## 1 Introduction  
As a vital resource, water is the basis for the survival of everything on earth. The availability and quality of water have become some of the most important priorities in today's society. Nowadays, water pollution in manufacturing and agricultural processes is becoming increasingly serious, which directly affects ecosystems and human health. Among various forms of water pollution, organic contaminants are the most serious problem. Organic pollutants are a diverse range of chemical compounds that can be detected in municipal, industrial, or agricultural wastewater, including but not limited to medications, insecticides, personal care products, and numerous home and industrial chemicals. Organic contaminants in water bodies can affect aquatic creatures and eventually pose a hazard to humans [1]. The commonly used technologies for wastewater purification include chlorination [2; 3; 4], ozonation [2; 5], ultraviolet (UV) radiation [2], filtration [6], boiling [7], and conventional water filtration technologies combined with advanced oxidation processes (AOP) [8; 9; 10; 11]. However, most of the traditional approaches have drawbacks. The chlorination of water with organic compounds can result in the formation of carcinogenic byproducts [2; 3; 4]. The ozonation treatments require expensive equipment [2; 5]. The penetrating strength of UV radiation is modest, and its power consumption is substantial [2]. Filtration can immediately produce drinking water without adding unpleasant odors, but it is costly and not suitable for removing viral particles [6]. Boiling treatments are time-consuming and expensive [7]. AOP is one of the most frequently and widely utilized methods in wastewater treatment [12]. The most common AOPs include heterogeneous photocatalytic oxidation [13; 14], ultrasounds [15], photo-Fenton oxidation [16; 17], etc. For example, photocatalysis is a clean AOP technique that converts water contaminants into CO\({}_{2}\) and H\({}_{2}\)O [18]. However, due to the additional equipment, traditional advanced oxidation is not one of the best or most cost-effective technologies available. To overcome these issues, extensive research has recently been carried out to find a cost-effective and suitable method for the one-step production of reactive oxygen and nitrogen species (RONS) [19; 20; 21; 22]. Recently, atmospheric pressure plasma (APP) as an efficient, eco-friendly and economical technology has shown great potential in wastewater treatment. As shown in Table 1, APP has superior application value relative to conventional AOP technologies: (1) No consumables are required, and plasma can be generated in either regular air or water. (2) Since no consumables are required, the cost of associated consumables and infra-structure is negligible. (3) During the advanced oxidation process of plasma, both contaminants disinfect as well as degrade, and the decomposition efficiency is superior to most chemical methods. In this regard, it is advantageous to consider plasma for the treatment of super-toxic wastes via the purification of water contaminated with bacteria and chemicals. APP is a neutral ionized gas containing electrons, UV photons, ions, electric fields, and various radicals (Figure 1) [23]. As a novel oxidation method for wastewater treatment, the APP process involves the interaction of free oxide species with UV light and organic contaminants. The main forms of APP discharge in the treatment of wastewater are classified as gas-phase discharge, liquid-phase discharge, and gas-liquid-phase discharge. Plasma interactions with liquid water involve complex physical and chemical processes [24]. Plasma discharge above or beneath the liquid water provides opportunities for the injection of gaseous RONS into water for sterilization or chemical treatment [18; 25; 26; 27]. The degradation of organic and inorganic pollutants will be massively advanced by plasma-generated RONS. Among these RONS, hydroxyl radical (-OH) has the ability to decompose complex toxin structures due to its high chemical reactivity.