Factors influencing the occurrence and distribution of neonicotinoid insecticides in surface waters of southern Ontario, Canada.

The widespread use of neonicotinoid insecticides and recent increased regulatory scrutiny requires the generation of monitoring data with sufficient scope and resolution to provide decision makers with a better understanding of occurrence and distribution in the environment. This study presents a wide-scale investigation of neonicotinoid insecticides used across the range of agricultural activities from fifteen surface water sites in southern Ontario. Using statistical analysis, the correlation of individual compounds with land use was investigated, and the relationship between neonicotinoid occurrence and hydrologic parameters in calibrated water courses was also assessed. Of the five neonicotinoids studied, imidacloprid, clothianidin and thiamethoxam exhibited detection rates above 90% at over half the sites sampled over a three year period (2012-2014). At two sites in southwestern Ontario, the Canadian Federal freshwater guideline value for imidacloprid (230 ng/L) was exceeded in roughly 75% of the samples collected. For some watersheds, there were correlations between the occurrence of neonicotinoids and precipitation and/or stream discharge. Some watersheds exhibited seasonal maxima in concentrations of neonicotinoids in spring and fall, particularly for those areas where row crop agriculture is predominant; these seasonal patterns were absent in some areas characterized by a broad range of agricultural activities.

Occurrence and Distribution of Carbamate Pesticides and Metalaxyl in Southern Ontario Surface Waters 2007-2010.

Surface water sampling in 2007-2010 measured the occurrence of carbamates and metalaxyl during base flow conditions and wet weather events in southern Ontario surface waters. Carbaryl, metalaxyl and pirimicarb were the most frequently detected compounds. In 2008 these three compounds were detected in over 50 % of the samples. Overall mean concentrations of carbaryl and metalaxyl over the course of the study (2007-2010) were 15 and 18 ng/L, respectively. Elevated concentrations of carbaryl (~100 to ~950 ng/L) appeared associated with wet weather (high flow) events, while highest concentrations of metalaxyl (~20-1330 ng/L) were correlated with base flow conditions. We attributed these observations as the result of runoff of carbaryl from the watershed during rain events, while metalaxyl contamination may have resulted primarily from spray drift.

Occurrence of glyphosate and acidic herbicides in select urban rivers and streams in Canada, 2007.

INTRODUCTION: Public and scientific concern has grown over the last decade in Canada over the cosmetic use of pesticides in urban centers. With this in mind, a national survey was designed to monitor eight commonly used herbicides in urban rivers and streams across Canada. MATERIALS AND METHODS: To coordinate sample collections across the country, samples were collected monthly on one of two predetermined dates from April to September, 2007 from 19 sites within 16 watersheds, including 15 sites downstream of urban lands and two reference sites. Water samples were also collected approximately three times from each watershed during or after precipitation events. All samples were collected using a common sampling protocol and all were analyzed using the same analytical laboratories. RESULTS AND DISCUSSION: The herbicides 2,4-D, mecoprop, dicamba, glyphosate and its major metabolite aminomethylphosphonic acid (AMPA) were most frequently detected. Using either herbicide concentrations upstream/downstream of urban centers or bromoxynil and clopyralid as indictors of agricultural inputs of herbicides to streams, it was clear that environmental concentrations of these herbicides downstream of urban areas were linked to urban use in Canada. Herbicide concentrations in streams draining urban areas were greater during or after significant rainfall events and, with the exception of glyphosate, were significantly greater in the Province of Ontario. Herbicide concentrations were not correlated to the proportion of the watersheds in urban land use. Also, there was no difference in seasonal patterns of herbicide concentrations across urban centers when grouped in five geographic areas. None of the herbicide concentrations measured exceeded existing Canadian Water Quality Guidelines for the protection of aquatic life. CONCLUSIONS: This is the first time a national survey of pesticides in urban rivers has been carried out in a consistent fashion across Canada. Concentrations of 2,4-D, mecoprop, dicamba, glyphosate, and AMPA were linked to urban use and frequently detected in all geographic areas. However, geographic differences in concentration suggested differences in usage or stream connectivity patterns among urban centers. Some jurisdictions in Canada have recently restricted cosmetic use of pesticides and it would be interesting to determine whether such restrictions will lead to reduced pesticide concentrations in urban streams.

Occurrence and distribution of sulfonylurea and related herbicides in central Canadian surface waters 2006-2008.

Surface water sampling in 2006-2008 measured the occurrence of sulfonylureas and related herbicides (SUs) during base flow conditions and wet weather events. Flumetsulam (29.2%), diuron (36.5%) and fomesafen (25.3%) were most frequently detected over the course of the study. Typical SU concentrations were in the low parts per trillion range; however, maximum concentrations of fomesafen (873 ng/L), linuron (856 ng/L) and diuron (2,900 ng/L) approached or exceeded 1 µg/L. The temporal trend in SUs showed a correlation with application periods. In general, detections of SUs were more frequent where rotation of row crops was more intense. Sampling during wet-weather events indicated potential for a range of SUs to be flushed into surface waters at relatively high concentrations.

Comparison of concentrations and stereoisomer ratios of mecoprop, dichlorprop and metolachlor in Ontario streams, 2006-2007 vs. 2003-2004.

Mecoprop, dichlorprop and metolachlor concentrations and enantiomer signatures were determined in Ontario streams in 2006-2007 and compared to results from 2003 to 2004. Median concentrations of dichlorprop and metolachlor were not significantly different between the two campaigns, but mecoprop was higher in 2006-2007. Concentrations of mecoprop and dichlorprop in Lake Ontario surface water were 1-2 orders of magnitude lower than stream averages. Enantiomer fractions (EFs) > 0.5 of mecoprop in high-concentration stream water samples during 2006-2007 were related to replacement of racemic mecoprop by single (+) enantiomer mecoprop-P after 2004. EFs <0.5 in low-concentration samples suggested enantioselective degradation and/or interconversion. Metolachlor profiles were expressed as SF, the fraction of herbicidally active/(active + inactive) stereoisomers. Samples with higher concentrations of metolachlor had SFs similar to S-metolachlor which is enriched in the active stereoisomers. Low concentrations were associated with lower and more variable SFs, suggesting mixed input of racemic and S-metolachlor or stereoselective degradation.

Chiral current-use herbicides in Ontario streams.

Concentrations of mecoprop, dichlorprop, and metolachlor were investigated in 393 samples from Ontario streams in 2003-2004. Maximum concentrations of mecoprop, dichlorprop, and metolachlor were 1900, 6.62, and 1560 ng L(-1), respectively in 2003, and 103,000, 110, and 5290 ng L(-1), respectively, in 2004. Concentrations of metolachlor in agricultural watersheds were significantly (p < 0.0001) higher than those in urban watersheds, whereas concentrations of mecoprop did not differ (p > 0.1) between the two watershed types. Enantiomer fractions (EFs) of the acid herbicide mecoprop ranged from 0.236 to 0.928 and for dichlorprop EFs ranged from 0.152 to 0.549. EFs of mecoprop did not differ significantly (p > 0.1) between agricultural and urban land usage. Mecoprop EFs > or = 0.5 were found in 54% of samples, a situation expected during the transition years when racemic mecoprop was replaced by mecoprop-P, consisting of only the R(+) enantiomer. However, EFs < 0.5 were found in 46% of samples, which suggests preferential degradation of R(+) or conversion of R(+) to S(-). The four stereopluisomers of metolachlor were separated by HPLC and are reported as the ratio of the two herbicidally active stereoisomers (aS,1'S and aR,1'S) to the two inactive stereoisomers (aS,1'R and aR,1'R). The average S/R of metolachlor in streams was 6.73 +/- 2.28 and ranged from 1.08 to 12.7. Samples with higher concentrations of metolachlor had S/R ratios similar to the S/R of S-metolachlor (enriched in aS,1'S and aR,1'S stereoisomers) whereas samples with lower concentrations display lower S/R ratios with greater variability, suggesting mixed input of racemic and S-metolachlor or stereoselective degradation. S/R values were significantly higher (p < 0.001) in agricultural than urban watersheds. Streamwater from row crop areas showed higher S/R ratios than streamwater from fruit growing areas (p = 0.036).

Effects on reproductive potential and endocrine status in the mummichog (Fundulus heteroclitus) after exposure to 17alpha-ethynylestradiol in a short-term reproductive bioassay.

A short-term reproductive bioassay with the mummichog (Fundulus heteroclitus) was developed to link changes in endocrine status to reproductive potential subsequent to endocrine disrupting substance (EDS) exposure. Sexually mature mummichog were separated by sex and exposed to the synthetic estrogen 17alpha-ethynylestradiol (EE2) at nominal concentrations of 0-100 ng/L for 21 days using a static daily renewal protocol. Half of the fish were sampled on Day 21. At 100 ng/L, male fish had induction of vitellogenin (VTG), increased gonadosomatic index (GSI), decreased testosterone production and decreased circulating 11-ketotestosterone (11-KT). Female fish had decreased circulating estradiol (E2) and testosterone (T) at 100 ng/L. There were some impacts at lower concentrations of EE2 in both sexes, though the results were not consistent. On Day 21, the remaining male and female fish were combined at each treatment and exposed for an additional 7 days during which spawning and fertilization success were also assessed. Males exposed to 100 ng/L EE2 exhibited VTG induction, increased GSI, and decreased T production on Day 28. Female fish had increased E2 and T production at 1 and/or 10 ng/L and circulating E2 levels remained depressed above 10 ng/L. Female fish exposed to 100 ng/L spawned fewer eggs; fertilization was also impaired. In a parallel exposure, measured EE2 water concentrations were approximately 10-20% of nominal for the 100 ng/L EE2 treatment over a 24-h static exposure; levels in the other treatments were below detectable levels. Fish exposed to nominal concentrations of EE2 below environmentally relevant levels (i.e., <10 ng/L) showed minimal effects while both the endocrine system and reproductive potential were affected at 100 ng/L EE2 (nominal).