*2.1.2 Livestock*

*Emerging Contaminants*

the environment as ECs.

*2.1.1 Agricultural soils*

environment lacking published health criteria. They may also be identified from sources that are unknown, new exposure to humans, or a new detection approach or technology [9]. Emerging contaminants (ECs) are not usually new chemicals. They could be substances or chemicals that have stayed long in the environment with their presence and importance being recognized now. There are many proposed and contradictory definitions of "Emerging Contaminants". Boxall [10] defines it as a contaminant from a chemical class that has not been studied extensively where either there is a concern from scientists, Regulators, NGOs or other Stakeholders that the contaminant class may be having an impact on human health or environment or where there is a concern that an existing environmental assessment

Recently, there has been a great concern on the environmental challenges caused by Emerging contaminants. These ECs emanate from by-products of a variety of materials such as paints and coatings, pharmaceuticals, personal care products, agrochemicals, veterinary medicines etc. Some natural products and those transformed through biochemical processes from synthetic chemicals may be formed in

Emerging Contaminants are released to the agricultural environment via different pathways. They may be released to the environment directly (veterinary medicines that are used in the treatment of animals at pasture) or enter indirectly to the soil during the application of manure, biosolids or other solid waste materials. Once they enter the soil, they may be transported by leaching, runoff and drainage processes to water bodies. The extent of the transport is dependent on the

The largest source of GHG emission from Agriculture is Nitrous oxide (N2O) and it accounts for 38% of the total global emission. Through the process of nitrification and denitrification, it is produced naturally from soil. Agricultural activity which is anthropogenic may add nitrogen directly or indirectly to soils. The use of nitrogen fertilizer, production of nitrogen-fixing crops and forages, retention of crop residues, application of managed livestock manure, sewage sludge and cultivation of soils with high organic matter content are the direct additions. Through indirect additions are surface runoff and leaching of applied nitrogen into surface and ground water, volatilization and atmospheric deposition of applied nitrogen [11]. Other anthropogenic sources of GHG emissions from agriculture include manufacture of equipment, pesticides, fertilizers, on-farm use of fuels and the transport of agricultural products [12]. Emissions of GHG from agricultural soils (N2O) and enteric fermentation and management of manure (CH4) linked with livestock production contribute to the largest share in agricultural sector. So, from agricultural sector, sources of GHG emissions are accounted for as follows: Residue burning/forest cleaning (13%), Methane and Nitrous oxide from Management of manure (7%), Methane from Rice cultivation (11%), Nitrous oxide from fertilizers (37%) and Methane from Livestock (32%) [11]. These emissions are expected to increase in future due to high demand for agricultural products and enhanced nutrition [13]. The direct addition of both synthetic and organic nitrogen containing fertilizers will possibly be a key source of rise in emission of N2O with the highest coming from developing countries that are seen using 36 million tons more

paradigms are not appropriate for the contaminant class.

**2.1 Emerging contaminants from agricultural activities**

persistence of the EC and on how it interacts with soil and air.

**152**

than the developed nations [14].

Emissions from Livestock constitute 9% of CO2 equivalent obtained from all human related activities and produces 65% of human-related nitrous oxide, and 37 percent of human induced methane, and 64% ammonia especially from manure. Considering agriculture sector, livestock account for nearly 80% of all emissions [15]. All these emissions from livestock make it a major target for mitigation options. Feed produced locally such as grass and other roughage, together with wastes that are rich in nutrient from farms and households when replaced with feed manufactured from feed mills containing some secondary plant metabolites able to reduce the emission of methane gas could lead to negative climate impact.

The natural digestive processes in ruminants otherwise known as enteric fermentation in sheep and cattle account for the key source of methane production under this category hence the second largest source of total agricultural emission with 34% global share and rice cultivation being the third with 11%. Other domesticated animals that also emit methane (methanogenesis) as a by- product of enteric fermentation include Horses, swine and poultry. The estimates of enteric methane from ruminants produced globally are about 80,000 Gg [16].
