Environmental Engineering Reference
In-Depth Information
Air and Water Quality
Increasing temperatures and changing precipitation intensity can also
affect air and water quality. Densely populated areas with warm summers
tend to have high levels of ozone precursor emissions (nitrogen oxides and
volatile organic compounds). These precursor species react in the presence
of sunlight, with key reactions proceeding faster at higher temperatures.
Ground-level ozone, the primary component of smog, is a respiratory irritant
that decreases lung function and may increase the development of asthma
in children (Tagaris et al., 2009).
In the future, warmer temperatures and changes in atmospheric circu-
lation patterns may bring oppressive summer weather patterns earlier in
the year (see Section 4.4), accelerating the formation rates of tropospheric
ozone and increasing the length of time photochemical smog remains over
any given location. Barring significant decreases in precursor emissions,
tropospheric ozone exceedences could become more common over most
densely populated areas in the United States, China, and elsewhere around
the world with warm summers (Mickley et al., 2004; Tao et al., 2007; Lin
et al., 2008). A study of 50 U.S. cities projected that a 1.6 to 3.2°C increase
in local temperature would lead to an average 4.8 ppb increase in ozone
levels by 2050, with the greatest increases occurring in cities with already
high ozone concentrations (Bell et al., 2007). Ozone levels were projected
to exceed the 8-hour regulatory standard an average of 5.5 more days
per summer, an increase of 68% over current conditions. Although ozone
mortality was projected to increase by 0.11 to 0.27% on average, certain
cities exhibited greater sensitivities (e.g., increases of 5% for New York City;
Knowlton et al., 2008). Given the sensitivity of ozone levels to precursor
emissions, climate effects on ground-level ozone and particulate matter may
depend less on direct temperature effects and more on the effectiveness of
pollution control measures and climate-driven changes in natural emissions
sources (Ebi and McGregor, 2008).
Increasing frequency of heavy downpours is already occuring and is
projected to continue to occur in many parts of the world, including the
eastern United States (Tebaldi et al., 2006; Karl et al., 2009). These increase
the risk of water contamination and spread of water-borne bacterial diseases,
with the risk being exacerbated by rising temperatures (Vorosmarty et al.,
2000). Current and future deficiencies in watershed protection, infrastruc-
ture, and storm drainage systems will likely increase the risk of contamina-
tion events as climate variability increases (Rose et al., 2000).
The length of the pollen season has already increased due to both earlier
onset of flowering (Parmesan, 2007) and lengthening of the season for late-
