250
Investigated groundwater samples that showed low NO 3
−
concentrations
(<10 mg/l) showed high HCO 3
−
(med 272 mg/l), As (med 27.9 μg/l), Fe (med
480 μg/l), and Mg (med 12.18 μg/l) concentrations, pH 7–8, as well as low PO 4
3−
(med 0.52 mg/l) and SO 4 (med 18.15 mg/l) concentrations suggesting that denitrification due to the reductive environment contributes in decreasing nitrate
concentration in this samples. To evaluate this, the chemical properties of groundwater samples were investigated according to Jurgen’s calculator in Excel for
identifying redox processes in groundwater (Jurgens et al. 2009). The obtained
result showed the presence of anoxic conditions in groundwater samples with a
low level of nitrate. Considering this it is expected to have low concentrations of
SO 4
2−
, too. Possible natural sources of sulfate in groundwater are dissolution of
sulfate-bearing minerals like barite (BaSO 4 ), epsomite (MgSO 4 ·7H 2 O), and gypsum (CaSO 4 ·2H 2 O), oxidation of pyrite (FS 2 ), atmospheric fallout, and decomposition of organic matter. Regarding anthropogenic activities, sulfate and sulfuric
acid products are used in the production of fertilizers, chemicals, dyes, glass,
paper, soaps, textiles, fungicides, insecticides, astringents, and emetics; mining;
wood pulp, metal, and plating industries; sewage treatment; and processing of
leather (Greenwood and Earnshaw 1984). Fertilizers based on potassium sulfate,
ammonium sulfate, and the sulfo- phosphate ammonium are usually applied in the
soil. Since sulfate is water-soluble and mobile in the soil, it is expected for soil
inputs to have an impact on shallow groundwater. Sulfate exists in groundwater
usually as sodium sulfate (Na 2 SO 4 ), calcium sulfate (CaSO 4 ), and magnesium sulfate (MgSO 4 ). In this study investigated groundwater samples with a depth greater
than 70 m showed no significant pollution with SO 4
2−
. The maximum concentration was 166.69 mg/l with a median of less than 5 mg/l. The maximum concentration found in shallow groundwater was 300 mg/l with a median of 21 mg/l.
Welch’s t-test showed a statistically significant difference between SO 4
2−
concentrations in deep and shallow groundwater, but the very low level of power analysis
(Table 8.4) excludes the possibility to accept this. A positive correlation between
SO 4
2−
, Cl
−
, and Na in factor analysis suggests that the majority of sulfate ions is
derived in groundwater leaching by rainwater (Table 8.5).
Water percolating through the soil and moving downstream to the aquifer reacts
with the surrounding environment composed of rock and minerals that contribute to
groundwater characteristic chemical composition. Silicate minerals that comprise
most rocks do not react readily with most groundwaters, while carbonate minerals
react quite readily with water and thus play an important role in the evolution of many
groundwaters. Carbonates are the most common forms of calcium in sedimentary
rock formations like calcite and aragonite (CaCO 3 ) and dolomite CaMg(CO 3 ) 2 . Other
calcium minerals common in sediments include gypsum (CaSO 4 /CaSO 4
.
2H 2 O) and
more rarely fluorite (CaF 2 ), some types of zeolites, and montmorillonite. Concentrations
of calcium in the investigated groundwater range between 7.4 and 411 mg/l with a
median value of 39.4 mg/l. No significant difference is observed between shallow and
deep groundwater regarding Ca concentration.
The detection frequency of Mn in groundwater in the Strumica region is high
which is predicted since it is one of the most abundant metals in earth’s crust,
B. Kovacevik et al.
Investigated groundwater samples that showed low NO 3
−
concentrations
(<10 mg/l) showed high HCO 3
−
(med 272 mg/l), As (med 27.9 μg/l), Fe (med
480 μg/l), and Mg (med 12.18 μg/l) concentrations, pH 7–8, as well as low PO 4
3−
(med 0.52 mg/l) and SO 4 (med 18.15 mg/l) concentrations suggesting that denitrification due to the reductive environment contributes in decreasing nitrate
concentration in this samples. To evaluate this, the chemical properties of groundwater samples were investigated according to Jurgen’s calculator in Excel for
identifying redox processes in groundwater (Jurgens et al. 2009). The obtained
result showed the presence of anoxic conditions in groundwater samples with a
low level of nitrate. Considering this it is expected to have low concentrations of
SO 4
2−
, too. Possible natural sources of sulfate in groundwater are dissolution of
sulfate-bearing minerals like barite (BaSO 4 ), epsomite (MgSO 4 ·7H 2 O), and gypsum (CaSO 4 ·2H 2 O), oxidation of pyrite (FS 2 ), atmospheric fallout, and decomposition of organic matter. Regarding anthropogenic activities, sulfate and sulfuric
acid products are used in the production of fertilizers, chemicals, dyes, glass,
paper, soaps, textiles, fungicides, insecticides, astringents, and emetics; mining;
wood pulp, metal, and plating industries; sewage treatment; and processing of
leather (Greenwood and Earnshaw 1984). Fertilizers based on potassium sulfate,
ammonium sulfate, and the sulfo- phosphate ammonium are usually applied in the
soil. Since sulfate is water-soluble and mobile in the soil, it is expected for soil
inputs to have an impact on shallow groundwater. Sulfate exists in groundwater
usually as sodium sulfate (Na 2 SO 4 ), calcium sulfate (CaSO 4 ), and magnesium sulfate (MgSO 4 ). In this study investigated groundwater samples with a depth greater
than 70 m showed no significant pollution with SO 4
2−
. The maximum concentration was 166.69 mg/l with a median of less than 5 mg/l. The maximum concentration found in shallow groundwater was 300 mg/l with a median of 21 mg/l.
Welch’s t-test showed a statistically significant difference between SO 4
2−
concentrations in deep and shallow groundwater, but the very low level of power analysis
(Table 8.4) excludes the possibility to accept this. A positive correlation between
SO 4
2−
, Cl
−
, and Na in factor analysis suggests that the majority of sulfate ions is
derived in groundwater leaching by rainwater (Table 8.5).
Water percolating through the soil and moving downstream to the aquifer reacts
with the surrounding environment composed of rock and minerals that contribute to
groundwater characteristic chemical composition. Silicate minerals that comprise
most rocks do not react readily with most groundwaters, while carbonate minerals
react quite readily with water and thus play an important role in the evolution of many
groundwaters. Carbonates are the most common forms of calcium in sedimentary
rock formations like calcite and aragonite (CaCO 3 ) and dolomite CaMg(CO 3 ) 2 . Other
calcium minerals common in sediments include gypsum (CaSO 4 /CaSO 4
.
2H 2 O) and
more rarely fluorite (CaF 2 ), some types of zeolites, and montmorillonite. Concentrations
of calcium in the investigated groundwater range between 7.4 and 411 mg/l with a
median value of 39.4 mg/l. No significant difference is observed between shallow and
deep groundwater regarding Ca concentration.
The detection frequency of Mn in groundwater in the Strumica region is high
which is predicted since it is one of the most abundant metals in earth’s crust,
B. Kovacevik et al.