hacheon geuncheoui sseuregireul sugeohaessseupnida.

Because 근처의 is being used to describe the noun 쓰레기.

• 하천 근처의 쓰레기 = the trash near the stream = literally, the stream-nearby trash

Here, 의 turns 하천 근처 into a noun-modifying phrase.

If you say 근처에, that usually marks a location for the whole action:

• 하천 근처에 쓰레기가 있습니다. = There is trash near the stream.
• 하천 근처에서 쓰레기를 수거했습니다. = We collected trash near the stream.

So:

• 근처의 = modifies trash
• 근처에 / 근처에서 = marks where something exists or happens

In this sentence, 의 links one noun phrase to another, kind of like of or an adjective-forming connector in English.

• 하천 근처 = the vicinity of the stream / near the stream
• 하천 근처의 쓰레기 = trash of/from/in the vicinity of the stream

A very natural English translation is just trash near the stream.

Korean often uses 의 in places where English would not use of literally. Its job here is to make 근처 describe 쓰레기.

A longer equivalent would be:

• 하천 근처에 있는 쓰레기 = trash that is near the stream

So 근처의 is a shorter, more compact way to say that.

Because 쓰레기 is the direct object of the verb 수거했습니다.

• 쓰레기를 수거했습니다 = collected the trash

The particle 을/를 marks what receives the action.

Here:

• 쓰레기 = trash
• 를 = object marker
• 수거했습니다 = collected

So the sentence structure is basically:

• [하천 근처의] [쓰레기]를 [수거했습니다]
• [near-the-stream] [trash]-OBJ [collected]

수거했습니다 comes from 수거하다, which means to collect, to gather up, or to pick up for removal. It often sounds a bit more formal, official, or administrative.

So this sentence has a slightly report-like tone, such as something you might see in:

• a clean-up report
• a news article
• a public notice
• an environmental activity summary

Comparison:

• 수거했습니다 = collected / gathered up
  
  • formal, official-sounding
• 주웠습니다 = picked up
  
  • more literal, everyday
• 치웠습니다 = cleaned up / removed
  
  • focuses more on clearing away

For example:

• 하천 근처의 쓰레기를 수거했습니다.
  = We collected trash near the stream.

  • formal/report style

• 하천 근처에 있는 쓰레기를 주웠어요.
  = I/We picked up trash near the stream.

  • everyday speech

• 하천 근처 쓰레기를 치웠어요.
  = I/We cleaned up the trash near the stream.

  • conversational

Because Korean often omits the subject when it is already understood from context.

So 하천 근처의 쓰레기를 수거했습니다 could mean:

• We collected the trash near the stream
• They collected the trash near the stream
• I collected the trash near the stream

The sentence itself does not specify who did it. Korean leaves that to context very often.

If you wanted to add the subject, you could say:

• 우리는 하천 근처의 쓰레기를 수거했습니다. = We collected the trash near the stream.

But in many real situations, Korean speakers simply leave 우리는 out.

Not exactly.

• 하천 = stream/waterway/river channel
  
  • more formal, technical, administrative, environmental
• 강 = river
  
  • common everyday word

So 하천 is a very natural choice in a sentence about cleanup, public works, or the environment.

Examples:

• 강 근처의 쓰레기
  = trash near the river

  • everyday and general

• 하천 근처의 쓰레기
  = trash near the stream/waterway

  • more formal or official

Depending on context, 하천 may refer to a smaller waterway than a big river, but the bigger difference for learners is usually tone/register.

Yes, but it sounds a bit formal.

하천 근처의 쓰레기를 수거했습니다. feels like:

• a report
• a written summary
• an announcement
• a formal statement

In casual speech, people might say:

• 하천 근처 쓰레기를 치웠어요.
• 하천 근처에 있는 쓰레기를 주웠어요.
• 강가에 있는 쓰레기를 치웠어요.

So the original sentence is natural, but it is not the most casual everyday phrasing.

It is in the formal deferential style, often called the -습니다 style.

• 수거했습니다 = past tense, formal polite
• dictionary form: 수거하다

This style is common in:

• presentations
• reports
• news
• official speech
• writing with a formal tone

Compare:

• 수거했습니다 = formal polite
• 수거했어요 = standard polite, less formal
• 수거했어 = casual

So the sentence sounds respectful and somewhat official.

Yes, and that slightly changes the focus.

• 하천 근처의 쓰레기를 수거했습니다 = We collected the trash that was near the stream

This version treats trash near the stream as one noun phrase.

• 하천 근처에서 쓰레기를 수거했습니다 = We collected trash at/near the stream

This version emphasizes the location of the action.

Both are natural, but they are not exactly identical.

A simple way to remember it:

• 근처의 → describes which trash
• 근처에서 → describes where the collecting happened

In careful pronunciation, 의 is often taught as ui.

But in real speech, pronunciation can vary. In a phrase like 근처의, many speakers pronounce it more naturally like:

• 근처에
• or something close to 근처의, depending on speaking style

So learners should know two things:

1. The spelling is 근처의
2. The actual spoken sound is often simplified in natural speech

This is normal in Korean. You should still write 의, even if the pronunciation sounds reduced.

Yes. Korean nouns usually do not have to mark singular vs. plural.

So 쓰레기 can mean:

• trash
• the trash
• pieces of trash
• garbage

The context tells you whether it is one thing or many things. In this sentence, English would most naturally translate it as trash or garbage, not necessarily a piece of trash.

If you really wanted to emphasize plural items, Korean sometimes uses 들, but with mass nouns like 쓰레기, that is usually unnecessary.

The structure is:

• 하천 근처의 = near-the-stream / of the stream’s vicinity
• 쓰레기를 = trash + object marker
• 수거했습니다 = collected

So the full pattern is:

• [describing phrase] + [object] + [verb]

This is very typical Korean word order:

• modifiers come before the noun
• the verb comes at the end

A very literal breakdown would be:

• stream vicinity-of trash-OBJ collected

A natural English version is:

• Collected the trash near the stream
• or, with an implied subject, We collected the trash near the stream