245
investigated area, both categories of groundwater have discharge that is dominated
by artificial exploitation.
8.3.1.1 Major Components
Descriptive analysis of major components (Tables 8.2 and 8.3) showed variations in
the wide range of concentrations regarding major groundwater constituents. HCO 3
−
values varied between 0.05 and 1116 mg/l, SO 4
2−
values varied between 0.5 and
300 mg/l, Cl
−
varied between 7.37 and 614 mg/l, and Ca
2+
and K
+
values also varied
greatly between 7.43 and 411 mg/l and 1.15 and 354 mg/l, respectively. The range
is also wide for Mn and Fe which values varied between 0.25 and 3329 mg/l and
0.03 and 3166 mg/l, respectively. This outcome suggests that groundwater in the
Strumica differs considerably in the major component concentrations. To investigate if there are significant differences between element concentrations in shallow
and deep groundwater, Welch’s t-test was performed for normal and Box-Cox transformed values. The result showed significant differences between shallow and deep
groundwater for Cl, NO 3
−
, NO 2
−
, SO 4
2−
, PO 4
3−
, Ca, Fe, and Mg when normal values
were processed and between Cl, NO 2
−
, NH 4
+
, SO 4
2−
, PO 4
3−
, Fe, Mg, K, and Mn
when Box-Cox transformed values were processed (Table 8.4). The power analysis
showed a high percentage of accuracy (>95%) only for NH 4
+
, PO 4
3−
, Fe, and Mn
when Box-Cox normalized values are processed. Therefore, future statistical analyses are performed on normalized values.
Environmental and agroecological characteristics of the Strumica region indicate
high contamination potential of groundwater with nitrate. Despite that, the investigation showed no significant pollution in the majority of investigated samples.
Almost 50% showed nitrate concentrations of less than 3 mg/l. Concentrations
above 10 mg/l were found in almost 35% of groundwater from which around 14%
have concentrations greater than 50 mg/l (max. 284 mg/l). Highly polluted groundwater samples were noticed mostly in shallow groundwater. Nitrate concentration
greater than 10 mg/l can cause methemoglobinemia (blue baby syndrome), an often
fatal disease in infants. Water with nitrate concentrations greater than 10 mg/l
should not be used in infant feeding, by pregnant women or by nursing mothers (US
Environmental Protection Agency 2002). The extensive analysis for threshold background concentrations of NO 3
−
in groundwater conducted in many different geographic locations showed that concentrations of 2–3 mg/l are usually attributable to
natural conditions (Mueller et al. 1995; Burow et al. 1998). Higher concentrations
are usually associated with leakage from agriculture fertilizers and sewage manures.
Nitrate is soluble in water and can easily pass through soil to the groundwater table
and persist in groundwater for decades accumulating at high levels. Research from
different regions in the world about nitrate leaching provides evidence for factors
that contribute to groundwater vulnerability. Shallow unconfined aquifers associated with agricultural systems as well as unconsolidated aquifers such as the alluvial type of aquifer are most susceptible to nitrate contamination. Groundwater in
many agricultural regions in the world was found to be polluted with NO 3
−
(Strebel
8 Groundwater Pollution Under the Intensive Agriculture Production
investigated area, both categories of groundwater have discharge that is dominated
by artificial exploitation.
8.3.1.1 Major Components
Descriptive analysis of major components (Tables 8.2 and 8.3) showed variations in
the wide range of concentrations regarding major groundwater constituents. HCO 3
−
values varied between 0.05 and 1116 mg/l, SO 4
2−
values varied between 0.5 and
300 mg/l, Cl
−
varied between 7.37 and 614 mg/l, and Ca
2+
and K
+
values also varied
greatly between 7.43 and 411 mg/l and 1.15 and 354 mg/l, respectively. The range
is also wide for Mn and Fe which values varied between 0.25 and 3329 mg/l and
0.03 and 3166 mg/l, respectively. This outcome suggests that groundwater in the
Strumica differs considerably in the major component concentrations. To investigate if there are significant differences between element concentrations in shallow
and deep groundwater, Welch’s t-test was performed for normal and Box-Cox transformed values. The result showed significant differences between shallow and deep
groundwater for Cl, NO 3
−
, NO 2
−
, SO 4
2−
, PO 4
3−
, Ca, Fe, and Mg when normal values
were processed and between Cl, NO 2
−
, NH 4
+
, SO 4
2−
, PO 4
3−
, Fe, Mg, K, and Mn
when Box-Cox transformed values were processed (Table 8.4). The power analysis
showed a high percentage of accuracy (>95%) only for NH 4
+
, PO 4
3−
, Fe, and Mn
when Box-Cox normalized values are processed. Therefore, future statistical analyses are performed on normalized values.
Environmental and agroecological characteristics of the Strumica region indicate
high contamination potential of groundwater with nitrate. Despite that, the investigation showed no significant pollution in the majority of investigated samples.
Almost 50% showed nitrate concentrations of less than 3 mg/l. Concentrations
above 10 mg/l were found in almost 35% of groundwater from which around 14%
have concentrations greater than 50 mg/l (max. 284 mg/l). Highly polluted groundwater samples were noticed mostly in shallow groundwater. Nitrate concentration
greater than 10 mg/l can cause methemoglobinemia (blue baby syndrome), an often
fatal disease in infants. Water with nitrate concentrations greater than 10 mg/l
should not be used in infant feeding, by pregnant women or by nursing mothers (US
Environmental Protection Agency 2002). The extensive analysis for threshold background concentrations of NO 3
−
in groundwater conducted in many different geographic locations showed that concentrations of 2–3 mg/l are usually attributable to
natural conditions (Mueller et al. 1995; Burow et al. 1998). Higher concentrations
are usually associated with leakage from agriculture fertilizers and sewage manures.
Nitrate is soluble in water and can easily pass through soil to the groundwater table
and persist in groundwater for decades accumulating at high levels. Research from
different regions in the world about nitrate leaching provides evidence for factors
that contribute to groundwater vulnerability. Shallow unconfined aquifers associated with agricultural systems as well as unconsolidated aquifers such as the alluvial type of aquifer are most susceptible to nitrate contamination. Groundwater in
many agricultural regions in the world was found to be polluted with NO 3
−
(Strebel
8 Groundwater Pollution Under the Intensive Agriculture Production