1 Introduction
Atmospheric dry sedimentation refers to the sedimentation process of aerosol particles, and wet sedimentation refers to the sedimentation process of various particles suspended in the atmosphere due to precipitation erosion. The chemical properties of atmospheric particles play a very important role in the formation of dry and wet sedimentation, affecting the ecological environment and biochemical processes of the underlying surface of the sedimentation. Domestic research on atmospheric dry and wet deposition started late, and the current research is mainly focused on acid rain and acid-induced factors, while dry and wet precipitation affects global material circulation and conversion, primary ecosystem productivity, heavy metal pollution, and trace elements. Of research is still inadequate. Due to the complex and diverse geographical situation in China, the resulting diversity of atmospheric movements determines the distribution characteristics of dry and wet deposition, so the current research is still far from enough.
2 Observation system design
2.1 Objective
The sample collection unit of the AZ-M0400 atmospheric dry and wet sedimentation observation system is made of stainless steel. All materials in contact with the sample, the size of the funnel and collection tray meet the VDI-3871 recommended standard, polyethylene or glass, quartz collection funnel. The sampling system can automatically and continuously collect dry and wet sedimentation, and at the same time can automatically monitor pH and conductivity, rainfall, rainfall time, collection time and other parameters.
The analysis unit uses automatic micro-injection and full-band (filter wheel) automatic colorimetric method for chemical composition analysis. The measurement parameters include: alkalinity, ammonia, chloride, hexavalent chromium, cyanide, hardness, soluble iron, nitrite , Nitrate, nitrate + nitrite, hydrazine, orthophosphate, volatile phenol, silicate, total phosphorus, total nitrogen, sulfate, etc., can perform multi-sample multi-parameter measurement analysis at a time, high efficiency, sample detection The speed can reach 120 ~ 140 times / hour.
According to the research needs, the laser spectrum analysis system can also be used for analysis, without sample pretreatment, almost no damage to the sample, high sensitivity, low detection limit, no waste liquid, and can be quickly detected in a few seconds. All element content.
2.2 Arrangement of sampling points
Select a representative typical area as a sampling plot and install a dry and wet sedimentation collector. The number of observation points is determined according to the purpose and needs of the study.
For general monitoring of urban ecosystems, cities with a population of more than 500,000 will have three sites, and cities with a population of less than 500,000 will have two sites. It is necessary to take care of meteorological topography and landform as much as possible. Observation points should be as far away as possible from local pollution sources, and there are no tall trees or buildings around to shield rain and snow.
The basic principles of ecosystems such as grasslands, wetlands, and oceans are similar, and a representative typical area is selected to establish 1 or 2 observation points. According to the research needs of forest ecosystems, it is usually necessary to collect the penetration rain in the forest while observing the dry and wet settlement outside the forest. Therefore, one sampling point or several are usually set in the forest and outside.
Soil or water samples are often collected at the same time for simultaneous analysis to illustrate the effect of dry and wet settlement on the physical and chemical properties of the underlying surface.
2.3 Sampling frequency
Wet settlement is usually sampled and analyzed immediately after each precipitation, and can also be collected once a month for long-term monitoring.
Dry sedimentation is usually collected once a month, and there are also long-term monitoring once a year. Each dry sedimentation collection must ensure that there is no precipitation in the early stage and during the collection process.
2.4 Observation indicators
Observation target
measurement standard
Acid deposition
pH, EC, SO42 +, NO3-, Cl-, NH4 +, precipitation
Ecosystem primary ecology
N, P, S
Heavy metal pollution
Pb (lead), Hg (mercury), As (arsenic), Cd (cadmium) and other heavy metals
Material circulation
Trace elements and even various elements on the entire periodic table
2.5 Composition of the observation system
The AZ-M0400 atmospheric dry and wet sedimentation observation system consists of a dry and wet sedimentation sampler and a sample analysis unit.
Sample analysis can choose automatic colorimetric analysis system (including sample tray, reagent tray, reaction cell, micro auto injector, colorimeter, software) or laser spectrum analysis system according to research needs.
3 data processing
3.1 Automatic colorimetric analysis system software:
l Sample analysis: The parameters listed separately are stored stably and can be selected during sample testing
l 3 levels of security protection;
l Automatically run sample pre-dilution;
l Automatically run a small amount of retest sample dilution;
l Automatically prepare standard samples from storage solutions;
l QC chart:
l Sample ID: alphabetical arrangement;
l Self-diagnosis: included
3.2 Laser spectrum analysis system:
1) Using multi-function system software, optimized sampling method to effectively identify the emission peak, and perform statistical analysis. In addition, use the chemical statistical analysis software module to identify and classify the different components of the sample through pre-set or wide-range spectral features;
2) Use the spectral database software to select a group or all elements for spectral line screening, and quickly and preparedly identify the spectral peaks of the sample;
3) Use powerful spectral analysis tools: arbitrarily select the spectral line and background, automatically calculate the area under the peak, and provide the "net" intensity of the spectral line;
4) Select the spectral segment, automatically remove the background intensity, and provide high-quality spectral data for future analysis;
5) Spectral lines can be saved in various data formats and can be called for comparative analysis at any time;
6) The system software uses multi-laser pulse technology to simultaneously perform statistical analysis of the spectral intensity during signal acquisition, and the results are used to optimize the sampling method;
7) Formulate calibration curve to complete high-precision quantitative analysis;
8) Use the various data analysis tools provided by the system software, such as PCA, PLS, multi-parameter linear regression, chemical statistical analysis, etc., to compare the spectral lines of random samples with the spectral lines in the database Quantitative analysis results of component samples.
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