1.  Impacts of International Shipping - NOx and Tropospheric Ozone
國際海運對氮氧化物及對流層臭氧的影響

1.1. Introduction
介紹

Although NOx and ozone are local and regional air pollutants that also produce global climate change, the local and regional air-pollution problem is quite different from the global climate-change problem.  The first part of this chapter describes the differences between the air-quality concerns and the global climate concerns surrounding NOx and ozone.  The remaining sections focus entirely on the global effects.
雖然氮氧化物和臭氧是當地和區域空氣污染物，也會產生全球氣候變化，全球氣候變化問題的地方和區域空氣污染問題是完全不同的。

1.2. Local and Regional Effects of Ozone
臭氧對局部和區域的影響

Unlike most traditional air pollutants, ozone (O3) is not emitted directly into the atmosphere.
Instead, it is formed in the atmosphere through a series of complex photochemical reactions.
Thus, it is referred to as a secondary pollutant, as opposed to a primary pollutant that is directly emitted.  In the troposphere, ozone is formed through reactions of volatile organic carbon (VOCs) and NOX in the presence of sunlight. However, this simple description belies the complex chemistry that is actually involved.  Ozone is only formed via the photolysis of nitrogen dioxide (NO2). Instead of actually playing a molecular role in the chemical reaction that directly forms ozone, the presence of VOCs affect the efficiency with which NOX forms ozone.
與大多數傳統的空氣污染物相比，臭氧（O3）沒有直接排放到大氣中。相反，它是通過一系列復雜的光化學反應，在大氣中形成。因此，它被稱為作為二次污染物，而不是直接排放到主污染物。

VOCs affect the formation of ozone through a chain of oxidation reactions. These chain reactions consume VOCs while recycling NO to NO2, which is then available to produce more ozone. In many areas, there may be hundreds of different species of VOCs as a result of pollution or naturally occurring processes (e.g., from forests   http://ukthesis.org/ygsslwdx/  ).  Each of these species follows a different reaction pathway at a different rate and produces different products. VOC species that have been observed in ambient air can be divided roughly into three equally sized groups: For one third, including the simplest organic compounds, the reaction pathways, rates, and products are well characterised. For the second third, the reaction pathways and products are known, but the rates and product yields are not. For the last third, including most aromatic compounds, scientists can only make educated guesses as to the reaction pathways, rates, and products, although research continues to make progress in this area.#p#分頁標題#e#
對于三分之一，包括簡單的有機化合物，反應途徑，價格，和產品是很好的特點。對于第三分之二部分，反應途徑和產品是已知的，但比率和產品收率都沒有。最后的三分之一，其中大多數是芳香族化合物，科學家們只能猜測反應途徑，比率和產品，在這方面研究會繼續取得進展。

The formation of ozone via the photolysis of NO2 competes with the formation of nitric acid, peroxyacetylnitrate (PAN), and other organic nitrates, which eventually remove nitrogen from the ozone-formation cycle.  Ozone is also eventually removed from the troposphere by photolysis, reaction with NO or VOCs, or surface deposition. Thus, the formation of ozone is dependent on the fate of NOX, which is in turn dependent on the quantity and composition of the VOCs present.
因此，臭氧的形成取決于氮氧化物的命運，反過來又依賴于在場的揮發性有機化合物的數量和組成部分。

The relationship between ozone formation and the initial concentrations of NOX and VOCs is highly nonlinear and varies during the year. An ozone isopleth diagram, such as Figure 4.1, best describes this relationship.  Initial concentrations of NOX are plotted along the vertical axis and initial concentrations of VOCs are plotted along the horizontal axis.  The series of curves show different maximum ozone concentrations associated with each combination of NOX and VOC.
該系列曲線顯示不同的最大臭氧濃度的氮氧化物和揮發性每個有機化合物組合。

For example, at Point A in Figure 4.1, ozone formation is VOC-sensitive; a change in VOC will significantly change the ozone level.  However, the opposite is true at Point B, which is NOx -sensitive. It is important to realize that these diagrams differ for each location in the atmosphere and vary with meteorological conditions and changes in the distribution and composition of emissions.  Thus, the control recommendations that are inferred from such a diagram are only valid for the conditions under which the diagram was constructed.
因此，從這樣一個圖推斷控制，建議僅適用于在何種條件下構造圖表。

Figure 4.2 shows that, in general, ozone formation in marine regions is more sensitive to the presence of NOx than of VOCs (NOx-sensitive).  The implication that ocean regions are not
VOC-sensitive is illustrated by the fact that increasing VOCs by a factor of ten while holding NOx  relatively constant (moving from the “marine box” to the “remote tropical forest” box) does not change the typical concentrations of ozone.  However, urban regions with the same VOCs as the remote tropical forest regions but increased NOx concentrations show significantly higher concentrations of tropospheric ozone (see Figure 4.2).  It appears that the naturally-occurring VOC concentrations over ocean regions may be sufficient to react with additional NOx concentrations in shipping lanes to produce higher ozone concentrations in those regions.  As discussed in 4.2.2 and in Appendix A2, this appears to be confirmed by model predictions of nitrogen and tropospheric ozone concentrations attributable to international shipping.#p#分頁標題#e#
與額外的NOx濃度相比，天然存在的揮發性有機化合物的濃度超過海洋區域可能是足夠的反應。在出貨通道，這些區域產生較高的臭氧濃度。正如在4.2.2和附錄A2，這似乎證實模型預測是由于國際航運氮和對流層臭氧濃度引起的。

While stratospheric ozone protects the surface of the earth from harmful ultraviolet radiation, tropospheric ozone is a powerful oxidant that damages human lung tissue, vegetation, and other materials.
Short-term exposures (1 hr to 8 hr) to high concentrations can cause a range of acute adverse human health effects from irritation and shortness of breath to decreased immune functions and increased inflammation and permeability of lung tissue.  Young children, the elderly, and individuals with preexisting respiratory disease are at particular risk of serious acute adverse effects from ozone exposure.  The chronic human health effects of ozone exposure are less well known, but there is the possibility of irreversible morphological changes of the lung, genotoxicity, and carcinogenicity.
年幼的孩子，老人，與原有的呼吸系統疾病的個人，有臭氧暴露嚴重的急性不良影響的特定風險。臭氧暴露的慢性人體健康的影響，是眾所周知的，但有肺癌，遺傳毒性，致癌性的不可逆的形態學變化的可能性。

Figure 4.1. An idealised example of the relationship between ozone and its precursors [Keating and Farrell,1999]
Figure 4.2.  Ranges of VOC, NOx and ozone concentrations in the atmospheric boundary layer for four regions of the atmosphere [National Research Council, 1991], with placeholder box for ozone in shipping lanes produced from NOx from ships.

The adverse effects of ozone exposure on vegetation include leaf yellowing, premature senescence, reduced growth, and increased susceptibility to pests and other risks.  These effects occur with agricultural crops and other vegetation.  While the magnitude of the concentration is often more important than the duration of exposure for human health effects, both are important with respect to impacts on plants.  A variety of metrics has been proposed for measuring ozone exposures to plants. Most involve counting the number of hours that exceed a threshold concentration during summer daylight (concentration hours).  Exposure to ozone also leads to the oxidation and deterioration of many important materials including paint, textiles, rubber, and plastics.
臭氧對植被的不利影響，包括葉片黃化，早衰，降低了增長，害蟲及增加其他風險的敏感性。這些影響發生在農作物和其他植物。

These concerns were the primary motivation for domestic and international (e.g., transboundary) policy attention on NOx and ozone.  In fact, the realisation that NOx from ships contributed significantly to air quality problems in regions with heavy ship traffic motivated action at IMO that resulted in MEPC Annex VI.#p#分頁標題#e#
這些擔憂是氮氧化物和臭氧（如，跨界）國內和國際的政策關注的主要動機。事實上，實現NOx的船舶貢獻顯著的地區的空氣質量問題與沉重的船舶交通動機的行動，在國際海事組織在MEPC附件VI。