Learn Hardcore Chinese: kōngqì wūrǎn zhème yánzhòng, yì gè yuányīn shì sùliào lājī tài duō. - For air pollution to be this serious, one reason is that there is too much plastic trash.

空气的污染 is not grammatically wrong, but it sounds less natural and more formal or bookish. In everyday speech and most writing, 空气污染 is the normal, idiomatic form.

What exactly does 这么 mean here, and how is it different from 很 or 那么?

In 空气污染这么严重, 这么 means “so / this (much)” and expresses a strong degree:

空气污染很严重 – The air pollution is serious. (quite serious, but neutral)
空气污染这么严重 – The air pollution is so serious (to this extent, more emotional).

Difference between 这么 and 那么:

这么 – “so … like this”, usually about something close to the speaker (in time, space, or context).
- 你怎么这么晚才回来？ – Why are you back this late?
那么 – “so … like that”, often about something more distant (or already mentioned).
- 他那边的空气污染那么严重。 – The air pollution over there is so serious.

In many casual contexts, 这么 / 那么 can be interchangeable, but 这么 feels more “here and now”.

Is 空气污染这么严重 a complete sentence, or is it just a phrase?

空气污染这么严重 is a complete sentence.

空气污染 works as the subject (“air pollution”).
这么严重 works as the predicate (“is so serious”).

In Chinese, you don’t always need a copula like 是 before adjectives. A very common pattern is:

[Subject] + [degree word] + [adjective]
- 天气很冷。– The weather is cold.
- 这个问题非常重要。– This problem is extremely important.
- 空气污染这么严重。– The air pollution is so serious.

So the first half is a full statement by itself; the comma just adds another related statement.

What is the role of the comma ， between the two parts of the sentence?

The comma is linking two related but separate clauses:

空气污染这么严重，
一个原因是塑料垃圾太多。

You can read it like English:

The air pollution is so serious; one reason is that there is too much plastic trash.

Chinese uses commas more freely than English. Here it functions similarly to a semicolon or “and/because/so” in English, but those connectors are often omitted when the logical relationship is clear from context.

Why do we say 一个原因是… instead of just 原因是…?

Both are possible, but they have different nuances:

原因是塑料垃圾太多。
– The reason is that there is too much plastic trash.
Implies this is the main or only reason.
一个原因是塑料垃圾太多。
– One reason is that there is too much plastic trash.
Clearly tells the listener that this is only one of several reasons.

So 一个原因是… signals that there are other causes besides the one being mentioned. It’s similar to English “one reason is …” vs “the reason is …”.

Why do we need 个 in 一个原因? Can we say 一原因?

Chinese almost always needs a measure word between a number and a noun. 个 is the default measure word for many abstract nouns, including 原因.

✅ 一个原因 – one reason
❌ 一原因 – unnatural / incorrect in modern standard Mandarin

There are some fixed phrases like 一原因是…一原因是… in old-style or classical Chinese writing where the measure word can be omitted, but in modern spoken and written Mandarin you should say 一个原因.

What does 塑料垃圾 mean, and could we also say 塑料的垃圾?

塑料垃圾 is a compound noun:

塑料 – plastic
垃圾 – garbage/trash

Together: 塑料垃圾 = plastic trash / plastic waste.

You could say 塑料的垃圾, but:

塑料垃圾 is the normal, concise, compound noun
塑料的垃圾 sounds more like “the trash that is plastic” and is less idiomatic in this environmental context.

Chinese tends to form tight noun–noun compounds (N1 + N2) before using 的. When N1 directly describes the material, type, or category of N2, you usually omit 的:

塑料袋 – plastic bag
纸箱 – cardboard box
玻璃瓶 – glass bottle

So 塑料垃圾 is the natural choice.

What’s the difference between 太多 and 很多 here? Could we say 塑料垃圾很多?

Yes, 塑料垃圾很多 is grammatically correct, but it’s slightly different:

太多 = too much / excessively many, with a negative or problematic feeling.
很多 = a lot / many, more neutral.

In this sentence we’re explaining a problem (serious air pollution), so 太多 is appropriate:

塑料垃圾太多。 – There is too much plastic trash. (It’s more than it should be / it’s causing problems.)
塑料垃圾很多。 – There is a lot of plastic trash. (Just stating quantity; may or may not be a problem.)

Because the sentence is about a cause of severe pollution, 太多 fits the logic better than just 很多.

Why doesn’t 太 have 了 after it, like in patterns such as 太贵了?

There are two common patterns with 太:

太 + adjective + 了
- expressing a strong, often emotional reaction:
- 这个菜太咸了。– This dish is way too salty.
- 天气太热了。– The weather is too hot.
太 + adjective / verb phrase (without 了)
- more descriptive, can be less emotional, especially in written or neutral style:
- 他太忙，没有时间休息。– He is too busy to rest.
- 塑料垃圾太多。– There is too much plastic trash.

With 多, it’s very common to say 太多, 这么多, 很多 without adding 了. Saying 太多了 is also possible and just a bit more emphatic or spoken. In this more neutral explanatory sentence, 太多 without 了 sounds fine and natural.

Can 严重 be used for people, or only for problems like pollution?

严重 is generally used for serious situations, problems, conditions, not for describing a person’s character.

Common uses:

病情很严重。– The (patient’s) condition is very serious.
交通堵塞特别严重。– The traffic jam is particularly serious.
空气污染非常严重。– The air pollution is extremely serious.
问题很严重。– The problem is serious.
伤得很严重。– (He) is seriously injured.

You would not normally say a person is 严重 as a personality trait. Instead, you might say:

他很严肃。– He is very serious (in manner).
他的问题很严重。– His problems are serious.

Why doesn’t the sentence end with 了? Would 空气污染这么严重了 be correct?

空气污染这么严重了 is possible, but the meaning changes slightly:

空气污染这么严重。
– States a fact / general situation: “The air pollution is so serious.”
空气污染这么严重了。
– Often implies a change of state or a recent realization:
“The air pollution has become so serious (now)!”

The 了 adds a sense of “already / by now / has reached this point”, often with some emotional coloring (surprise, complaint, concern). In a neutral explanatory sentence (like in a textbook or article), it’s natural not to use 了.

How is 一 pronounced in 一个原因 in real speech?

In isolation, 一 is yī (first tone), but it changes tone in connected speech:

Before a fourth-tone syllable, 一 usually becomes second tone (yí).
Before a first, second, or third tone, it usually becomes fourth tone (yì).

In 一个原因:

个 = gè (fourth tone)
So 一 is pronounced yí: yí gè yuányīn.

In very careful or emphasized speech, you might still hear yī gè, but in natural speech yí gè is standard.