soil characteristics and soil pollution.ppt
TRANSCRIPT
Soil characteristics and soil pollution
Prof. Xuyin YuanCollege of Environment
Outline
• Major characteristics of soils• Sources of soil pollutants• Environmental and ecological effects of soil pollution• Risk assessment of soil pollution• Prevention and remediation of soil pollution
Major characteristics of soils
• Soil formation• Soil compositions• Soil properties
Soil formation
• Soil has two important functions. One is a precious source, which can be used as an agricultural basis for food production. The other is a substance with the assimilation and metabolism ability.
• The weathering process makes rocks break up and the broken rocks form structural loose matter, which is defined as parent matter. The parent matter undergoes climate changes, biological action and other physiochemical actions to form soils .
Brown soil profile
Podzolic soil profile
Red soil profile
Yellow soil profile
Soil compositions
• Soil minerals• Soil organic matter• Soil water• Soil air• Insects• Microorganism• Plant litter
Chemical compositions of soil minerals
岩石圈和土壤的主要化学组成(重量%)
元素 岩石圈 土壤 元素 岩石圈 土壤
O
Si
Al
Fe
Ca
Na
K
47.2
33.0
8.8
5.1
3.6
2.64
2.6
49.0
27.6
7.13
3.8
1.37
0.63
1.36
Mg
S
Mn
P
N
Cu
Zn
2.1
0.09
0.09
0.08
0.01
0.01
0.005
0.6
0.085
0.085
0.08
0.1
0.002
0.005
Soil organic matter
• Soil organic matter is comprised of plant root, stalk , leaf, soil animal body and organic fertilizer.
• Humus is dominated in soil organic matter , which includes the plant and animal residual, humic acid and fulvic acid.
• Humus has strong adsorptive ability, buffer ability and complexing ability, which take significant effects on soil structure, soil properties and soil quality.
Soil water and soil air
• Soil water originates from atmospheric precipitation, snow and surface runoff, and sometime from groundwater.
• Soil air exists the pore without water, which reveals less proportion oxygen, more proportion CO2 compared to atmospheric air. Soil air is also comprised of CH4, H2S,H2 and NOx.
Soil particle composition
我国土壤质地分类
颗粒组成(%)
质地组 质地名称 砂粒
(0.05-1 mm)
粗粉粒
(0.001-0.05mm)
粘粒
(<0.001 mm)
砂土 粗砂土
细砂土
面砂土
>70
60-70
50-60
- <30
砂粉土
粉土
>20
<20 >40
粉壤土
粘壤土
>20
<20 <40
壤土
砂粘土 >50 -
>30
粘土 粉粘土
壤粘土
粘土
- -
30-35
35-40
>40
Soil Texture Terminology Refects Paricle Size Not Mineralogy
Sources of soil pollutants
Industrial source
Transport source
Agricultural source
Domestic source
Pollutants in soils mainly come from industrial
emissions, fertilizer, pesticides, urban sewage, waste.
Soil pollutants
Industrial discharge, Wastewater irrigation
Pesticides, fertilizer, agricultural waste
Tail gas
Household garbage, domestic sewage
Inorganic pollutants
Organic pollutants
Harmfulmicroorganism
Classification of soil pollutants
Heavy metals, nonmetals, radioative
elements, inorganic acids and alkalis.
Pesticides, antibiotics, hydrocarbon compounds, phenols
Polluted microorganism, pathogenic bacteria
Environmental and ecological effects of soil pollution
Harmfulness of soil pollution
• Reduction of crop production• Decline in food quality• Health hazard of human being through food web• Other environmental issues(Atmospheric quality,
surface water quality, groundwater quality, ecological
degeneration)
Some guidelines of heavy metals for non-pollution vegetables in China(maximum residue limit)
重金属 最高残留限量 (mg/kg )
汞 0.01
砷 0.5
铅 0.2
镉 0.05
Degeneration of soil quality
Soils, Agriculture and Desertification
1. Soil degradation is mainly caused by agricultural
plowing breaking up soil structure and increasing
erosion rates.
2. Deterioration of soil quality can lead to desertification.
3. Destruction of rainforests leads to release of soil
organic carbon as atmospheric carbon dioxide.
4. Over-pumping of groundwater for irrigation depletes
this resource and causes subsidence.
5. Farming methods, such as drip irrigation and
minimum tillage planting, can lead to less water usage
and soil conservation.
Soil Degradation Varies Around the World
Soil Erosion
Soil particles sizes are carried relatively easily by streams.Vegetation, especially root structures, hold soils together.Cutting down natural vegetation (e.g., trees to clear land for
farming increases erosion rates).Plowing of soils further breaks up soils allowing erosion.Irrigation can enhance normal erosion rates.
Loss of vegetation leads to decreased stability
Excess erosion caused by agricultural runoffCentral Valley, CA
Desertification• Extended periods of drought can lead to
desertification.
• Over-grazing by cattle and sheep can also
destroy existing vegetation and decrease
soil quality.
• Over-cropping, planting too many times
per season, in semi-arid land can turn
them into arid lands.
Desertification of farmland –Danakil Depression, Egypt
Extent sub-Saharan desertification
Barren Fields Buried Under Windblown Soil
Deforestation of Amazonian rainforest nearMaraba, Brazil
Risk assessment of soil pollution
Environmental risk of soil pollution
• Risks related to one soil pollutant• Ecotoxicological risks• Biological availability• Combination effects
Environmental risk assessment of soil pollution
Ecological risk assessment of soil pollution
Remediation of polluted soils
Classification of remediation techniques for polluted soils
Based on restoration site
In-situ remediation
Ex-situ remediation
In-situ treatment
Ex-situ treatment
Based on restoration principle
Phytoremediation technique
Microorganism technique
Chemical technique
Physical technique
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Hyperaccumulation plants of heavy metals
1)Strong tolerance to high level heavy metals2)Accumulating high concentrations of heavy metals3)Fast growth ratio4) Higher biomass5) Well developed root system
Species of hyperaccumulation plants
Chemical washing remediation of polluted soils
Injecting the leacheate into contaminated soils and dissolving pollutants like heavy metals. Then extracting the liquids with pollutants from soils.
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Remediation of organic pollutants in soils
Microorganism remediation of organic pollutants in soils
①Microorganism degradation of petroleum pollutants
② Microorganism degradation of pesticides
③ Microorganism degradation of polycyclic aromatic hydrocarbon
④ Microorganism degradation of pentachlorophenol
Bioremediation
① Phytoremediation of organic pollutants
② Combined remediation of plant and microorganism for organic pollutants
Other remediation techniques
① In-situ washing technique② In-situ soil vapor extraction technique③ Photochemical degradation technique④ In-situ covering technique
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Contour Plowing/Planting Impedes Water Flow
Terracing Creates “Steps” of Shallower Slope
That is all for this lecture
Thank you for your attention