根据国家颁布的有关法令，科学技术期刊必须使用法定汁量单位，并一律使用国际符号。本刊从1992年开始实行，并不断刊出有关法定计量单位的修订情况，但至今仍有一部分读者对单位符号的含义不大明确，因此，现根据本刊经常使用的土地面积单位及浓度单位再作如下说明。 According to the relevant decrees promulgated by the state, science and technology journals must use the legal juice units, and all the international symbols should be used. The publication has been in operation since 1992 and has been publishing the revision of statutory units of measurement. However, there are still some readers whose meanings of unit symbols are not clear enough. Therefore, according to the land area units and concentration units frequently used in this issue, Then make the following explanation.