NL10 Trips against a Loose passive

[Mr_Pathetic]

Do you call this guy or raise him? He plays pretty loose passive preflop an passive till river where he makes all his plays. With that said about his river aggression, what is he doing this with and how often is he doing it?

Poker Stars - No Limit Hold'em Cash Game - $0.05/$0.10 Blinds - 5 Players - (LegoPoker Hand History Converter)

SB: $10.00
Hero (BB): $10.05
UTG: $9.25
CO: $2.05
BTN: $32.20

Preflop: Hero is dealt 8 7 (5 Players)
2 folds, BTN calls $0.10, SB folds, Hero checks

Flop: ($0.25) 7[img]/images/graemlins/heart.gif[/img] 2 7 (2 Players)
Hero checks, BTN checks

Turn: ($0.25) 9 (2 Players)
<font color="red">Hero bets $0.30</font>, BTN calls $0.30

River: ($0.85) A[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">Hero bets $0.50</font>, <font color="red">BTN raises to $5.10</font>, Hero????