This outdoor small-scale automatic water quality monitoring station adopts an integrated design principle, including a water sampling and distribution system, a detection unit (five measurement modules for total phosphorus, total nitrogen, permanganate index, ammonia nitrogen, and conventional five parameters), a quality control unit, and an auxiliary unit (waste liquid collection, lightning protection, air conditioning, etc.). Among them, the core unit is the detection unit. The total phosphorus, total nitrogen, permanganate index, and ammonia nitrogen strictly follow the chemical analysis methods stipulated in the national standards. The conventional five parameters (dissolved oxygen, electrical conductivity, turbidity, temperature, and pH) are measured using a multi-electrode integrated method.
In an acetic acid buffer medium with a certain pH value, fluoride reacts with the fluoride reagent and lanthanum nitrate to form a blue ternary complex. Within a certain range, the absorbance of the complex at a specific wavelength is proportional to the fluoride ion concentration, which conforms to Lambert-Beer's law. Thus, the fluoride can be quantitatively determined.
This analyzer employs the potassium dichromate method. Sulfuric mercury is used as a masking agent and sulfuric silver as a catalyst. After thermal and high-pressure digestion, the COD value is determined by spectrophotometry.
When the fluoride electrode comes into contact with the fluoride-containing solution, the electromotive force E of the battery changes with the variation of the fluoride ion activity in the solution, following the Nernst equation.
