Motivation

Contamination is a mayor and continuously growing worldwide problem. As only 2.5% of the water is available for human consumption and just 1% of it supplies ecosystems and human populations, contamination in natural springs is a key issue to be addressed. Health problems in developing countries many times derive from unsuitable water supply or incorrect treatment, and waterborne diseases are still a concern and a substantial cause of death in these regions. Limited access to pure water is a problem that tends to worsen. Making water suitable for human consumption could be easy and inexpensive, although this depends on the type of contamination, complexity and abundance. Even if this was not possible, information on pollutant levels could be used to modify consumption patterns and seek alternative sources. At present, the spatial and temporal quantification of contaminants is limited by the difficulty in processing samples, remoteness of some of the locations and its associated costs. Moreover, the lack of centralization and systematization of data makes it very difficult to obtain information. Our central goal is to help solve this situation, so we thought of a biosensor that is cheap and easy to use by people without previous training or equipment. There are many types of contamination and corresponding decontamination processes. The pollutants that render water unsuitable for human consumption can vary from just a single toxic substance to a highly complex mixture of these and harmful microorganisms. Heavy metals, such as mercury or arsenic and nitrites derived from agricultural runoff are two world-spread examples of groundwater contamination. Because of that, we decided to make arsenic and nitrite biosensors as a prototypes. However, we have made the design modular so the detected pollutant can be easily changed. Nitrites are an essential component of fertilizers used in agriculture. When fertilizers are inappropriately applied, the excess of these chemicals ends up in nearby rivers or lakes. This additional amount of nutrients derives in overgrowth of certain plant and algae populations which then supports growth of bacteria and microorganisms, generating an ecological unbalance, hypoxia and death of other organisms. This process is called eutrophication and implies not only an ecological unbalance but also the loss of a fresh water source. On the other hand, Arsenic is naturally present in soil and ground water in certain regions. Argentina, the United States, Bangladesh and Chile are on the top of the list of countries with high natural arsenic concentration in ground water of certain zones. Population without access to treated water living in these areas is exposed to Arsenic consumption. This derives in certain health complications such as skin lesions, skin, lung and bladder cancer, and gastro-intestinal and pulmonary disorders. Because of the spatial variability of arsenic in groundwater aquifers, there are often arsenic-free sources in zones with general high levels of arsenic contamination. For this reason, having an accurate knowledge of the ground water contamination grade could help populations at risk to discern between contaminated and safe water sources.