St. Helens Chronicle. The St. Helens woman has been missing for two weeks. Her boyfriend, currently in the Lane County jail for other offenses, is now considered a person of interest. Police are currently searching for St. Helens woman, Cheryl Hart, who has been missing for nearly two weeks.
First, there are typically two varieties, or species, of arsenic in water: arsenic 3 and arsenic 5.. This is significant because arsenic 3 is very difficult to remove from water and must be changed or oxidized to arsenic 5 before it can be removed.
Water can be classified by the level of Total dissolved solids (TDS) in the water: Fresh water: less than 500 mg/L TDS=500 ppm - Pure drinking water. Brackish water: 500 to 30,000 mg/L TDS=500-30 000 ppm - Acceptable after water purification.