The water of Deckers Creek is seriously polluted by Acid Mine Drainage (AMD). The geochemically study and graphical analysis are based on the surface water samples of Deckers Creek. This paper is to find out the pollution sources and suggest the pollution control methods. Introduction
Analytical Chemical Contents Total Acidity pH Total Alkalinity Total Iron(Fe) Total Sulfate(SO 4 2- ) Total Nitrate(NO 3 - ) Total Chloride(Cl - ) Total Calcium (Ca) Total Magnesium(Mn) Total Sodium(Na) Total Potassium(K) Conductivity Table 1
1. Water Quality Generally speaking, the surface water of Deckers Creek has been seriously contaminated by the acid and dissolved metals. Factor analysis reveals that the acidity of the water is mainly caused by sulfide, low pH, iron, Mn and so on. D19-TK27 are in the mining area, where acid mine drainage makes the water quality worse with lower pH and higher dissolved salts (Cluster Analysis). Cluster analysis points out that the water at the point (TH3) is very toxic because an abandoned mine discharges the acid mine drainage and pollutes the stream. From D17 to D10, the acidity begins to reduce because there exist limestone that can neutralize a part of acidity. Conclusion
2. Acid Formation The formation of the Deckers Creek acidity water mainly results from that the pyrite is oxidized by the O 2 and water. The precipitation of iron and Mn oxide can generate acid, too. 2FeS 2 + 7O 2 + 2H 2 O ===== 2Fe 2+ + 4SO 4 2- + 4H + 4Fe 2+ + O 2 + 4H + ===== 4Fe 3+ + 2H 2 O FeS 2 + 14Fe 3+ + 8H 2 O ===== 15Fe 2+ + 2SO 4 2- + 16H + Fe 3+ + 3H 2 O===> Fe(OH) 3 + 3H + 2Mn 2+ +O 2 + 2H 2 O===> 2MnO 2 + 4H + Limestone can neutralize the water acidity by promoting pH. CaCO 3 + H + ===== Ca 2+ + HCO 3 -
3. Total Acidity Equation The acidity of the Deckers Creek water does not result from NO 3 -, Cl -, Na and K, which can be removed from regression analysis. Comparing the equation with the theoretical equation, we may find both the equations are similar. The acidity equation from Regression Analysis: Acidity = 2.27[Fe] - 0.779[Mn 2+ ] + 87.4[H + ] + 3.51 + 0.130[SO 4 ] The theoretical equation: Acidity = 50( [M]/Equivalent Weight + 10 3-pH ) = 50( 3[Fe 3+ ]/56 + 2[Fe 2+ ]/56 + 2[Mn 2+ ]/55 + 10 3-pH ) 2.68[Fe 3+ ] + 1.79[Fe 2+ ] + 1.82[Mn 2+ ] + 50[H + ]
4. Problem and Suggestion After flowing over limestone generation industrial region, the acidity of was neutralized a little. However, the deficient limestone can not meet more addition of acid mine drainage, it is necessary to add limestone into the stream water. For some very toxic water such as point TH3, the discharge has to be collected and treated separately, then let it mix into Deckers Creek. There still exist some unknown points waiting to be further studied, where the water quality unstable and the analysis results of the water samples are controversy with what we have expected.