Daily stream samples reveal highly complex pesticide occurrence and potential toxicity to aquatic life

Abstract

Transient, acutely toxic concentrations of pesticides in streams can go undetected by fixed-interval sampling programs. Here we compare temporal patterns in occurrence of current-use pesticides in daily composite samples to those in weekly composite and weekly discrete samples of surface water from 14 small stream sites. Samples were collected over 10-14 weeks at 7 stream sites in each of the Midwestern and Southeastern United States. Samples were analyzed for over 200 pesticides and degradates by direct aqueous injection liquid chromatography with tandem mass spectrometry. Nearly 2 and 3 times as many unique pesticides were detected in daily samples as in weekly composite and weekly discrete samples, respectively. Based on exceedances of acuteinvertebrate benchmarks (AIB) and(or) a Pesticide Toxicity Index (PTI) N1, potential acute-invertebrate toxicity was predicted at 11 of 14 sites from the results for daily composite samples, but was predicted for only 3 sites from weekly composites and for no sites from weekly discrete samples. Insecticides were responsible for most of the potential invertebrate toxicity, occurred transiently, and frequently were missed by the weekly discrete and composite samples. The number of days with benthic-invertebrate PTI ≥0.1 in daily composite samples was inversely related to Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness at the sites. The results of

Environmental Risk of Pesticides for Fish in Small- and Medium-Sized Streams of Switzerland

“…Contamination of surface water bodies with pesticides has been reported around the world [1,2] and attributed primarily to agricultural and, to a lesser extent, urban sources [3]. In Switzerland, several long-term monitoring studies conducted between 2012 and 2018 detected high numbers and concentrations of pesticides in small-and medium-sized streams predominantly flowing through agricultural land [4][5][6].…”

“…1 Chronic refers to time-proportional two-week composite samples (2012, 2018) and time-weighted averages over 14 day (2015, 2017), respectively; 2 acute refers to: 0.5-day composite samples (up to 24-day during dry periods, 2015) and 3.5-day composite samples (2017); a pyrethroids were analyzed at only 1 of 5 sites in 2017; b monitoring in 2018 was focused exclusively on 23 pyrethroid insecticides and chlorpyrifos/-methyl, c samples collected from one site (Chrümlisbach, BE) in 2017 were additionally analyzed for chlorpyrifos with a lower LOQ as part of a special study; the period of exceedance based on that dataset was 91 days.…”

Ecological consequences of neonicotinoid mixtures in streams

“…Pesticides were frequently detected (86% of samples) and occurred ubiquitously (97% of sites) in Coastal California streams. While pesticide concentrations ranged from below the laboratory reporting level to as high (sum of all pesticides) as 115 g/liter, our monitoring missed many daily peak exposure events (35). Of the greater than 120 pesticides detected in Coastal California streams (52), mixtures of six neonicotinoid compounds accounted for a large fraction of the total predicted pesticide toxicity (CIBQ neonicotinoids comprised 94% of mean CBIQ total ).…”

“…We conducted a 30-day mesocosm experiment to test the effects on aquatic communities of unary and binary exposures to IMI and CLO—two of the most toxic neonicotinoids ( 34 , 35 ) observed to co-occur frequently in U.S. streams ( 8 , 16 , 36 , 37 ). Our aim was to identify whether neonicotinoid mixtures might propagate lethal and sublethal ecological effects (i.e., emergence, trophic cascades, and predator-prey interactions) that diverge from predictions based on respective individual neonicotinoid exposures.…”

Investigating the Effects of Pesticides on Ramshorn Snails (Planorbella [Helisoma] trivolvis) Infected with Echinostoma spp.

“…Although the insecticides we used are rarely detected at concentrations above the nominal concentrations we used (maximum concentration observed in surface water: carbaryl 33.5 µg/L; malathion 9.58 µg/L US Geological Survey 2014), they have been observed at concentrations far exceeding those used in the present study (i.e., carbaryl 1737 µg/L [Walters et al 2003]; malathion: 539 µg/L [Odenkirchen and Wente 2007]). However, it should be noted that insecticides are less likely to be detected using common monitoring regimes (i.e., weekly sampling) because they can degrade more quickly than some herbicides (Norman et al 2020). Thus the nominal concentration for the insecticide treatments is representative of short‐term pulses following a runoff event or direct application to wetlands.…”