ABSTRACT
The colloidal borescope, using colloidal particle motion, is used to monitor the flow velocities and directions of groundwater. It integrates advanced techniques such as microscopy, high-speed photography, and big data computing and enjoys high sensitivity at the micron level. However, In the same well, the groundwater flow velocity monitored by colloidal hole mirror is varies greatly from that obtained by conventional hydrogeological monitoring, such as pumping test. In order to solve this problem, the stability catcher and stratified packer are designed to control the interference of the vertical flow in drilling, and to monitor the flow velocity and direction of groundwater velocity at the target aquifer and target fracture. Five wells with different aquifers and different groundwater types were selected for monitoring in south-central China. The instantaneous velocity and direction are converted into east-west component and north-south component, the average velocity and direction is calculated according to the time of 10 min, and the particle trajectory diagram is established. Based on these results, it proposed a concept of cumulative flow velocity. Using curve-fitting equations, the limits of cumulative flow velocities as the monitoring time tends to infinity were then calculated as the actual flow velocities of the groundwater. The permeability coefficient of aquifer is calculated by using the fissure ratio of aquifer, hydraulic slope and flow velocity, and compared with the permeability coefficient obtained by pumping test. The results are as follows: (1) The variation coefficient of the instantaneous flow velocity measured at the same depth in the same well at different times is greater than that of the time average flow velocity and greater than that of the cumulative flow velocity. The variation coefficient of the actual velocity is the smallest, indicating that the risk of using the actual flow velocity is lower. (2) The variation coefficient of the flow rate monitored at different depths in the same well is mainly controlled by the properties of the aquifer. The more uniform water storage space in the aquifer, the smaller the variation coefficient. (3) The comparison between the permeability coefficient obtained by monitoring and the permeability coefficient obtained by pumping test shows that the flow of structural fissure water controlled by planar fissure is more surface flow, and the results are consistent. When the groundwater flow is controlled by pores and solution gaps, the flow channel is complicated, which is easy to produce turbulent flow, and the result consistency is poor. (4) According to different research accuracy requirements, different monitoring and calculation methods can be selected for different aquifers and groundwater types. Researches show that, the permeability coefficient calculated for the actual flow velocity in well DR01 is the same as that calculated for the pumping test. The aquifer characteristics reflected by the coefficient of variation of the actual flow velocity in the same aquifer are more realistic. The pumping test method obtains the comprehensive parameters of a certain aquifer, and this method can be used to monitor a certain fissure. In this paper, the new technology developed for monitoring, and the new algorithm established for data processing, can accurately obtain the flow velocity and direction of groundwater, using capsule hole mirror monitoring method. The key parameters of hydrogeology can be obtained by using one well, which can reduce the time and cost input and improve the work efficiency.
ABSTRACT
Cadmium (Cd) pollution poses a threat to human health, and research on Cd bioavailability as well as its ecological risk assessment can help prevent and mitigate Cd hazards. The enrichment characteristics and variability of Cd were investigated in sea-land interaction soil fractions and the associated environmental and ecological risks were evaluated using the accumulation index (Igeo), potential ecological hazard index (Er), and risk assessment coding (RAC). The results showed that:â The Cd content of miscellaneous fill material was typically lower than 0.3 mg·kg-1 and that of plain full was higher than 0.3 mg·kg-1. The Cd content of marine sediment was significantly higher than that of continental sediments, averaging 0.36 and 0.10 mg·kg-1, respectively. The concentration of Cd in marine sediments buried at shallow depths (<5 m) was generally higher than at greater depths (>5 m). â¡ There was a moderate correlation between Cd and CEC in artificial fill (Q4ml; correlation coefficient=0.52, P<0.05). There was a weak correlation between Cd and organic matter in the marine sediments (correlation coefficient=0.49, P<0.05). Total cadmium and the physical and chemical properties of soil had a significant influence on the fraction of soil cadmium. ⢠The Igeo of artificially fill and marine sediment was dominated by the relationship 1 < Igeo < 2, which indicated a moderate level of pollution. The Er of artificial fill and marine sediment was mainly 80 < Er < 160, indicating a high potential ecological hazard. Soil acid-extractable Cd accounted for more than 50% of the total Cd in each drill hole, which generally indicated a very high potential ecological risk. These results provide a basis for environmental and agricultural decision-making and provide theoretical guidance for soil pollution investigations and remediation.
