| 
                                                                                        Emerging pollutants           | 
              
          
                                                                                           
           | 
                                                                                        Alkali metals, alkaline earth metals and their compounds           | 
              
          
                                                                                           
           | 
                                                                                        Transition metals, post-transition metals and their compounds           | 
              
          
                                                                                           
           | 
                                                                                        Metalloids and their compounds           | 
              
          
                                                                                           
           | 
                                                                                        Lanthanoids, actinoids and their compounds           | 
              
          
                                                                                           
           | 
                                                                                        Nonmetals (halogens, other nonmetals and their compounds, noble gases)           | 
              
          
                                                                                           
           | 
                                                                                        Organophosphorous compounds           | 
              
          
                                                                                           
           | 
                                                                                        Alcohols           | 
              
          
                                                                                           
           | 
                                                                                        Ionic liquids           | 
              
          
                                                                                           
           | 
                                                                                        Hydrocarbons           |