incidences of stillbornbirths, miscarriages and birth defects. Officials soonrealized that there were over 400 toxic substances inthe air, water and soil -- many of them cancerous. Asit turns out, the area had been used as a chemicaldumping ground for more than 22,000 tons of toxicwaste at the turn-of-the-century, when no one wasaware of the hazardous impact it could have decadeslater.
Another one of the most infamous cases of soilpollution happened in Chernobyl, a small town inRussia. A nuclear power plant exploded in Aprilof 1986, which caused a sevenfold increase inbirth defects, a marked increase in cancer thatwas passed down to future generations, livestockdeath and mutation and tainted agriculture. Itsestimated that 40 percent of Chernobyl is stilluninhabitable due to radiation contaminationthat is ten times the normal level in some places.
Ethiopia is filled with both air and soil pollution.The worst area is in Somalias Ayaha valley nearHargeysa. To boost their economy, many farmersbegan using chemical fertilizers and pesticides toincrease productivity without understanding thefull ramifications. Over their war-torn years,metal drums holding 14,200 liters of chemicalslike fenitrothion, malathion, diazionon anddurban were punctured. As a result, landpollution has caused widespread famine andsickness.
China is a nation that is developing rapidly --perhaps faster than safety permits. "It isestimated that nationwide 12 million tons ofgrain are polluted each year by heavy metals thathave found their way into soil," ZhouShengxian, director of the State EnvironmentalProtection Administration, announced in July2006. "Direct economic losses exceed 20 billionyuan (about 2.5 billion U.S. dollars). Soil pollutionhas worsened. According to incompletestatistics, about 150 million mu (10 millionhectares) of arable land in China has beenpolluted."
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"When old factories are relocated, they just dismantle the houses, carry away the machines and nothing else is left to be done. The land that used to be a production site either is turned into farmland or real estate. Few understand that this land has become sick," explains Zhao Qiguo of the Chinese Academy of Sciences Institute of Soil Science.
People living near polluted land have higherincidences ofmigraines, nausea, fatigue, miscarriage andskin disorders. Long-term effects of pollutioninclude cancer, leukemia, reproductivedisorders, kidney and liver damage, as well ascentral nervous system failure. Children oftensuffer from developmental problems andweakened immune systems.
In addition to direct health effects, soilpollution also harms plants that feedAmericans. Chemicals can sometimes absorbinto food like lettuce and be ingested. Othertimes, the pollutants simply kill theplants, which has created widespread cropdestruction and famine in other parts of theworld. The entire ecosystem changes whennew materials are added to the soil, asmicroorganisms die off or move away fromcontaminants.
Predators who feed off the microorganisms andworms in the polluted soil will also be affected.Researchers found that some species of birds --like the Peregrine Falcon, the Brown Pelican andthe Bald Eagle -- fell prey to DDTpoisoning, which caused egg shells of futuregenerations to thin. Mother birds would arrivehome to omelets in their nests, as the thin shellscould not support the weight of the incubatingoffspring. Mortality rates increased, nearlysending the birds to extinction.
If nothing is done to clean up soilpollution, water supplies could becomecontaminated, threatening the humanspecies. Sudden fires or explosions will occurfrom underground landfill gases, pipelinesand building structures may corrode andonce beautiful regions will turn intocesspools, experts warn.
The conventional methods of soil pollution are verytime-consuming and very costly. EPA officialsexcavate the soil to dispose of it elsewhere -- aband-aid for the problem, no doubt, but essential fortoxic disasters in highly populated places. Soils canbe aerated, heated up in a process called thermalremediation, contained with pavement or caps,extracted with an active electromechanical system orpropagating the soil with microbes that will digestorganic pollutants.
New processes are being developed tocombat the problem in a natural, lesslaborious way. By studying plants that grewnaturally in toxic mines, scientist ChenTongbin discovered that certain plants lovedto eat heavy metals like arsenic, bronze, lead,zinc, cobalt and cadmium. The contaminantscan then be retrieved from the plants leavesand used in industrial materials. This safeand effective method isnt perfect, but its astart.
Naturally, prevention is the bestcure for soil pollution. Most stateshave enacted tougher legislationto stop illegal dumping. Forinstance, one can expect fiveyears in jail and a fine of$100,000 for soil pollution inTexas.
Educating consumers about the dangers oflittering, while encouraging recyclingprograms, is a good way to ensure everyonedoes their part to keep debris where itbelongs. Consumers can also make aconcerted effort to buy organic foods todemand that chemical pesticides arent usedon their foods.
People who grow their own food can keep excessnitrogen and phosphorus out of the soil bychoosing crops that do not need as manynutrients from the soil, by applying fertilizerduring the growing season to replenish thesoil, by shortening the grazing season / cattledensity, by using organic compost, by keepingthe surface moist and mulched, and by choosingfruiting crops like tomatoes, squash, peas andcorn. Gardens should be situated away from oldpainted buildings and roadways. Outer leaves oflettuce should be discarded and all vegetablesshould be washed before eating.
Over the years, stronger and moreindestructible bins were created to storehazardous materials. Researchers willcontinue to look for ways to improvemanufacturing and agricultural processes toavoid the need for toxic byproducts. Businessleaders, miners and community officials willwork together to reduce wastefulness andcontaminants to keep the world a clean placefor future generations.
Excavation showing soil contamination at a disusedgasworks.
This type of contamination typically arises from thefailure caused by corrosion of underground storagetanks (including piping used to transmit thecontents), application of pesticides, percolation ofcontaminated surface water to subsurface strata, oiland fuel dumping, disposal of coal ash, leaching ofwastes from landfills or direct discharge of industrialwastes to the soil. The most common chemicalsinvolved are petroleum hydrocarbons, lead,polynuclear aromatic hydrocarbons (such asnaphthalene and benzo(a)pyrene), solvents,pesticides, and other heavy metals. This occurrenceof this phenomenon is correlated with the degree ofindustrialization and intensities of chemical usage.
The concern over soil contamination stemsprimarily from health risks, from direct contactwith the contaminated soil, vapors from thecontaminants, and from secondarycontamination of water supplies within andunderlying the soil. Mapping of contaminatedsoil sites and the resulting cleanup are timeconsuming and expensive tasks, requiringextensive amounts ofgeology, hydrology, chemistry, computermodeling skills, and GIS in EnvironmentalContamination, as well as an appreciation of thehistory of industrial chemistry.
It is in North America and Western Europethat the extent of contaminated land is mostwell known, with many of countries in theseareas having a legal framework to identifyand deal with this environmental problem;this however may well be just the tip of theiceberg with developing countries very likelyto be the next generation of new soilcontamination cases.
The immense and sustained growth of the PeoplesRepublic of China since the 1970s has exacted a pricefrom the land in increased soil pollution. The StateEnvironmental Protection Administration believes it to be athreat to the environment, to food safety and tosustainable agriculture. According to a scientificsampling, 150 million mi (100,000 square kilometers) ofChina’s cultivated land have been polluted, withcontaminated water being used to irrigate a further 32.5million mi (21,670 square kilometers) and another 2million mi (1,300 square kilometers) covered or destroyedby solid waste. In total, the area accounts for one-tenth ofChina’s cultivatable land, and is mostly in economicallydeveloped areas. An estimated 12 million tonnes of grainare contaminated by heavy metals every year, causingdirect losses of 20 billion yuan (US$2.57 billion).
This type of contamination or pollution typicallyarises from failure due to corrosion ofunderground storage tanks or of the pipingassociated with them, historical disposal of coalash, application of pesticides, percolation ofcontaminated surface water to subsurface strata,oil and fuel dumping, leaching of wastes fromlandfills or direct discharge of industrial wastesto the soil. The most common chemicals involvedare petroleum hydrocarbons, solvents, lead,pesticides, and other heavy metals. Theoccurrence of this phenomenon is correlated withthe degree of industrialization and intensities ofchemical usage.
Historical deposition of coal ash used forresidential, commercial, and industrial heating, aswell as for industrial processes such as oresmelting, is a common source of contamination inareas that were industrialized before about 1960.Coal natually concentrates lead and zinc during itsformation, as well as other heavy metals to a lesserdegree. When the coal is burned, most of thesemetals become concentrated in the ash (the principalexception being mercury). Coal ash and slag maycontain sufficient lead to qualify as a "characteristichazardous waste", defined in the USA as containingmore than 5 mg/L of extractable lead using the TCLPprocedure.
In addition to lead, coal ash typically containsvariable but significant concentrations ofpolynuclear aromatic hydrocarbons (PAHs; e.g.,benzo(a)anthracene, benzo(b)fluoranthene,benzo(k)fluoranthene, benzo(a)pyrene,indeno(cd)pyrene, phenanthrene, anthracene,and others). These PAHs are known humancarcinogens and the acceptable concentrations ofthem in soil are typically around 1 mg/kg. Coalash and slag can be recognized by the presenceof off-white grains in soil, gray heterogeneoussoil, or (coal slag) bubbly, vesicular pebble-sizedgrains.
Treated sewage sludge, known in the industryas biosolids, has become controversial as afertilizer to the land. As it is the byproduct ofsewage treatment, it generally containscontaminants such as organisms, pesticides,and heavy metals than other soil.
Contaminated or polluted soil directly affectshuman health through direct contact with soilor via inhalation of soil contaminants whichhave vaporized; potentially greater threatsare posed by the infiltration of soilcontamination into groundwater aquifersused for human consumption, sometimes inareas apparently far removed from anyapparent source of above groundcontamination.
Health consequences from exposure to soilcontamination vary greatly depending onpollutant type, pathway of attack andvulnerability of the exposed population. Chronicexposure to chromium, lead and othermetals, petroleum, solvents, and many pesticideand herbicide formulations can becarcinogenic, can cause congenital disorders, orcan cause other chronic health conditions.Industrial or man-made concentrations ofnaturally-occurring substances, such as nitrateand ammonia associated with livestock manurefrom agricultural operations, have also beenidentified as health hazards in soil andgroundwater.
Chronic exposure to benzene at sufficientconcentrations is known to be associatedwith higher incidence of leukemia. Mercuryand cyclodienes are known to induce higherincidences of kidney damage, someirreversible. PCBs and cyclodienes are linkedto liver toxicity. Organophosphates andcarbamates can induce a chain of responsesleading to neuromuscular blockage.
Many chlorinated solvents induce liverchanges, kidney changes and depression ofthe central nervous system. There is an entirespectrum of further health effects such asheadache, nausea, fatigue, eye irritation andskin rash for the above cited and otherchemicals. At sufficient dosages a largenumber of soil contaminants can cause deathby exposure via direct contact, inhalation oringestion of contaminants in groundwatercontaminated through soil.
Not unexpectedly, soil contaminants can havesignificant deleterious consequences forecosystems. There are radical soil chemistrychanges which can arise from the presence ofmany hazardous chemicals even at lowconcentration of the contaminant species. Thesechanges can manifest in the alteration ofmetabolism of endemic microorganisms andarthropods resident in a given soil environment.The result can be virtual eradication of some ofthe primary food chain, which in turn could havemajor consequences for predator or consumerspecies.
Even if the chemical effect on lower life formsis small, the lower pyramid levels of the foodchain may ingest alien chemicals, whichnormally become more concentrated for eachconsuming rung of the food chain. Many ofthese effects are now well known, such as theconcentration of persistent DDT materials foravian consumers, leading to weakening ofegg shells, increased chick mortality andpotential extinction of species
Effects occur to agricultural lands which havecertain types of soil contamination.Contaminants typically alter plantmetabolism, most commonly to reduce cropyields. This has a secondary effect upon soilconservation, since the languishing cropscannot shield the Earths soil mantle fromerosion phenomena. Some of these chemicalcontaminants have long half-lives and inother cases derivative chemicals are formedfrom decay of primary soil contaminants.
Microbes can be used in soil cleanup
Clean up or environmental remediation is analyzed by environmental scientists who utilize field measurement of soil chemicals and also apply computer models (GIS in Environmental Contamination) for analyzing transport and fate of soil chemicals. There are several principal strategies for remediation: Excavate soil and take it to a disposal site away from ready pathways for human or sensitive ecosystem contact. This technique also applies to dredging of bay muds containing toxins.
Aeration of soils at the contaminated site (with attendant risk of creating air pollution) Thermal remediation by introduction of heat to raise subsurface temperatures sufficiently high to volatize chemical contaminants out of the soil for vapour extraction. Technologies include ISTD, electrical resistance heating (ERH), and ET-DSPtm. Bioremediation, involving microbial digestion of certain organic chemicals. Techniques used in bioremediation include landfarming, biostimulation and bioaugmentating soil biota with commercially available microflora.
Extraction of groundwater or soil vapor with an active electromechanical system, with subsequent stripping of the contaminants from the extract. Containment of the soil contaminants (such as by capping or paving over in place). Phytoremediation, or using plants (such as willow) to extract heavy metals
Along with air and water pollution, soil pollution is an equally serious issue that the modern-day world is confronted with. For all those who are concerned about the soil pollution causes and effects, this article is a must-read.Soil pollution!! One of the gravest problems existing on the earth today. Well, (on the earth?), the earth itself is getting contaminated and polluted! Collectively, arent we all responsible for this? The conquest of utilizing land and soil resources and conducting experiments on it for our benefits is quite understandable, but it certainly is not at the cost of its health and wellness! Mankind has been trying out several different things and has made several arrangements in the soil, to make life happy and comfortable. However, how often have we thought about the contamination of soil? Its never too late in life, so I think this is the right time to know about all the important soil pollution causes and effects.
Soil pollution is defined or can be described asthe contamination of soil of a particular region.Soil pollution mainly is a result of penetration ofharmful pesticides and insecticides, which onone hand serve whatever their main purposeis, but on the other hand bring aboutdeterioration in the soil quality, thus making itcontaminated and unfit for use later. Insecticidesand pesticides are not to be blamed alone for soilpollution, but there are many other leadingcauses of soil pollution too. Let us have a look atsome of them in the following text.
Soil pollution is a result of many activities and experiments done by mankind which end up contaminating the soil. Here are some of the leading soil pollution causes: Industrial wastes such as harmful gases and chemicals, agricultural pesticides, fertilizers and insecticides are the most common causes of soil pollution. Ignorance towards soil management and related systems. Unfavorable and harmful irrigation practices.
Improper septic system and management and maintenance of the same. Leakages from sanitary sewage. Acid rains, when fumes released from industries get mixed with rains. Fuel leakages from automobiles, that get washed away due to rain and seep into the nearby soil. Unhealthy waste management techniques, which are characterized by release of sewage into the large dumping grounds and nearby streams or rivers.
The intensity of all these causes on a local orregional level might appear very small and youmay argue that soil is not harmed by aboveactivities if done on a small scale!However, thinking globally, it is not your regionor my place that will be the only sufferer of soilpollution. In fact, it is the entire planet andmankind that will encounter serious problems, asthese practices are evident almost everywhere inthe world. Want to know what are thoseproblems which can turn more serious in thenear future?
The effects of pollution on soil are quite alarming and can cause huge disturbances in the ecological balance and health of living creatures on earth. Some of the most serious soil pollution effects are: Decrease in soil fertility and therefore decrease in the soil yield. How can one expect contaminated soil to produce healthy crops? Loss of soil and natural nutrients present in it. Plants also would not thrive in such soil, which would further result in soil erosion. Disturbance in the balance of flora and fauna residing in the soil. Increase in salinity of the soil, which therefore makes it unfit for vegetation, thus making it useless and barren.
Generally crops cannot grow and flourish in polluted soil. Yet, if some crops manage to grow, they would be poisonous enough to cause serious health problems in people consuming them. Creation of toxic dust is another potential effect of soil pollution. Foul smell due to industrial chemicals and gases might result in headaches, fatigue, nausea, etc., in many people. Soil pollutants would bring in alteration in the soil structure, which would lead to death of many essential organisms in it. This would also affect the larger predators and compel them to move to other places, once they lose their food supply.
I hope the above discussion was enough to makeyou understand the severity of the soil pollutioncauses and effects. Soil pollution can be cured bytransporting the contaminated soil layer to someremote place, thus making it once again fit foruse. Harmful chemicals from the soil can also beremoved by aerating it. These are just tentativesolutions. However, let us remember theproverb, prevention is better than cure, andfollow proper a soil managementsystem, maintain sewage systems, and avoid theoveruse of fertilizers and pesticides in the soil.So let us begin the movement of soil pollutionprevention from our own lands itself!!!
Past and present economicactivities have often resultedin the pollution of theunderlying soil where theseactivities take place.
The most common toxic soil pollutants includemetals and their compounds, organicchemicals, oils and tars, pesticides, explosiveand toxic gases, radioactivematerials, biologically activematerials, combustible materials, asbestos andother hazardous materials. These substancescommonly arise from the disposal of industrialand domestic waste products in designatedlandfills or uncontrolled dumps.
Soil pollution by heavy metalsSoil pollution by pesticides and organiccontaminatesSoil pollution by nitrates and phosphorusSoil pollution by artificial radionuclides
The existence of unauthoriseddumps is one of the environmentalproblems in Europe that deservesutmost attention. The remediationcosts of polluted areas in Europeare roughly estimated at more thanEUR 100 billion.
Soil contamination by heavy metals, such ascadmium, lead, chromium, copper, zinc,mercury and arsenic, is a matter of greatconcern.Heavy metals are present naturally in the soil,but their levels are increased by:
• industry (non-ferrous industries, powerplants, iron, steel and chemical industries);• agriculture (irrigation with polluted water, useof mineral fertilisers)• waste incineration;• combustion of fossil fuels; and• road traffic.
Pollution of agricultural soils by heavy metalsmay lead to reduced yields and elevated levels ofthese elements in agricultural products, and thusto their introduction into the food chain.Heavy metal deposits on grassland soils remainpredominantly in the top few centimetres and aredirectly ingested with soil by grazing animals.
Heavy metals are toxic and inhibit the soilsmicroorganic activity. Their concentration in thesoil can remain for decades or even centuries.Reduction of heavy metal emissions is the mostdirect way to decrease the atmosphericdeposition of these elements and their build-upin the soil. Despite the great increase intraffic, for example, a reduction in leademissions has been achieved through incentivesto use unleaded petrol.
Nevertheless,emissions of heavymetals from industrialplants in Central andEastern Europe are stillprevalent.
Implementing complex measures that reducesoil acidification could more efficientlyreduce heavy metals. On agriculturalland, heavy metal quantities can be decreasedby using low-metal content resources forfertilisers, replacing inorganic pesticides withorganic products, and other similar methods.
Nitrogen and phosphorus are elements essentialto all forms of life and are therefore relevant tosoil systems and food crops. Although they areimportant plant nutrients, excessive applicationmay lead to nitrogen or phosphate saturation inthe soil, and eventual contamination of thegroundwater. The amount of leaching dependson the soil, the local climate and the style of cropmanagement.
PhosphorusPhosphorus accumulates in the upper layer ofsoil in regions with high livestock densities.In soils saturated with phosphorus, especiallythose with shallow groundwater, highphosphorus concentration occurs in theupper groundwater layer and in surfacewater, resulting in eutrophication.
NitrogenThe problem of nitrate pollutionis recognised internationally andis usually associated withintensive agriculture practices.Good agricultural practices thatalleviate the problem are:
• the selection of crops that require fewernutrients;• a timely application of fertiliser (in the growingseason);• improved methods of manure application;• shortening the length of the grazing season;and• reducing the intensity of grassland use (bylowering cattle density).
Pesticides pollute the soil directly byaffecting the organisms that reside in it.Soil, however, can act as a vector for thepollution of surface water and groundwater.Organic pollutants enter the soil viaatmospheric deposition, direct spreadingonto land, contamination by wastewater andwaste disposal.
In addition to pesticides, organiccontaminants include many othercomponents, such as oils, tars,chlorinated hydrocarbons, PCBsand dioxins. There is such a widevariety of organic substances thattheir detection and monitoring inthe soil is practically impossible.
Pesticides (mainly fungicides, herbicides andinsecticides) are used in agriculture to protectcrops and to ensure a quality harvest.Persistent or mobile pesticides are especiallydangerous, as are those that affect non-targeted organisms.
The use of pesticides may lead to:• destruction of the soils micro-flora andfauna, leading to both physical and chemicaldeterioration;• severe yield reduction in crops; and• leaching of toxic chemicals into groundwaterand potentially threatening drinking waterresources.
Some improvements in application andlegislation may reduce the side effects ofpesticides, such as:• banning broad-spectrum and highly mobilepesticides;• employing integrated pest-management;• enforcing biological control; and• developing biotechnologies.
Primordial radionuclides are left over from the creation of the Earth. They typically have half- lives of hundreds of millions of years. Examples include uranium-235, uranium-238, thorium- 232, and potassium-40. Primordial radionuclides end up in soil as part of the rock cycle, which includes weathering. Tree or plant roots dig down into cracks in the earth, prying the rock apart and turning it into soil. Natural radioactivity in soil varies on soil type, mineral make up and density. Man-made activities, such as mining, may accelerate the movement of primordial radionuclides into soil.
Radionuclides are continuously produced by bombardment of stable nuclides by cosmic rays, primarily in the atmosphere. These cosmogenic radionuclides can have long half-lives, but the majority have shorter half-lives than the primordial radionuclides. Cosmogenic radionuclides include carbon-14, tritium-3, and beryllium-7; worldwide, cosmic radiation is the primary source of these radionuclides. Another way radionuclides become part of the soil is through natural cosmic radiation, radiation produced in outer space when heavy particles from other galaxies (nuclei of all known natural elements) bombard Earth. Some of these radionuclides fall to Earth and are deposited on the soil.
The third way radionuclides enter the soil is through man- made activities, such as the fallout from atmospheric testing of nuclear weapons and radiological events like the Chernobyl accident. Deposition studies of these activities indicate that radioactive particles travel around the world on streams of air. The weight of the particle and weather determine how soon they fall to the ground. Sometimes a heavy rain will bring the radioactive particles to the ground quickly. Improper disposal of radioactive material also may contribute to radionuclides in the soil. Radionuclides in the soil can move into the water, air and even our food supply. Many different agencies are involved in setting standards and monitoring to keep us safe.