A couple months ago, we collected soil samples to send off to the Filippelli lab. Dr. Gabe Filippelli is an earth scientist with international expertise in soil lead contamination and works at IUPUI. He is also a wonderful person and tremendous advocate for urban gardeners. He provides a FREE service to the community by testing for soil lead contamination. We decided to be ‘in the know’ and get our community garden soil tested. Soil lead contamination is very common problem in Indianapolis and other urban areas due to lead-based paint, leaded gasoline and the presence of lead smelters. We sampled along 3 east-west trajectories along the length of the lot (north, middle and south) in 4 places each (12 samples). We took a generous sample of soil up to about 6 inches deep and sent it off. Yesterday, Gabe contacted me with results:
|
Name
|
|
Organic matter
|
Pb
|
Mn
|
Ba
|
Cr
|
Cu
|
Zn
|
|
|
%
|
ppm
|
ppm
|
ppm
|
ppm
|
ppm
|
ppm
|
| S1 |
|
11.2
|
239
|
1062
|
119
|
26
|
20
|
211
|
| S2 |
|
9.6
|
292
|
981
|
126
|
21
|
15
|
265
|
| S3 |
|
10.2
|
182
|
952
|
116
|
32
|
19
|
186
|
| S4 |
|
11.6
|
137
|
804
|
114
|
19
|
17
|
180
|
| M1 |
|
8.8
|
104
|
954
|
109
|
22
|
12
|
166
|
| M2 |
|
10.6
|
105
|
974
|
110
|
21
|
13
|
151
|
| M3 |
|
9.5
|
191
|
932
|
124
|
20
|
15
|
172
|
| N1 |
|
10.9
|
158
|
952
|
126
|
25
|
20
|
193
|
| N2 |
|
9.7
|
135
|
1027
|
108
|
22
|
15
|
147
|
| N3 |
|
9.2
|
126
|
977
|
109
|
22
|
12
|
149
|
| N4 |
|
8.1
|
127
|
934
|
101
|
19
|
11
|
135
|
|
|
|
|
|
|
|
|
|
| Average of all gardens |
9.8
|
297
|
631
|
108
|
20
|
20
|
262
|
Unfortunately, we have lead-contaminated soil. Thankfully, we took the appropriate precautions and anticipated this possibility. The EPA says that it is not safe to plant vegetables in areas where the soils has more than 200 ppm of lead. As shown above, we have several areas where this is the case. Luckily, these are solely in areas where we do not have garden beds as they are shaded areas of the lot. Even in the borderline middle areas, there are no beds as this is where our wood-chipped area for hanging out has been designated. In the remaining areas, we have raised beds with a thick layer of cardboard beneath or the plan for fruit trees (soil lead contamination does not threaten fruit). The other benefit learned from this soil testing is that our garden lot has higher than average organic matter. This is surprising since the soil has not been amended. In addition, we would only anticipate the organic matter will improve as we add compost to our beds over the years. In any case, higher organic matter reduces the likelihood of individual plants to absorb lead thus further reducing the likelihood of food contamination. We will reduce remaining risks by making sure raised beds are 12″ or more deep with clean topsoil/compost and, if not, refraining from planting root crops (carrots, radishes, etc). We will also make sure to have covered surfaces throughout the lot – either woodchips, garden beds, or grass. The bare ground offers another source of health risk, particularly for kids, who are more likely to ingest dirt while playing (or afterwards from not washing their hands).
For more information on Dr. Filippelli’s free soil lead testing program and other lead contamination resources, please check out the IndyTilth website under ‘local soil contaminant testing’. We will keep you posted on whether we find ways to test our bounty for lead contamination – the true test of whether our soil remediation is successful. Please stay tuned…
