Natural Dusts Flashcards
(22 cards)
What is loess?
Fine sedimentary soil blown by wind, susceptible to erosion
What is the loess plateau?
Located in Northern/mid-China with an area of 640,000km^2
- Was highly fertile area and heavily used for easy farming in ancient times
- Centuries of overuse and overgrazing = one of the highest erosion rates in the world and widespread poverty
What causes desertification?
- Overgrazing by sheep, goats, and other livestock
- Cutting down trees or other vegetation
What are some methods of ecological rehabilitation at the loess plateau?
- Terrace side of ravines
- Fish scales terraces for single trees
- Introduce trees (fruit trees)
- Dune/soil stabilization with grasses, bushes
- Feed livestock in pens rather than herding
- Warping dams to create rich fertile fields in valleys (dams to capture sediment so it accumulates and can’t leave the area)
Why is it important that local people be involved in rehabilitating the land?
- Sense of shared responsibility, stewardship
- Paid for rehabilitation work
- Personal achievement and pride
- Sustainability/maintenance
China has about 22% of the world’s population, but only about
7% of it is arable land
Restoration of the loess plateau
- Occurred over an area of ~35,000km^2 (~5% total area of plateau)
- Results have reduced the massive silt loads to the Yellow River by ~1%
Where does the loess come from?
Alluvial fans in mountainous regions nearby
Dust sources (deserts) are transported and deposited by
monsoon and surface winds
Why is so much dust formed here?
- Highest known uplift rates in the world in the Himalayas
- Rapid river incision and therefore sediment production
- Unstable slopes
- Glaciation
- Erosion from freeze-thaw fracturing
- High Asia is the world’s most efficient producer of silty sediment (2-63um)
What minerals is loess composed of?
- Quartz grains (60%)
- Feldspar
- Mica
- Carbonate
How thick are loess deposits?
Up to 500m
What are some physical characteristics of loess?
- Low density
- Soft
- High porosity
- Easily erodible
- Collapse when wet
Dust particles in the body
- Smaller than 1um = absorbed into bloodstream
- Smaller than 10um = trapped in the lungs
- Size of dust on the loess plateau is mainly 5-15um
- Particles less than 100um can be inhaled into nose/mouth, but get trapped in upper airways
- Only the smallest particles (<10um) can reach the alveoli, where they contribute to the risk of disease
Most countries have an Occupational Exposure Limit Values (OELV) of
0.1mg/m^3, over an 8hr avg for respiratory crystalline silica (<10um)
Dust measurements during storms
- 4.2mg/m^3 (outdoor)
- 20mg/m^3 indoor
- But this doesn’t report the % of dust that was in the respirable fraction
Silicosis prevance of
1.03%, rising to 10% in ppl over 70
- Silicosis may be public health problem in North China, but there is an absence of stats on morbidity lvls in this region
Silicosis
- Slow to develop
- Occurs when respiratory crystalline silica embeds into alveolar sacs, causing inflammation and scarring (nodular lesion in the lungs)
Signs and Symptoms of Silicosis
- Dyspnea (shortness of breath) exacerbated by exertion
- Cough, often persistent and sometimes severe
- Fatigue
- Tachypnea (rapid breathing) which is often labored
- Loss of appetite and weight loss
- Chest pain
- Fever
- Gradual darkening of skin (blue skin)
Al Eskan Disease
- Lung disorder thought to be caused by exposure to v fine sand dust
- Resulted in immunosuppression that could be aggravated by opportunistic infections
Valley Fever
- Caused by fungus, C. immitis, that lives in desert soils of SW USA
- Dormant during long dry spells
- Develops as a mold with filaments that break off into airborne spores when it rains
- Spores swept into air by disruption of soil
- Infections usually occur due to inhalation of the spores after soil disruption
Symptoms of Valley Fever
- Profound feeling of tiredness
- Fever
- Cough
- Headaches
- Rash
- Muscle pain
- Joint pain
