钟理环境工程专业英语unit5

Unit 5 Chemistry of the Atmosphere

Introduction to Chemistry of the Atmosphere

The thin gaseous envelope that surrounds our planet is integral to the maintenance of life on earth.

环绕我们星球的薄气层是地球上维持生命所不可或缺的。

The composition of the atmosphere is predominately determined by biological processes acting in concert with physical and chemical change.

大气的组成主要是由与物理和化学变化协同作用的生物过程决定的。

Though the concentrations of the major atmospheric constituents oxygen and nitrogen remain the same,the concentration of trace species, which are key to many atmospheric processes are changing.

虽然大气中主要成分氧和氮的浓度保持不变，但对许多大气过程起关键作用的微量物种的浓度正在发生变化。

It is becoming apparent that man's activities are beginning to change the composition of the atmosphere over range of scales, leading to, for example, increased acid deposition, local and regional ozone episodes, stratospheric ozone loss and potentially climate changem. In this part.

越来越明显的是，人类的活动开始在一定范围内改变大气的组成，例如，导致酸沉降增加、局部和区域臭氧事件、平流层臭氧损失和潜在的气候变化。在这部分。

We will look at the fundamental chemistry of the atmosphere derived from observations and their rationalization.

我们将通过观测和合理化推算出大气的基本化学。。

In order to understand the chemistry of the atmosphere we need to be able to map the different regions of the atmosphere.

为了理解大气的化学，我们需要能够绘制大气的不同区域。

The atmosphere can be conveniently classified into a number of different regions which are distinguished by different characteristics of the dynamical motions of the air.

大气可以地划分为若干不同的区域，这些区域是根据空气动力运动的不同特征来区分的。

The lowest region. from the earth's surface to the tropopause at height of 10-15 km. is termed the troposphere.

大气层最低的区域是从地球表面到高度10-15公里，被称为对流层。

The troposphere is the region of active weather systems which determine the climate at the surface of the earth.

对流层是活动天气系统的区域，它决定了地球表面的气候。

The part of the troposphere at he earth's surface. the planetary boundary layer, is that which is influenced on a daily basis by the underlying surface.

地球表面对流层的一部分，也称之为行星边界层，是指每天受下垫面影响的边界层。

Above the troposphere lies the stratosphere, a quiescent region of the atmosphere where vertical transport of material is slow and radiative transfer of energy dominates.

对流层的上方是平流层，这是一个静止的大气区域，在那里物质的垂直传输是缓慢的，能量的辐射传输占主导地位。 对流层上方的

In this region lies the ozone layer which has an important property of absorbing ultraviolet ( UV) radiation from the sun, which would otherwise be harmful to life on

earth.

这一地区的臭氧层具有吸收太阳紫外线(UV)辐射的重要特性，否则会对地球上的生命有害。

The stratopause at approximately 50 km altitude marks the boundary between the stratosphere and the meso-sphere, which extends upwards to the mesopause at approximately 90 km altitude. The mesosphere is region of large temperature extremes and strong turbulent motion in the atmos-phere over large spatial scales.

海拔约50公里的层顶标志着平流层与中球的边界，在90公里的高度向上延伸到中高层。在大的空间尺度上，中间层是大温度极值区和大尺度大气中强湍流运动的区域。

Above the mesopause is a region characterized by a rapid rise in temperature, known as the thermosphere. In the thermosphere, the atmospheric gases, N2 and O2, are dissociated to a significant extent into atoms so the mean molecular mass of the atmospheric species falls.

在中间层以上是一个以温度迅速上升为特征的区域，被称为热层。在热层中，大气中的气体N2和O2在很大程度上被分解成原子，因此大气物种的平均分子质量下降。

The pressure is low and thermal energies are significantly departed from the Boltzmann equilibrium.

这一区域压力较低，热能明显偏离玻耳兹曼平衡。

Above 160 km gravitational separation of the constituents becomes significant and atomic hydrogen atoms, the lightest natural species, moves to the top of the atmosphere. The other characteristic of the atmosphere from mesosphere upwards is that above 60 km, ionisation is important. This region is called the ionosphere.

超过160公里重力分离的成分变得特别重要，原子氢原子，最轻的自然物种，移动到大气顶部。这一区域另一个特征是在60公里以上，电离很重要。这一区域称之为电离层。

It is subdivided into three regimes, the D, E and F region, characterized by the types of dominant photo ionisation.

它被细分为三个区，即D区、E区和F区，其特征是主要的光电离类型。

With respect to atmospheric chemistry, though there is a great deal of interesting chem-istry taking place higher up in the atmosphere, we shall focus in the main on the chemistry of the troposphere and stratosphere.

关于大气化学，虽然大气中有许多有趣的化学现象，主要集中于对流层和平流层。

Sources of trace gases in the atmosphere

As previously described, the troposphere is the lowest region of the atmosphere extending from the earth ’ s surface to the tropopause at 10-18 km.

如前所述，对流层是从地球的表面延伸到对流层顶的最低区域，在10-18公里处。

About 90 % of the total atmospheric mass resides in the troposphere and the greater part of the trace gas burden is found there.

约占大气总质量的90%存在于对流层中，其中大部分痕量气体存在于对流层中。

The troposphere is well mixed and its bulk composition is 78 % N2 , 21 % O2 , 1 % Ar and 0. 036 % CO2 with varying amounts of water vapor depending on temperature and altitude.

对流层混合良好，其体积组成为78%N2，21%O2，1%Ar和0.036%的二氧化碳与取决于温度和海拔不同数量的水蒸气。

The majority of the trace species found in the atmosphere is emitted into the troposphere from the surface and are subject to a complex series of chemical and physical transformations.

大气中发现的大多数痕量物种从表面发射到对流层，并受到一系列复杂的化学和物理变化的影响。

Trace species emitted directly into the atmosphere are termed to have primary sources, e.

g. trace gases such as SO2 , NO and CO.

痕量物种被称为主要来源，痕量气体如SO2、NO和CO。 直接排放到大气中的。 Those trace species formed as a product of chemical and/ or physical transformation of primary pollutants in the atmosphere, e.g. ozone, are referred to as having secondary sources or being secondary species.

这些痕量物种是大气中初级污染物(如臭氧)化学和(或)物理转化的产物，被称为有次级来源或次级物种。

Emissions into the atmosphere are often broken down into broad categories of anthropo genic or “mass-made sources” and biogenic or natural sources with some gases also having geogenic sources.

排放到大气中的气体通常分为人类源或“大量制造的源”和生物或自然源，一些气体也有地质源。

For the individual emission of a primary pollutant there are a number of factors that need to be taken into account in order to estimate the emission strength, these include the range and type of sources and the spatio-and temporal-distribution of the sources.

对于单个主要污染物的排放，为了估计排放强度，需要考虑许多因素，其中包括源的范围和类型以及源的时空分布。

Often these factors are compiled into the so called emission inventories that combine the rate of emission of various sources with the number and type of each source and the time over which the emissions occur.

这些因素通常被汇编成所谓的排放清单，该清单将各种源的排放率与每个源的数量和类型以及排放发生的时间结合起来。

It is clear from the data obtained, for example, SO2 has strong sources from public power generation whereas ammonia has strong sources from agri culture.

从所获得的数据可以清楚地看出，二氧化硫有很强的来源于公共发电，而氨则有很强的来源于农业养殖。

In essence, it has been apportioned spatially according to magnitude of each source category ( e. g. road transport, combustion in energy production and transformation, sol-vent use) .

从本质上讲，它是根据每个污染源类别的大小进行空间分配的。比如说道路运输，燃烧在能源的生产和转化，溶胶的使用。

For example, the major road routes are clearly visible, showing N02 has a major automotive source. It is possible to scale the budgets of many trace gases to a global scale.

例如，主要的道路路线是明显可见的，显示NO2有一个主要的汽车来源。将许多微量气体的预算规模扩大到全球范围是可能的。

It is worth noting that there are a number of sources that do not occur within the bound ary layer ( the decoupled lowest layer of the troposphere), such as lightning production of nitrogen oxides and a range of pollutants emitted from the combustion-taking place in aircraft engines

值得注意的是，在约束层(对流层中解耦的最低层)中有一些源是不存在的，例如闪电产生氮氧化物，以及飞机发动机燃烧产生的一系列污染物。

The non-surface sources often have a different chemical impact owing to their di rect injection into the free troposphere ( the part of the troposphere that overlays the bounda-ry layer)

非表面源由于其直接注入自由对流层(对流层覆盖边界层的部分)，通常会产生不同的化学影响。

In summary, there are a range of trace species present in the atmosphere with a myriad of sources varying both spatially and temporally.

总之，大气中存在着一系列的微量物种，各种来源在空间和时间上都有变化。

It is the chemistry of the atmosphere that acts to transform the primary pollutants into simpler chemical species.

正是大气的化学作用将主要污染物转化为简单的化学物种。

Initiation of photochemistry by light

Photodissociation of atmospheric molecules by solar radiation plays a fundamental role in the chemistry of the atmosphere.

太阳辐射对大气分子的光解作用在大气化学中起着至关重要的作用。.

The photodissociation of trace species such as ozone and formal-dehyde contributes to their removal from the atmosphere, but probably the most important role played by these photoprocesses is the generation of highly reactive atoms and radicals.

臭氧和甲醛等痕量物质的光解离有助于它们从大气中的去除，但这些光解过程最重要的作用可能是产生高活性的原子和自由基。

Photodissociation of trace species and the subsequent reaction of the photoproducts with other molecules is the prime initiator and driver for the bulk of atmospheric chemistry 痕量物种的光解离和光产物与其他分子的反应是大气化学物质的主要引发和驱动因素。