Damaging Air Pollution

Introduction

A survey of the available literature shows just how damaging air pollution can be to the flora and fauna that inhabit the natural world. The leading pollutants include tropospheric ozone and carbon monoxide from automobile exhaust, the burning of diesel fuel in combustion engines and coal ash from electric power plants that creates particulate matter, and nitrogen dioxide from agricultural manure and fertilizers as well as the combustion of fossil fuels. These airborne pollutants can eventually fall out of the atmosphere and deposit onto the land and bodies of water. The uptake, inhalation or consumption of these pollutants can be harmful to many plant and animal species such as the birch, pine, and maple trees of the temperate forest, the mice, birds, and fish of the urban ecosystem, and the fish, insects, and crayfish of the aquatic ecosystem. The role of air pollution in biodiversity, local habitat modification, and climate change are also examined.

A survey of the world's biomes

Several of the Earth's biomes will be referred to in the pages to come. It is therefore important to have an understanding of the biomes as it pertains to what makes a biome and why they are where they are. Climate, topography, and soil - and parallel influences in aquatic environments- determine the changing character of plant and animal life over the surface of Earth. Although no two locations harbor exactly the same assemblage of species, we can group biological communities in categories based on their dominant plant forms, which give communities their overall character. These categories are referred to as biomes (Ricklefs 99).

Contributions of Heinrich Walter

German ecologist Heinrich Walter devised a terrestrial classification system which he termed ?climate zones'. These zones were broken down by annual precipitation and temperature trends across the globe. He was careful to note signature plant and or animal traits that seemed to occupy these zones (Ricklefs).

Contributions of Robert H. Whitaker

Robert H. Whitaker, an ecologist from Cornell University, would devise his own classification system with a slight twist. He first established the vegetative structure of biome, then developed a diagram on which he plotted the annual precipitation and temperature norms. It should be noted that in the intermediaries between forest and desert, he took into account soil type, seasonal climate patterns, and fire to determine woodlands, shrublands, and grassland locations (Ricklefs).

Courtesy of The Economy of Nature by Robert E. Ricklefs

It is important to note the following when it comes to the animals and plants that share a biome: (1) animals and plants adapt to match their environments, (2) some fauna and flora overlap at the boundaries between neighboring biomes in response to local climate feedback loops, (3) while climate is the key factor in determining plant distribution, soil types and changes in topography are also influences, and (4) aquatic biomes are classified by salinity, water flow rate and water depth rather than temperature, precipitation and vegetation structure (Ricklefs).

A biome map of the world courtesy of The Economy of Nature by Robert E. Ricklefs.

The demarcations more or less follow Heinrich Walter's biome structure. Walter noted the boreal and polar zones have annual average temperatures below 5, the temperate regions experience annual average temperatures between 5 and 20(central Ohio is located in the Temperate seasonal forest), and the tropical and equatorial biomes exceed 20 as an annual average temperature.

Nitrogen Dioxide (NO2 or Nitrite) Pollution In the aquatic ecosystem

The three major pollutants of freshwater ecosystems are sulfur dioxide (SO2), nitrogen oxide (NO), and nitrogen dioxide (NO2). The most common non-point sources of airborne NO2 pollution are the volatilization of manure and fertilizers and the combustion of fossil fuels. Airborne NO2 can enter the aquatic ecosystem by depositing on lakes, streams, and rivers. If introduced, nitrite can exhibit lethal toxicity of fish and invertebrates in doses of 3 mg NO2-N/L in a 96-hour exposure time (Camargo and Alonzo, 2006). This is mainly achieved by rendering oxygen-carrying cells incapable of transporting oxygen. This results in hypoxia and death in fish and crayfish. Nitrite can also be toxic in the following ways: reduction of Cl- ions in and outside of cells causing an imbalance of electrolytes, reduced function of cardiac and skeletal muscles and decreased neurotransmission from imbalance of K+ , formation of mutagenic and carcinogenic N-nitroso compounds, acute damage to mitochondria in liver cells contributing to free oxygen shortage in the tissue, and a compromised immune system leading to increased susceptibility to parasites and infections diseases (Camargo and Alonzo, 2006).

Nitrite can, through chemical reactions with other materials in the water, produce compounds that have lasting, disruptive effects. Nitrite lowers the pH of lakes and streams making them more acidic. According to Bobbink et al., fresh waters are among the most sensitive ecosystems with respect to atmospheric acidification (1998, p.718). Acidification of water that has low turnover rates, specifically lakes, can upset the delicate balance of nutrient cycles (and therefore food chain) required for the ecosystem to function properly. Low pH can also encourage the development of toxic algae which starves the other organisms of dissolved oxygen in a process called eutrophication. With low availability of food and oxygen, reproductive rates of aquatic animals suffer. Eutrophication reduces water clarity and light availability which can negatively impact photosynthesis rates in aquatic plant life (Hernandez et al., 2016). According to Camargo and Alonzo, Anthropogenic discharges containing elevated nitrite concentrations have been associated with fish kills in aquatic ecosystems (Camargo and Alonzo, 2006, p. 840).

The US Fish and Wildlife Service (FWS) lists vertebrate species impacted by reactive nitrogen. In the FWS Great Lakes Big River region there are five (5) such species. The Jollyville plateau salamander and the Smalleye shiner are listed as ?potentially endangered' due to direct toxicity or lethal effects of N and eutrophication causing algal blooms that alter habitat by covering up substrate, respectively. The other three (3) species are listed as ?threatened' by the FWS: the Arkansas River shiner and the Neosho Madtom for eutrophication lowering dissolved oxygen levels, and the Desert Tortoise (Sonoran population) for N pollution increasing non-native plant species that kill off the tortoise's food sources (Hernandez et al., 2016).

In species-rich grasslands

Some nitrogen deposition studies have been conducted in western and central Europe concerning pH neutral grasslands which are moist to semi arid (Bobbink et al., 1998). This biome type tends to have soil that is nitrogen-poor hence the need for fertilization. In the UK, the Park Grass experiment has been ongoing since 1856 (Williams, 1978 and Dodd et al., 1994 as cited by Bobbink et al., 1998). Enrichment of nitrogen as sodium nitrate fertilizer is applied to select plots of neutral grassland in the amount of 48 kg N per hectare per year. This has resulted in a population explosion of a few, nitrophilic grasses such as the Meadow foxtail grass (Alopecurus pratensis) and Tall oat-grass (Arrhenatherum elatius). These have crowded out the abundance of smaller, more regular perennials (Bobbink et al., 1998). Additional land management is necessary to reintroduce and maintain biodiversity.

In forest ground vegetation

Drastic changes in ground flora have been noted in many studies over the years due to acidification of nutrient-poor soil by airborne nitrogen deposition. In their 1989 study of a central Netherlands forest, Dirkse & Van Dobben observed a disappearance of all lichen species when nitrogen deposition increased from around 20 kg N per hectare per year in 1958 to near 40 kg N per hectare per year by 1981 (Bobbink et al., 1998). In a semi-natural forest in northeastern France, a large increase in nitrophilic plants was observed on 50 permanent vegetation plots when nitrogen deposition of 15-20 kg N per hectare per year raised soil pH to 6.9 (Thimonier et al., 1994).
Coniferous forests have also been impacted by increased nitrogen inputs. The shoot density of Wavy hair-grass (D. flexousa) showed significant increase in a central Sweden coniferous forest where experimental ammonium nitrate enrichment reached 10 kg N per hectare per year (Kellner & Redbo-Torstensson, 1995). This along with similar results in Finland seems to point to decreased biomass of shrubs and mosses that thrive in nutrient-poor areas. Competitive exclusion modifies the local, vegetative landscape to favor grasses and mosses that prosper in nutrient-rich soils. (Bobbink et al., 1998).

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