NO3− circulation and associated driving factors in the unsaturated zone of southwestern Tengger Desert, Northwestern China

Soil NO3− storage from oasis development in deserts: Implications for the prevention and control of groundwater pollution

“…These findings revealed the response of groundwater quality to the vigorous agricultural development of in oasis environments. The δ 15 N‐NO 3 − and δ 18 O‐NO 3 − values found in groundwater and in pore water in the deep vadose zone in the LW and YC profiles were similar (Qi et al, 2019) (Figure 6). These results would suggest that the natural NO 3 − content in soil can also migrate to the groundwater through atmospheric precipitation, contributing to nitrate pollution of the groundwater.…”

“…In contrast, the Cl − concentrations ranged from 47.72 to 465.82 mg l −1 . The mNO 3 − /Cl − values ranged from 0.04 to 0.35, far less than the m[NO 3 − + NH 4 + ]/Cl − values found in atmospheric precipitation (1.13–2.72, Ma et al, 2012), but more similar to the mNO 3 − /Cl − values found in the soil water of the unsaturated zone (Qi et al, 2019). These results would indicate that the groundwater's NO 3 − source may be soil N. NO 2 − pollution in the groundwater of the Dengmaying Basin appears to be a more serious problem, indicating that groundwater resources have been significantly impacted by human activity.…”

“…The δ 18 O‐NO 3 − values in the cultivated land and forest profiles were noticeably lower than in the desert profiles, indicating that the influence of inorganic N fertilizer and groundwater irrigation was stronger than that of atmospheric precipitation (Qi et al, 2019). The differences observed in nitrogen and oxygen isotopic contents between the cultivated land, forest and desert profiles were clearly due to the complexities of cultivated land and forest NO 3 − sources.…”

“…Extreme precipitation events and irrigation water can intensify the leaching of solutes in the vadose zone. Furthermore, in a study of the chemical characteristics of soil water, a positive correlation was evident for the Cl − , NO 3 − and soil moisture contents (Qi et al, 2019). These findings appear to reflect the migration of solutes within soil water.…”

“…Some groundwater data are quoted from Ma et al (2009). The detailed experimental processes used to measure soil moisture content, NO 3 − and Cl − , δ 2 H‐H 2 O, δ 18 O‐H 2 O, δ 15 N‐NO 3 − and δ 18 O‐NO 3 − can be found in Qi et al (2019). Moisture contents were determined by oven‐drying the samples for 12 hr at 110°C (the soil moisture content referenced in this paper being mass water content).…”