Great post as usual. That roundup is powerful stuff. I wonder how much is making its way down the Mississippi to the Gulf dead zone?

In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world

... this is what the EPA says about it, BioD

Glyphosate is most often applied as a spray of the isopropylamine salt and is removed from the atmosphere by gravitational settling. After glyphosate is applied to forests, fields, and other land by spraying, it is strongly adsorbed to soil, remains in the upper soil layers, and has a low propensity for leaching. Iron and aluminum clays and organic matter adsorbed more glyphosate than sodium and calcium clays and was readily bound to kaolinite, illite, bentonite, charcoal and muck but not to ethyl cellulose.

Glyphosate readily and completely biodegrades in soil even under low temperature conditions. Its average half-life in soil is about 60 days. Biodegradation in foliage and litter is somewhat faster. In field studies, residues are often found the following year.

Glyphosate may enter aquatic systems through accidental spraying, spray drift, or surface runoff. It dissipates rapidly from the water column as a result of adsorption and possibly biodegradation. The half-life in water is a few days. Sediment is the primary sink for glyphosate. After spraying, glyphosate levels in sediment rise and then decline to low levels in a few months. Due to its ionic state in water, glyphosate would not be expected to volatilize from water or soil.

Based on its water solubility, glyphosate is not expected to bioconcentrate in aquatic organisms. It is minimally retained and rapidly eliminated in fish, birds, and mammals. The BCF of glyphosate in fish following a 10-14 day exposure period was 0.2 to 0.3.

So I wouldn't expect much of it reaches the Dead Zone.

That was very informative.

In the end, it all comes down to biodiversity. Poison Darts--Protecting the biodiversity of our world