Mountain Aroma: A Fragrant Adventure Above The Clouds

The air in mountains has a distinct aroma that feels purer, crisper, and fresher. This aroma is a result of various factors, including the lack of pollution due to lower human habitation and industrial activities, the unique vegetation found in mountainous regions, and the rainfall that cleans the air. The vegetation in mountains releases volatile organic compounds (VOCs) through a process called phytoncide, contributing to the pleasant, woody, and green scents. Additionally, the lower temperatures at high altitudes affect our perception of smell, as cold air carries fewer odor molecules, contributing to the fresh smell. The Aroma Mountain incense burner is a product inspired by the natural beauty of a calm volcano, designed to refine any space with its elegant look and soothing scent.

Lack of pollution

The air in higher altitudes is typically less contaminated by pollutants due to their distance from human habitation and industrial areas. This lack of pollution is a significant factor in the freshness of mountain air.

Mountainous regions are often far removed from urban centres and industrial facilities, which are the primary sources of air pollution. This distance means that the air in these regions is less affected by harmful pollutants, such as those emitted by power plants, factories, and vehicles.

In addition, mountains can sometimes act as barriers to air pollution, trapping pollutants on one side and creating cleaner air on the other. This phenomenon is influenced by various factors, including wind patterns and the physical structure of the mountains. For example, the Great Smoky Mountains in the US have been affected by pollution from outside sources, which has resulted in a whitish haze that obscures the views and damages the environment.

The lack of pollution in mountain air is further enhanced by the presence of dense vegetation, which acts as a natural filter, removing pollutants from the air. This combination of factors contributes to the fresh and pure scent that is often associated with mountain air.

It is important to note that mountains can also have a negative impact on air quality. Under specific conditions, mountains can trap air pollutants, leading to increased concentrations in certain areas. Additionally, mountains can catalyze chemical reactions that contribute to air pollution. However, the overall effect of mountains on air quality is complex and depends on various geographical and meteorological factors.

Vegetation and flora

Mountainous regions are known for their unique flora, which includes pine and cedar forests as well as wildflower meadows. These plants release volatile organic compounds (VOCs) into the air, a process known as 'phytoncide'. Phytoncides are responsible for the pleasant, woody, and green scents we often associate with nature.

Pine and cedar forests are common in the lower slopes of mountains in north temperate regions, such as those found in North America, Europe, and northern Asia. These lower slopes typically feature conifer-dominated forests that give way to alpine vegetation at higher altitudes. Other typical conifers in these regions include firs, spruces, and deciduous larches. In some areas, broad-leaved deciduous trees can also be found, along with a variety of smaller plants, especially in moister spots. For example, mountains in the northern half of Japan that are over 1,400 to 1,500 meters have a subarctic coniferous forest belt, with dominant trees from the genera Abies, Picea, and Larix. Heathers, poppies, and the large carrot relative Oplopanax are some of the other plants that grow in these forests.

In south temperate mountain regions, tree line forests are often dominated by a single type of tree, such as Eucalyptus in Australia or Nothofagus species in New Zealand, Argentina, and Chile. These forests differ from those in north temperate regions, which typically have greater species diversity.

In the tropics, species-diverse forests that can be described as stunted evergreen rainforests typically grow up to the uppermost limits of tree growth. This is the case in New Guinea, Southeast Asia, and East Africa. However, in parts of the tropical Andes, a single species of Polylepis often grows at high altitudes, especially on screes or rock debris at the base of cliffs.

Above the tree line, alpine vegetation includes grasslands, mires, low heathlands, and crevice-occupying vegetation. Treeless alpine vegetation is common on mountains above 2,500 meters in central Japan, descending to 1,400 meters in northern Hokkaido. Japanese stone pine, heathers, and grasses are particularly prominent in these regions. Like most other plants in alpine vegetation, these plants have close relatives in other mountainous, north temperate regions. The prostrate shrubs of the stone pine form dense, low thickets about one meter tall on ridges and are mixed with deciduous shrubs of alder and service tree in moister places.

Other types of alpine communities occupy wet sites, where tall grassy meadows or bog communities are often found alongside abundant tiny primroses. Stunted dwarf shrubs, especially members of the heather family and their relatives, can be found in areas where winter snow is blown from exposed surfaces. In contrast, snowbed communities dominated by heather or sedges are found in places where snow accumulates as deep drifts in sheltered spots, remaining until late spring or summer.

Despite the diverse geographic and ecological contrasts across different mountain regions, it is remarkable that they often exhibit a similar number of plant species in the diverse array of alpine vegetation subtypes. For example, the flora in the alpine vegetation subtypes in Japan and New Guinea both consist of around 200 different plant species. Furthermore, many of the same types of plants are found in most alpine regions, represented by different but related species in each region and on each mountain within those regions. Gentians, plantains, buttercups, and members of the heather, grass, and sedge families are widespread examples.

Rainfall

The fresh scent of mountain air is partly due to rainfall. Mountainous regions are prone to rainfall, which helps to 'clean' the air. After a downpour, the air often smells fresh and pure, thanks to a compound called geosmin, which is released from the wet earth. This scent is known as 'petrichor'.

When air reaches a mountain, it is forced to rise and cool, leading to increased humidity and the formation of clouds and precipitation. As the air moves up the windward side of a mountain, the moisture in the air condenses and falls as rain. This process results in the distinctive aroma associated with mountain regions.

The rain also elicits other smells in the environment, particularly from plants. According to air quality scientist Sahil Bhandari, plants can secrete unique smells when rained on. However, our noses cannot separate these smells, so we end up smelling a mixture of many odours.

In some cases, people can detect the scent of rain even before it starts to rain. Bhandari explains that lightning and thunderstorms produce a lot of ozone, which has a fresh, clean-room smell. This scent can be detected by humans and often signals an upcoming rainfall.

The combination of geosmin, plant scents, and ozone creates the refreshing and invigorating aroma of mountain air after rainfall.

Temperature

The temperature of the air plays a significant role in the aroma of mountains. Lower temperatures at high altitudes affect how we perceive smells. Cold, dense air carries fewer odour molecules than warm air, resulting in scents that appear less intense. This contributes to the clean, fresh smell of mountain air.

The temperature has a direct impact on the volatility of odour molecules. In warmer temperatures, these molecules become more volatile, dispersing more quickly in the air, especially when combined with low humidity. This increased volatility leads to a more intense perception of smells as our olfactory receptors absorb a higher concentration of fragrance molecules.

Conversely, cold temperatures can cause temporary nasal congestion, reducing airflow and potentially impairing our sense of smell. Similarly, very hot weather can dry out the nasal passages, also affecting our olfactory perception.

The temperature and humidity work together to influence the movement and availability of odour molecules in the air. In high humidity, the air becomes more saturated with water vapour, causing odour molecules to mix and spread less. This results in fragrances that are less intense and less perceptible.

However, in high-humidity environments, odour molecules can linger in the air for longer, collecting in certain areas and potentially increasing olfactory perception. The vapour pressure of the odorant is influenced by temperature and humidity, affecting the rate of evaporation. Higher humidity reduces the volatility of certain compounds, making them less likely to evaporate and reach our olfactory receptors, thereby reducing the intensity of certain odours.

The interplay between temperature, humidity, and other atmospheric factors creates the unique aroma of mountains, contributing to the overall sensory experience of being in such environments.

Petrichor

The phenomenon was first scientifically described in a 1964 paper by Australian researchers Isabel Bear and Dick Thomas, who coined the term "petrichor" to refer to what had previously been known as "argillaceous odour". They found that the scent is derived from an oil exuded by certain plants during dry periods, which is then absorbed by clay-based soils and rocks. When it rains, the oil is released into the air along with another compound, geosmin, which is emitted by wet soil and produces the distinctive earthy scent.

The intensity of the petrichor smell can vary depending on the type of soil and the heaviness of the rainfall. Lighter rains tend to produce more petrichor, as raindrops that fall slowly produce more aerosols, which carry the scent.

In addition to the oil released by plants and the geosmin emitted by soil, the petrichor scent can also be influenced by the presence of ozone, which may be carried by downdrafts during rainfall, especially if there is lightning.

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