Tracking pesticide use in the Saint Lawrence River and its ecological impacts during the World Exposition of 1967 in Montreal, Canada

Ecological Legacy of DDT Archived in Lake Sediments from Eastern Canada

“…This lack of chemical recovery in our NB lakes differs considerably from other paleolimnological studies of DDT contamination in North America ,,, and may be related to the unprecedented amounts applied in this province relative to most other North American regions. Between 1946 and 1962, the Fraser River watershed, British Columbia, had heavy aerial applications of DDT-based organochlorines; , however, total DDTs in modern sediments approached background values in all 6 study lakes and were well below PELs. , Similarly, contaminant levels in modern NB lake sediments far exceed even peak levels of Rhothane (ΣDDD; 50 μg/kg) observed from dated sediment records at Lake Saint-Pierre, ∼100 km downstream of Montréal, where this larvicide was applied directly to the river prior to the World Exposition in 1967 . Only Goodwin Lake located in the Northwest Miramichi River watershed, NB, shows ΣDDT less than the PEL in its two recent-most sediment intervals that date to post ∼1997; however, ΣDDE and ΣDDD from those intervals exceed the PEL values by 3.7 and 1.5 times, respectively.…”

“…Collectively, our NB headwater lakes record among the greatest regional contamination of DDT and its breakdown products within lakes in North America. ,,− Maximum levels recorded are striking and range from ∼139 μg/kg at Goodwin Lake to ∼4500 μg/kg at Upsalquitch Lake for total DDTs (Figure ), and historic levels in the latter exceeded probable effect levels (PELs) by 18, 212, and 452 times for ΣDDT, ΣDDE, and ΣDDD, respectively. Only Clear Lake, California (U.S.A.) shows consistently higher sedimentary organochlorine values after DDD was added directly to the lake between the ∼1940s and 1950s .…”

“…Freshwaters become contaminated with organochlorines via atmospheric deposition and terrestrial runoff, ,, but direct applications to surface waters has also occurred. For example, to reduce nuisance insects, ∼16 000 kg of dichlorodiphenyldichloroethane (DDD as Rhothane) were applied to the Saint Lawrence River near Montréal, Canada just before and during the World Exposition in 1967 . The low water solubility, high partitioning to organic matter and lipids, and resistance to biodegradation result in the accumulation of DDT and its breakdown products in sediments , and also its biomagnification through food webs .…”

“…For example, to reduce nuisance insects, ∼16 000 kg of dichlorodiphenyldichloroethane (DDD as Rhothane) were applied to the Saint Lawrence River near Montreál, Canada just before and during the World Exposition in 1967. 13 The low water solubility, high partitioning to organic matter and lipids, and resistance to biodegradation result in the accumulation of DDT and its breakdown products in sediments 6,14 and also its biomagnification through food webs. 15 The sediment half-life of DDTrelated organochlorines is generally >20 years but varies depending on site-specific conditions.…”

Regulation of Algal Bloom Hotspots Under Mega Estuarine Constructions in the Changjiang River Estuary

“…The other one occurs in the estuary, such as sea-crossing bridges, tidal flat reclamation, and deep-water channel constructions, which directly regulate the spatial characteristics of the hydrodynamic environment in the estuary and adjacent waters (Luan et al, 2016;. Numerous attention have been paid to how the river basin engineering projects affect the physical processes and ecosystem in the receiving coastal waters (e.g., Humborg et al, 1997;Pelletier et al, 2016;Bargu et al, 2019). By contrast, the impacts of estuarine engineering constructions were often considered to be at a local scale, with very few studies discussing its far-reaching consequence in the coastal water.…”