Impacts of municipal reclaimed water used in snowmaking on plants and soil microbiota

Background/Question/Methods

: As water shortages intensify, businesses and municipalities increasingly use reclaimed municipal wastewater (RMWW) to reduce consumption of natural water for irrigation and other uses. One use of RMWW is production of artificial snow at ski resorts. RMWW generally has higher pH, salt, and nutrient (nitrogen and phosphorus) levels than natural precipitation, and these differences could impact the structure and function of communities of plants and soil microorganisms. We tested this hypothesis in two studies using soil and snow samples collected from a ski resort where RMWW has been used to make artificial snow since 2012. A field study examined soil organisms in 20 soil cores collected on a ski run, half from areas receiving artificial snow made from RMWW and half from areas receiving only natural snow. Nematodes and microarthropods were extracted and quantified using a dissecting microscope. A greenhouse experiment examined plant growth, mycorrhizal colonization and decomposition using 20 corn plants grown in ski resort soil. Half of the plants were watered with melted RMWW snow and half with melted natural snow. Pots received ion resin probes and museum board (cellulose) decomposition disks. After 3-months, corn plants were dried and weighed and root colonization by mycorrhizal fungi was measured.

Results/Conclusions

: Nematodes tended to be more abundant in soil cores collected from areas receiving natural snow (10.1 per g dry soil) compared to areas receiving artificial snow (7.9 per g dry soil; p=0.1). Among the feeding guilds, only predator nematodes were more abundant with natural snow (1.3 nematodes per g soil compared to 0.6 in RMWW; p=0.04) There was no effect of the two water sources (snowmelt from natural versus artificial snow made with RMWW) on the biomass and root:shoot ratio of the greenhouse-grown corn or decomposition of the museum board (p>0.1). The ion probes showed no influence of water treatment on any ions except for sulfur (p< 0.001) and aluminum (p=0.04) which were higher in RMWW pots. Total root mycorrhizal colonization and the abundance of vesicles and arbuscules were not affected by the water treatment, but intraradical hyphae was 17% higher in corn roots that were watered with RMWW compared to natural snowmelt (p=0.05). We recognize the need for a long-term study to further investigate how nutrients may accumulate in ecosystems over time with RMWW, allowing land managers to make informed decisions about using RMWW in snowmaking.