Water quality monitoring

Water is a primary resource for the presence of life on earth, and access to clean water is critical for humans and the ecosystem. Only 1% of the world's water supply is used to meet all of humanity's needs, i.e., agricultural, domestic, industrial, municipal, and residential. During the last decades, water quality has been negatively influenced by a continuously increasing population, rapid industrialization, increasing urbanization, and careless utilization of natural resources [1]. Heavy metals, organic matter, pharmaceutical and personal care products, pesticides, radionuclides, plastics, nanoparticles and pathogens are among the pollutants of major concern [2]. Nearly 2.2 billion people globally lack reliable access to safely managed drinking water [3]. Approximately 40% of the lakes and rivers of the planet have been polluted by heavy metals [4]. For example, around 140 million people in 50 countries regularly drink water that contains arsenic with concentrations higher than the World Health Organization (WHO) reference value of 10 μg/L [5]. Sustainable Development Goals (SDGs), which were set up in 2015 by the United Nations General Assembly, ensure availability and sustainable management of water and sanitation for all as Goal 6. The sources of these pollutants can be natural and anthropogenic. Heavy metals, such as Pb, Cr, Cd, Hg, and As, tend to bio-accumulate, which is their overtime increase of concentration in living organisms. Even at very low concentrations they can induce multiple organ damage affecting lungs, kidneys, liver, prostate, esophagus, stomach and skin, and can also cause neurodegenerative disorders and diseases. Natural sources include the interactions with metal containing rocks, normally present in the environment, and volcanic eruptions [6]. The contribution of volcanoes can occur due to large but sporadic emissions, explosive volcanic activity, or continuous low emissions, including geothermal activity and degassing [7]. Anthropogenic sources include those associated with industrial, agricultural and domestic activities [8]. Mining also produces large amounts of heavy metals that are released by mineral extraction and transported through rivers and streams [9]. More than 80 percent of wastewater resulting from human activities is discharged into rivers or sea without any pollution removal. For developing countries, one of the main limitations is a low economic capacity to develop and apply remediation technologies [10]. Anthropogenic activities, urbanization, and industrialization represent key factors in increasing the concentration of these pollutants, particularly in recent decades. It should be taken into account that micro-pollutants are not found in water resources individually. Therefore, this mixture can cause synergistic effects, making it more difficult their detection, quantification, and removal [11]. The need to analyze and manage water quality and supply to sustain human activities and ecosystems is widespread. Monitoring the aquatic environment and applying efficient methods for its protection is impossible without employing adequate chemical analytical methods. The technique to be selected for this purpose should be cost-effective, environmentally friendly, selective, and sensitive enough to detect traces with good precision [12]. The portable X-ray fluorescence (PXRF) equipment has relatively high detection limits [13], although it has a great advantage, which is the non-destructive analysis of liquid and solid samples [14]. Electrochemical techniques, such as the potentiometric, amperometric, voltammetric, coulometric, impedance, and electro-chemiluminescence methods, have their advantages because of their simplicity, low cost and speed. In addition, their derivations of these techniques have produced linear sweep anode (LSASV), square wave anode sweep (SWASV), differential pulse anode sweep (DPASV), cyclic cathodic sweep (CSV), cyclic (CV) voltammetry, and chrono-potentiometry (CP) * Hirofumi Tazoe tazoe@hirosaki-u.ac.jp