Spatiotemporal Variation of nutrient concentrations in the Upper Shule River Basin, the Qinghai-Tibetan Plateau, China

This study aimed to understand the spatiotemporal variation of nutrient concentrations in stream water, using analyses of total nitrogen (TN), NO3−-N, NH4+-N and total phosphorus (TP) concentrations from April to October in 2016 in the upper Shule River basin in the northeastern margin of the Qinghai-Tibetan Plateau. Dissolved inorganic nitrogen (DIN; NO3−-N + NH4+-N) concentrations in both groundwater and stream water were the predominant form of TN, accounting for about 88%. Median concentrations in stream water were 815 μg L−1 for TN, 459 μg L−1 for NO3−-N, 253 μg L−1 for NH4+-N, and 25 μg L−1 for TP. Great spatiotemporal variations of nitrogen and phosphorus concentrations in stream water were observed, which likely resulted from varying recharge sources (snow and groundwater) and biogeochemical processes. Monthly variations in nutrient concentrations in stream water had a reciprocal pattern between nitrogen and phosphorus concentrations. Our results demonstrated that the quality of steam water in the upper reach of Shule River basin was basically good for drinking purposes according to the environmental quality standards for surface water, China. The results also improved our understanding of how nutrient concentrations varied in stream water and provided baseline information for future studies on nutrients in the Qinghai-Tibetan Plateau

Aging Relevant Metabolite Itaconate Inhibits Inflammatory Bone Loss

Progressive bone loss during aging makes osteoporosis one of the most common and life impacting conditions in geriatric populations. The bone homeostasis is maintained through persistent remodeling mediated by bone-forming osteoblast and bone-resorbing osteoclast. Inflammaging, a condition characterized by increased pro-inflammatory markers in the blood and other tissues during aging, has been reported to be associated with skeletal stem/progenitor cell dysfunction, which will result in impaired bone formation. However, the role of age-related inflammation and metabolites in regulation of osteoclast remains largely unknown. In the present study, we observed dichotomous phenotypes of anti-inflammatory metabolite itaconate in responding to inflammaging. Itaconate is upregulated in macrophages during aging but has less reactivity in responding to RANKL stimulation in aged macrophages. We confirmed the inhibitory effect of itaconate in regulating osteoclast differentiation and activation, and further verified the rescue role of itaconate in lipopolysaccharides induced inflammatory bone loss animal model. Our findings revealed that itaconate is a crucial regulatory metabolite during inflammaging that inhibits osteoclast to maintain bone homeostasis

Spatial-temporal trends of hydrological transitions in thermokarst lakes on Northeast Qinghai-Tibet Plateau based on stable isotopes

Regarded as the water towers of numerous large rivers in Asia, the Source Area of Yellow River (SAYR) on Northeast Qinghai-Tibet Plateau (QTP) contains substantial thermokarst lakes, which have exerted significant roles on the regional hydrology and water resources under permafrost degradation. To address the potential impact of climate- and permafrost-induced changes in surface hydrological processes in the SAYR, the hydrological transitions and water balance of thermokarst lakes were characterized on large scales during three years using stable isotope method. Spatial and seasonal deviations in hydrological processes of thermokarst lakes were remarkable. Calculations of evaporation-to-inflow (E/I) ratios based on an isotope-mass balance model revealed substantial evaporation for all thermokarst lakes during June due to the control of climate conditions and limited input water. Substantial feeds from summer/fall rain and permafrost meltwater resulted in lower evaporation and positive water balance of lakes during July, August, September, and October. Based on the relationship between lake-specific input water isotope compositions (δ ) and annual average isotope value of precipitation (δ ), the recharge patterns of thermokarst lakes in the SAYR were classified: supra-permafrost water/rainfall-dominated lakes were mainly concentrated during June and October regardless of spatial divergences, and summer precipitation/ permafrost thaw-dominated lakes are popular during July and August. Qualitatively, seasonal diversities in the water balance of thermokarst lakes are combinatively controlled by air temperature, precipitation regimes, permafrost degradation in the SAYR. Lastly, the future hydrological trajectories of thermokarst lakes are expected under climatic warming and permafrost degradation. This study serves as an important contribution for understanding future hydrological changes and allocation of water resources on the QTP, as well as an indication of permafrost degradation under climate warming

Source waters and flow paths in an alpine catchment

[1] Source waters and flow paths of streamflow draining high-elevation catchments of the Colorado Rocky Mountains were determined using isotopic and geochemical tracers during the 1996 snowmelt runoff season at two subcatchments of the Green Lakes Valley, Colorado Front Range. A two-component hydrograph separation using d 18 O indicates that new water dominated (82 ± 6%) streamflow at the 8-ha Martinelli catchment and old water dominated (64 ± 2%) at the 225-ha Green Lake 4 (GL4) catchment. Snowmelt became isotopically enriched as the melt season progressed, complicating the interpretation of source water models. Thus old water may be underestimated if the temporal variation in d 18 O of snowmelt is ignored or extrapolated from point measurements to the catchment. Two-component hydrograph separations for unreacted and reacted waters using a single geochemical tracer were not always meaningful. Three-component hydrograph separations using end-member mixing analysis indicated that subsurface flow contributed more than two thirds to the streamflow at both catchments. Talus fields contributed more than 40 % of the total discharge during summer at the GL4 catchment. A conceptual model was established for flow generation based on these results. It is suggested that surface water and groundwater interactions are much more important to the quantity and quality of surface water in high-elevation catchment

Determining hydrologic pathways of streamflow using geochemical tracers in a claypan watershed

Despite the low permeability of claypan soils, groundwater has been heavily contaminated by nitrate in agricultural watersheds dominated by claypan soils. However, it is unclear how nitrate concentrations in groundwater affect stream water quality. In this study, streamflow pathways were investigated using natural geochemical tracers in the 73‐km2 Goodwater Creek Experimental Watershed in northeastern Missouri. Samples were collected from 2011 to 2017 from stream water (weekly‐biweekly), precipitation (event‐based), groundwater in 25 wells with screened depths varying from 2 to 16 m (bimonthly–seasonal) and interflow above the claypan in 7 shallow piezometers (weekly–monthly). The results of endmember mixing analysis using major ions indicate that streamflow was dominated by near‐surface runoff (59 ± 20%), followed by interflow (25 ± 16%) and groundwater (16 ± 13%). Analysis of endmember distances using the mixing space defined by stream water chemistry suggests that groundwater contributions to streamflow came primarily from the intermediate to deep glacial till aquifer near and below 8 m. Near‐surface runoff was persistent and dominant even after isolated precipitation events during a prolonged dry period. It is hypothesised that the alluvial aquifer near stream banks acts as a mixing zone to receive and store various source waters, resulting in persistent delivery of runoff to the stream. Groundwater, even though its contribution was limited, plays a significant role in regulating streamflow NO3− concentrations. This study significantly improves our understanding of claypan hydrology and will lead to the development of models and decision support tools for implementation of management practices that improve groundwater and stream water quality in restrictive layer watersheds

Characterizing Groundwater Chemistry and Recharge in the Critical Zone of an Agricultural Claypan Watershed

Soils with low permeability horizons (e.g., claypans) are vulnerable to loss of nutrients through surface runoff along with preferential flow paths through the restrictive horizon to deeper aquifers. Partitioning between these hydrologic pathways is important to determine transport processes and develop strategies that mitigate stream contamination. Our objective was to investigate controls on groundwater chemistry and recharge pathways using natural geochemical tracers in the Goodwater Creek Experimental Watershed in Missouri, U.S. Groundwater samples were collected during 2011–2017 from 32 piezometers ranging from 0.13 to 16 m deep along with stream water and precipitation. Diagnostic tools of mixing models indicated that chemistry of perched water directly above the claypan and shallow groundwater immediately below was controlled primarily by chemical equilibrium. Five solutes behaved conservatively in most deep piezometers (\u3e5 m), reflecting mixing of two end members and the lack of significant denitrification processes. End member mixing analysis showed that the deeper groundwater originated primarily from groundwater at similar depths, often upslope or from strata directly above, with small contributions from perched water, highlighting the importance of both horizontal and vertical preferential recharge pathways. Vertical pathways are likely dictated by soil heterogeneity throughout the critical zone and do not occur synchronously with precipitation events or simultaneously over all piezometer locations. The complex recharge pathways provide stochastic conduits for nitrate transport to deeper aquifers where legacy stores accumulate, presenting a significant challenge for water quality management in watersheds with restrictive soil horizons and spatially and temporally heterogeneous preferential flow pathways, including the Mississippi River Basin

Joint impacts of future climate conditions and invasive species on black ash forested wetlands

Wetlands around the globe are being impacted by changing temperature and precipitation patterns. Simultaneously black ash forested wetlands are expected to lose much of their overstory canopy due to the invasive Emerald Ash Borer (EAB). Field experiments and modeling efforts have provided information on species tolerance of post-EAB conditions and future climate adapted species. No studies have yet examined the interaction of the loss of ash and future climate scenarios on wetland hydrologic conditions. We developed daily wetland hydrology models for three vegetation conditions: black ash forest, alternate non-ash forest, and non-forested. Model simulations were evaluated under current climate conditions and under two future climate scenarios representing warm & dry (T: +1.9°C, P: −2.6 cm) and hot & wet (T: +8.9°C, P: +6.2 cm) scenarios. For each combination of vegetation condition and climate scenario, 10,000 annual synthetic weather sequences were used as inputs to the wetland hydrology models. Simulated wetland hydrology remained highly variable based on seasonal precipitation and evaporative demand. We compared the occurrence probability of stream-network connectivity, surface inundation, and dry conditions. Effects ranged from slightly drier under non-forested and warm & dry conditions to much wetter under alternate-forested and hot & wet conditions. Non-forested conditions resulted in a median increase of 15 and 20% of daily observations of connectivity to stream networks and surface inundation, respectively, and 7% (median) fewer daily observations of dry conditions. Alternate-forested conditions resulted in larger median impacts: 40 and 35% more daily observations of connectivity to stream networks and surface inundation, respectively and 10% fewer daily observations of dry conditions. Projected climate change-induced water deficits resulted in 3–9% fewer days with connectivity and surface inundation, respectively and 0–10% more days with dry conditions (values represent the range of median values for combination of vegetation and future scenario). Our results show vegetation change as an equal or greater individual driver of future hydrologic conditions in black ash wetlands relative to climate change. Non-forested conditions and projected climate change-induced impacts each effectively negated the other. Management decisions around vegetation transition and establishment should consider the interaction with future climate scenarios and the large effect that poorly inundation-adapted plant communities could have on hydrologic conditions