Heavy Metal Contamination in New Mexico Soils after 2015 Gold King Mine Spill.

Alfalfa and forage hays dominate much of the irrigated agricultural landscape in San Juan County in the “Four Corners” region of New Mexico. There are commercial apple orchards and grape vineyards in addition to farms that grow high value specialty horticultural crops including vegetables, herbs and cut flowers. Irrigation ditches along the Animas/San Juan Rivers divert water to fields beginning around late April and ending in late October. In early August 2015, three million gallons of acidic, heavy metal contaminated water were accidentally released from the Gold King Mine into the Animas River in Colorado. A plume of orange colored sediment laden with Pb, As, and other metals passed through Colorado, New Mexico and Utah and was evident along the river months after the spill. Irrigation ditches were closed by the State Engineer for about 10 days following the spill allowing us to sample the dry ditches and establish base-line measurements of soil chemistry. Thirteen irrigation ditches from the Colorado border to Farmington, NM were sampled from August 11-14, 2015 to three depths (0 – 60 cm in 20 cm increments) and locations recorded with GPS. Through repeated measures, we resampled the same irrigation ditch locations during 2015-2016, while the main intakes were closed for the winter. Total metals in the soil were measured following USEPA method 3051A using inductively coupled plasma optical emission spectrometry analysis. Baseline and subsequent soil metal concentrations were compared and reported.