Can the U0001f4a6 emoji be used to represent semen?

Yes; see Why is the splashing sweat emoji associated with semen?

For evidence that this is happening:

• Definitions offered by the public under: U0001f4a6 Sweat Droplets Emoji
• Urban Dictionary: U0001f4a6

• A boy sends this emoji when he is horny. ” Hey send nudes?? [math]unicode{x1F4A6}unicode{x1F4A6}[/math]”
• A girl would send this to her man, basically telling him that she was wet, while a man would send this to his girl saying that he came. Also it could just mean cum.
  Girl (text): Make me wet big daddy[math]unicode{x1F4A6}unicode{x1F4A6}unicode{x1F4A6}[/math] Boy (text): You made me cum so much[math]unicode{x1F4A6}unicode{x1F4A6}[/math]

And, well, Google. Lots of instances where it means sweat. Lots of instances where it means water. And lots of instances where it means vaginal secretions or semen. Disambiguating emoji, such as the eggplant or the tongue, may be present, and they may not.