Many studies reported pyrethroid concentrations in total water samples: the water
collected is directly adsorbed on a SPE cartridge or is directly solvent-extracted,
without previous filtration [12, 17, 22, 30]. Therefore, in these reports, both
dissolved and particle-bound pyrethroids are jointly extracted and reported. A
filtration step before pre-concentration was the preferred approach in some studies
[26, 28, 29, 31, 33, 48], and the concentrations reported herein are that of dissolved
pyrethroids, which includes the truly dissolved form and the colloidal-associated
pyrethroids as part of the dissolved organic carbon pool. Pollutants associated to
dissolved organic carbon are also retained in the adsorbents designed for sampling
truly dissolved pollutants, together with pollutants associated to colloids, as known
to occur for other hydrophobic chemicals [56]. Distinguishing concentrations of
dissolved active compounds from those of particulate ones is important because both
modes of occurrence are affected by distinct processes of transport and degradation
rates (see later), in turn shaping differently the ultimate fate of pesticides. A strong
recommendation for futures studies is to analyze separately the dissolved and
particulate phases [21], and in any case, to state clearly which phase is characterized.
The first part of Table 1 reviews dissolved and particle-bound pyrethroid concentration ranges. Whereas dissolved pesticides are bioavailable, it is not clear if the sorbed
pyrethroids are toxic through feeding intake or as a transient repository, being
desorbed later on and supporting the dissolved phase levels [31].
Pyrethroids dissolved in fresh and marine waters have been measured in a number
of studies worldwide with the objective to check whether their concentrations were
below thresholds of water quality guidelines. The dissolved form of pesticides is the
form that is bioavailable and represents a threat for arthropods and fish. Dissolved
pyrethroids were detected in agricultural drains, creeks, streams, and also in their
collecting large rivers downstream agricultural land (Table 1). For example, in seven
counties of California, 65–153 metric tons of pyrethroids were sold for licensed use
between 1999 and 2008 [52], and 422 tons for the whole California state in
2010 [18].
The occurrence of individual pyrethroids varies geographically and seasonally as
a response to agricultural use [19], and the consequent emission to the water, but
probably also to different seasonal and site degradation potential. In Hospital Creek,
a tributary of the San Joaquin River (Central California), bifenthrin was responsible
for the greatest part of the toxicity of particles, whereas cyhalothrin was the
prominent toxicant of particles in Ingram Creek, another tributary located less than
50 km away from the former [14]. Esfenvalerate and permethrin occurred in some
water samples of tributaries of the Sacramento River after storm events in 2003
[15]. In tributaries of the San Joaquin River, cyfluthrin and cyhalothrin were the most
frequent pyrethroids detected after winter storms, whereas bifenthrin and cyhalothrin
were only identified in samples collected in March [17]. In central California, several
surveys also reported bifenthrin as the main pyrethroid detected, its occurrence being
related to storm events [13, 14, 16], while cyhalothrin and esfenvalerate dominated
in the San Joaquin watershed [16]. Another study in Southern California sampled
San Diego River during storm events and showed that six pyrethroids were present
for 80% of the particle samples: bifenthrin, λ-cyhalothrin, permethrin, deltamethrin,
Fate of Pyrethroids in Freshwater and Marine Environments
89
collected is directly adsorbed on a SPE cartridge or is directly solvent-extracted,
without previous filtration [12, 17, 22, 30]. Therefore, in these reports, both
dissolved and particle-bound pyrethroids are jointly extracted and reported. A
filtration step before pre-concentration was the preferred approach in some studies
[26, 28, 29, 31, 33, 48], and the concentrations reported herein are that of dissolved
pyrethroids, which includes the truly dissolved form and the colloidal-associated
pyrethroids as part of the dissolved organic carbon pool. Pollutants associated to
dissolved organic carbon are also retained in the adsorbents designed for sampling
truly dissolved pollutants, together with pollutants associated to colloids, as known
to occur for other hydrophobic chemicals [56]. Distinguishing concentrations of
dissolved active compounds from those of particulate ones is important because both
modes of occurrence are affected by distinct processes of transport and degradation
rates (see later), in turn shaping differently the ultimate fate of pesticides. A strong
recommendation for futures studies is to analyze separately the dissolved and
particulate phases [21], and in any case, to state clearly which phase is characterized.
The first part of Table 1 reviews dissolved and particle-bound pyrethroid concentration ranges. Whereas dissolved pesticides are bioavailable, it is not clear if the sorbed
pyrethroids are toxic through feeding intake or as a transient repository, being
desorbed later on and supporting the dissolved phase levels [31].
Pyrethroids dissolved in fresh and marine waters have been measured in a number
of studies worldwide with the objective to check whether their concentrations were
below thresholds of water quality guidelines. The dissolved form of pesticides is the
form that is bioavailable and represents a threat for arthropods and fish. Dissolved
pyrethroids were detected in agricultural drains, creeks, streams, and also in their
collecting large rivers downstream agricultural land (Table 1). For example, in seven
counties of California, 65–153 metric tons of pyrethroids were sold for licensed use
between 1999 and 2008 [52], and 422 tons for the whole California state in
2010 [18].
The occurrence of individual pyrethroids varies geographically and seasonally as
a response to agricultural use [19], and the consequent emission to the water, but
probably also to different seasonal and site degradation potential. In Hospital Creek,
a tributary of the San Joaquin River (Central California), bifenthrin was responsible
for the greatest part of the toxicity of particles, whereas cyhalothrin was the
prominent toxicant of particles in Ingram Creek, another tributary located less than
50 km away from the former [14]. Esfenvalerate and permethrin occurred in some
water samples of tributaries of the Sacramento River after storm events in 2003
[15]. In tributaries of the San Joaquin River, cyfluthrin and cyhalothrin were the most
frequent pyrethroids detected after winter storms, whereas bifenthrin and cyhalothrin
were only identified in samples collected in March [17]. In central California, several
surveys also reported bifenthrin as the main pyrethroid detected, its occurrence being
related to storm events [13, 14, 16], while cyhalothrin and esfenvalerate dominated
in the San Joaquin watershed [16]. Another study in Southern California sampled
San Diego River during storm events and showed that six pyrethroids were present
for 80% of the particle samples: bifenthrin, λ-cyhalothrin, permethrin, deltamethrin,
Fate of Pyrethroids in Freshwater and Marine Environments
89