of pyrethroids has developed in the recent decade. Sediment toxicities toward the
benthic amphipod Hyalella azteca, toward the cladoceran Ceriodaphnia dubia, and
toward the midge of the Diptera Chironus dilutus are common tools to survey
environmental quality of freshwater sediments. When pesticides are also measured,
it allows to identify which toxicant causes the observed impairment [11, 38, 49, 59].
Recent monitoring studies document the occurrence of several pyrethroids in
riverbed sediments (Table 2) and have been reviewed at the global scale by Stehle
and Schulz [60]. Their residual occurrence in sediments is presently recognized as a
threat to diversity of sediment-dwelling invertebrates and also as the cause of a
decrease of diversity in aquatic environments at a global scale. Table 2 reports
sediment pyrethroid concentrations at sites covering several continents. In some
studies, sediment pore water concentrations are also given together with solid phase
sediment concentrations. The occurrence of pyrethroids in sediments evidences
clearly the propensity of pyrethroids to sorb onto and into particles. Owing to the
large organic carbon pool comprised in sediments, sediments have the potential to
act as a sink for pyrethroids. Organic carbon content, silt, and clay fractions are
sediment bulk characteristics that usually correlate with pesticide levels [11, 24].
The concern about pyrethroid sorption to sediments in Californian streams
exposed to agricultural and urban emissions led to the development of monitoring
programs addressing the benthic environment in addition to water-based surveys.
The considerable amount of data generated by those programs points to bifenthrin
being the most commonly found residues in the sediments (Table 2). In Del Puerto
Creek, a northern California stream flowing through agricultural land, it was the
main contributor to sediment toxicity, with a smaller contribution of cyhalothrin,
esfenvalerate, and cyfluthrin [37]. In sediments from the Santa Maria River (central
California), the pesticide chlorpyrifos was the main contributor to the toxicity to the
benthic amphipod Hyalella azteca, while cyhalothrin and permethrin also contributed to sediment toxicity in some locations in June 2002, but not in May 2003
[38]. In sediments collected in California from 2008 to 2012, the most frequent
pyrethroid detected was bifenthrin; the other active compounds cyfluthrin,
cyhalothrin, cypermethrin, deltamethrin, esfenvalerate/fenvalerate, fenpropathrin,
or permethrin, occurred in one fifth to one third of the samples [11]. Bifenthrin
was also the main pyrethroid in sediments of rivers alimenting Salton Sea in southern
California [41]. In an urban estuary of southern California (Ballona Creek, Los
Angeles), permethrin dominated over bifenthrin, while cypermethrin and cyfluthrin
were next in abundances [52]. In Minnesota, permethrin and bifenthrin were at the
top of pyrethroid sales, permethrin for animal care, structural applications, home and
garden holding, while bifenthrin was mostly used as crop chemical [44]. In this state,
33% of sediments of stormwater ponds contained permethrin and 20% bifenthrin;
this pattern was in line with results from other urban locations statewide as reviewed
by Crane [44]. Another nationwide study addressed metropolitan streams in the USA
and found bifenthrin detected in 47% of the bed sediments followed by cyhalothrin,
while permethrin, resmethrin, and cypermethrin occurred with much lower frequency [43]. Recent observations in 99 streams across Midwest USA also found
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L. Méjanelle et al.
benthic amphipod Hyalella azteca, toward the cladoceran Ceriodaphnia dubia, and
toward the midge of the Diptera Chironus dilutus are common tools to survey
environmental quality of freshwater sediments. When pesticides are also measured,
it allows to identify which toxicant causes the observed impairment [11, 38, 49, 59].
Recent monitoring studies document the occurrence of several pyrethroids in
riverbed sediments (Table 2) and have been reviewed at the global scale by Stehle
and Schulz [60]. Their residual occurrence in sediments is presently recognized as a
threat to diversity of sediment-dwelling invertebrates and also as the cause of a
decrease of diversity in aquatic environments at a global scale. Table 2 reports
sediment pyrethroid concentrations at sites covering several continents. In some
studies, sediment pore water concentrations are also given together with solid phase
sediment concentrations. The occurrence of pyrethroids in sediments evidences
clearly the propensity of pyrethroids to sorb onto and into particles. Owing to the
large organic carbon pool comprised in sediments, sediments have the potential to
act as a sink for pyrethroids. Organic carbon content, silt, and clay fractions are
sediment bulk characteristics that usually correlate with pesticide levels [11, 24].
The concern about pyrethroid sorption to sediments in Californian streams
exposed to agricultural and urban emissions led to the development of monitoring
programs addressing the benthic environment in addition to water-based surveys.
The considerable amount of data generated by those programs points to bifenthrin
being the most commonly found residues in the sediments (Table 2). In Del Puerto
Creek, a northern California stream flowing through agricultural land, it was the
main contributor to sediment toxicity, with a smaller contribution of cyhalothrin,
esfenvalerate, and cyfluthrin [37]. In sediments from the Santa Maria River (central
California), the pesticide chlorpyrifos was the main contributor to the toxicity to the
benthic amphipod Hyalella azteca, while cyhalothrin and permethrin also contributed to sediment toxicity in some locations in June 2002, but not in May 2003
[38]. In sediments collected in California from 2008 to 2012, the most frequent
pyrethroid detected was bifenthrin; the other active compounds cyfluthrin,
cyhalothrin, cypermethrin, deltamethrin, esfenvalerate/fenvalerate, fenpropathrin,
or permethrin, occurred in one fifth to one third of the samples [11]. Bifenthrin
was also the main pyrethroid in sediments of rivers alimenting Salton Sea in southern
California [41]. In an urban estuary of southern California (Ballona Creek, Los
Angeles), permethrin dominated over bifenthrin, while cypermethrin and cyfluthrin
were next in abundances [52]. In Minnesota, permethrin and bifenthrin were at the
top of pyrethroid sales, permethrin for animal care, structural applications, home and
garden holding, while bifenthrin was mostly used as crop chemical [44]. In this state,
33% of sediments of stormwater ponds contained permethrin and 20% bifenthrin;
this pattern was in line with results from other urban locations statewide as reviewed
by Crane [44]. Another nationwide study addressed metropolitan streams in the USA
and found bifenthrin detected in 47% of the bed sediments followed by cyhalothrin,
while permethrin, resmethrin, and cypermethrin occurred with much lower frequency [43]. Recent observations in 99 streams across Midwest USA also found
92
L. Méjanelle et al.