Biber et al. (2011) [12] research between L1 spoken language and written language based on different register. And they proposed a series of developmental stages for L1 writers of academic English. This can distinguish Phrasal complexity features of academic writing from academic spoken discourse, these five stages can be summarized as: in terms of grammatical form, it will be developed from finite dependent clause to non-finite dependent clause then it will be dependent phrase. As for syntactic function: the stages will be from using clausal constituents (such as direct objects or adverbial) to using noun phrase modifiers.

As can be seen from Table 3, this article has many applications for language expression of attributive adjectives with the Mean Statistics of which in this corpus is 56.2 and nouns as pre-modifiers whose Mean Statistics in this corpus is 47.8, which is the most frequent phrase unit used in the text. And it reflects the high complexity of phrases and the important role of nominal phrases.

This aim of this table is to make an overall agreement of the major types of noun modifiers in the corpus. Noun phrase modifiers play an important role in measuring the complexity of noun phrases, and they have specific discourse functions in a register. For instance, Lim (2012, p. 236) [14] reports that when referring to the research gap in academic writing, expert writers use “adjectives signaling insufficiency (e.g., ‘little’, ‘few’, etc.)… to modify nouns denoting investigations (e.g., ‘research’, ‘studies’)”. In this argumentation expository text, in order to make the readers have a better understanding of the destruction situation, many proper nouns such as “chlorinated hydrocarbon” and “the chlorofluorocarbons responsible” are used.

Noun phrases (NPs) are “strings of words with an internal structure centered around an obligatory head, which may be supplemented by determiners, pre-modifiers and post-modifiers” (Ni, 2003, pp. 159e160) [15]. According to Biber et al. (1999) [16], the basic structure of noun modification includes four key components: Determiner + (pre-modification) + head noun + (post-modification and complementation).

De Hana (1987) [8] pointed out that, in non-fiction, complex noun phrases occur in various grammatical functional positions of sentences. Most of the noun phrases in subject position are simple noun phrases, especially those consisting of one word. However, as direct object and object complement, the composition of noun phrases is more complex and more diverse. Elliott and Joseph (2019) [17] points out that the types of noun phrases include nouns modified by adjectives, nouns modified by prepositions, nouns modified by participles, nouns modified by all words, nouns modified by attributive clauses, etc., and concludes that the highest density of complex noun phrases occurs in high-scoring compositions.

As mentioned in Table 2, noun phrases account for 38% of the total number of phrase types in this whole article. Noun phrase can function as subject or object for verb in whole text.

There is only one kind of example that there is only one headword in noun phrases used as subjects, which is a pronoun or a kind of appellation. In the passage, the author mainly describes his own experience on doing an investigation on environmental pollution. Such as “Two and a half years later/I/slept/under the midnight sun/at the other end of our planet, /in a small tent”. In the forth paragraph. This kind of noun phrase has simple structure and strong subjective color. These are all the author’s personal experiences, which also enhance the authenticity of the article.

In the example of m + h + q, it is common to use preposition phrase such as “of…” to act as post-modifiers of noun phrase. Multiple prepositional phrases can also appear as post-modifiers to nouns, as shown in stage 5 in Table 3. For example, “The 600 percent increase in the amount of chlorine in the atmosphere during the last forty years”, these noun phrases are long and complex.

The nominal phrases act as the object with one headword are proper nouns, such as “Washington D.C.” or the personal pronoun “me”, “them” etc. The structure of “d + h” accounted for the largest proportion in the statistics of noun phrases as objects. There are many determiners used in this article, such as “the military”, “the earth”, which shows the preciseness of the words choosing. The structure of “d + m + h + q” such as “all animal and plant life will face a new threat to their survival…”. The more modifiers, the higher the complexity of noun phrases. As can be seen from the statistics in the table, noun phrases with modifiers and post-attributive account for 78%. Therefore, we can say that this paper has a high complexity of noun phrases, and the register of this text is formal.

According to the comparison of Table 4 and Table 5, we can find that the length of subject-position noun phrases is generally shorter than that of object

M = modifier; h = headword; q = qualifier; d = determiner.

M = modifier; h = headword; q = qualifier; d = determiner.

position noun phrases, in which the constituent structure of a noun phrase is mostly “h” and “m + h”. This feature is consistent with the grammar rules of English, and is also the two important principles affecting the order of English word, namely “End weight” and “End focus”. Noun phrases functioning as subject should not be too long, otherwise it will give the reader a sense of unbalance.

The situation of Prepositional phrases acting as post-modifiers has the largest variety and the longest average length, which is an important factor in the study of the complexity of noun phrases. For instance, “The increased levels of chlorine” and “the amount of ultraviolet radiation” are nominal phrases, because its central word is a noun, but it includes a preposition group working as the post modifier. We can look at the following Table 6. Halliday has a special discussion on the phrases about preposition “of”, and believes that the “of” phrases are usually used as the post modifier of noun phrases, but it is not a typical prepositional phrase, because in most cases, “of” is not a process or predicate, but a structural marker in noun phrases. Its function is similar to that of particle to in verb phrases.

The nominal phrase with preposition of functioning as post-modifiers in this corpus can be regarded as a measure and can be replaced by the possessive form. For example, the amount of ultraviolet radiation can be expressed by “ultraviolet radiation’s amount”, it shows a kind of relation process. Li (2012) [18], analyzes the internal functional structure of this kind of noun phrases from the perspective of experiential function and interpersonal function. To be exact, as a qualifier of a noun phrase, a prepositional phrase cannot form a complete phase structure alone, but a clause is formed by the prepositional phrase and the headword it modifies, and the headword acts as a participant.

First of all, from the statistics of various phrase types in the text, we can conclude that, in the analysis of functional syntax, phrases are the main resources to create meaning, and the analysis of clauses is particularly important. For research question3: Based on the table above, we can say this corpus has high proportion of nominal phrases, verb phrases and preposition phrases. The complexity of Noun Phrases is related to the level of sentences. This shows that the language of this article is more difficult and the register is more formal which accord with the characteristics of written language.

And the using of Prepositional Phrases means the author gives a detailed description of the object in the text. Prepositional phrases also play an important role in the integrity of the article structure. Prepositional phrases and group are at the same rank between clauses and words but they have different concepts. A prepositional phrase consists of a preposition plus a nominal phrase, such as “in the atmosphere”, “during the last forty years”. As far as its function is concerned, prepositional phrases are either used as adjuncts to clauses, or as post modifier of nominal phrases (Halliday 1994: 311) [19]. When a prepositional phrase is used as an adjunct to a clause, it is used to tell us what the environment in which the clause occurs is like. In other words, it is used to answer interrogative pronouns such as when, where and how, such as “in the air above every country”. It tells us the place where the polluted air came out.

In corpus, Subordinate Phrases also accounts for a large proportion. They are used to express the relationship between different clauses, sometimes it is a parallel relationship, and sometimes it is a progressive relationship. Attributive clauses are used many times, relative pronouns such as “that” and “which” replaces the elements in the previous sentence. The clever use of complex sentence patterns also shows that the article is logically connected. However, the adjective phrases and adverbial phrases only count 8% in the whole corpus, which illustrate that it is not about describe some scenery, it is to explain an objective fact and let people pay attention to the seriousness of environmental pollution by way of reasoning.

In this analysis, I first considered the distributional patterns of different noun modifiers in the corpus based on their normalized frequency. According to the statistics, the most common types of noun pre-modifiers in the text are attributive adjectives and nouns, while prepositional phrases were the most common form of post-modification. Biber et al. (1999) [16] pointed out that, the highly using of noun phrases with nouns and adjectives as phrasal pre-modifiers as well as prepositional phrases as post-modifiers in conversation, are highly characteristic features of formal writing register.

Then in the comparison of different nominal phrases functioning as subject or object, we can find that noun phrases that appear in the subject position are short and mostly they are pronouns with only one headword, which are used to express the author’s opinion such as “we have by now all witness…”. This has reflected the argumentative nature of this article. Moreover, the frequent use of modifier phrases reflects the author’s meticulous description of the article and high level of language application. The structure and complexity of noun phrases are also restricted by the structural characteristics of English sentences, so noun phrases functioning as object are longer and more complex. Finally, the number of noun phrases in subject position is more than object-position noun phrases, but not by much. It shows that the author uses a lot of nominalization and in this way, the sentence structure is balanced, which reflects the completeness of the language use in the exposition.

This paper selects 12 paragraphs in the expository text Ships in the Desert to make statistics on the frequency of noun modifiers in the corpus, and then analyzes the complexity of noun phrases from the aspects of the function of noun phrases, phrase structure and average length of noun phrases. After analyzing the phrase structure, I have a better understanding of the internal structure between sentences. It also has a better understanding of the characteristics of language use and sentence connection as an argumentative expository text. That is, when the author needs to express his own point of view, the subject often uses the first person, using real experience to illustrate facts and it can enhance credibility. Besides, I also found that there are many writing skills in the paper. For example, in the ninth paragraph, many rhetorical questions trigger people’s thinking. This writing skill can be skillfully applied to argumentative writing, which is worth our learning.

First of all, there are still inaccurate and uncertain factors in the division of phrase structure. Secondly, it takes a lot of time in data statistics and calculations. In the case of a large amount of corpus, I hope to find a more labor-saving way. Finally, as for the judgment criteria of the complexity of noun phrases, different scholars hold diverse ideas and we can only learn from the views of authoritative scholars to analyze the complexity of noun phrases. Further research in this area needs to be improved and accomplished.

Firstly, in the future study, I want to research some special phenomenon in grammar, such as how to analyse “take place” this kind of verb phrase act as the gradual verbalization of noun phrases. And there are also some idiomatic uses that are established, such as “over all”, (in para 5), “acre by acre” etc.

Secondly, the corpus I chose is not complete in terms of all phrase types, and Genitive Phrases are not included in the corpus. Such phrases mainly express the meaning of ownership. Quirk et al. (1985: 328) [20] explained that “the genitive ending is not a case inflection of the noun but rather a ‘postposed enclitic’ and the function of genitive phrases are parallel to that of a preposition”. Under these explanations, the principal syntactic difference between the normal prepositional phrase and the genitive phrase is the sequence of the head element (h) and the complement (c). Later, it can be further studied in what types of text the genitive phrases are often used.

The analysis of noun phrase complexity is mostly used to test the writing level of second language acquisition students. The analysis and research on noun phrase complexity of different genres and corpus need to be further expanded.

Thirdly, the analysis of noun phrase complexity is mostly used to test the writing level of second language acquisition students. And its application of different genres and register need to be further expanded. For example, in newspaper texts, noun phrases show different features when applied to different sections, which further confirms the argument that noun phrases are used as important parameters to distinguish stylistic signs proposed by Jucker (1992) [7]. Wang and Zhang (2005) [21] studied noun phrase complexity in different pages of the Guardian in 2005. The results show that the pages with strong written features use more noun phrases and have more complex structures. The colloquial layout uses fewer noun phrases and has a simpler structure.