Environmental Stewardship/Watershed Protection Grant
ME# 350-488
Voluntary Minimal Lawn Chemicals Campaign
Sustainable Society Action Project, Inc.
Report on Sampling and Analysis Activities
Aug – Oct 2002
Laura Toran, Temple University
This report summarizes the NO3 and NH4 data collected in the summer of 2002. The
summer herbicide analysis is also reported here. Data from more detailed sampling of a
storm in September is presented as well.
There was a severe drought during this sampling period, but we managed to collect
samples for 2 storms per month nonetheless. However, it is possible that the drought
reduced use of lawn care chemicals, and this question should be pursued further through
homeowner surveys.
The NO3 concentrations were low at all of the sites this summer, mostly less than 1 or 2
mg/L. At Ridings, the NO3 reached 3 mg/L in June. This contrasts with the summer of
2001, in which concentrations rose to 3 or 4 mg/L in July or August. The highest
concentration was observed in the “control” site in Robbins Park that drains a field that is
not treated. In July, a sampled collected there had a NO3 concentration of 5 mg/L. NH4
and K were also high (see below). The park manager doesn’t know of any activity in the
field that would have introduced lawn chemicals. There is a house next door to the park,
and it is possible that runoff from their lawn on occasion drains to the park. The control
site data were not used in any statistical calculations, and it is clear that there is enough
uncertainty about source waters that they may not be a reliable control point for zero
lawn chemicals.
The NH4 concentrations were also low in the summer. Most were 1 mg/L or less.
Ridings saw concentrations around 2 mg/L, and the Robbins Park field had a
concentration of 1.8 mg/L in July at the same time the high NO3 was observed. The
highest NH4 concentrations were observed in the spring this year, reaching 5 to 7 mg/L at
Ridings, Greystone, and Wissahickon North.
Temple University obtained a new piece of equipment, an ICP-MS, which can analyze
trace levels of metals. We selected samples from the spring and summer of 2002 to
analyze trace metals at Ridings and Wissahickon North. The metals included As, Cd, Cr,
Fe, Pb, Se, U, and Zn. Except for Fe, which is widely varying in nature, the
concentration were all low, less than 5 mg/L. Although As is found in some herbicides,
there was no relationship between NO3 concentrations and As concentrations, so it would
not be a useful indicator of lawn chemical at these sites.
Samples for herbicide analysis were collected twice in the summer, one at the end of July
and another at the end of August. Samples were collected at the four remaining
neighborhood storm drain sites, but the sampler at the “control” pipe in Robbins Park did
not collect water for these storms. The samples were analyzed by the Philadelphia Water
Department. For July, all of the herbicides were below detection. For August, there was
a trace level (less than 1 ppb) of triclopyr and of bentazon at Ridings. The analytical
uncertainty for MCPP and MCPA was too high to report detection or not, but these
herbicides have not been prevalent in past sampling. Because the levels were low, the
absence of the control site data is not a severe problem.
Another goal for the summer was to attempt discrete sampling of a storm. A more
expensive sampler with 24 bottles (instead of only 2) was made available to the project.
This sampler could be set to collect at any interval, and a one hour interval was selected
for storm monitoring. In addition, we obtained a conductivity meter with a logger, which
collected data on overall ion concentrations at 30 minute intervals. A storm on 9/15/02
was monitored at two sites: Robbins Park Headwall (which drains the neighborhood next
to the park) had the discrete sampler, and Wissahickon North had the conductivity meter.
About 0.5 inch of rain fell in two periods: one period began around 4 pm and one began
around 9 pm. The sampler began collecting data around 6 pm, and the samples were also
collected in two periods with a gap in sampling when the water level dropped below the
intake tube. The concentrations of NO3 in the analysis peaked at 3 hours after sampling
began then peaked again at 13 hours. The peak concentrations were around 1 mg/L and
the low concentration was 0.2 mg/L. Two spikes were also observed in overall
conductivity at Wissahickon North. This sampling shows that there are significant
temporal variations in the storm water discharge. The storm monitored here had low
concentrations, so it would be premature to state that the composite sampler would have
missed the signal. Some additional storms should be studied to further understand the
implications.
The long term monitoring program was completed on Oct 11, 2002. A large storm with
flooding was predicted the week following, so the samplers were removed to prevent
damage. As it turns out, the flooding did not occur. However, since the samplers would
have been removed within the month because of cold weather, there did not seem to be
much benefit to re-installing the samplers after the October storm merely to collect data
during the off season.