We also live in landscapes that are continually and increasingly transformed by man. The surfaces of permeable soils in our urban areas have decreased significantly as a result of development and as such we are removing the critical water purification ability of the natural landscapes. In terms of these new chemicals, we are now finding that the quality of the water extracted from rivers and lakes for treatment into potable water is starting to very much resemble the quality of water we discharge. For humans, consuming potable water is the primary route of exposure to trace concentrations of these chemicals and little is known about their long-term effects. 

 

The bright side is that there is already an increasing awareness of the consequences of this new generation of pollutants and of the problem of impervious surfaces. For example, many municipalities now require that a percentage of a lot (e.g. 15 percent) be green space, and also, that the amount of an impervious surface cannot exceed 50 percent. In other words, only half of your property can be covered with impervious surfaces and 15 percent of the remaining open space has to be green space. In some cases impervious surfaces are heavily taxed as an incentive to minimize paved surfaces. Increasingly sophisticated high-resolution remote sensing technologies are now available to local officials to better regulate impervious surfaces, but although these are all moves in the right direction, much more needs to be done.

This new generation of pollutants is creating a demand for new sensors and systems to continuously monitor natural waters. Fortunately, all this is happening at a time where great innovations are coming out of the digital and communications revolution. It is now possible to deploy sensors in remote locations, powered by solar panels that continuously measure water quality, and transmit these measurements to central locations where they are analyzed. Considering the possibilities that lay ahead, it would be probably safe to say that we are just emerging from the “stone age era” of water monitoring. It is my belief that we are entering an era with great incentives and new ideas to develop new sensor technologies, and to improve data collection and communication, and develop applications that can automatically analyze large amounts of data and synthesize these into tactical information for remedial action. 

" A new generation of pollutants is creating a demand for new sensors and systems to continuously monitor natural waters. "

It has been about 10 years since we have had a reliable water quality sensor truly designed for long-term deployment. The most trusted parameters measured by these sensors in water include temperature, conductivity/salinity, pH, dissolved oxygen, oxidation-reduction potential, turbidity, and depth. Now available too are sensors that measure chlorophyll and a suit of ions such as Cl-, NO3- and Ca2+. A new form of sensor called biosensors consists of deployable probes containing specialized bacteria that are modified with a lux bioluminescence gene designed to light up when the bacteria are exposed to a stressor factor such as a genotoxicant. Electronic multipliers then take this bioluminescence signal, amplify it and convert it into a digital reading. Newer versions of biosensors based on biopolymeric materials make possible the detection of viruses, bacteria, parasites and other pathogens as well as pollutants and DNA segments. These sensors consist of a single molecule fabricated into a thin film. This molecule has a two-part composite structure so that when the surface of the biofilm molecule binds with a specific molecular arrangement of target bacteria, it triggers a color-changing signaling system that in the future may be possible to amplify and convert into a digital signal. Lately, metal-specific DNAzymes, functional DNA molecules that can catalyze a reaction in the presence of a particular metal ion, have emerged as a new class of metal-ion sensors. Research and development in this area is starting to mature and as we move forward new technologies will emerge to detect and monitor new potentially problematic compounds discharged into our waters.   

 

 

The least developed aspects of these monitoring systems, in my opinion, are the data modeling, analysis and data visualizations components. Today, data is usually transmitted to a central computer where basic functions are graphed and displayed in real time on the Internet. While this is giant step from times when samples were collected in a cup by hand and results took two to three weeks, the potential for innovation is so immense that claiming to be in the “stone age era” of data modeling and visualization is not such an overstatement.