TABLE 2-7 Average Annual Input (1990-1999) of Petroleum Hydrocarbons (tonnes) for the Gulf of Mexico and Puerto Rico

ZONE (Coastal)

F

G

H

I

Sum Seepsa

na

na

na

na

Platforms

traceb

90

ndc

na

Atmospheric

trace

trace

ndc

na

Produced

trace

590

trace

na

Sum Extraction

trace

680

tracec

nad

Pipelines

trace

890

trace

trace

Tank vessel

140

770

80

trace

Coastal facilities

10

740

nde

130

Atmospheric

trace

trace

trace

trace

Sum Transportation

160

2400

90

130

Land-based

1600

11000

1600

tracef

Recreational vessels

770

770

ndg

ndg

Vessels >100GT (spills)

30

100

trace

trace

Vessel >100GT (op discharge)

trace

trace

trace

trace

Vessel <100GT (op discharge)

trace

trace

trace

trace

Atmospheric

60

90

100

50

Aircrafth

na

na

na

na

Sum Consumption

2500

12000

1700

50

ZONE (Offshore)

F

G

H

I

Sum Seeps

70000

70000

naa

naa

Platforms

trace

50

61c

na

Atmospheric

trace

60

40

na

Produced

trace

1700

130

na

Sum Extraction

trace

1800

231

nad

Pipelines

trace

60

ndi

na

Tank vessel

10

1500

ndi

490

Atmospheric

trace

trace

trace

trace

Sum Transportation

10

1600

trace

490

Land-basedj

na

na

na

na

Recreational vesselsk

na

na

na

na

Vessels >100GT (spills)

70

120

trace

10

Vessel >100GT (op discharge)

trace

25

trace

trace

Vessel <100GT (op discharge)

trace

trace

trace

trace

Atmospheric

1600

1200

3600

70

Aircraft

80

80

20

20

Sum Consumption

1800

1400

3600

100

Grand Total

74000

91000

5600

790

Sum of Anthropogenic

4400

21000

5600

790

aNo known seeps in these regions

bEstimated loads of less than 10 tonnes per year reported as “trace”

cLack of precise locations for platforms in this zone precluded determining whether spills or other releases occurred less than 3 nmiles from shore (see Chapter 3 and Appendix D). Thus, all values for this zone reported as “offshore.”

dNo known oil and gas production in this region

eNo information on the existence of coastal facilities was available for this region (see Chapter 3 and Appendix G).

fInsufficient water quality data exist to calculate input in this region, but existence of some urban landscape suggests it is a non-zero number (see Chapter 3 and Appendix I).

gPopulations of recreational vessels were not available for these regions (see Chapter 3 and Appendix F)

hPurposeful jettisoning of fuel not allowed within 3 nmiles of land (see Chapter 3 and Appendix E)

iNo information on transportation-related spills was available for this region (see Chapter 3 and Appendixes D, E, and G)

jLand-based inputs are defined in this study as being limited to the coastal zone (see Chapter 3 and Appendix I)

kRecreational vessels are defined in this study as being limited to operations within 3 miles of the coast (see Chapter 3 and Appendix F)1

of magnitude, and the upper limit, if reasonable, would dominate all other inputs. This uncertainty reflects a variety of limitations, including a lack of adequate background data. To refine estimates associated with non-point sources, Federal agencies, especially EPA and the USGS, should work with state and local authorities to routinely collect and share data on the concentration of petroleum hydrocarbons in major river outflows and harbors in storm-and wastewater streams.

The estimates presented here demonstrate the important role of air-sea exchange of hydrocarbons in (1) the persistence of petroleum hydrocarbons in surface waters and (2) the potential degradation of coastal air quality. These estimates are limited both by the lack of detailed field measurements of hydrocarbons in seawater and the coastal atmosphere under a variety of conditions and by the relatively poor knowledge of the fundamental physics of air-sea exchange. Directed research is needed that (1) conducts specific coupled field studies of air-sea interaction and (2) applies these studies to the modeling of petroleum hydrocarbon exchange at regional and global scales. On-going and growing investigations of air-sea exchange of carbon dioxide, conducted to better understand global climate change, provide a significant opportunity to improve the estimates of petroleum hydrocarbon exchange between the atmosphere and the surface ocean.

During 1990-1999, spillage from vessels in U.S. waters was less than 40 percent of that during the prior decade, and it now represents less than 2 percent of the petroleum hydrocarbon inputs into North American waters. Significant reductions in spillage were also realized worldwide. Improvements in vessel operation and design and the introduction of related federal and international regulations contributed to this decline in oil spills. In U.S. marine waters, the largest spills come from vessels, followed by pipelines and facilities. Vessels have produced 109 spills of greater than 34 tonnes (10,000 gallons) in size since 1990, and these larger spills had an average size of about 400 tonnes. During the 1990s, tanker vessels were responsible for about 89 percent of the spillage from vessels. The comprehensive port control regime, administered by the U.S. Coast Guard, cooperative programs with ship owners and the boating community, and active participation of the International Maritime Organization in developing effective international regulatory standards have contributed to the decline in oil spills and operational discharges. These efforts and relationships should be continued and further strengthened where appropriate.

Estimated operational discharges from vessels contribute very significant inputs. More than 99 percent of the estimated volume of operational discharge is related to non-compliance, because existing regulations restrict operational discharges of oil or limit them to not more than 15 ppm. The extent of non-compliance is difficult to assess, and therefore these estimates have a high level of uncertainty. Federal



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