Question

This being his first visit there, he found a great deal to interest him.这里this是什么用法

为什么这样用，怎样翻译,,

Answer 1

This being ... 这是一个独立主格结构.
如果去掉This，句子就变成：Being his first visit there, he found ...
这时，he就成为being这个分词的逻辑主语了，但是，he和being不能构成逻辑上的主语，这个句子是不成立的。
解决的办法之一就是在分词前加上它本身自己的主语，即构成独立主格结构了。如本句话，前面半个句子实际上是This was his first visit there，因此就变成了This being his first visit there了。

独立主格结构有两部分组成，前一部份是名词或者代词，后一部分是非谓语动词。前后两部分具有逻辑主谓关系。独立主格结构在句中做状语，多用于书面语。 独立主格结构本身不是句子，在句子中作状语，表示时间、原因、条件、伴随、目的等，相当于一个状语从句或并列句。

题目中的句子，独立主格表示的就是原因，可以翻译为：这是他第一次去那儿参观，他发现有很多他感兴趣的东西。

再如：It being Sunday (= Because it is Sunday), we needn't go to school.
The work done(=After the work had been done), we went home.
Weather permitting (=If weather permits), they will go to the beach tomorrow.
He was lying on the grass, his hands crossed under his head (=and his hands were crossed under his head).

Answer 2

This being his first visit there, he found a great deal to interest him.

翻译：这是他第一次在那参观，他发现了很多吸引他的事物。
this　指代的是这个/这次，即这次参观活动。

Answer 3

This being his first visit there,这是一个独立结构，this在独立结构中做其逻辑主语。相当于一个原因状语；since this was his first visit there.

Answer 4

这里面的this是指示代词和being构成独立主格结构。
翻译为“这是他第一次到访那里，发现了很多令他感兴趣的事”。