Autumn Maintenance for Surface Water Automatic Monitoring Stations

Surface water automatic monitoring stations serve as the “frontline sentinels” of water environment quality monitoring. Their operational stability and data reliability bear directly upon the scientific validity of water environment assessment and management. Autumn, as a transitional season bridging summer and winter, brings gradually falling temperatures, widening diurnal temperature ranges, increased wind-blown dust, and rising suspended solids in water bodies. 

These environmental shifts pose multiple challenges to monitoring equipment. Systematic autumn maintenance, conducted in accordance with the Technical Specifications for Operation and Maintenance of Surface Water Quality Automated Monitoring Stations (Conventional Five Parameters, CODMn, NH₃-N, TP, TN) (HJ 915.3-2024), is a critical step in ensuring the station’s safe passage through winter and guaranteeing that monitoring data remain “true, accurate, and complete”.

Station Environment and Infrastructure Maintenance

Autumn maintenance should begin with the station environment. Operators must thoroughly clear weeds and standing water from around the station building, inspect door and window seals, and reinforce sealing where necessary. Given the significant diurnal temperature fluctuations characteristic of autumn, condensation may form inside instruments, potentially causing short circuits in electrical systems or moisture damage to optical components. 

The station’s temperature and humidity control systems should be verified to maintain instrument operating temperatures between 10 °C and 30 °C and relative humidity between 10 % and 90 % RH. Power supply lines, uninterruptible power supplies, and network communication modules must be inspected to ensure data transmission links remain unobstructed. The station interior should be kept clean and tidy, with doors and windows closed promptly to prevent direct sunlight from affecting analytical instruments.

Deep Cleaning of Sampling and Water Distribution Systems

Autumn brings increased wind-blown dust and elevated suspended solids, together with fallen leaves and other debris entering water bodies, raising the risk of blockages in sampling and water distribution systems. Operators should perform deep cleaning of inlet filtration devices to prevent solid impurities from entering reaction chambers. Specific tasks include cleaning the sampling head, settling tank, filter head, sample cup, valves, and associated pipelines; components that cannot be adequately cleaned should be replaced promptly. 

The secure fixation of the sampling buoy, the operating status of the sampling pump and booster pump, and the integrity of sampling and drainage pipelines—checking for leaks or blockages—should all be verified. Waste discharge lines also require particular attention to prevent blockage by debris such as twigs and leaves.

Instrument and Reagent System Inspection and Maintenance

Equipment maintenance constitutes the core of autumn upkeep. First, instrument internal pipelines should be thoroughly flushed to remove crystals and precipitates adhering to tube walls; core reaction components—including reaction cups, digestion tubes, and colorimetric cells—should be disassembled and cleaned, and optical windows wiped to maintain clarity. 

Autumn is also a critical juncture for reagent replacement. Summer heat may accelerate the decomposition of certain unstable reagents; entering autumn, freshly prepared reagents—particularly chromogenic agents and digestion solutions—should be promptly introduced. Replacement cycles should be determined based on reagent stability and shelf life; shorter cycles are advisable when indoor temperatures are elevated, and in principle the reagent replacement interval should not exceed 30 days. Following any reagent change, the instrument must be recalibrated.