V. Pollution

 

A. Acidification and pH

 

Acidification is a naturally occurring process in nature.  In high rainfall tropical areas, natural acidification of soils and surface waters is common.  However, tropical areas are especially sensitive to further acidification by increased atmospheric deposition of sulfate and nitrate ions (Rodhe et al, 1988).  The following describes the three necessary conditions for the acidification of an aquatic ecosystem by atmospheric deposition:

 

1)       Atmospheric deposition of sulfate or nitrate or of some anion must increase.

2)       Adjacent soils to the aquatic ecosystem must not retain the anion that is increased in deposition.

3)       Aquatic ecosystem must have a low alkalinity for acidification to result in biological damage (Rodhe et al, 1988).

           

The major rivers and tributaries of the southeastern region of Brazil have varying levels of pH.  Figure 2 below is a map of the major rivers of the southeastern region of Brazil.  Table 5 gives the pH and SO4-2 and NH4+ concentrations for these rivers and their tributaries (Moreira-Nordemann, 1988).

 

Figure 2: Rivers of Southeastern Brazil


Table 1: Sγo Francisco River and Tributaries (T); minimum and maximum values based on one sample per year (1982-1983) at several points on each river (Moreira-Nordemann, 1988)

 

River Name

pH

SO42- (mg/L)

NH4+ (mg/L)

Sΰo Francisćo

4.8 – 7.8

< 1.0 – 16.2

0.1 - 0.5

Sΰo Miguel (T)

7.6 – 7.7

< 1.0 – 2.7

< 0.1 – 0.5

Parΰ (T)

7.2 – 7.6

< 1.0 – 5.0

0.1 – 0.3

Lambari (T)

7.3 – 7.5

< 1.0 – 3.0

--

R. das Velhas (T)

6.5 – 8.7

< 1.0 – 55.0

< 0.1 – 2.1

R. Jequitai (T)

7.1 – 8.0

1.2 – 2.3

0.1

Pacuν (T)

7.2 – 7.8

1.8 – 2.1

< 0.1 – 1.0

Prata (T)

6.5 – 7.0

--

0.1 – 0.2

Verde Grande (T)

6.2 – 8.2

12.4 – 16.1

--

Urucuia (T)

6.2 – 6.5

--

< 0.1 – 0.1

Abaetι (T)

7.9

--

0.3

Pandeiros (T)

7.2 – 7.6

< 1.0

--

Paracatu (T)

6.3

--

< 0.1 – 0.1

Paraopeba (T)

6.5 – 7.5

< 1.0 – 6.0

< 0.1 – 3.9

 

Table 2: Paraνba do Sul basin and tributaries (T), in Rio de Janeiro state in 1984 (Moreira-Nordemann, 1988)

 

River Name

pH

NO3- (mg/L)

NH4+ (mg/L)

SO42- (mg/L)

Paraνba do Sul (SP)*

6.2 – 6.8

0.4 – 1.8

0.2 – 0.4

--

Jaguari (SP-T)*

6.4 – 7.1

0.3 – 1.6

0.2 – 0.3

--

Paraibuna (MG-T)†

6.7 – 7.2

--

0.3 – 1.6

4.0 – 5.0

Pomba (MG-T)†

6.8 – 7.4

--

0.1 – 0.3

< 1.0 – 1.5

 

 

Table 3: Tietι River and tributaries (T); minimum and maximum values obtained during 1981, 1983 and 1984 in monthly measurements (Moreira-Nordemann, 1988)

 

River Name

pH

NO3- (mg/L)

NH4+ (mg/L)

Tiete

6.2 – 7.5

0.1 – 4.5

0.1 – 8.2

Biritiba-Mirim (T)

6.3 – 6.4

0.4 – 0.6

0.04 – 0.14

Jundiai (T)

5.9 – 6.3

0.2

0.03 – 0.13

Taiacupeda (T)

6.6 – 6.9

0.1 – 5.8

0.13 – 1.08

Buquirivu-Guacu (T)

6.4 – 6.6

5.8 – 9.3

0.96 – 2.24

Represa Juqueiri (T)

6.4 – 7.0

0.3 – 1.9

0.06 – 1.86

Pinheiros (T)

6.6 – 6.8

0.4 – 1.5

4.95 – 15.84

Tamanduatei (T)

6.7 – 7.6

0.1 – 2.2

13.44 – 25.93

Jacare-Gaucu (T)

6.1 – 6.9

0.1 – 0.6

0.05 – 0.27

Jacare-Pepira

7.0 – 7.3

0.8 – 0.9

0.12 – 0.18

Piracicaba (T)

6.9 – 7.1

0.9 – 1.2

0.18 – 0.70

Cotia (T)

6.8 – 6.9

0.4 – 0.6

1.20 – 7.39

Sorocaba (T)

6.5 – 7.1

0.6 – 2.7

0.14 – 1.87

 

Table 4: Panapanema basin and tributaries (T), Sao Paulo state.  Minimum and maximum mean values obtained for 1981, 1982 and 1983 in monthly measurements (Moreira-Nordemann, 1988)

 

River Name

pH

NO3- (mg/L)

NH4+ (mg/L)

Paranapanema

6.5 – 7.2

0.4 – 1.1

0.12 – 0.23

Taquari (T)

6.7 – 7.4

0.5 – 0.6

0.13 – 0.25

Pardo (T)

7.3 – 7.4

0.7 – 0.9

0.15 – 0.18

Itarare (T)

6.5 – 7.3

0.5 – 0.9

0.08 – 0.17

 

 

Table 5: Grande basin and tributaries, Sao Paulo state; minimum and maximum mean values obtained in 1981, 1982 and 1983 in monthly measurements.

 

River Name

pH

NO3- (mg/L)

NH4+ (mg/L)

Grande

6.8 – 7.2

0.3 – 0.35

0.01 – 0.04

Sapucai-Mirim

6.9 – 7.2

0.5 – 0.7

0.05 – 0.13

Pardo

6.6 – 7.1

0.5 – 0.8

0.03 – 0.17

Turvo

6.6 – 6.9

0.4 – 0.9

0.06 – 0.15

Preto

6.6 – 6.7

1.2 – 1.7

0.08 – 0.10

 

 

According to the authors of Chapter 8:  Acidification in Southeastern Brazil, “The differences in nitrogen and sulfur concentrations observed in river waters of the southeastern region of Brazil cannot be explained by geological, pedological, or climatic factors.  Higher NO3-, NH4+ and SO42- contents were determined in rivers crossing urban and industrial areas, the same areas that also present a polluted atmosphere.” 

 

These increases may be caused by “acid deposition.”  Acid deposition is caused by pollution from motor vehicles, industrial process, and the burning of fossil fuels in power-stations, releasing sulfur dioxide, nitrogen oxide, and hydrocarbons.  These pollutants react with water and sunlight to form dilute sulfuric acid, nitric acid, ammonium salts, and other mineral acids (Mayhew, 1997).

 

There are two types of “acid deposition” from the atmosphere:  wet and dry (Fig. 2). 

 

Acid Rain diagram

Figure 3: Acid deposition (EPA, 2002)

 

Wet deposition refers to acid rain, fog and snow.  According to the Environmental Protection Agency, “the strength of the effects [of acidic water] depends on a variety of factors, including how acidic the water is, the chemistry and buffering capacity of the soils involved, and the types of fish, trees, and other living things that rely on the water.”

 

Dry deposition refers to acidic gases and particles.  Ions in the atmosphere fall down as dry particles.  These particles are deposited onto buildings and other structures, or are washed from trees and other surfaces by rain.  This runoff water exaggerates the acidity of acid rain (EPA, 2002).

 

Many organisms cannot tolerate high levels of acidity, and furthermore, many of the species that are able to tolerate the increased acidity are faced with diminished food supplies due to the increased acidic conditions.  As acidity in a water system increases, the number and diversity of organisms decreases.  Also, when acid rain flows through soils in a watershed, aluminum, which is toxic to fish, is released into the water system.  At a pH of 5, most fish eggs cannot hatch (EPA, 2002).   Table 10 details the harmful effects of acidification on aquatic biota.

 

Table 6: Effects of acidification on aquatic biota (Mills, 1984)

Physical and chemical changes

·  Water transparency has increased, along with rates of hypolimnetic heating and thermo cline deepening

·  Concentrations of Mn, Na, Zn, H+, S2O4-, Al increased

·  Aluminum has been implicated as a major cause of fish mortality during lake acidification

·  S2O4- was reduced by bacteria to sulfide, followed by permanent sedimentation as FeS. Alkalinity, generated as byproduct of sulfate reduction, has neutralized approximately one-third of the hydrogen ion added to the lake.  Therefore, a pH refuge has persisted below throughout the acidification, but the long-term trend has been for this refuge to become progressively more acidic, although temporally lagging behind the epilimnion.

 Primary production and Invertebrates

·  Primary production has increased in Lake 223 above pre-acidification levels

·  Phytoplankton species composition has changed with Chlorophyceae and Peridineae replacing Chrysophyceae

·  Appearance of hypolimnetic algal peak of Chlorella

·  Three members of the zooplankton community Mysis relicta, Epischura lacustris, Diaptomus sicilis disappeared as pH declined to 5.4, while Daphnia catawba x schoedleri appeared

Responses of Fish Populations to Acidification (pH lowered by 6.7 to 5.1)

·  The fathead minnow population declined rapidly and almost disappeared when pH was 5.6. In addition, complete reproductive failure, rapid collapse of population were observed

·  The pearl dace population rapidly expanded to become the major minnow species when pH was 5.4. This was probably due to its greater tolerance to low pH by pearl dace than fathead minnow

·  White sucker (seen as relatively acid-tolerant species) showed no stress as the pH of the lake was lowered. Its individual fish growth remained consistently high.

·  The population of lake trout fish, which are relatively acid sensitive, decreased when pH was lowered from 6.7 to 5.4. However, its population did not decrease at the rate which was expected - it was much slower.

 

Because the water system of the Amazon is so large and complex, it is difficult to understand the true nature of the effects of acidity and acid deposition.  From the data collected thus far, there seems to be a relationship between changes in the acidity of water and pollution.  Further research is vital to the understanding of this relationship.

 

 

B. Mining

 

Mining has contributed to the amount of mercury found in the Amazon’s rivers.  It is estimated that 2000 tons of mercury have been dumped into the Amazon’s rivers over the past century alone (Brown et al., 2002). It has been demonstrated that at times, the rate of mercury production is equivalent to the rate of gold production (Veiga).

 

The processes currently employed by miners utilize mercury to clean the gold. Often mercury is not properly disposed of, and instead is subsequently passed on to nature for disposal.  Although mercury storied in the soil is in a harmless, organic form, mercury in the water is converted to methyl-mercury, which is one of the most poisonous substances known to man (Veiga).

 

Methyl-mercury filters down the river systems to communities down stream of the mining sites. Studies have proven that villagers in these areas suffer from the effects of mercury in their waters. Miners themselves have been victims of mercury poisoning as well.

 

In summary, mining requires a new cleaning method, one that either does not employ mercury at all, or makes clean up of the mercury used more effective. The trouble here will be convincing miner to switch to a new gold extraction method.

 

Another problem with mining is that it leaves large holes in the earth. As a result, mining sites are often covered by stagnant pools of water.  Such pools are breeding grounds for mosquitoes, an in particular, mosquitoes which carry malaria (Brown et al., 2002). These mosquitoes are notably feared as they cause malaria in the local populations. Recently, malaria has become a widespread epidemic in Brazil.  Nearly one-third of those diseased are less than 10 years old.

 

Fortunately, malaria is a simple disease to prevent.  The simplest solution is to remove the stagnant pools of water.  Miners should be required to cover any holes which are created during the mining process. This simple method is not performed by the miners although they are largely responsible for the increase in malaria cases in Brazil.

 

To improve mining and decrease its negative effects on the environment requires a fundamental change in the minds of miners. Incentives could be awarded to miners whose mining sites have been found to be compliant with certain standards established for environmental protection.

 

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