It is well known that specific pollutants or classes of pollutants have damaging effects on the environment, such as ozone depletion (triatomic oxygen) and global warming, and on our health when pollutants exceed “acceptable” levels. Vineyards are often located in areas with low levels of pollution and are therefore not of great concern. This does not mean that contamination should be ignored; however, limited research has been done on the impact of pollution on vineyards. It is a very complex research area. Let’s examine the chemistry of pollutants and their impact on vine growing specifically.
Earth’s atmosphere includes several gases, primarily diatomic nitrogen and oxygen, as well as carbon dioxide and water vapor. And every second of every day, pollutants from car emissions, landfills and industrial processes are released into the atmosphere and react with their components. The main pollutants are sulfur oxides, carbon dioxide, nitrogen oxides, chlorofluorocarbons (CFCs) and, when they reach the atmosphere, they react with sunlight and atmospheric (diatomic) oxygen to form harmful substances.
Sulfur dioxide is known to have harmful effects on plants when in high concentrations; It is the result of the oxidation of elemental sulfur, as in the processes of burning coal. It also reacts with atmospheric oxygen to form sulfur trioxide, which then reacts with water vapor to form sulfuric acid in acid rain. A second component of acid rain is carbonic acid, formed in a similar reaction from emitted carbon dioxide. And the most damaging component is hydrofluoric acid, formed from hydrogen fluoride, released from smelting operations and the production of phosphorous fertilizers, and water vapor in the atmosphere. When acid rain hits the vineyard soil, it lowers the pH, unbalancing soil chemistry and making it difficult to grow premium quality grapes. Some of these acids are particularly corrosive and toxic and harmful to vine growing.
Nitrogen oxide is found in automobile exhaust gases and is the result of nitrogen (diatomic) combustion at high temperatures. In the atmosphere, nitrogen oxide reacts with molecular oxygen to form nitrogen dioxide, the reddish-brown gas responsible for smog. The nitrogen dioxide is then photochemically converted back to nitrogen oxide along with an oxygen atom. The oxygen radical then reacts with molecular oxygen to form ozone in the lower atmosphere. Ozone is a strong irritant and is harmful to vines and crops.
Car exhaust also releases hydrocarbons that react with nitrogen oxide to form peroxyacetyl nitrate, a compound that belongs to the class of peroxyacyl nitrates, or PAN, powerful toxic irritants found in photochemical smog that cause build-up. ozone. PANs are highly damaging to vine physiology, resulting in reduced yields. And until leaded gasoline (tetraethyl lead) was phased out, wines produced in vineyards located very close to high-traffic roads demonstrated higher levels of lead, a potent neurotoxin responsible for lead poisoning. If lead enters the bloodstream, it can interfere with and deactivate the enzymes delta-aminolevulinic acid dehydratase (ALAD) responsible for producing hemoglobin. Hemoglobin is the iron-containing protein pigment found in vertebrate red blood cells, which functions primarily to transport oxygen from the lungs to body tissues. Lead poisoning can cause irreversible neurological damage, as well as abdominal pain, gastrointestinal problems, headaches, anemia, reproductive problems, and a host of other effects.
Chlorofluorocarbons (CFCs) belong to the class of haloalkanes, that is, alkanes, such as methane or ethane, were understood with halogens, such as chlorine or fluorine, and they are known to have harmful effects associated with the depletion of the ozone. The halogen in CFCs reacts with ozone to form an oxide of the halogen plus molecular oxygen.
Regarding pesticides, it has been clearly shown that, despite environmental impacts, residues in wine are negligible. Of course, this assumes that pesticides are applied correctly and within the recommended treatment period before harvest. And the various winemaking processes, that is, crushing, pressing, fermentation, clarification, filtration and aging, make pesticide residues disappear.
And what about the thick, thick smoke from the devastating wildfires of the summer of 2008 that covered the Northern California wine country? Some red wines from hard-hit areas like Mendocino County have decidedly smoky and charred aromas and flavors of burnt wood and ashen. The compounds responsible for the smoke smell are guaiacol and 4-methylguayacol, volatile phenols that are absorbed into the skin of grapes, especially in fine-skinned varieties, such as Pinot Noir, and are then extracted during maceration and exacerbated by fermentation. . The whites are preserved mainly since there is no maceration of the skin with the must. Much research has been done on smoke-contaminated wines in Australia, where, in 2003, smoke from forest fires also heavily affected vineyards.
Using reverse osmosis and nanofiltration technologies, Australians have been able to reduce culprit compounds to undetectable levels. VA filtration (VAF), a company specializing in services such as volatile acidity removal (VA), Brett (yeast infection), and TCA (corked wine), claims they can now remove up to ninety-nine percent of specific sensory characteristics through treatment of the affected wine. with a food grade resin developed in Germany. Interestingly, if not puzzling, the VAF website states that “the offending compounds being removed have not yet [known]. “
But the astute reader will also know that guaiacol and 4-methylguayacol are compounds found in oak-aged roasted wines, where they are highly desirable. It is quite a dichotomy!