00:00:01 A liquid planet. There are more than one and a half million lakes in the United States, and none is quite like the other.

00:00:11 But some may share one thing in common. They are changing.

00:00:16 Beneath the surface of some of our lakes, there is a growing mystery.

00:00:30 It started as early as 1872, when chemists began to puzzle over the increasing acidity of rain falling around industrial centers.

00:00:39 Scientists called the altered precipitation acid rain. The name stuck, and so did the phenomenon.

00:00:46 Today it's known to scientists as acidic deposition. It occurs in snow, fog, and dry forms, as well as rainfall.

00:00:55 A century later, acidic deposition has become one of the most controversial and elusive of environmental problems.

00:01:04 It does not fall only on industrial centers. It also falls on rural areas. It falls on vegetation and surrounding soils.

00:01:13 It falls on the watersheds, which feed the nation's many streams and lakes.

00:01:17 The biological balance of some of these lakes is being altered, and possibly destroyed, by these acids.

00:01:26 Today, government agencies and private concerns are working to determine the causes and effects of acid deposition on our country's water systems.

00:01:36 But the information that would help us understand the acid deposition phenomenon has been scattered.

00:01:42 It was frequently collected for other purposes, limiting its usefulness.

00:01:47 Evidence suggests that aquatic ecosystems are the first to be adversely affected.

00:01:52 They respond to both periodic shocks of acidity, such as those occurring during snow melt, and to long-term inputs of acidity and acidifying substances.

00:02:02 What remains a mystery, and what is most important for policy makers to know, is the extent and severity of the problem, and if it is likely to get worse.

00:02:14 We need to know about those lakes that have been affected, and equally important, about those that haven't, but might be in the future.

00:02:22 To gain this knowledge, it's important to survey lakes which are representative of those in a region, to avoid making generalizations from individual, perhaps atypical lakes.

00:02:36 The chemical and biological composition of a lake, a complex of variables, can differ greatly from lake to lake.

00:02:44 However, by studying a carefully selected sample of lakes, scientists can draw conclusions about all of the lakes within entire regions of the country.

00:02:54 To learn about the total potential extent of acid deposition damage, research must be done on a large scale.

00:03:05 The Environmental Protection Agency has taken to the air with just such a program. It's called the National Lake Survey.

00:03:25 This effort is one part of the National Acid Precipitation Assessment Program, an interagency acid rain research effort mandated by Congress.

00:03:34 The long-term goals of the lake survey are ambitious, to see which lakes are potentially sensitive to acid deposition, and to see how many are presently acidic.

00:03:44 The survey will also help scientists to choose lakes which are representative of others in a particular region, such as the Adirondack Mountains.

00:03:52 Representative lakes will be closely monitored in the future for changes that might be caused by acid deposition.

00:04:00 The first step of the lake survey, phase one, is like a snapshot, a cross-section to determine the chemical status of a lake.

00:04:09 The objective is to get an index sample, that is a single sample from a lake that is most representative of the chemistry for that year, and for a chemistry that can be compared among lakes.

00:04:23 When we have that information, the first phase will essentially be completed, and we'll be able to determine how many acid lakes there are in these regions that we've sampled,

00:04:31 how many lakes have low alkalinity, that is, have low buffering capacity, and might be susceptible to change as a result of acidic deposition.

00:04:39 And we'll be able to move on to phase two, which is to pick representative systems, as it's very difficult to study so many lakes in great detail.

00:04:52 Thousands of lakes have been selected for sampling throughout the northeast, southeast, upper midwest, and high elevation regions of the Rockies, Cascades, and Sierras.

00:05:04 Each one of them was selected to avoid any bias in sampling, something which could distort and perhaps invalidate the survey's scientific conclusions.

00:05:13 The four regions of the country expected to be most sensitive to change from acidic deposition were divided into sub-regions based on differences in elevation or geology.

00:05:25 Then each lake was given a number and entered into a computer.

00:05:29 From this list of all lakes in the area, a subset was randomly selected, ensuring that the survey results will be unbiased.

00:05:38 Approximately 150 lakes were selected for sampling in each of the sub-regions, enough to give an accurate statistical picture of lakes in general.

00:05:47 All told, nearly 3,000 lakes are to be sampled throughout the country.

00:05:53 Approximately 2,000 lakes were selected for sampling in the three eastern regions, and another 1,000 lakes will be sampled in the mountainous west.

00:06:02 These samples, a subset of the potentially sensitive lake population, will enable scientists to estimate the total percentage of lakes with problems related to acidification.

00:06:14 The work must be done quickly. Sampling must be completed within a very short time.

00:06:25 During the autumn months, lake surface water begins to cool and circulate.

00:06:30 This turnover, as it's called, removes chemical and temperature differences between the upper and lower layers of the lake.

00:06:38 This is the best time for sampling, the time when a single sample from a lake best represents the entire lake.

00:06:46 But autumn is a brief period of time to sample so many lakes.

00:06:50 Winter sets in early in many of these northern high-altitude areas. Speed becomes very important.

00:06:57 Not only do samples need to be taken from 2,000 lakes in this short time period, each sample must be delivered within hours to the field laboratory.

00:07:06 This enables scientists to filter, analyze, and preserve the water before significant deterioration of the samples occurs.

00:07:14 For some critical measurements, such as aluminum, which is toxic to fish, samples cannot be held for longer than four to six hours prior to being prepared for analysis.

00:07:25 The solution to the time crunch? Aircraft.

00:07:30 Throughout the eastern survey regions and in parts of the west, helicopters are providing the solution through the short sampling window.

00:07:40 Many of the western lakes lie in designated wilderness areas where motorized access is restricted by law.

00:07:47 In these areas, the U.S. Forest Service is assisting EPA in sampling lakes by ground access wherever possible.

00:07:56 Some lakes will also be sampled by both methods, and a special study will compare the results.

00:08:02 Both methods allow us to move very quickly to complete our lake sampling during the fall period when the lakes begin to turn over.

00:08:13 Important measurements are taken at every lake.

00:08:16 Crews check temperatures at different depths to make sure the lake's temperature is uniform.

00:08:22 This indicates that waters have turned over as they should during the fall season.

00:08:27 Many lakes in the regions being sampled are naturally clear.

00:08:31 However, acidification sometimes can make an otherwise cloudy or turbid lake become crystal clear.

00:08:38 As lakes become acidic, various forms of life and dissolved materials are depleted in the water.

00:08:44 Ironically, the pristine beauty of a lake often represents the loss of life in that lake.

00:08:50 So crews check the color and clarity of the water.

00:08:54 They also check pH levels.

00:08:57 pH is a measure of acidity.

00:09:00 The lower the pH value, the more acidic the water is.

00:09:05 After these measurements are made, samples are flown back to EPA mobile labs built especially for this survey.

00:09:12 The mobile laboratories were constructed because we felt it was necessary to actually handle the water samples very quickly when they came out of the field.

00:09:21 They arrive at the mobile laboratory within hours of their collection.

00:09:26 We felt it was the most expedient way to ensure that the samples we collected were analyzed in the quickest possible time, which is required for some of these analyses.

00:09:38 The mobile lab processes the samples for transport to analytical laboratories for final chemical analysis.

00:09:44 They filter and in some cases treat samples with chemicals to ensure that the water chemistry doesn't change during transport.

00:09:52 The mobile lab is also equipped to do some analyses on site.

00:09:56 For two measurements, scientists analyze samples which have had no direct contact with the atmosphere.

00:10:03 This technique is necessary because water exposed to the air may experience a change in dissolved carbon dioxide and pH.

00:10:11 Such a change would make it difficult to know what the pH of the water was when the sample was actually taken.

00:10:18 So keeping some samples airtight is important.

00:10:22 It enables scientists in the field laboratory to approximate more closely what the fish or other members of the ecosystem are experiencing.

00:10:31 The scientists also prepare extractions of aluminum.

00:10:34 Too much aluminum can disrupt the ecosystem of a lake.

00:10:38 As the pH of water declines, dissolved aluminum concentrations increase, often reaching levels which can threaten sensitive life stages of fish.

00:10:49 Working in tight quarters, sometimes all night, the lab technicians make sure that samples are prepared correctly for shipment to the analytical labs.

00:10:57 There, the analysis of aluminum and other critical parameters is undertaken.

00:11:02 I think all the measurements we're taking are important.

00:11:05 Some will be used more than others.

00:11:08 In the review process of this program, and by review I mean the peer review of the scientific community,

00:11:14 we have very painstakingly looked at every measurement that we're taking.

00:11:19 Each measurement, of course, costs money, and we've deleted those that we thought were extraneous or not essential.

00:11:28 All told, some 25 measurements are made, 19 at analytical laboratories.

00:11:34 The data obtained, however, would be useless if the strictest quality control measures weren't employed.

00:11:40 Field instruments are checked and calibrated twice daily.

00:11:44 Duplicate samples are taken at lake sites to spot any problems in the sampling and testing routines.

00:11:50 Sample crews meet daily to discuss and record any potential problems and to answer questions that might affect test results.

00:11:58 Quality control is designed into such a study to ensure scientific integrity.

00:12:04 Information accumulated from the survey is being processed and analyzed at the Oak Ridge National Laboratory.

00:12:12 Later, data are entered into the computers so that sophisticated analyses can be easily performed.

00:12:19 But survey results are already proving useful.

00:12:22 Existing alkalinity maps showing potential regional sensitivity to acid deposition are being updated and improved.

00:12:30 Important questions are being answered.

00:12:33 Is lake acidity related to elevation and watershed size?

00:12:38 Is there a relationship between soil properties, land use, and the acidity of water in certain regions?

00:12:45 The lake survey is EPA's first step to finding out.

00:12:49 There is much more work to be done, and the survey will be a springboard for further research.

00:12:56 Soon, we'll know the percentage of acidic lakes in the most sensitive areas of our country.

00:13:02 Scientists will be able to better monitor and predict the effects of acidic deposition.

00:13:07 And we'll be closer.

00:13:09 Closer to understanding a century-old problem.

00:13:13 Closer to providing policymakers with information they need to manage the acidification of our nation's surface waters.

00:13:20 Information on how acid deposition is affecting freshwater lakes on a liquid planet.

00:13:29 Find out more at www.nasa.gov

00:13:34 NASA Jet Propulsion Laboratory, California Institute of Technology

00:13:58 NASA Jet Propulsion Laboratory, California Institute of Technology

00:14:28 NASA Jet Propulsion Laboratory, California Institute of Technology