A snapshot of environmental iodine and selenium in La Pampa and San Juan provinces of Argentina

Soil and water samples were collected from farmsteads and provincial towns across the provinces of La Pampa and San Juan in Argentina. Inductively coupled plasma mass spectrometry was used for the determination of iodine in water following addition of TMAH to 1% v/v and soils extracted with 5% TMAH. Iodine in agricultural soils was in the range of 1.3–20.9 mg/kg in La Pampa located in central Argentina and 0.1–10.5 mg/kg in San Juan located in the northwest Andean region of Argentina, compared to a worldwide mean of 2.6 mg/kg. Mean selenium concentrations for soils from both provinces were 0.3 mg/kg, compared to a worldwide mean of 0.4 mg/kg. The majority of soils were slightly alkaline at pH 6.7 to 8.8. The organic content of soils in La Pampa was 2.5–5.9% and in San Juan 0.1–2.3%, whilst, mobile water extractable soil-iodine was 1–18% for La Pampa and 2–42% for San Juan. No simple relationship observed for pH and organic content, but mobile iodine (%) was highest when organic content was low, higher for lower total iodine concentrations and generally highest at pH > 7.5. Water drawn for drinking or irrigation of a variety of crops and pasture was found to range from 52 to 395 µg/L iodine and 0.8 to 21.3 µg/L selenium in La Pampa and 16–95 µg/L iodine and 0.6 to 8.2 µg/L selenium in San Juan. The water samples were all slightly alkaline between pH 8 and 10. Water–iodine concentrations were highest at pH 7.8 to 8.8 and in groundwaters positively correlated with conductivity. Raw water entering water treatment works in La Pampa was reduced in iodine content from approximately 50 µg/L in raw water to 1 µg/L in treated drinking water, similar to levels observed in regions experiencing iodine deficiency.