In this study, we demonstrate a unique method for the detection of heavy metals such as chromium (Cr), copper (Cu), lead (Pb), and nickel (Ni) at trace levels in aqueous solutions via laser-induced breakdown spectroscopy (LIBS) enriched using chelating resin. Reduction in sample time preparation was shortened by tailoring the sample processing time with the aid of an enrichment method. The calibration curves and LODs of CH-90 chelating resin for enriching Cr, Cu, Pb, and Ni cations were established under the optimal conditions. The linear correlation coefficients were all above 0.98, and the detection limits were 0.148 mg/L, 0.150 mg/L, 0.149 mg/L, and 0.240 mg/L, corresponding to Cr, Cu, Pb, and Ni, respectively. The quantitative evaluation of the obtained results signifies that the proposed method is highly sensitive for detecting trace elements and offers a good correspondence of the acquired linear correlation with its calibration model. Results comparison with past studies suggests that the proposed method is able to achieve lower LODs for elements under investigation.

To investigate the molecular structure and micropore structure of organic matters in coal-measure shale, the black shale samples of the Shanxi formation were collected from Xishan Coalfield, Taiyuan, and a hybrid experimental–simulation method was used for realistic macromolecular models of organic matter (OM). Four experimental techniques were used to determine the structural information of OM, including elemental analysis, state ¹³C nuclear magnetic resonance (¹³CNMR), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). With structural parameters, two-dimensional (2D) average molecular models of OM were established as C₁₇₇H₁₆₀O₈N₂S with a molar weight of 2474, which agreed well with the experimental ¹³C-NMR spectra. A realistic three-dimensional (3D) OM macromolecular model was also reconstructed, containing 20 2D molecules with a density of 1.41 g/cm³. To determine the connectivity and spatial disposition of the OM pores, focused ion beam microscope (FIB-SEM) and transmission electron micrographs (TEM) were utilized. The 3D OM pores models were developed. The results show that whether the OM pores varied from 20 to 350 nm as obtained from FIB-SEM images or less than 10 nm as observed in the TEM images, both were of poor connectivity. However, the ultra-micro pores from the 3D OM macromolecular model varied from 3Å to 10 Å and showed certain connectivity, which may be the main channel of diffusion. Furthermore, with the pressure increased, the methane adsorption capacity of the 3D OM model increased with a maximum value of 103 cm³/g at 7 MPa, indicating that OM pores less than 1 nm have a huge methane adsorption capacity. Therefore, our work provides an analysis method that is a powerful and superior tool in further research on gas migration.

Ca, Mg, as the main components in water, are not only essential nutrients for life but are also an important index of water hardness. Rapid detection of the element content is of great significance for water quality evaluation and nutrient balance in planting and breeding water. Traditional laboratory analysis methods are time consuming and involve complex procedures. Ion cross sensitivity and response drift also limit the application of online sensors. These disadvantages are not in line with the precise control and rapid response required for practical applications. Here, we propose a rapid automatic Ca, Mg ion concentration detection method using Laser-induced breakdown spectroscopy. Based on a cation exchange membrane, an automatic control system integrating water sampling, hybrid reacting, attachment drying and spectra measuring was constructed. The testing time for one sample could be compressed to 5 min. Consequently, it met the requirements of accuracy and timeliness of water element regulation. The proposed system can provide new technical means for large-scale aquaculture, soilless cultivation of facilities and other scenarios aiming at accurate measurement and control of elements in water body.

Ca and Mg are key constituents in surface water that are essential nutrients and vital indicators of water hardness. Rapid on-site measurement of Ca and Mg concentrations in surface water is important. However, traditional laboratory detection methods are complex and time-consuming, and on-site detection is difficult. In this study, a portable surface water detection method was developed using laser-induced breakdown spectroscopy with a miniaturized spectrometer LIBS and a liquid jet device for sample introduction. The device enables the rapid online in situ measurement of elemental concentrations in the water. The limits of detection for the rapid on-site detection of Ca and Mg in surface water were 11.58 and 2.57 mg/L, respectively. We applied this method to assess the concentrations of Ca and Mg in authentic water samples collected from rivers and ponds. The recovery rates for Ca and Mg were 90.83–101.74% and 93.43–108.74%, respectively. This method is suitable for rapid, on-site, and highly sensitive monitoring of Ca and Mg concentrations in the environment.

In order to realize low-cost automatic control of field irrigation and water metering, an integrated low-power irrigation monitoring terminal based on wireless data communication was designed. Powered by battery or solar, the terminal could acquire and store data of sensors and water meters in real-time. Taking valve as control object, the terminal can provide safe irrigation strategy based on multiple control logic, such as data overrun, time and manual operation. The detection of fault on-site and reasonable judgment of irrigation can be carried out by using self-check function, querying of local data and remote data transmission based on GPRS and Modbus Protocol. Experimental results showed that the terminal could work stably, and control irrigation water usage accurately with low power cost.