Term
| What is the Earth's crust mostly made of? |
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Definition
| Oxygen, silicon and aluminium (80%) |
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Term
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Definition
| From the weathering of rocks by microbial, chemical or physical means. |
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Term
| What are the four components of soil? |
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Definition
| Inorganic matter, water, air and small amounts of organic matter. |
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Term
| Why does soil composition vary? |
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Definition
| It is affected by the amounts of air and water, which affect bacteria and fungi that decay organic matter (-> humus). |
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Term
| What are the inorganic components of soil mostly based on? |
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Definition
| Silica, silicates and aluminosilicates. |
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Term
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Definition
| Silicon (IV) oxide or SiO2, the silicon forms a tetrahedron with four oxygen atoms. |
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Term
| What happens if aluminium replaces the silicon in the silica structure? |
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Definition
| The compound can acquire a negative charge. |
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Term
| What does the negative charge in aluminosilicates and highly electronegative oxygen lead to? |
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Definition
| The ability of soil to hold plant nutrient cations such as potassium and magnesium. |
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Term
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Definition
| When small amounts of dissolved ions from salts accumulate in the soil, leading to a decrease in plant growth. |
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Term
| What is nutrient depletion? |
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Definition
| The loss or reduction of soil nutrients; influences crop yields |
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Term
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Definition
| The contamination of soil with man-made chemicals such as herbicides, pesticides and fungicides and through industrial wastes (heavy metals). |
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Term
| What is soil organic matter (SOM)? |
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Definition
| The organic matter present in soil. Includes humic substances which contain acid that form anions which can bind cations. |
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Term
| What does soil organic matter contribute to soil? |
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Definition
| It increases the soil quality and crop yields by binding mineral nutrients, improving the soil structure, increasing its water absorption capacity and decreasing erosion. |
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Term
| What are the biological effects of soil organic matter? |
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Definition
| It contains mineral nutrients (nitrogen, sulphur, phosphorus) that are given to the plant roots via decomposing bacteria and fungi. |
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Term
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Definition
| The slow process through which organic matter is broken down to release nutrients (N, P, S) |
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Term
| What are the most common organic soil pollutants? |
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Definition
| Petroleum hydrocarbons, chemicals from fertilisers and pesticides, VOCs and semi-VOCs, solvents like hexane and methyl benzene, polyaromatic hydrocarbons (PAHs) which can be carcinogenic, polychlorinated biphenyls (PCBs), organotin compounds |
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