Agriculture Reference
In-Depth Information
Table 11.1. Hydrochemistry of precipitation and groundwater in the vicinity of
Kellogg Biological Station.
Measurement
*
Precipitation
Groundwater
USGS
a
NADP/NTN
b
Hamilton
c
USGS
-Kalamazoo
d
WMU-Barry
e
# dates or sites
14 dates
1240 dates
18 sites
46 sites
170-179 sites
Conductance
(μS cm
−1
; 25
o
C)
34.0
21.7
556
587
403
pH
4.3
4.47
7.48
7.34
NA
ANC
*
(mg HCO
3
−
L
−1
)
~0
~0
318
259
240
Ca
2+
(mg L
−1
)
0.19
0.21
80.6
81.0
70.0
Mg
2+
(mg L
−1
)
<0.01
0.04
25.0
25.0
23.0
Na
+
(mg L
−1
)
<0.2
0.08
6.40
5.1
9.30
K
+
(mg L
−1
)
<0.1
0.02
1.54
1.0
1.60
Cl
−
(mg L
−1
)
0.25
0.13
11.0
11.0
0
SO
4
2−
(mg L
−1
)
3.5
2.25
36.7
32.0
35.00
NO
3
−
(mg N L
−1
)
0.61
0.39
1.85
0.19
0
NH
4
+
(mg N L
−1
)
0.56
0.35
0.035
0.04
0.06
Si (mg Si L
−1
)
0.0
NA
6.96
1.69
3.04
DOC
*
(mg L
−1
)
NA
NA
1.65
NA
NA
TDN
*
(mg L
−1
)
1.6
NA
NA
0.46
NA
TDP
*
(mg L
−1
)
0.03
NA
0.011
0.01
NA
*
DOC = dissolved organic carbon. ANC = acid-neutralizing capacity (also known as total alkalinity). TDN = total
dissolved N. TDP = total dissolved P.
a
Rheaume (1990: Tables 7 and 8 in that report); data are means of wet deposition for a precipitation station near the
mouth of Gull Creek, sampled for most variables 14 times between November 1986 and September 1987.
b
National Atmospheric Deposition Program (NRSP-3)/National Trends Network means of annual volume-weighted
means in wet deposition for 1979-2010 from the KBS station (MI26), downloaded August 14, 2011. NADP/NTN
Coordination Office, Illinois State Water Survey, Champaign, IL.
c
Mostly residential water-supply wells at homes on KBS property and most were sampled once; Hamilton lab
database queried December 2009.
d
Rheaume (1990: Table 20); data are medians for 46 observation wells located throughout Kalamazoo County. The
mean concentration of NO
3
−
was 3.64 mg N L
−1
.
e
Kehew and Brewer (1992: Table 2); data are medians for 170-179 domestic wells located throughout Barry County
(excludes wells judged to be contaminated by anthropogenic NO
3
−
, NH
4
+
, or Cl
−
).
Notably, long-term monitoring of precipitation chemistry at KBS has shown a
marked reduction of SO
4
2−
and NO
3
−
wet deposition since the 1980s and a conse-
quent increase in the pH of precipitation (NADP/NTN 2011). Wet deposition of
SO
4
2−
has fallen from a mean annual rate of 28.8 kg ha
−1
yr
−1
in the 1980s to a mean
annual rate of 12.2 kg ha
−1
yr
−1
in recent years (2006-2010). A less marked but
significant decrease in NO
3
−
wet deposition is also apparent, falling from a mean
annual rate of 4.23 kg N ha
−1
yr
−1
in the 1980s to 2.51 kg N ha
−1
yr
−1
from 2006 to
2010. There is no apparent trend for NH
4
+
over this period. Precipitation acidity has
decreased greatly in conjunction with SO
4
2−
and NO
3
−
decreases; precipitation pH
