The harm of sulfide to aquaculture and its detection plan
Sulfides are compounds of -2 valent sulfur, and metal sulfides can be regarded as salts of hydrosulfuric acid. Metal and sulfur are directly reacted, or hydrogen sulfide gas is passed into the metal salt solution, or sodium sulfide is added to the salt solution, metal sulfides can be produced.
Under hypoxic conditions, it is produced by anaerobic decomposition of sulfur-containing organic matter in the residual bait or feces. Hydrogen sulfide can combine with the metal salt in the bottom mud to make the bottom mud black. Whether the hydrogen sulfide in the pond exceeds the standard, the simple criterion is whether there is the smell of rotten eggs at the downwind of the pond. Hydrogen sulfide is highly toxic and has strong irritation. It has corrosive and paralytic effects on the gill tissue of aquatic animals, and affects the respiration of aquatic animals. Shrimp hydrogen sulfide poisoning is manifested as anorexia, turmoil, and frantic swimming on the water surface. Therefore, hydrogen sulfide is required to be less than 0.2 mg/L in aquaculture water.
3. Testing plan:
Detection scheme 1:
① Methylene blue colorimetry (national standard). Lohand Biological Sulfide Kit Detection range: 0.02-0.8mg/L
② Detection principle: The sample is acidified, the sulfide is converted into radon sulfide, the hydrogen sulfide is blown out with nitrogen, and transferred to the absorption color tube containing zinc acetate-sodium acetate solution. With N,N-dimethyl-p-phenylenediamine It reacts with ferric ammonium sulfate to produce a blue complex methylene blue, measured at a wavelength of 665nm.
1.) Take a clean colorimetric tube and add the water sample to be tested to the scale line.
2.) Add the sulfide reagent I powder packet, slowly invert it, and shake it to dissolve it.
3.) Add 0.5ml (10 drops) of Sulfide Reagent II again, plug it quickly, slowly invert, and after standing for 5 minutes,
4.) Lift the tube to about 1cm away from the color card, and the standard color gradation from the top Under visual color comparison, the color gradation that is the same as the color of the solution in the tube is the sulfide content in the water (mg/L).
Note: The measuring temperature is 10～30℃. The water sample contains sulfite, thiosulfate, nitrite, thiocyanate, iodide, lead, mercury, copper and other heavy metals which interfere with the analysis of sulfide.
Detection scheme 2: Portable sulfide detector LH-M900
1.) Take a clean colorimetric bottle, add 10mL of the water sample to be tested, put it into the "sample colorimetric tank", press "Zero" to adjust the zero, and take out the zero colorimetric tube.
2.) Add 0.5mL reagent 1 to the colorimetric bottle.
3.) Add 4 drops of Reagent 2 again, shake it evenly, react for 5 minutes, and put it in the instrument for reading.
②Interference factors: 1.) The thiosulfate, sulfite and other reducing substances that react with iodine in the water sample produce positive interference. 2.) Suspended matter and chromaticity also interfere with the measurement.
③Precautions: When collecting samples, use clean brown glass bottles or plastic bottles, and fill them with sample solution, close the bottle cap tightly, seal and avoid light, avoid shaking the sample too much, and avoid prolonged contact with air due to aeration. Test immediately after sampling.