Due to its high mobility and risk for leaching, understanding what may influence nitrate availability is important for land managers. Although there are some clear associations between the available nitrogen and the measured physicochemical properties, it appears that surface temperature is the only physicochemical parameter measured that may be a suitable predictor for nitrate availability when looking at all extraction phases together. We are aware that this statement is woefully simplistic and additional parameters, such as peat pH, EC, and carbon:nitrogen ratios are currently being assessed.

Overall, it appears that extracted sites can be characterized by higher ammonium, nitrate, and higher surface temperatures. Soil moisture was higher than expected in the extraction sites despite lowered water tables from ditching. This may be due to smaller peat pore spaces in the older peat that are able to retain moisture even with drainage is present (Price et al., 2003). Depth of rust was comparable to the natural site due to the wide range of values observed. Surface temperatures were elevated, but below ground temperature was variable. This may be due to the thin layer of very dry peat at the surface which could reduce evapotranspiration. It appears that higher temperatures at extraction sites may increase decomposition and augment the availability of ammonium and nitrate. This suggests that extraction fields may be a major source of nitrogen that may leach off site.

The restored sites are characterized by high soil moisture and low depth of rust. This is likely due to the presence of shallow water at or near the surface that inhibits aeration. The belowground temperature was moderate, while the surface temperatures were cooler. The presence of vegetation may shade surface peat, and evapotranspiration from the open water may keep temperatures cool.

A perMANOVA using 999 permutations and Euclidean distance was used to test for significant differences between extraction phases (natural hummock, natural hollow, extracted, restored). When PRS nitrogen availability and physicochemical measurements were scaled and assessed, extraction phases were deemed significantly different (pseudo-F = 15.7, p-value < 0.001, alpha = 0.05). When adjusted for pairwise comparisons using the Holm-Bonferroni method, the p-value was still significant (p-value = 0.006). The strong statistical significance is not unexpected, considering the clear separation of groups in Figure 34. Additional sites should be sampled in the future to confirm these findings because the current study has a relatively small sample size and poor independence within treatments.

Seasonal Nitrate Mobility - Seba Beach, AB

Figures 35. & 36. suggest no nitrate is leaching off site at the outflow locations from natural, extracted, and restored peatlands. However, this is inherently misleading when considering seasonal variability. The study was conducted in summer, when vegetation in the natural and restored peatlands are actively taking up nutrients and microbes are active. Available nitrate may be removed from the system during this time and not show up on the PRS probes or in the outflow water chemistry. During periods when vegetation is dormant, nitrate may be freely available to leach off site. Similarly, frozen ground during spring can facilitate overland water flow that moves through nitrate-rich surface peat, resulting in pulses of nitrate following spring melt events. Finally, and most importantly, there were no major rain events that occurred during the PRS sampling period. Nitrate is highly mobile, but the peat pores need to be saturated to facilitate transport from the field to the outflow. Older (mature and complete) extracted sites have significantly higher rates of nitrate in the peat, but there was poor hydrologic connectivity between the peat field and the outflow. Similarly, Proctor (2003) observed increased nitrate during winter months when biologic activity was low and following large rain events.

What is an Acceptable Nitrate Concentration?

The Canadian drinking water quality guideline for nitrate is 10 000 µg /L as nitrate-nitrogen (Health Canada, 2020), while the guidelines for the protection of aquatic life use 3000 µg /L as nitrate-nitrogen as the upper limit for long-term exposure (CCME, 2012). However, peatlands are natural sources of nitrate, and can frequently export concentrations higher than the CCME guidelines. In their review paper synthesizing chemistry in disturbed and natural peatlands, Bourbonniere (2009) reports that the natural range of nitrate concentrations in Canada found in the literature is between 20 - 1700 µg /L of nitrate for bogs, and 10 - 10 000 µg /L for poor fens. However, they note that the maximum values are considered low and suggest higher values are common. Although the nitrate concentrations in the mature and complete extracted peatlands in this study are higher than the natural site and begin to exceed the CCME guidelines, they remain within safe drinking water guidelines and are well within the natural range found on the landscape. Further, it appears that elevated nitrate concentrations are not detected at the site outflow (Figure 37., "MixedMin"), suggesting that the increased concentration is overwhelmed by low nitrate water, or biological activity consumes available nitrate before it is able to leave the site.

This study is predominantly descriptive, and future work is needed to tease out the nuances associated with each extraction phase. Adding additional water quality parameters, such as phosphorus, dissolved organic carbon, and major ion concentrations will help pinpoint relationships between extraction phases and determine additional risks, if any, to downstream ecosystems. Further understanding of the hydrologic connectivity between the peat field and the outflow is needed. Pairing the measured concentrations with volumetric flow estimates taken during sampling will provide a rough export value which may be critical for putting the total mass of nutrients exported from each extraction phase into context.

Although preliminary, this study shows that there is a clear distinction between extraction phases. As predicted, extracted peatlands had higher surface temperature and nitrogen availability; however, soil moisture and aeration were moderate despite lowered water tables from ditching. Water leaving the extracted sites was similar to the natural site in pH, EC, and nitrogen concentrations during the summer. In contrast, when considering seasonal variability, extracted sites had elevated nitrate concentrations compared to natural sites. Restored peatlands had lower aeration and higher soil moisture compared to the natural peatland as predicted. Nitrogen availability and concentrations were variable between the restored peatlands. While the overall outflow nitrate concentrations were similar to natural peatlands, the electrical conductivity and pH were higher in restored peatlands.

In conclusion, when assessing risk to downstream water bodies, land managers should consider:

1. The hummocks and hollows in natural peatlands have different physicochemical properties and nitrogen availability. Understanding the range of "natural" values should be taken into consideration when comparing disturbed and undisturbed peatlands.

2. Older extracted peatlands have higher ammonium and nitrate availability and pose the highest leaching risk; nitrate concentrations at outflow locations following rain events may exceed CCME guidelines, but fall within the Canadian drinking water guidelines.

3. Hydrologic linkage between the peat field and the outflow is required for nitrate transport from the field to the outflow; understanding when large rain events typically occur and accounting for frozen ground which may facilitate overland flow should be considered.