DOI: 10.5061/dryad.qbzkh18tg
title: Latitudinal gradients of snow contamination in the Rocky Mountains associated with anthropogenic pollutant sources

description: Seasonal snow is an important source of drinking water, recreation, and
 agriculture in the Rocky Mountain region. Monitoring snow-water quality is
 important to assess potential impacts to downstream water resources,
 impacts to the albedo and energy balance of the snowpack, and assessing
 sources of natural and anthropogenic aerosols and gases.  Here, a
 suite of metals were measured from seasonal snowpack from water year (WY)
 2018. Calcium, lanthanum, and cerium concentrations support the importance
 of mineral dust to the southern Rocky Mountains. Mercury (Hg), zinc (Zn),
 and cadmium (Cd) concentrations show a similar spatial pattern to mineral
 dust, whereas antimony (Sb) concentrations are highest in the northern
 Rocky Mountains. Using enrichment factors to adjust for the contributions
 from mineral dust, it was demonstrated the pollution fraction of Hg, Zn,
 Sb and Cd was greater in the northern Rocky Mountains. These observations
 were compared to spatial trends of the pollution fraction of Hg from
 WY2009 to WY2018, regional monitoring networks, and back trajectory
 analyses. The agreement between these datasets revealed temporally
 consistent pollution sources and transport processes to the northern Rocky
 Mountains snowpack. Potential sources include current and historical
 mining and smelting in the region. Strategies to limit the emissions of
 these metals to the Northern Rockies would need to focus on remediation of
 contaminated sites and continued monitoring and mitigation of active
 mining and smelting
description: Samples analyzed for this study consisted of integrated snowpack
 samples collected during the spring of WY2018. Samples were collected near
 peak accumulation, but prior to snowmelt conditions (Ingersoll et al.,
 2009). Snowpits were dug to the ground and one depth-integrated sample was
 collected from a clean face of the snowpit. For DRI metal analysis, 49
 sites were sampled. One depth-integrated sample was collected using
 plastic scoops that were  pre-cleaned with 1% nitric acid
 (HNO<sub>3</sub>) and rinsed with ultrapure water. Samples
 were stored in Whirl-Pak bags and kept frozen until analysis. 
 At DRI, samples were kept frozen until sample preparation, when
 they were melted in Whirl-Paks and sonicated for 3 minutes. Samples were
 then poured into pre-cleaned (1% nitric acid washed), metal-free, 15 mL
 vials that were pre-rinsed with ultrapure water and dried. Snow samples
 were then acidified to 1% HNO<sub>3</sub> and stored for three
 months to allow for acid leaching of all elements in the sample (Arienzo
 et al., 2019). After three months, samples were analyzed for Ca, Ce, La,
 Cd, Sb, and Zn concentration using a Thermo-Finnigan Element2 (Thermo
 Scientific, Bremen, Germany) High-Resolution Inductively Coupled Plasma
 Mass Spectrometry (HR-ICP-MS) instrument at DRI. Samples were introduced
 to the HR-ICP-MS instrument using an autosampler and prior to injection
 into the HR-ICP-MS, each discrete sample was acidified to 2%
 HNO<sub>3</sub> with the addition of
 <sup>115</sup>In as an internal standard, similar to the
 technique used in previous studies (Arienzo et al., 2019). Calibration of
 the instrument was conducted prior to analysis using a suite of standards
 with known concentrations that bracketed the sample concentrations.
 Detection limits were calculated as three times the standard deviation of
 10 measurements of blank ultrapure 1% HNO<sub>3</sub> that
 ranged from 0.0001 mg/L for Ce and La to 0.12 mg/L for Ca (Table
 2).
description: # Latitudinal gradients of snow contamination in the Rocky Mountains
 associated with anthropogenic pollutant sources
 [https://doi.org/10.5061/dryad.qbzkh18tg](https://doi.org/10.5061/dryad.qbzkh18tg) ## Description of the data and file structure Two datasets are available, concentrations of metals studied and HYPLIT results ### Files and variables #### File: Concentrations.csv **Description:** concentrations of metals measured via ICP-MS ##### Variables * Station Name: This is the name of the sample location * Latitude: decimal degree of sample location * Longitude:decimal degree of sample location * State: US state * CO - Colorado * ID - Idaho * MT - Montana * NM - New Mexico * UT - Utah * WY - Wyoming * elevation: elevation in meters * Cd: Cadmium concentration in ug/L * Sb: Antimony concentration in ug/L * La: Lanthanum concentration in ug/L * Ce: Cerium concentration in ug/L * Ca: Calcium concentration in ug/L * Zn: Zinc concentration in ug/L #### File: HYSPLIT\_results.xlsx **Description:** Hybrid Single-Particle Lagrangian Integrated Trajectories (HYSPLIT) results ##### Variables * DPWY_24hr - this is the result for the Divide Peak location: Elevation:   8,730 ft. Latitude: 41.3, Longitude:  -107.15, Snow Sample: March 22, 2018 * FPNM_24hr - this is the result for the Fremont Pass location: Elevation: 11,326 ft., Latitude: 39.38, Longitude: -106.2, Snow Sample: March 27, 2018 * HNM_24hr - this is the result for the Hopewell location: Elevation: 10,095 ft., Latitude: 36.72, Longitude: -106.26, Snow Sample: March 12, 2018 * LMMT_24hr - this is the result for the Lone Mountain location: Elevation: 8,880 ft., Latitude: 45.27, Longitude: -111.43, Snow Sample: March 6, 2018 * MLCO_24hr - this is the result for the Mesa Lakes location: Elevation: 10,168 ft., Latitude: 39.06, Longitude: -108.06, Snow Sample: March 22, 2018 * NBMT_24hr - this is the result for the Noisy Basin location: Elevation: 6,040 ft., Latitude: 48.16, Longitude: -113.95, Snow sample date: February 28, 2018 * PBWY_24hr - this is the result for the Philips Bench location: Elevation: 8,200 ft., Latitude: 43.52, Longitude: -110.91, Snow Sample: March 12, 2018 * SMMT_24hr - this is the result for the Saddle Mountain location: Elevation: 7,940 ft., Latitude: 45.69, Longitude: -113.97, Snow Sample: March 2, 2018 Each tab contains the following information: * Date (YYYYMMDD) - date of precip event * Total # points - total number of points analyzed * Sampling days - number of days sampled * Precip amount (inches) - the amount of precipitation each day * &lt;1 Km - these are the results for less than 1 km above ground level. * Canada/Alaska - number of points in this source box * US Northwest - number of points in this source box * US Southwest - number of points in this source box * US W midwest - number of points in this source box * &gt; 1 Km - these are the results for greater than 1 km above ground level. * Canada/Alaska - number of points in this source box * US Northwest - number of points in this source box * US Southwest - number of points in this source box * US W midwest - number of points in this source box