4.particle.matter.10

4.particle.matter.10 - Particulate Matter in the...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Particulate Matter in the Environment Introduction Atmospheric Aerosols Properties and Environmental Behavior Aquatic Matter Properties and Environmental Behavior Summary and Conclusions II. Atmospheric Aerosols Definition: Aerosol is a suspension of tiny solid or liquid particles in gas. (Commonly refer to the particulate component only) Aerosols = Particles = Particulate Matter (PM) Size: 2 nm < diameter < 20 m Fine particles = dp<2.5 m Shape: spherical & irregular Concentration: 102 ~ 105 #/cc <1 ~ 100+ g m-3 Phase: solid, liquid, or complex Composition: highly variable PM Sizes (aerodynamic diameter) Nanoparticles 0.01 m (10 nm) or smaller Ultrafine particles 0.1 m (100 nm) or smaller PM2.5 2.5 m or smaller PM10 10 m or smaller Fine vs. coarse particle Atmospheric Aerosol Composition 2003 NARSTO Assessment s H2O H2O Typical composition : Soil erosion, dust: metals/crustal materials. Sea-salt: Na, Cl Fossil fuel / biomass combustion: Black carbon Secondary inorganics: Sulfate, nitrate, ammonium Organics: a complex mixture of many individual organic compounds H2O Fine Aerosol Composition Org SO42- NO3- NH4+ Zhang et al., Geophys. Res. Lett., 34, L13801, 2007. Why do we care about aerosols? Visibility reduction: Visibility definition: "the farthest distance one can see a large black object against the background sky." Influencing factors: aerosol loading, size, RH Economical concerns (tourism) 2.5 -3 2.5 -3 Pittsburgh, USA July 2, 2001 July 18, 2001 7/25/08 1 -3 Beijing, China 8/31/08 1 -3 Influence of aerosol on clouds Ships burn high-sulfur fuel sulfate aerosols (CCN) clouds Satellite image of ship track over the ocean Effects of Aerosol on Climate Global-Mean Radiative Forcing (RF); Pre-industrial to present Direct scattering effect: Absorb and scatter solar radiation and outgoing IR radiation Indirect cloud effect: Act as CCN (cloud condensation nuclei), affecting cloud formation and properties Aerosols are counteracting the warming effects from green house gases LARGEST sources of uncertainty in assessment of anthropogenic climate change Effects of Aerosol on Health Global Estimates of Deaths Attributable to Urban PM, 2006 Total: 777,000 WHO Subregions based on latitude Epidemiological evidence: affect cardiorespiratory system, cause cancer, impair lung development of children More deadly than car accidents (est. kills ~ 60,000 people / year in US) Toxicological Significance Aerosols >1 u dia. are filtered out in upper respiratory tract (nasal passages, trachea, bronchial region). Aerosols <1 u dia. penetrate into the alveolar region, where they can cause: Pulmonary edema Pneumoconioses (various forms of fibrosis) 2003 NARSTO Assessment Atmospheric Aerosols Lifecycle Sources (emission & formation) Transformation Transport Removal Chemical Sources of atmospheric aerosol: EMISSIONS Primary PM REACTIONS Secondary PM Transport Physical Transformations Condensation Evaporation Coagulation Transformations Aqueous Photochemical Heterogeneous Aerosols (PM) Wet , Dry Deposition Wet deposition = deposition via precipitation. Dry deposition = settling due to sedimentation or impaction with surfaces (e.g. mountains). Atmospheric Aerosols Sources Classes (Based on Sources) Primary Sources Secondary Sources (typically from oxidation of gaseous precursors) Soil Dust (coarse particles) Sea Salt (coarse particles) Sulfate (fine particles) Carbonaceous or Organic (fine particles) Major Classes (Based on Composition) Note: particle "aging" and physical processes make distinction of particle classes more difficult Factors that affect Aerosol Lifecycle Aerosol properties control its atmospheric lifetime size (surface area/volume) and composition Availability of forms of environmental energy: Thermals rising warm air (bare soil, asphalt, etc.). Updrafts where winds are forced upward (cliffs, mountains, etc.). III. Aquatic Matter Suspended sediments: mineral and organic > 0.01 u dia. Colloids: mineral and organics < 0.01 u dia. Chemical Adsorption Desorption Adsorption Influences Bioavailability Bioavailability = degree to which a chemical is free to be absorbed by an organism (freely dissolved, not adsorbed fractions. Toxicity tests are often run in using filtered water. Question: a chemical has a measured LC50 = 5 ppm for pesticide X in trout. You sample a local lake and measure pesticide X in the water at 10 ppm, yet the lake has a healthy trout population. Why?? Sediments and Suspended Particles Stability depends on particle density and diameter. Stability also depends on thermals, currents and bubbles. They can dissolve, aggregate, or be ingested. Colloids Consist of minerals, organic macromolecules or small organisms (algae, microbes). Three types hydrophilic, hydrophobic and association. Aggregation reduces stability (ability to remain suspended). Surface hydration (water layer) and like charge will repel (most are -), increasing stability. Hydrophilic Colloids Organic macromolecules (amino acids, proteins, polymers). Strongly interact with water polymer via Hbonding, water layer (surface hydration) prevents aggregation. Not subject to "salting out." Hydrophobic Colloids Small clays or oil drops possessing negative or positive charges and surrounded (neutralized) by counter ions. Stable (do not aggregate) due to electrostatic repulsion of charged bilayer (like charges). Coagulate with more ions to form bridges ("salting out"). Hydrophobic Colloid Aggregation Coagulation = reduction of electrostatic repulsion via addition of excess salts ("salting out"). Causes sediment deposition in estuaries to form deltas. Flocculation = "bridging" compounds form chemically-bonded links between similar colloids to form large floc networks. Colloid Aggregation Via Flocculation Hydrophobic colloids bridged by polyelectrolytes and facilitated by counter ions. Negative colloids bridged by anionic polyelectrolytes. Positive colloids bridged by cationic polyelectrolytes. Association Colloids Aggregations of surfactants (soaps, detergents), form micelles with hydrophobic tails inward and hydrophilic heads outward. Can aggregate with themselves or around oil droplets, and attract Na+ counter ions. IV. Summary and Conclusions Atmospheric aerosol characteristics, important parameters (e.g.,: composition, size, shape ... ) Lifecycle depends upon composition and size, as well as environmental energy. Aerosol removal is via wet and/or dry deposition. Aquatic particulates include sediments and colloids. Particulate matter influences chemical bioavailability. Colloids can be hydrophilic, hydrophobic, or ...
View Full Document

This note was uploaded on 06/29/2011 for the course GENETICS 101 taught by Professor Debrakimbrell during the Summer '09 term at UC Davis.

Page1 / 25

4.particle.matter.10 - Particulate Matter in the...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online