~生化需氧量（Biochemical Oxygen Demand）可以定义为水体中的有机物被好氧微生物分解成无机物质这一过程中所消耗的溶解氧量，简称BOD。这一指标的大小间接反映了水体中有机污染物的量的多少，是表征水体污染程度的一项重要指标。在我国国家环境保护标准HJ505-2009中，规定了测量水体BOD的稀释与接种法。此方法需要付出5天的时间来测量BOD，测量周期太长，无法及时、高效地反映水体中有机物的污染状况，在需要快速测量水体中有机污染物含量的场合无法适用。因此，研发一款能在现场实时监测BOD的传感器是十分有必要的。
针对以上所研究的目的，本文探究了基于荧光分析法的海水BOD荧光原位传感器检测海水BOD的可能性。它的基本测量原理是通过紫外波段的光激发水体中的色氨酸产生荧光，探测器检测此荧光信号并由传感器内置的校正参数将色氨酸荧光信号转化为与之相关的生化需氧量，利用色氨酸间接测量BOD，解决BOD实时监测问题。相比国家环境保护标准中提到的稀释与接种法需要将水样采集回实验室并需要5天时间才能得到最终结果，本传感器在环境现场就能将BOD实时检测出来，而且不需要往水体中加入任何化学物质，对环境没有污染，并且具备快速、简单、便携、性能稳定等优点，在一些对BOD检测精度要求不太高，需要实时、稳定测量的场合具有很强的适用性。本文的海水BOD荧光原位传感器以基于ARM Cortex-M3的STM32单片机为核心，实现对激发光源的调制。使用光电倍增管PMT检测色氨酸荧光信号，转变为电压信号，由ADC进行采集并送给STM32单片机进行数据处理，得到的BOD值传给上位机显示。在光路结构方面本文采用激发光路与探测光路垂直的方式以减小激发光对所探测的荧光信号的干扰。本文的主要内容是BOD荧光原位传感器硬件电路设计及其软件部分的开发。硬件电路部分主要包含对LED驱动电路、数据采集控制电路、数据采集电路、接口电平转换电路的设计。软件部分主要是对单片机的配置以及对数据进行处理。最终结合实验测试与海水现场测试完成海水BOD荧光原位传感器的研制。
与其它测量BOD的传统传感器相比，本BOD荧光原位传感器所采用的测量机理比较新颖，传感器测量结果的线性度较好。并且本传感器具备一定的稳定性、可靠性以及良好的便携性，具有一定的实用价值。

~Biological oxygen demand (BOD) can be defined as the amount of dissolved oxygen consumed in the process of decomposition of organic matter in water by aerobic microorganisms into inorganic substances. This index indirectly reflects the amount of organic pollutants in water, which is an important indicator of the degree of water pollution. In China's national environmental protection standard HJ505-2009, the method of dilution and inoculation for the measurement of BOD in water is stipulated. This method requires 5 days to measure BOD. The measurement cycle is too long to reflect the pollution status of organic matters in water timely and efficiently, and it cannot be applied in the case that the content of organic pollutants in water needs to be measured quickly. Therefore, it is necessary to develop a sensor that can monitor BOD in real time on site.

According to the above research, this paper explores the possibility of detecting the seawater BOD by the seawater BOD fluorescence in-situ sensor based on fluorescence analysis. The excitation of the tryptophan in water through the ultraviolet band could generate fluorescence, which is basic measuring principle of the sensor. The detector detects the fluorescence signal and converts the tryptophan fluorescence signal into the related biochemical oxygen demand by the built-in correction parameters of the sensor. The BOD is indirectly measured by tryptophan, and the problem of real-time monitoring of BOD is solved. Compared with the dilution and inoculation method mentioned in the national environmental protection standard which needs to collect water samples back to the laboratory and take 5 days to get the final result, this sensor can detect BOD in real time, without taking samples back to the laboratory, and does not need to add any chemical substances into the water. Therefore, there is no pollution to the environment, and it has the advantages of fast, simple, portable, stable performance and so on. It has strong applicability in some occasions where the BOD detection accuracy is not too high and real-time and stable measurement are required. The seawater BOD fluorescence in-situ sensor based on STM32 MCU of ARM Cortex M3 to achieve the modulation of the light source. The photomultiplier PMT was used to detect the tryptophan fluorescence signal, which was converted into a voltage signal. The signal was collected by the ADC and sent to STM32 MCU for data processing. The obtained BOD value was transmitted to the upper computer for display. In the aspect of optical path structure, the excitation light path is perpendicular to the detection optical path to reduce the interference of the excitation light on the detected fluorescent signal. The main content of this paper is the development of the hardware circuit design and software part of BOD fluorescence in-situ sensor. The hardware circuit part mainly includes the design of the LED driving circuit, the data acquisition control circuit, the data acquisition circuit, and the interface level conversion circuit. The software part mainly deals with the configuration of the microcontroller and the processing of the data. Finally, the development of seawater BOD fluorescence in-situ sensor was completed by combining experimental test and seawater field test.

Compared with other traditional sensors for measuring BOD, the measurement mechanism adopted by the BOD fluorescence in-situ sensor is relatively novel, and the linearity of the sensor measurement results is better. And the sensor has certain stability, reliability, good portability, and certain practical value.

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