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Hematite-rich iron ore. Iron ore is a mixture of rocks and minerals containing enough iron content and sufficient volume and accessibility for mining and transportation to be economically mined. [5] Around five percent of the Earth's crust is composed of iron making it the fourth most abundant element. [6]
Iron can also be oxidized by marine microbes under conditions that are high in iron and low in oxygen. [53] Iron can enter marine systems through adjoining rivers and directly from the atmosphere. Once iron enters the ocean, it can be distributed throughout the water column through ocean mixing and through recycling on the cellular level. [54]
Nutrient pollution is a major cause of algal blooms and excess growth of other aquatic plants leading to overcrowding competition for sunlight, space, and oxygen. Increased competition for the added nutrients can cause potential disruption to entire ecosystems and food webs, as well as a loss of habitat, and biodiversity of species.
The oxide is toxic to humans. [11] oxygen: 8: 5: Ubiquitous, essential for all forms of life; essentially all biological molecules (not to mention water) contain substantial amounts of oxygen. [11] In high concentrations, oxygen toxicity can occur. palladium: 46: 2a: Has no known biological role. [11]
Iron reaches the atmosphere through volcanism, [8] aeolian activity, [9] and some via combustion by humans. In the Anthropocene, iron is removed from mines in the crust and a portion re-deposited in waste repositories. [4] [6] The iron cycle (Fe) is the biogeochemical cycle of iron through the atmosphere, hydrosphere, biosphere and lithosphere.
Ocean iron fertilization is an example of a geoengineering technique that involves intentional introduction of iron-rich deposits into oceans, and is aimed to enhance biological productivity of organisms in ocean waters in order to increase carbon dioxide (CO 2) uptake from the atmosphere, possibly resulting in mitigating its global warming effects.
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Air pollution can occur naturally or be caused by human activities. [4] Air pollution causes around 7 or 8 million deaths each year. [5] [6] It is a significant risk factor for a number of pollution-related diseases, including heart disease, stroke, chronic obstructive pulmonary disease (COPD), asthma and lung cancer.