Abstract:

The content and the proportion of soluble ions in water are important indicators to assess water quality,but common methods used in hydrochemistry cannot reflect the two relationships simultaneously.Maucha diagram not only reflects the total concentration of eight main anions and cations in water(i.e.CO₃^2-,HCO₃^-,Cl^-,SO₄^2-,Mg²⁺,Ca²⁺,Na⁺ and K⁺),but also indicates relative and absolute concentrations for each ion simultaneously.Thus,the Maucha diagram is deemed to be very practical.However,due to the lack of professional software to plot Maucha diagram,the application of this diagram is very limited in hydrochemical research.In this paper,firstly,we introduced the evolution history of Maucha diagram which was proposed by Maucha in 1932 and developed by Hedgpeth and BROCH.Secondly,we introduced the components of Maucha diagram and its implications.This diagram makes up of a circle and eight quadrangles inside.The area of the tangent 16-sided polygon in the circle is utilized to represent the total concentration of eight anions and cations,and the area of the eight quadrangles represents the content of eight ions.In addition,the total cations and anions are supposed to submit the charge balance principle and the mass balance principle.Thirdly,the methods of how to establish a coordinate system and determine the coordinates of the circle and quadrangles in Maucha diagram were introduced in detail.Fourthly,the program flow of how to plot Maucha diagram based on Matlab was stated.Finally,taking the eastern Hunshandake Sandy Land in Inner Mongolia,China as an example,this paper illustrated the applications of Maucha diagram in the field of hydrochemical analysis for natural waters.The Hunshandake Sandy Land belongs to a climate transition zone near the middle-latitude boundary of semi-humid and semi-arid to arid climate.Elevations in Hunshandake Sandy Land decrease from ca.1 300 m in the southeast to ca.1 000 m a.s.l.in the northwest,while mean annual precipitation decreasing from ~450 mm in the southeast to 150 mm or so in the northwest.Since natural water in Hunshandake Sandy Land is characteristic of high concentration of NO₃^-and very low concentration of CO₃^2-,we used NO₃^- instead of CO₃^2- to plot Maucha diagram with Matlab.Before plotted Maucha diagram,we checked the ion data and only charge balance and mass balance data were used.Applications show that Maucha diagram has strong advantages in reflecting the total concentration of anions and cations,indicating the relative and absolute concentrations ions,judging the hydrochemical type of water body and spatial analysis for hydrochemical data.Compared to other computer languages,the Maucha diagram program written by Matlab can run on almost all kinds of computer systems,and have better readability and visualization.Moreover,based on hydrochemical characteristics of certain study area,the program can be developed to adapt to new situations,such as in this paper we use NO₃^- rather than CO₃^2- to plot Maucha diagram.Thus,the application of the diagram may improve the visual expression ability for hydrochemical data,enrich the application of diagrams in hydrochemistry,and provide a reference for further analysis of hydrochemical data.

Key words: Maucha Diagram')">

Maucha Diagram, hydrochemistry, Matlab, plotting, applications