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one located in Everglades National Park (site FL11; Lat: 25.39, Lon:-80.68; Table 2.1). |
Concentrations and fluxes of NO3 and NH4 increased in atmospheric deposition until |
2007 (Fig 2.6). On the other hand, Ca, Mg, K, Na and Cl have declined and the pH |
experienced a sharp decline from 5.42 to 5.07 pH units during 1994. Sodium and |
chloride display similar pattern and their molar relationships are very close to that of sea |
water indicating their origin as cyclic salts. The decline in these salts is important |
because it suggests changes from ocean to land source of rainwater. |
As shown in Table 2.1, average concentration of inorganic nitrogen species in |
rain water (NH4=0.159 mg/l and NO3=0.811 mg/l), are significantly higher than those |
found in South Florida estuarine and coastal waters (mean NO3=0.016 mg/l; mean |
NH4=0.028 mg/l) . That chemistry has the potential to cause impact especially in |
waterbodies like BB where rainfall contributes 40% of the freshwater budget with |
concentrations one order of magnitude above those of Bay waters. Additionally, the pH |
drop of about half a pH unit in 1994 has important environmental implications especially |
23 |
for potential impacts on soil biogeochemistry and nutrient release/fixation processes |
(Burns et al. 1998, 2006; Hejzlar et al. 2003; De Wit 2007; Briceño and Boyer 2009). |
Figure 2.6: Zcusum charts picture detailed and complex patterns, where NH4 and NO3 have |
similar increasing trends (cup-shaped cusums), while Ca, Mg, K, Na and Cl declined (skewed |
dome-shaped cusum), and the pH shifted from above to below average tendency in 1995. |
Table 2.1. Descriptive statistics of rainwater chemical composition at station NADP FL11, |
Everglades National Park for the period Jun/1980 to Jan/2011 (units are mg/l except for pH) |
-25 |
-20 |
-15 |
-10 |
-5 |
0 |
5 |
10 |
15 |
20 |
Jan-79 |
Jan-81 |
Jan-83 |
Jan-85 |
Jan-87 |
Jan-89 |
Jan-91 |
Jan-93 |
Jan-95 |
Jan-97 |
Jan-99 |
Jan-01 |
Jan-03 |
Jan-05 |
Jan-07 |
Jan-09 |
Jan-11 |
Jan-13 |
Zcusum (sd) |
NH4 CT Zcusum NO3 CT Zcusum |
-10 |
0 |
10 |
20 |
30 |
40 |
50 |
Jan-79 |
Jan-81 |
Jan-83 |
Jan-85 |
Jan-87 |
Jan-89 |
Jan-91 |
Jan-93 |
Jan-95 |
Jan-97 |
Jan-99 |
Jan-01 |
Jan-03 |
Jan-05 |
Jan-07 |
Jan-09 |
Jan-11 |
Jan-13 |
Zcusum (sd) |
Ca CT Zcusum Mg CT Zcusum K CT Zcusum |
-10 |
0 |
10 |
20 |
30 |
40 |
50 |
60 |
70 |
80 |
4.0 |
4.5 |
5.0 |
5.5 |
6.0 |
6.5 |
7.0 |
Jan-79 |
Jan-81 |
Jan-83 |
Jan-85 |
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