Ammonia nitrogen, nitrate nitrogen and nitrite nitrogen are important nitrogen‑pollution indicators in surface water. Nitrogen pollutant overload is one of the main inducements of water eutrophication. Sudden pollution accidents, farmland surface runoff after rainfall and domestic sewage leakage may lead to sharp fluctuation of three‑nitrogen indexes in river and lake water bodies. In emergency monitoring scenarios, laboratory off‑line testing cannot deliver results rapidly. Compact hand‑held rapid detecting devices can arrive at sampling points quickly and complete on‑site data reading, providing real‑time basis for environmental risk early warning. YUNTANG hand‑held three‑nitrogen water‑quality detector targets field rapid screening for these three typical nitrogen indexes.

The hand‑held instrument runs on Android intelligent operating system and is fitted with a 3.5‑inch color touch screen. Visualized built‑in operation guidance simplifies operating steps, so on‑site personnel can master detection flow without long‑term professional training. It adopts imported cold‑light source with optical service‑life up to 100 000 hours, showing stable optical output and low daily maintenance demand. Detection depends on decomposition‑colorimetric reaction inside φ16 mm integrated digestion‑colorimetric tubes. Users can set dilution multiple for high‑concentration water samples, and the instrument will automatically convert original sample concentration value. The host weighs merely 325 g with compact dimension, convenient for operators to carry among scattered sampling points in river‑lake basins.

Equipped with a built‑in 5600 mAh lithium battery, continuous working time can reach 8 hours, satisfying long‑duration outdoor field investigation. More than 80 000 groups of test records can be saved locally. It supports Type‑C data export, Wi‑Fi and Bluetooth wireless transmission. Detection data can be uploaded wirelessly to cloud‑monitoring platform to realize long‑term statistical analysis of water‑quality changing trend. Bluetooth portable printer can be optionally equipped for on‑site report output. The equipment adapts to wide environmental condition: working temperature ranges from 0 ℃ to 50 ℃ and relative humidity 0‑90%, suitable for complex field environment of river‑lake field survey in different seasons.

In the river‑basin emergency‑simulation investigation project, we used this hand‑held three‑nitrogen detector to carry out spot‑check at multiple sampling sections. The measuring ranges cover ammonia nitrogen, nitrate nitrogen and nitrite nitrogen common concentration intervals of natural water bodies, repeatability <0.5% and stability <0.5%. Partial water samples were brought back to laboratory for comparative analysis. Field‑screening data have good correlation with laboratory reference results. This hand‑held instrument is not designed for high‑precision arbitration testing, but it performs excellently in early‑warning screening, patrol inspection and rapid preliminary judgment for water‑pollution accidents. It can be widely deployed for environmental emergency teams, aquaculture bases, university field‑scientific‑research groups and sewage‑treatment stations to complete on‑site three‑nitrogen rapid detection for surface water, wastewater and breeding water.