In-Situ water quality sensors (optical and ion selective) become increasingly accessible, and the number of measured parameters is growing as well. By taking in consideration that datalogging techniques and data analysis procedures are readily available for a long while, it becomes clear that we have at hand excellent and completely new possibilities for monitoring and collecting high density groundwater quality data.
The main advantage of traditional sampling procedures is that the samples are analyzed at reliable accredited laboratories, which provide you with accurate results for a given sample. Nonetheless, several disadvantages are associated with this procedure: sample preservation is not perfectly reliable for each component, reproducibility of the sample collection is difficult in space and time (e.g., identical sampling location and depth, or same sampling time, etc.), relatively high specific costs (personnel, transport, analytical, etc.), and last but not least, the results bear only small amounts of information.
As against, the advantages of high frequency sampling techniques are numerous even though one has to be cautious when comparing the accuracy of measured concentrations using sensors with laboratory analytical results. The question arises: what is more important? Do we need accurate results incorporating a low amount of information, or we rather prefer high density data series including a lot more information allowing us to draw deliberate and fast decisions? Let's take a look at the figures below, and the extra information included in the high density data series is obvious. Although the discrete pH data presented in this example does not require laboratory analytical instruments, it is obvious that similar differences will become apparent in the case of species such as nitrate, chlorophyll, chloride, etc. that are normally detected using laboratory instrumentation.
pH values measured occasionally using a portable instrument
10 pH values logged every 10 minutes using a permanently deployed sensor
When do we need high density online monitoring systems?
Several answers to this question can of course be given. As a general rule, we may say that an online monitoring system and high resolution data series are required when parameter trends or their absolute values require immediate actions to be taken, or when relationships between different parameters are sought for (e.g., nutrient, oxygen balance, etc. analysis). By taking in consideration the economical benefits of the information gained, we can definitely say that the overall costs associated with such monitoring systems are much lower.
How to build monitoring systems generating high density online datasets?
Jakab Ã©s TÃ¡rsai Ltd. has all the tools required to build high density, multi-parameter (water quality and water quantity) online or even offline monitoring systems. Our modems and dataloggers have low power consumption and they are reliable, data is transmitted encrypted through highly secure channels, and the interactive web based graphical interface allows individualized levels of access depending on user rights. Water quantity monitoring systems can be built using the Diver family of dataloggers (water level, temperature, and electrical conductivity), or water quality & quantity monitoring systems can be built by deploying the Aquaprobe family of multi-parameter probes. The two can be even combined without the need for compromises.