Method for collecting underwater bubbles and method for monitoring underwater bubble flux under hydrodynamic conditions

Abstract

The invention discloses a method for collecting underwater bubbles and a method for monitoring underwater bubble flux under hydrodynamic conditions. A counterweight pendant is connected with the open part of an inverted funnel of a collection device through a rope; a tubular connector is arranged at the top of the inverted funnel, and is connected with a gas inlet pipe of a gas collecting bottle through a gas hose; and a buoy is connected with the outer surface of the inverted funnel through a rope, ant the gas collecting bottle is fixed together with the buoy. The monitoring method comprises the steps of placing a bubble collecting device in a water body, floating the buoy on the water surface and tying on a water surface anchor rope, and fixing one end of the water surface anchor rope on the bank side and the other end of the water surface anchor rope on a channel buoy or a far bank; and collecting gas, and considering an inclination angle theta of the inverted funnel when the bubble release flux is calculated. The methods disclosed by the invention are convenient for operation, have low sampling errors, and are suitable for collecting underwater bubbles and monitoring underwater bubble flux under complex hydrodynamic conditions of natural water bodies (high water level fluctuation or distinct flow rate in water).

Description

technical field [0001] The invention relates to an ecological environment monitoring method, in particular to the collection and flux monitoring of underwater air bubbles in natural waters, and is especially suitable for the collection and monitoring of underwater air bubbles under hydrodynamic conditions such as river courses and reservoirs, and belongs to the field of environmental science research . [0002] Background technique [0003] Bubble release is one of the two main ways (the other way is diffusion transport) of various gaseous substances in natural water bodies (rivers, lakes) to the atmosphere. In natural waters, gaseous substances (such as CO 2 、CH 4 、H 2 S, etc.) under specific physical and chemical conditions (temperature, pressure, physical and chemical properties of water quality, etc.) aggregate into tiny bubbles that adhere to the surface of soil particles at the bottom of the water, and under suitable conditions (such as hydraulic disturbance, tempe...

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Problems solved by technology

[0006] 1) The volume of the inverted funnel is too large, the diameter of the cone is 1m, and the height is 1m. It is inconvenient to carry and is not suitable for field observation; due to the large surface of the device facing the water, a small flow rate can cause the device to tilt significantly, which deviates from the original design intention of vertical collection , affecting the flux calculation

[0007] 2) The device is sewn with soft PVC / PU material canvas fixed by metal brackets, so in actual use, wrinkles often occur in individual places, and it is easy to make air bubbles locally adhere and accumulate in these parts, preventing them from quickly converging to the top layer in the bubble trap of

At the same time, it is not easy to achieve sealing at the seams of canvas sewing, and it is easy to leak air bubbles at the seams

[0008] 3) Under the action of large water flow and water pressure, the soft canvas layer facing the water is prone to sag, which affects the gas collection and makes the test results deviate

At the same time, after the sampling is completed, the bubble collection device located under the water must be completely retracted. Under the action of pressure changes, the side of the device is prone to collapse and depression, which interferes with the stability of the internal air pressure, causing the gas to leak or redissolve in the water. , the sampling monitoring error occurs

[0009] 4) The top of the inverted funnel is directly embedded with the gas collector, and the airtightness is not high enough; due to interference from conditions such as flow velocity and water level amplitude, the seams are torn severely, and air bubbles at the seams are prone to leakage. cause test error

[0010] 5) Since the funnel collection device is made of thicker materials, long-term placement in natural water bodies (especially eutrophic water bodies) is likely to cause a large number of adherent algae or fungi to grow on the inner and outer walls, which interferes with the upward movement of air bubbles along the inner wall of the device The process of converging; and the growth of a large number of sessile algae (filamentous algae, moss, etc.) on the outer surface of the device not only creates certain obstacles for the device to be retracted from the water, but also greatly increases the resistance of the flow around, and also makes the appearance of the device difficult to clean. Device re-use creates major hassle

[0011] 2. Deficiencies in bubble collection and monitoring methods

[0015] However, under the condition of flow rate, the circumvention resistance makes the gas collection device tilt significantly, which makes the actual collection area of ​​the bubbles have a certain deviation from the bottom area of ​​the inverted funnel, and there is an error in the flux monitoring results.

[0016] 2) Deficiencies in the bubble collection method

This method is relatively complicated to operate, and is only suitable for the steady state of still water, and cannot be applied to complex hydrodynamic conditions such as large fluctuations in the water level in a short period of time, and large flow rates in the water.

When the water level fluctuates greatly (when the reservoir is adjusted and stored), it is easy to cause the device to move or submerge the buoy and it cannot be collected; when the flow velocity is large (when the flood peak passes), it is easy to cause the device to "tip". The phenomenon

[0018] At the same time, the entire funnel device needs to be completely retracted each time the air is taken, and due to the existence of hydrostatic pressure, not only is it not easy to retract, but the field test work is intensive, and the change of internal air pressure during the retraction process will cause the bubbles to leak or reappear. Dissolved in water, resulting in the failure of the entire sampling process or large errors

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