A method for removal of reduced sulfur compounds from a fluid containing reduced sulfur compounds comprising: (a) contacting an alkaline aqueous ferric iron salt solution that contains anionic ferric iron-carbonate complexes with a reduced sulfur-containing fluid; (i) wherein the alkaline aqueous ferric iron salt solution comprises ferric ions (Fe 3+), potassium ions (K +), carbonate ions (CO 3 2-) and bicarbonate ions (HCO 3 -), wherein the alkaline aqueous ferric iron salt solution further comprises nitrate ions (NO 3 -), and one or more organic additives; (ii) wherein a molar ratio of the potassium ions to the ferric ions is at least 9; (iii) wherein the alkaline aqueous ferric iron salt solution comprises one or more organic additives, wherein the molar ratio of ferric ion to each organic additive is 2 or more; (iv) wherein the alkaline aqueous ferric iron salt solution is a fully soluble aqueous alkaline ferric iron salt solution; (v) wherein the alkaline aqueous ferric iron salt solution has a pH of at least 8: (b) producing, due to the contacting, a reduced alkaline iron solution, wherein the producing comprises: (i) forming one or more iron sulfide compounds in the alkaline aqueous ferric iron salt solution to thereby remove at least a portion of the reduced sulfur compounds from the reduced sulfur-containing fluid; and (ii) oxidizing at least a portion of the at least one reduced sulfur compound and reducing at least a portion of the ferric ions to ferrous ions (Fe 2+). (a) contacting an alkaline aqueous ferric iron salt solution that contains anionic ferric iron-carbonate complexes with a reduced sulfur-containing fluid; (i) wherein the alkaline aqueous ferric iron salt solution comprises ferric ions (Fe 3+), potassium ions (K +), carbonate ions (CO 3 2-) and bicarbonate ions (HCO 3 -), wherein the alkaline aqueous ferric iron salt solution further comprises nitrate ions (NO 3 -), and one or more organic additives; (ii) wherein a molar ratio of the potassium ions to the ferric ions is at least 9; (iii) wherein the alkaline aqueous ferric iron salt solution comprises one or more organic additives, wherein the molar ratio of ferric ion to each organic additive is 2 or more; (iv) wherein the alkaline aqueous ferric iron salt solution is a fully soluble aqueous alkaline ferric iron salt solution; (v) wherein the alkaline aqueous ferric iron salt solution has a pH of at least 8: (i) wherein the alkaline aqueous ferric iron salt solution comprises ferric ions (Fe 3+), potassium ions (K +), carbonate ions (CO 3 2-) and bicarbonate ions (HCO 3 -), wherein the alkaline aqueous ferric iron salt solution further comprises nitrate ions (NO 3 -), and one or more organic additives; (ii) wherein a molar ratio of the potassium ions to the ferric ions is at least 9; (iii) wherein the alkaline aqueous ferric iron salt solution comprises one or more organic additives, wherein the molar ratio of ferric ion to each organic additive is 2 or more; (iv) wherein the alkaline aqueous ferric iron salt solution is a fully soluble aqueous alkaline ferric iron salt solution; (v) wherein the alkaline aqueous ferric iron salt solution has a pH of at least 8: (b) producing, due to the contacting, a reduced alkaline iron solution, wherein the producing comprises: (i) forming one or more iron sulfide compounds in the alkaline aqueous ferric iron salt solution to thereby remove at least a portion of the reduced sulfur compounds from the reduced sulfur-containing fluid; and (ii) oxidizing at least a portion of the at least one reduced sulfur compound and reducing at least a portion of the ferric ions to ferrous ions (Fe 2+). (i) forming one or more iron sulfide compounds in the alkaline aqueous ferric iron salt solution to thereby remove at least a portion of the reduced sulfur compounds from the reduced sulfur-containing fluid; and (ii) oxidizing at least a portion of the at least one reduced sulfur compound and reducing at least a portion of the ferric ions to ferrous ions (Fe 2+).