I10-14

Question

The Stibnite mining area was intermittently mined for most of the 20th century, and decades after mining ceased, water quality in the area continues to be impaired. Concentrations of dissolved arsenic and antimony generally increased from upstream to downstream in the East Fork of South Fork of the Salmon River. Based on the majority of arsenic and antimony occurring in the dissolved phase, and inverse relationships with streamflow at most sites, the primary route of arsenic and antimony to surface waters is likely from groundwater. Mercury, in contrast, was directly related to streamflow and was associated with particulates, suggesting erosion of surface materials to be the primary route to surface waters.

TetyanaRokobit · Answer

Official Solution:   
 
The passage states that "the primary route of arsenic and antimony to surface waters is likely from groundwater", which would be at the upstream or headwaters of the river. In the passage the source of Mercury is contrasted to the inverse relationship to streamflow of arsenic and antimony, so it must occur downstream and in the final sentence of the passage it states posits the "erosion of surface materials to be the primary route to surface waters."

Correct answer:

Source of arsenic  "Headwater chemical infiltration"

Source of mercury  "Downstream sedimentary erosion"

Tpownage1 · Answer

I was unfamiliar with the term headwater, which was integral to answering the question correctly. This question may benefit from a term change i.e upstream in compliance with GMATs standard of not requiring outside, industry-specific information

Bunuel · Answer

This question was deactivated and removed from the database.

I10-14

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Source of arsenic	Source of mercury
		Downstream sedimentary erosion
		Upstream mining activities
		Headwater chemical infiltration
		Downstream mineral dissolution
		Upstream particulate contamination