This is actionable intelligence for those who deal with bees favoring
neighbors' water, about the only time that civilians even notice bees.
The full paper is not online yet, but not that Na = Sodium, Mg = Magnesium,
K = Potassium.

http://ncbi.nlm.nih.gov/pubmed/26823100

Abstract
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The importance of dietary salt may explain why bees are often observed
collecting brackish water, a habit that may expose them to harmful
xenobiotics. However, the individual salt preferences of water-collecting
bees were not known. We measured the proboscis extension reflex (PER)
response of Apis mellifera water foragers to 0-10% w/w solutions of Na, Mg,
and K, which provide essential nutrients,. We also tested phosphate, which
can deter foraging. Bees exhibited strong preferences: the most PER
responses for 1.5-3% Na and 1.5% Mg. However, K and phosphate were largely
aversive and elicited PER responses only for the lowest concentrations,
suggesting a way to deter bees from visiting contaminated water. We then
analyzed the salt content of water sources that bees collected in urban and
semi-urban environments. Bees collected water with a wide range of salt
concentrations, but most collected water sources had relatively low salt
concentrations, with the exception of seawater and swimming pools, which had
>0.6% Na. The high levels of PER responsiveness elicited by 1.5-3% Na may
explain why bees are willing to collect such salty water. Interestingly,
bees exhibited significant high individual variation in salt preferences:
individual identity accounted for 32% of PER responses. Salt specialization
may therefore occur in water foragers.

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