American Journal of Anal yt ical Chemistry, 2011, 2, 962-970
doi:10.4236/ajac.2011.28112 Published Online December 2011 (
Copyright © 2011 SciRes. AJAC
Phenoxyacid Herbicides in Stormwater Retention Ponds:
Urban Inputs
Renata Raina*, Michele L. Etter, Katherine Buehler, Kevin Starks, Ywomo Yowin
Department of C hemist ry & Biochemistry, Trace Analysis Facility, University of Regina, Regina, Canada
E-mail: *
Received October 2, 2011; revised November 4, 2011; accepted November 14, 2011
Surface water runoff from urban centers is a major source of environmental pollution which impacts water
quality in downstream aquatic habitats. Phenoxyacid herbicides are some of the most widely globally used
herbicides in agriculture and urban environments for weed control. Their transformation products which in-
clude chlorophenols can be more toxic than the active ingredients. We used LC/MS/MS to analyzed simul-
taneously these acid herbicides and their transformation products in stormwater retention ponds taken from
an urban environment to examine the occurrence and potential release of these herbicides from urban inputs
into downstream waters. 2,4-dichlorophenoxyacetic acid and mecoprop were detected in all samples col-
lected from the ponds and at the highest concentrations, while 2-methyl-4-chlorophenoxyacetic acid was de-
tected only in spring and summer. Two transformation products, 4-chloro-2-methylphenol and 2,4-di-
chlorophenol were detected in samples primarily at inlet locations on the ponds indicating that degradation
had occurred in surface soils prior to surface water runoff.
Keywords: Phenoxyacid Herbicides, Chlorophenols, Stormwater Retention Ponds, LC/MS/MS
1. Introduction
Phenoxyacid herbicides were introduced in the 1940s
and have widespread use in agriculture and urban areas
to control the growth of broad-leaved weeds in cereal
grains, oil seed, and legume crops and grasses. To im-
prove their efficacy agricultural formulations often con-
tain more than one acid herbicide such as 2,4-D (2,4-
dichlorophenoxyacetic acid) with dichlorprop or bro-
moxynil (a nitrile herbicide); and MCPA (4-chloro-2-
methylphenoxyacetic acid) with bromoxynil, MCPB
(4-chloro-2-methylbenzoic acid), or dicamba [1]. Com-
mercial formulations are also available for bromoxynil,
MCPA and 2,4-D as an ester (2-ethylhexylesters) or al-
kaline salts (potassium or dimethylamine) rather than the
free acid. However, the ester or salts of these herbicides
undergoes hydrolysis in the environment to form the free
acid [2]. The highest agricultural usage is expected in
spring to early summer for crops such as wheat, barley,
and flax [3,4].
Phenoxyacid herbicides have been less widely studied
than other herbicides but have been detected at ng·L–1
concentrations in surface waters throughout the prairies
including wetlands, small prairie communities, and farm
dugouts with 2,4-D > MCPA > dicamba bromoxynil >
dichlorprop > MCPB [2-6]. Numerous other surface wa-
ters worldwide impacted by agricultural lands have re-
porting 2,4-D, mecoprop, or dichlorprop [7-14]. Pesti-
cides can move in the environment by atmospheric
transport, wet deposition, or be transported by surface
rain-generated runoff from soils or surfaces [2,5,14-18].
As phenoxyacid herbicides have high water solubility
ranging from 44 mg·L–1 to 4500 mg·L–1 (Table 1) sur-
face water runoff is the major transport pathway. They
are non-persistent in soil with t1/2 < 20 days (except
MCPA which is moderately persistent) [15,19], and have
low volatility relative to other herbicides [6]. Factors
important to surface water runoff include high precipita-
tion events, mode of application, soil moisture, soil tex-
ture and topography, type and amount of ground cover,
and distance of transport. Lower pesticide concentrations
have been observed when there is less erosion, dry
coarse textured soils, ground cover, shallow slopes for
transport on surfaces, and soil-incorporated pesticides
Urban herbicide usage includes weed control for lawn
and gardens, roadsides, golf courses, and parks and al-
though not well documented nonagricultural usage may
Table 1. Physical properties of the phenoxyacid herbicides.
Compound Soil half-life
Water solubility
MCPA 5 825
Mecoprop 21 620
MCPB 14 44
2,4-D acid 10 900
2,4-D iso-octyl ester 0.03‡
2,4-D dimethylamine salt 796000‡
Dichlorprop 10 710
2,4-DB 5 46
2,4,5-TP n.a. 200
Bromoxynil 7 130
Dicamba 4 4500
CMP n.a. 2300
DCP n.a. 4600
TCP n.a. 1200
DBHBA n.a. n.a.
†, MacKay et al., 2006; ‡, Waite et al., 2002; n.a., indicates va lues are not
account for up to 25% of total pesticide usage in some
regions of North America. The phenoxyacid herbicides
MCPB, dichlorprop, 2,4-DB and bromoxynil are not
registered for use in urban areas and the use of 2,4,5-TP
is not registered for both urban and agricultural use in
Canada. Common domestic products generally include
combinations of 2,4-D, MCPA, mecoprop and dicamba
such as Killex 500™ which contains 385 g·L1 2,4-D, 75
g·L1 mecoprop and 19 g·L1 dicamba, CIL Golfgreen
Weed & Feed™ which contains 0.99 wt% 2,4-D and
0.495 wt% mecoprop, and Ortho® Weed B’Gon® Max
which contains 0.22 wt% mecoprop, 0.12 wt% 2,4-D and
0.05 wt%. dicamba [20-23]. The common phenolxyacid
herbicides such as 2,4-D have been detected in urban
streams as well as surface and ground waters around golf
courses throughout North America [24,25].
Phenoxyacid herbicides such as 2,4-D and MCPA are
within the top 5 pesticides used for agriculture in the
province of Saskatchewan (Canada) with 2003 provincial
usage at 90,300 kg, and 88,700 kg, respectively. In 2003
dichlorprop, dicamba, mecoprop, and MCPB were used
in much smaller quantities in agriculture at 26,700, 9800,
5800, and 140 kg, respectively [26]. Bromoxynil is often
used in combination with the phenoxyacid acid herbi-
cides and its 2003 usage was 27,500 kg, similar to di-
chlorprop. No agricultural usage data is available for
Canada for 2007. The population of Regina continues to
grow and is currently approximately 199,000. Retail
sales are not available for homeowner usage, however
2007 usage in parkland and roadside areas by the City of
Regina for 2,4-D, mecoprop and dicamba were 235, 46,
and 11 kg, respectively with no reported usage of MCPA
or dichlorprop [27]. The objective of this study was to
examine the occurrence of phenoxyacid herbicides in
two stormwater retention ponds in an urban environment
(the City of Regina) as phenoxyacid herbicides are reg-
istered for use in urban areas. For selected periods we
also examined concentrations of phenoxyacid herbicides
on Wascana Creek aquatic environment which receives
inputs from the urban storm sewer system.
2. Materials and Methods
2.1. Study Site Description and Sampling
A total of 76 surface water samples were collected from
two stormwater retention ponds from May to October,
2007 during the expected period of usage for herbicides.
The stormwater retention ponds are located in the Win-
dsor Park residential area of the City of Regina and are
less than 1 km apart (Figure 1). The effluent from the
stormwater ponds enters the City of Regina’s under-
ground storm sewer system which drains into Wascana
Creek at the Prince of Wales storm trunk outlet just up-
stream of Rainbow Bridge. This storm trunk also collects
water from storm drains in the east residential portion of
the city. Several smaller creeks which receive stormwa-
ter runoff also directly release water into Wascana Creek.
Two sampling locations were selected on Wascana Creek,
a site upstream of urban inputs from the City of Regina
in the Mckell Wascana Conservation Park (labeled Was-
cana View Bridge) which can be impacted by agricul-
tural inputs, and a downstream site at Rainbow Bridge.
This downstream site is also just upstream of the Was-
cana Country Club golf course (Figure 1). The two storm-
water ponds are Windsor Park South and North. Windsor
Park South water samples were collected at the north
inlet structure and outlet of the pond, while Windsor
Park North water samples were collected at the East dock
nearby to the east inlet and at the west dock nearby to the
outlet of the pond. Windsor Park South is a more estab-
lished pond (1987) with surface area of 21,000 m2 and
operating depth of 1.8 m, while Windsor Park North was
built in 2005 designed as a modified natural wetland.
The surface area is 9000 m2 and its operating depth var-
ies from 0.5 to 2.7 m with deeper areas near the inlet and
outlet locations. At the time of the study the Windsor Park
North pond was surrounded by new home construction
and the landscape was not fully established. Water sam-
Copyright © 2011 SciRes. AJAC
Copyright © 2011 SciRes. AJAC
SouthIn let
We st Dock
Figure 1. Map of Southeast Regina showing Windsor Park North (WPN), Windsor Park South (WPS), and Wascana Creek
Upstream and Downstream Sampling Locations. Shown on right are expanded views of WPN and WPS stormwater ponds.
ples (1 L) were collected 10 cm below the surface of the
ponds and a number of samples were also collected from
a boat at different water depths (surface, approximately
half-depth, and full depth) which did not show significant
variation in concentrations. Precipitation data were ob-
tained from Environment Canada for the City of Regina.
2.2. Chemicals and Reagents
The Individual herbicide or transformation product stan-
dards were prepared at 1.0 mg·mL1 from solids supplied
by Chem Service Inc. (West Chester, PA, USA) and in-
cluded (3,6-dichloro-2-methoxy)benzoic acid (dicamba),
3,5-dibromo-4-hydroxybenzonitrile (bromoxynil), 2-
methyl-4-chlorophenoxyacetic acid (MCPA), 2,4-dichlo-
rophenoxyacetic acid (2,4-D), 2-(2-methyl-4-chloro-
phenoxy)propanoic acid (mecoprop), 2-(2,4-dichlorophe-
noxy)propanoic acid (dichlorprop), 4-(2,4-dichlorophe-
noxy)butanoic acid (2,4-DB), 2-(2-methyl-4-chlorophe-
noxy)butanoic acid (MCPB), 2,4,5-tichlorophenoxy pro-
panoic acid (2,4,5-TP), 3,5-dibromo-4-hydroxybenzoic
acid (DBHBA), 4-chloro-2-methylphenol (CMP), 2,4-
dichlorophenol (DCP), 2,4,5-trichlorophenol (TCP).
Deuterated internal standard (2,4-dichlorophenoxy-3,5-
6-d3-acetic-d2-acid (d5-2,4-D) was purchased as a solid
from C/D/N Isotopes Inc. (Pointe-Claire, Quebec, QC,
Canada) and 13C6-2,4,5-trichlorophenoxyacetic acid
(13C6-2, 4,5-T) and 13C6-2,4-D were purchased from
Cambridge Isotopes Laboratories (CIL) Inc., at 100
µg·mL1. These solutions were further diluted to 1000
ng·mL1 with pesticide grade methanol (Fisher Scientific,
Ottawa, ON, Canada) for standard solution preparation.
It should be noted that 2,4,5-trichlorophenoxy-3, 6-d2-
acetic-d2-acid (d4-2,4,5-T) is now available from C/D/N
isotopes and can be used to replace 13C6-2,4,5-T. Stock
solutions were diluted to 1000 ng·mL1 with pesticide
grade methanol for use.
Materials used for sample preparation included ethyl
acetate and methanol (pesticide grade, Fisher Scientific).
Deionized water was (<18 M cm resistivity) obtained
from a Nanopure diamond™ system (Barnstead Interna-
tional, Dubuque, Iowa, USA). OmniPur ammonium ace-
tate (>97%) and OmniTrace Ultra ammonia hydroxide
(>99%) were obtained from EMD Biosciences (Gibbs-
town, NJ, USA) and used in mobile phase and post-
column reagent preparation required for LC/MS/MS
analysis. All mobile phase solvents were passed through
0.45 µm membrane filters from Nucleopore (Whatman,
Florham Park, NJ, USA). HPLC grade glacial acetic acid
was obtained from EMD Biosciences (Gibbstown, NJ,
USA) and used for pH adjustment of water samples.
2.3. Sample Preparation and LC/MS/MS
A detailed description of the sample filtration, solid
phase extraction (SPE), and liquid chromatography-tan-
dem mass spectrometry (LC/MS/MS) analysis used for
quantifying the acid herbicides and their transformation
products can be found in Raina and Etter [28]. Filters
used for water sample filtration included Whatman
934-AD, Whatman 41 ashless and Whatman 0.45 µm
nylon membrane filters (Canadawide Scientific, Ottawa,
ON, Canada). A sequential filtration approach to smaller
pore size filters was used to reduce plugging of filters
and to speed up the filtration process. Following filtra-
tion samples were acidified to pH 4.9 and 10 mL of pes-
ticide grade methanol was added to facilitate flow for
SPE. ENVI-Chrom P, 1 g, 6 mL SPE tubes (Sigma-Al-
drich, Oakville, ON, Canada) were used to concentrate
the pesticides. Water samples were drawn through the
SPE cartridge at a rate of 200 mL·hr–1 by vacuum mani-
fold and then the SPE cartridges were dried with nitrogen
for 5 minutes until constant weight was achieved. The
filtration and SPE procedures were completed within 24
hours of sample collection and dried SPE cartridges were
stored at –4˚C until analysis. Herbicides were eluted with
8 mL of 60/40 v/v% methanol/ethylacetate and dried to
~0.95 mL followed by addition of a dilution standard
13C6-2,4,5-T (50 µL of 1.0 µg·mL–1). SPE recoveries
evaluated with 13C6-2,4-D were 90% ± 10%. An internal
standard d5-2,4-D (50 µL of 1.0 µg·mL–1) was used for
the LC/MS/MS analysis [28]. LC/MS/MS analyses were
performed at the Trace Analysis Facility at the Univer-
sity of Regina using a Waters LC system consisting of a
1525 µ binary pump, column heater, and a Quattro Pre-
mier tandem mass spectrometer (Waters-Micromass,
Milford, MA, USA) with electrospray ionization oper-
ated in negative ion mode. Post column reagent addition
of ammonium in methanol into a mixing tee using a
Shimadzu model LC-20AD pump (Man-Tech Associates,
Guelph, ON, Canada) was used to improve the sensitive-
ity of the transformation products. Herbicide concentra-
tions reported herein represent the dissolved fraction.
The method detection limits (MDLs) are 2 ng·L–1 for
TCP; 5 ng·L–1 for bromoxynil, MCPA, dichlorprop, and
2,4-DB; 10 ng·L–1 for 2,4-D, mecoprop, MCPB, 2,4,5-TP,
and DCP; 20 ng·L–1 for CMP; and 30 ng·L–1 for dicamba
and DBHBA. The MDL represents the minimum con-
centration showing <25% deviation of peak area from
the best-fit regression lines of the calibration curves for
both the quantitative and confirmation selected reaction
monitoring transitions [28]. Calibration standards ranged
from MDL to 150 ng·L1 with internal standard (d5-2,4-D)
at 100 ng·L1. Higher concentration samples were diluted
into the calibration range.
3. Results
3.1. Occurrence of Herbicides in Urban
Stormwater Retention Ponds
A total of 9 herbicides and 4 transformation products
were analyzed in water samples collected from the two
stormwater ponds. Herbicides MCPB, 2,4-DB, 2,4,5-TP,
dicamba and bromoxynil as well as the two transforma-
tion product of 2,4,5-TP and bromoxynil (TCP and
DBHBA) were not detected in any of the samples.
MCPB, 2,4-DB, 2,4,5-TP, and bromoxynil are not Regis-
tered for use in urban areas. However, dichlorprop which
is also not registered for use in urban areas was detected
in both Windsor Park South and North ponds (Table 2).
The City of Regina is surrounded by one of Canada’s
Table 2. Concentrations of Phenoxyacid Herbicides and Transformation Products Detected at Inlet and Outlet Locations for
two stormwater retention ponds.
Analyte Inlet Range (Average) ng·L–1 Inlet Df (%) Outlet Range (Average) ng·L–1 Outlet Df (%) p-value
Windsor Park South
2,4-D 111 - 1341 (593) 100 137 - 1538 (570) 100 0.81
Mecoprop 281 - 1094 (666) 100 361 - 1625 (750) 100 0.27
MCPA 21 - 186 (52) 60 19 - 180 (53) 85 0.94
Dichlorprop 47 - 1260 (816) 7 54 - 58 (56) 10 0.22
CMP 27 - 33 (31) 13 n.d. 15 0.29
DCP 22 - 50
(38) 20 n.d. 0 -
Windsor Park North
2,4-D 105 - 2755 (795) 100 136 - 1961 (562) 100 0.30
Mecoprop 351 - 2403 (917) 100 326 - 1528 (815) 100 0.55
MCPA 12 - 379 (178) 70 11 - 189 (81) 73 0.05
Dichlorprop 77 - 116 (102) 11 59 - 96 (73) 20 0.17
CMP 33 - 101 (53) 19 n.d. 0 -
DCP 302 (302) 4 n.d. 0 -
Copyright © 2011 SciRes. AJAC
Copyright © 2011 SciRes. AJAC
highest production regions for cereal grains and oil seeds
worldwide and suggests that there may be some unregis-
tered use of agricultural formulations within city limits.
Dichlorprop is used in agricultural formulations such as
Estaprop or Turboprop, both which contain 300 g·L1 of
dichlorprop and 282 g·L1 of 2,4-D [22]. In addition Ta-
ble 2 shows that the concentration range of dichlorprop
at Windsor Park South was much greater than at Windsor
Park North which is a new residential area. Figure 2(a)
shows higher levels of 2,4-D for August 21 which also
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2,4-D (ng/L)
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Mecoprop (ng/L)
5/1/075/31/07 6/30/07 7/30/07 8/29/07 9/28/0710/28/07
MCPA (ng/L)
5/1/075/31/07 6/30/07 7/30/07 8/29/07 9/28/0710/28/07
Precipitation (mm)
Figure 2. Phenoxyacid Herbicide Concentrations in Two Stormwater Retention Ponds and Precipitation Amounts in the City
of Regina. (a), 2,4-D; (b), mecoprop; (c), MCPA; (d), daily precipitation amount. WPN: Windsor Park North stormwater
pond; and WPS, Windsor Park South stormwater pond. Note: MCPA was not detected in samples collected during Sept-Oct,
2007. WPS Inlet; WPN Inlet; WPS Outlet; WPS Outlet; Wascana Creek Upstream; Wascana Creek Downstream;
nd total daily precipitation (obtained from Environment Canada). a
Copyright © 2011 SciRes. AJAC
had the highest concentrations of dichlorprop at the inlet
of Wascanca Park South. Both dichlorprop and 2,4-D are
present in the Turboprop formulation. Dichlorprop has a
short half-life (Table 1) [19] and its presence is expected
to be due to recent residential usage. Dichlorprop was
not detected at the upstream Wascana Creek site which
receives water inputs from agricultural land indicating
that the concentrations detected in the ponds is from re-
cent urban inputs.
Table 2 shows that 2,4-D and mecoprop were detected
in all samples taken from the two ponds and observed the
highest concentrations of the herbicides analyzed with
concentrations of 2,4-D and mecoprop reaching 2755
ng·L1 and 2403 ng·L1, respectively at Windsor Park
North inlet and 1204 ng·L1 and 1528 ng·L1, respec-
tively at Windsor Park South inlet. MCPA had a lower
detection frequency and was observed at lower concen-
trations in the two ponds than 2,4-D or mecoprop. CMP,
a transformation product of mecoprop and MCPA as
well MCPB (not detected) was detected in only 5 sam-
ples collected from Windsor Park North and 5 samples
collected from Windsor Park South. The detections in
Windsor Park North (June 12, 18, August 7, 21 and Sep-
tember 5) were all from the inlet location. The detections
in Windsor Park South were at both the inlet location
(June 11 and 26) and the outlet location (June 12, 18 and
July 25). DCP, a transformation product of 2,4-D and di-
chlorprop as well as 2,4-DB (not detected) was found in
only 1 sample on August 21 at the inlet location in Win-
dsor Park North, and 3 samples at the inlet location in
Windsor Park South (June 15, October 3 and 17). Given
that these detections of CMP and DCP occur primarily in
water samples taken at the inlet locations, this suggests
that degradation of the phenoxyacid herbicides has oc-
curred in soils from residential areas surrounding the
stormwater ponds prior to surface water runoff after a
rainfall event. Previous studies on contaminated agricul-
tural soils have shown that photodecomposition domi-
nates over microbial action in surface soils with t1/2 ~5
days and peak concentrations after 8 days with no irriga-
tion [29] thus indicating recent usage. Rainfall had oc-
curred on the day or previous day to sampling for all
periods where DCP or CMP were detected at the inlet. In
aquatic systems the aerobic biogradation of phenoxya-
cids is expected to be fast (within 14 days) [30], however
DCP and CMP had a lower frequency of detection at
outlet locations and indicates that the residence time of
water in the ponds was too short or microbial communi-
ties were not sufficient to provide significant biodegra-
dation of the herbicides. Figure 2(d) shows that there
was frequent rainfall during our study period (39% of
days), and 13 periods with rainfall for several days in a
weekly period and the majority of these periods with one
day or more with precipitation greater than 5 mm. The
stormwater ponds release water based upon the water
level in the ponds and generally these rainfall events
were sufficient to see movement of water to the storm
sewer system. Water flows at inlet and outlet locations
were not available.
3.2. Seasonal Variations in Herbicide
Phenoxyacid herbicides are used for lawn care for weed
control including during periods of fertilizing. 2,4-D
shows a maximum in concentrations in May, and a sec-
ond maximum in concentrations during late summer-
early fall (Figure 2(a)). Although 2,4-D inlet concentra-
tion range is smaller at Windsor Park South than Win-
dsor Park North (Table 2), the spring maximum is more
evident and the second maximum in 2,4-D concentra-
tions occurs latter in the season (September) at Windsor
Park South than at Windsor Park North (August). This
may be partially related to the fact that Windsor Park
South is a more establish pond and residential area,
whereas at the time of this study there was still new
home construction around Windsor Park North pond
with incomplete landscaping (ground cover) and high
flow of surface runoff and flooding apparent during
some rainfall events. Mecoprop observes similar sea-
sonal maximum at both ponds (Figure 2(b)) and is often
used in combination with 2,4-D. The higher concentra-
tions of 2,4-D and mecoprop are expected to be depend-
ent upon both fresh usage and rainfall. The rainfall event
at the start of the study on May 13-14 did not observed
high phenoxyacid concentrations, however samples col-
lected after the period of rainfall on May 19-23 showed
much higher concentrations. Greater dilution effect for
periods on or just after days with heavier rainfall (May
24, August 7 and 21) could be observed between inlet
and outlet concentrations particularly for Windsor Park
North stormwater pond.
MCPA, which has a lower detection frequency than
2,4-D and mecoprop, observes detectable concentrations
only during spring and summer. At the more established
pond (Windsor Park South) the highest concentration was
observed in mid-June, while at Windsor Park North high
concentrations were observed during this period as well
as on July 25 when rainfall occurred (Figure 2(c)). These
shifts in seasonal trends are related to the different phe-
noxyacid formulations in use during the summer months.
A number of formulations including Killex 500, CIL
Weed n’Feed, and Weed B’Gon contain both 2,4-D and
mecoprop which were the two most abundant phenoxya-
cid herbicides detected. Figure 3(a) shows the ratio of
,4-D/mecoprop determined for water samples collected 2
Copyright © 2011 SciRes. AJAC
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Ratio 2,4-D/Mecoprop
5/1/075/16/07 5/31/07 6/15/07 6/30/077/15/07 7/30/07 8/14/07
Ratio MCPA/Total Pehnoxyacid
Figure 3. Ratio of 2,4-D/Mecoprop and MCPA/Total Phenoxyacid Herbicides in Water Samples collected from two stormwa-
ter retention ponds. (a), 2,4-D/Mecoprop; and (b), MCPA/Total Phenoxyacid Herbicides. WPN: Windsor Park North storm-
water pond; and WPS, Windsor Park South stormwater pond. Note: MCPA was not detected in September and October,
2007. WPS Inlet; WPN Inlet; WPS Outlet; WPS Outlet; Wascana Creek Upstream; Wascana Creek Downstream;
and Ratio 2,4-D/Mecoprop (shown as line in A): Killex, 5.15; CIL Weed n’Feed, 2.0; and Weed B’Gon, 0.55.
from the ponds. The ratio is generally between the range
expected for the Weed B’Gon and CIL Weed n’Feed
formulations and lower than the Killex 500 formulation.
Some periods of higher ratio of 2,4-D/mecoprop latter in
the season (October 3 and 17) may also be influenced by
Killex 500 usage such as by City of Regina in parkland
areas or may be the result of 2,4-D from unregistered use
of formulations containing dichlorprop (which also con-
tains 2,4-D). In general Wascana Creek downstream con-
centrations also indicated similar ratios as the storm-
water ponds with exception of the August 7th at the
downstream Wascana Creek site (Rainbow Bridge) which
had higher concentrations and may be due to applications
of Killex 500 in parklands nearby to Wascana Creek.
Upstream ratio of 2,4-D/mecoprop in spring can be
higher than that of the stormwater ponds, however the
downstream ratio was reduced to similar range to that of
the stormwater ponds.
MCPA is present in formulations that contain bro-
moxynil and dicamba and not expected to be used in
combination with 2,4-D or mecoprop. The Killex formu-
lation used by the City of Regina does not contain
MCPA. There are formulations available for retail sales
to homeowners such as Yates Liquid Weed’n’Feed™
which contains 15 g·L1 MCPA and 2.3 g·L1 dicamba
[31]. Figure 3(b) shows the ratio of MCPA/total phe-
noxyacid herbicides for those sampling periods with de-
tectable concentrations of MCPA in spring and summer.
These ratios like MCPA concentrations are higher during
early to mid-summer with the higher ratio at Windsor
Park North indicating a greater influence of usage of
MCPA formulations in the new home construction resi-
dential area. In this new residential area we may be ob-
serving both homeowner and lawncare providers use of
different formulations for landscape of new properties.
The Windsor Park North site observed more direct sur-
face runoff from lawns directly adjacent to the ponds as
attributed to less established ground cover to retain water
and the steeper topology of the surrounding area.
3.3. Stormwater Ponds and Wascana Creek
Herbicide Concentrations
Although the range in phenoxyacid herbicide concentra-
tions varied significant during March-October 2007,
there was no significant difference in average concentra-
tions between the two ponds except for MCPA which
showed higher average concentrations at Windsor Park
North (132 ng·L1) as compared to Windsor Park South
53 ng·L1 (p = 0.0008). For 7 sampling periods where
rainfall had occurred the concentrations of phenoxyacid
herbicides and their transformation products were also
measured at the upstream and downstream locations on
Wascana Creek. Dichlorprop was detected in some water
samples collected at the outlet of the Windsor Park South
but was not detected in Wascana Creek samples. The
detection frequency of 2,4-D, mecoprop, MCPA, and the
two transformation products (DCP and CMP) was higher
at the downstream site than the upstream site on Was-
cana Creek. Average concentrations of 2,4-D, and meco-
prop in Windsor Park South were significantly higher
than the upstream Wascana Creek site, but only MCPA
was significantly higher than the downstream location.
This indicates that urban inputs from the storm sewer
system influenced concentrations downstream and in
general as previously discussed the ratio of 2,4-D/me-
coprop at the downstream location was similar to the
stormwater ponds. Windsor Park South pond is a sig-
nificant source of inputs and is also in closer proximity
to the release point of the storm sewer system into Was-
cana Creek than Windsor Park North and consequently
would exhibit less dilution during water transport. Me-
coprop average concentration was also higher at the
Wascana Creek North pond than water samples taken
from the upstream location on Wascana Creek for these
sampling periods. During the study period of May-Oc-
tober, 2007 only 3 sampling periods in Windsor Park
North and one of the seven sampling periods on Wascana
Creek downstream exceeded the Canadian water quality
guideline for the protection of aquatic life (4000 ng·L1
for total phenoxyacid herbicides) [32].
4. Conclusions
The most frequently detected phenoxyacid herbicides in
the two urban stormwater ponds were 2,4-D and meco-
prop consistent with phenoxyacid formulations such as
Weed b’Gon and CIL Weed n’Feed. Higher concentra-
tions of these phenoxyacid herbicides were observed in
spring and late summer-fall. Ratios of 2,4-D/mecoprop
were similar for samples collected at a downstream site
on Wascana Creek and indicate that urban usage influ-
enced concentrations of phenoxyacids on Wascana Creek.
However, most sampling periods had total phenoxyacid
herbicides below the Canadian water quality guideline
for the protection of aquatic life. MCPA was detected
only in spring and summer and had a different seasonal
variation than 2,4-D and mecoprop. There were higher
average concentrations of MCPA for Windsor Park
North where new home construction was still taking
place during this study period. It indicates in these two
residential areas that there are differences in formulations
used for control of weeds on lawns. Dichlorprop, which
is not registered for use in urban areas, was detected in
both ponds and indicates that there may be unregistered
usage of agricultural formulations in urban areas such as
Regina which is surrounded by a high production agri-
cultural region for grains and oil seeds. Detection of
transformation products (CMP and DCP) were more
commonly observed at inlet locations on the ponds. This
indicates that their degradation had occurred prior to
surface water runoff to the ponds. Rainfall events often
occurred over several days with insufficient time or en-
vironment within the ponds to observe further degrada-
tion of the phenoxyacid herbicide. Higher detection fre-
quency of CMP and DCP were also observed during
warmer months (summer-fall) although concentrations
and detection frequency were much lower than their
parent phenoxyacid herbicides.
5. Acknowledgements
This work was financially supported by Natural Sciences
and Engineering Research Council (NSERC) Discovery
Grant, and instrumental and facility support for the Trace
Analysis Facility from Canadian Foundation for Innova-
tion (CFI). Staff from City of Regina and National Re-
search Council-Centre for Sustainable Infrastructure Re-
search assisted with sampling, and total precipitation
data was obtained from Environment Canada.
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