Contaminants plants

In addition to their direct role in the bioremediation of contaminants, plants can play an important role in their dissemination through consumption by ruminants. The detoxification and metabolism of higher plants has been reviewed by Sandermann (1994), and some illustrative examples include the following ... 

Carpenter et al. 1959), and decreased lactation and delayed estrus in cows after oral ingestion of Fyrquel-150-contaminated plant tissue at unspecified dose levels (Beck et al. 1977). 

Mechanism Media Typical Contaminants Plant Types... 

The levels of lead may build up in plants and animals from areas where air, water, or soil are contaminated with lead. If animals eat contaminated plants or animals, most of the lead that they eat will pass through their bodies. Chapters 4 and 5 contain more information about what happens to lead in the environment. 

Potential obstacles for the large-scale application of phytoremediation technologies, however, include the time required for remediation, the pollutant levels tolerated by the plants used, the disposal of the contaminated plants, and the fact that only the bioavailable fraction of the contaminants will be treated. This means that phytoremediation does not achieve 100% removal or reduction of the contaminants From the ecological, toxicological, and medical (health) points of view, the... 

Soils amended with arsenic-contaminated plant tissues were not measurably affected in C02 evolution and nitrification, suggesting that the effects of adding arsenic to soils does not influence the decomposition rate of plant tissues by soil microorganisms (Wang et al. 1984). The half-life of cacodylic acid is about 20 days in untreated soils and 31 days in arsenic-amended soils (Hood 1985). Estimates of the half-time of inorganic arsenicals in soils are much longer, ranging from 6.5 years for arsenic trioxide to 16 years for lead arsenate (NRCC 1978). 

The project was dropped. Even if phytoremediation tried on this site and if it were considered successful in remediating the soils, the fundamental question of what to do with the contaminated plants and trees would still pose a huge challenge. 

The spores can lie dormant for at least 12 years. Infection of healthy roots occurs in wet conditions. It is spread on contaminated plants and in soil on tools and boots. 

Viruses, invisible to the naked eye, exist in living plant material, where they do not necessarily cause symptoms. They are spread by sapsucking insects, such as aphids, by contact (on hands and on tools, especially cutting tools such as pruners), by birds, and by propagation from contaminated plants. Some viruses are plant-specific, while others will infect a number of unrelated plants. 

While the soil-io-plam segment of ihe fond chain contains some built-in safeguards against fluorine loxicily. this loxicily occurs as a result nf Ihe deposition of airborne fumes and dusts on the above-ground parts of plants, followed hy ihe consumption of these contaminated plants by animals, including humans. Also, fluorine toxicity hits been caused hy direct inhalation of the fumes and dusts, or hy drinking water with abnormally high fluorine levels. If the fumes and dusts anc mixed into the soil, they wilt be inactivated, and they will nol find their way into the food chain in toxic amounls. 

Inadvertent human intrusion into hazardous waste. Inadvertent human intrusion is relevant to disposal of virtually all hazardous substances, especially in near-surface facilities. Typical scenarios assume that an unknowing individual (1) digs or drills into the waste and brings some of it to the surface where it is then available for dispersal and uptake, or (2) lives on the disposal site after waste has been exhumed or the cover removed, and consumes contaminated plant and animal products. Scenarios for inadvertent intrusion usually are assumed to occur after some period of active institutional control over the disposal site, which is typically 100 to 300 y. Intrusion scenarios are not very sensitive to site-specific parameters because the nature of intrusion (by digging or drilling) effectively bypasses the site-specific protection features, such as small amounts of groundwater,... 

Organic farmers, unlike conventional farmers who may use herbicides, are unable to control volunteer plants from contaminated plants in the field (e.g. in oilseed rape) or volunteers which may originate from field-to-field transfer by machinery (e.g. combine, harvester). 

There are two possible sources of PCDD/Fs to vegetation the atmosphere and soil. Initially it was thought that PCDD/Fs would not be present in the atmosphere in quantities sufficient to contaminate plants owing to their low volatility, and early research in this area focused on uptake from soil. There are three possible pathways of soil-bound PCDD/Fs to aerial plant parts root uptake and translocation, volatilization followed by adsorption to foliage, and transfer of soil particles (see Figure 1). The first of these pathways has received the most attention. 

With respect to ventilation systems, we employ standard design criteria for volume flow rate, negative pressure, and face velocity requirements in contaminated and potentially contaminated areas. In contaminated plant areas, we employ a minimum of 20 air changes per hour, while in clean operating areas we use a minimum of 6 air changes per hour. All entries to the contaminated areas incorporate airlocks to prevent migration into the clean areas. 

Trifluralin can enter the body by inhalation of contaminated air or absorption through the skin or by diet if contaminated plants or animals are consumed. 

Plants that grow in contaminated soils can absorb these pollutants. Once absorbed, such toxic chemicals are taken up by animals that feed on the contaminated plants and are passed up the food chain, in many instances, to humans. Following are examples of such an effect. 

Weis, 2004). If the rhizosphere plays an important role in the sequestration of metals in wetland soils, fluxes of potentially toxic metals out of the wetland to adjacent aquatic systems will, in theory, be reduced. However, plants may also increase metal mobilization through rhizosphere acidification and the oxidation of metal-sulfide complexes (Jacob and Otte, 2003). They may also represent only a temporary sink for metals if rhizosphere Fe plaque is reduced following plant senescence. Furthermore, metals can be exported from the ecosystem if contaminated plant parts are consumed by people or wildlife. The pathways and possible health effects of metal consumption have been especially well studied in Southeast Asia, where metal contamination (notably As) of rice crops is a serious public health issue (e.g., Meharg and Rahman, 2003 Meharg, 2004). 

Iodine-131 is a beta and gamma emitter and has a short physical half-life of approximately 8 days. It is efficiently absorbed and used by the body. 1-131 will contaminate plants that will be eaten by grazing animals. Smaller amounts can also be absorbed by breathing contaminated air. Cattle will excrete a large amount of 1-131 in milk. 1-131 will be concentrated in the thyroid gland. The intake of 1-131 will have its greatest impact the first few days to weeks following a nuclear explosion. 

Since Herring Gulls and coho salmon accumulate these residues from their common food supply, it seemed logical to consider the human exposure routes thoroughly, particularly the food supply. An early study by Bennet 2 ) followed total non-occupational environmental exposure of PCB to humans. This study showed that for PCB the atmospheric pathway contaminates plants directly, livestock indirectly, and ultimately contributes the major human environmental dosage of PCB. Exposure from drinking water and the atmosphere directly are inconsequential relative to food exposure. A more recent modelling effort (1J7) for... 

The slow decomposition by ultraviolet light of TCDD reaching the environment from other sources can be considerably accelerated by the process developed in the Diibendorf Laboratory of Givaudan SA. In this method the contaminated plants are sprayed with an oil-in-water emulsion of olive oil and water (Anonym,... 

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