No explosion, but yes toxic-smelling sort of burn-y odor.

...Oops.

She'll stand so she can evaluate the damage, and also start moving away from the odor - probably not great to breathe in. 

Looks like some of the compounds in that reservoir don't especially like to be exposed to oxygen. The whole thing's kind of melting into a sad waxy lump.

...She should not get close enough to the toxic-smelling lump to analyze it, at least not without creating and testing some kind of breathing aparatus - actually, she can make a basic gas mask very quickly, to enable such poking before it finishes melting. 

She can get a sense of some of the interesting chemistry going on there! Maybe even without losing the tips of her fingers!

It's going to be no good for the local ecosystem, that much is for sure.

She'll create a protective glove for her flesh hand - the automail should be fine - and after a quick analysis she'll alchemize the lot into something harmless - hydrogen and oxygen naturally can be clumped into water, the excess hydrogen can pretty much just react with oxygen in the air, it's fine, it'll do that on its own if she purifies it and sets it on fire - metals she sorts out by potential danger, uses the numerous carbon atoms to wrap anything deeply iffy in layers of diamond, any radioactive atoms will be a pain in the ass but she can manage those fine with a casing of alternating layers of diamond and water - most metals can just be turned into rocks by attaching them to carbonate or carbonate hydroxide - which she has the atoms for in abundance, though heavy metals will have to be prevented from just leeching out later -

If she gets into the chemistry enough, she may not notice someone else showing up to the scene of the crime.

"Yo, what the fuck are you doing," comes a voice from above.

She looks up - blinks - one of the natives, clearly, is her entire body automail - she's got a few missing skin panels so possibly - 

"Uh, I kind of accidentally destroyed it, and then I didn't want it damaging the local environment so I'm neutralizing the more dangerous compounds."

"Fuckin' prodigy of destruction, huh. Didn't they tell you not to mess with the YoRHa shit, kid?"

"YoRHa???"

Bellona's interlocutor descends from her perch in the tree (by doing a completely unnecessary frontflip down) and stalks closer. The underbody below the missing panels of skin is the same black as the remnants of cloth that cling to her torso. Combined, the effect looks something like tattered lingerie. A wickedly sharp sword hovers just behind her back, a ring of the same yellowy-gold circling around a weirdly complicated-looking hilt.

"Yeah, YoRHa, the self-important space commandos. I thought you were Resistance. Who the hell are you?"

"Bellona Elric - I'm not from this universe actually, and I got dropped here with, uh, kind of minimal explanation."

"What the fuck. I do not get paid enough for this shit."

"You're- human?"

She pulls her gas mask away - she's neutralized the toxins anyways - and smiles a bit sheepishly. "Yeah."

"Aw, hell."

"What's wrong?"

"People are going to flip their shit when they find out and it'll be a huge pain in the ass."

She probably should've guessed it'd be something like this when Zera said she'd be the 'only living human,' oops. 

"I'm not really... Politics." Being the Herald of Andraste sucked enough, especially after the Truth took her hand and her ability to close the stupid Fade tears with it, meaning she was both a figure of tremendous religious focus and an abject failure who'd given up on even trying to save her timeline in favor of saving a girl she hadn't even met for the sake of a timeline she'd never see - 

Annnd now she's sad. 

"Well, I'm not about to tell anyone. You don't either, problem solved."

"Thanks." Might not work for long, but hopefully she'll have enough time to get adjusted to this world. 

"...Gonna keep wandering around breaking stuff, then?"

She laughs a bit. "I just wanted to know what it was! But I'll try to be more careful, especially if poking things will get attention."

Okay great now just walk away walk away walk away walk away-

"Got a plan for where to go?" FUCK

"...I was just going to wander."