を-marked 非情-Passive in Adjectival Phrase

Question

I've come across this sentence in a publicly available preview of ノルウェイの森:

何日かつづいたやわらかな雨に夏のあいだのほこりをすっかり洗い流された山肌は深く鮮かな青みをたたえ。

I see two different ways of parsing the adjective phrase describing the topic, and I'm not sure which is correct.

1. 雨にほこりを流れる。 (S1)

In this interpretation, 山肌 is very loosely semantically linked to the phrase 雨にほこりを流す, as the location in which S1 occurred. 山肌 then, isn't an argument of the passive form 流される。Another example of this kind of loose relationship might be ケーキを食べるパーチ ->　ケーキを食べられるパーチ. I find this a bit odd that we have an agent and を-marked direct object but no clear subject in this passive construction, but I could believe that using を to mark the subject instead of が is motivated to de-emphasize the ほこり since we're in a subordinate clause. I'm not sure if this is correct, or if we outright have no subject in this clause.

In this case, I'd wager it's just more literary or objective to use the passive voice (ほこりを流される　vs　ほこりを流す), though literary and objective seem like contradictory ideas.

2)　山肌が雨にほこりを流される。(S2)

In this interpretation, 流される is an indirect passive, and 山肌 is adversely(?) affected by ほこりを流される, from the perspective of the speaker. This interpretation is syntactically correct, as far as I'm aware, but doesn't make much sense to me. Why does washing away dust adversely affect the mountain?

Are both interpretations valid for the text of the sentence? If #1 is correct, what are some other examples of this subject-less direct passive, and what's the semantic difference with the active form? If #2 is correct, is there an adverse connotation to the use of the passive form, why or why not?

Answer 1

That part is an indirect passive sentence.

山肌は雨にほこりを流された。
The mountain surface got its dust washed off by the rain.

  ↓ relativize

雨にほこりを流された山肌
the mountain surface whose dust has been washed off by the rain

But note that 持ち主の受け身 sentences are not always suffering passive sentences. For example, the following sentences have no negative meanings:

• 先生に息子をほめられた。
• 周囲を山に囲まれた町

(雨にほこりを流れる and 雨にほこりを流す are ungrammatical. ほこりを流れる might mean something like "to proceed within dust", but it doesn't make sense.)