In this paper, the content and speciation of Cd, Cr, Pb, As, Cu, Zn and Ni in 87 groups of soil samples collected by grid method were determined by Inductively Coupled Plasma-Atomic Emission Spectrometry, to explore the speciation characteristics and ecological risk status of heavy metals in surface soil around Qinghai Lake. The results show that: Cd and Pb, compared with Cr, As, Cu, Zn and Ni, in the surface soil around Qinghai Lake are the most seriously polluted, Heavy metal speciation analysis showed that the proportion of weak acid soluble components of Cd was relatively high, with strong mobility and high environmental risk. The reducible components of Zn and Pb account for a relatively high proportion, while the oxidizable components of Cu, Cd and Pb account for a relatively high proportion. The high percentage of residual Cr, Ni and As indicates that they are relatively stable. The extractable content of Cd, Pb and Zn is relatively high, and their activities are strong, which have a great impact on the food chain. The results of Inductively Coupled Plasma-Atomic Emission Spectrometry and the ratio of secondary phase and primary phase showed that Cd and Pb had more serious ecological risk than other heavy metals. According to the results of soil speciation and ecological risk assessment of heavy metals around Chinese and foreign lakes, although the speciation characteristics of heavy metals are different, the pollution of Cd is relatively large. To sum up, heavy metal pollution in soil around Qinghai Lake area has occurred, and there is a serious ecological risk, so it is urgent to take corresponding monitoring and formulate treatment plan.

The design of this paper is a 12bit SAR ADC,in order to optimize its performance and be able to achieve high accuracy, there are certain requirements for certain modules of the ADC. The design uses the bottom plate sampling, access to the common mode level Vcm on the upper pole plate of the DAC capacitor array is accessed by a higher precision bootstrap switch to reduce the non-linearity brought by the Vcm level access switch. By performing FFT simulation on the sampling points, it can be used at a sampling rate of 50Ms/s when the input signal frequency is 0.8301MHz and ENOB is 15.64bit. The capacitor array uses a combination of segmentation and splitting to greatly reduce the number of total capacitors, achieving only 188 unit capacitors, a 97.7% reduction in number compared to the conventional structure, for the entire ADC digital circuit The power consumption as well as the area of the ADC digital circuit has been significantly improved. The comparator uses a dynamic latching comparator to reduce power consumption while reducing the equivalent input noise of the comparator. The logic circuit uses dynamic SAR logic to control the analog-to-digital converter's successive comparisons. Sampling and analysis of the entire SAR ADC output achieves a valid bit count of 11.93 bits at a low frequency input signal of 0.1953MHz, enabling the conversion of a 12bit SAR ADC.

Sensors have a wide range of applications in environmental monitoring, for example, as temperature transmitters in industrial control processes. In order to reduce the chip area and improve the digital-to-analogue conversion accuracy, large loads are driven. This study proposes a current-shunted DAC for sensor interfaces with an R-2R structure, using a Class-AB amplifier to buffer or amplify the signal. Spectre simulation shows that the DAC has a current consumption of 63uA when the supply voltage and reference voltage are 1.8V and can drive a 15pF capacitive load.

In order to find the action potential hidden in the neural signal, this study proposes a method of detecting the action potential through adaptive threshold, and designs an adaptive threshold detection circuit which can be used for the action potential. Different from the past, the circuit controls the gain by the current of the input signal itself, so as to generate an appropriate adaptive comparison threshold. This circuit not only retains the advantages of the traditional threshold detection method, but also can quickly respond to the input signal, generate an appropriate comparison threshold and detect the action potential without external supervision. The spectre simulation shows that when the power supply voltage is 1.8V, the adaptive threshold generation circuit can accurately detect the action potential without missing or wrong detection.