Agricultural fertilizers nitrous oxide and the ozone layer

When concern for the ozone layer was at its height, compounds other than CFCs were identified as potentially harmful. These included nitrous oxide, carbon tetrachloride and methyl chloroform. Methyl bromide has recently been added to the group. It is used extensively as a fumigant to kill pests in the fruit and vegetable industry, and may be responsible for as much as 10 per cent of existing ozone depletion. However, its actual impact is still a matter of dispute (MacKenzie 1992). Nitrous oxide (N2O), as one of the oxides of nitrogen group, known for their ability to destroy ozone, has received most attention. It is produced naturally in the environment by denitrifying bacteria which cause it to be released from the nitrites and nitrates in the soil. It is an inert gas, not easily removed from the troposphere. Over time, it gradually diffuses into the stratosphere where the higher energy levels cause it to be oxidized into NO, leading to the destruction of ozone molecules. This process was part of the earth/ atmosphere system before human beings came on the scene, and with no outside interference, natural ozone levels adjust to the output of N2O from the soil and the oceans.

One of society's greatest successes has been the propogation of the human species, as a glance at world population growth will show. This has occurred for a number of reasons, but would not have been possible without a growing ability to supply more and more food as population numbers grew. By the late 1940s and 1950s, this ability was being challenged as population began to outstrip food supply. In an attempt to deal with the problem, new agricultural techniques were introduced into Third World countries, where the need was greatest. A central element in the process was the increased use of nitrogen fertilizers along with genetically improved grains, which together produced the necessary increase in agricultural productivity. Since that time, continued population growth has been paralleled by the growth in the use of nitrogen-based fertilizers (Dotto and Schiff 1978).

The nitrogen in the fertilizer used by the plants eventually works its way through the nitrogen cycle, and is released into the air as N2O to initiate the sequence which ultimately ends in the destruction of ozone. Thus, in theory, the pursuit of greater agricultural productivity through the increased application of nitrogen fertilizers is a threat to the ozone layer. There is, however, no proof that increased fertilizer use has, or ever will, damage the ozone layer, through the production of N2O. If proof does emerge, it will create a situation not uncommon in humankind's relationship with the environment, in which a development designed to combat one problem leads to others, unforeseen and perhaps undiscovered until major damage is done. As Schneider and Mesirow (1976) point out, the dilemma lies in the fact that nitrogen fertilizers are absolutely essential to feed a growing world population and improve its quality of life, yet success might lead to a thinning of the ozone layer with consequent climatic change and biological damage from increased ultraviolet radiation. If monitoring does reveal that N2O emissions are increasing, some extremely difficult judgements will have to be made; judgements which could have a far greater impact than the grounding of SSTs or the banning of CFCs from use in aerosol spray cans.

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    Can agricultural fertilizers help the ozone layer?
    3 years ago

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