•Multi-tracer models are applicable to constrain the solute mass balance & water budget in the mega-brine lakes.•Hydrothermal groundwater discharge delivers disproportionate Li and B loadings to the ...brine lake.•Ra-226 is dominated by co-precipitation in the lake, with a coefficient of 4.72 to 6.07 y−1.
Brine lakes are good natural laboratories to investigate groundwater influences on the hydrologic and chemical evolutions in arid environments, and the mineralization processes under intensive evaporation. Lacustrine groundwater discharge (LGD) is the vital conveyor for the loadings of resource elements in the brine lakes. Da Qaidam Lake, located in the Qaidam basin of the Qinghai–Tibet Plateau (QTP), is one of the largest brine lakes for boron and lithium resources in China. Lithium and boron in the lake are considered to be dominantly sourced from deep hydrothermal groundwater and shallow groundwater, but the partitioning of deep and shallow components to the lake and the derived lithium and boron loadings remain unknown, LGD derived boron and lithium provide the primary source of the salt lake. vitally regulates the formation, evolution and mineralization of Li and B resources in the brine lake. This study performs systematical investigations of radium isotopes (226Ra, 228Ra, 224Ra and 223Ra), lithium, boron, and other hydrogeochemical parameters in different water endmembers around the brine lake. The results indicate that radium isotopes are significantly enriched in the hydrothermal groundwater and will be removed by co-precipitation with barite precipitates in the lake water. The multi-tracer models coupled radium bass balance, conservative tracer buildup and water budget were deployed to precisely constrain radium co-precipitation rates, and to quantify the deep and shallow LGD (total LGD = LGDD + LGDS) and the derived lithium and boron loadings. Radium co-precipitation coefficient is obtained to be 4.7–6.1 y−1. LGDD and total LGD are estimated to be 8.8 × 106 and 3.3 × 107 m3 y−1, respectively, which account for 11.9% and 57.2% of the total water input. LGDD and total LGD derived lithium/boron loadings constitute up to 70.2/60.1%, and 79.0/77.7% of the total loadings, respectively, indicating the significance of disproportionate LGDD in delivering resource elements into the brine lake. This study presents the first attempt to partition the deep hydrothermal and shallow LGD to a mega the QTP brine lake by multi-tracer models and the findings contribute to the understanding of lithium and boron budgets in the brine lakes of the QTP and worldwide.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Qinghai Lake, the largest lake in China with a surface area of 4260 km2, lies in the northeastern Qinghai-Tibet Plateau (QTP) at a mean altitude of 3194 m above sea level. The lake has a water volume ...of 71.6 × 109 m3, a salinity ranges of 4.18 ± 0.14 ppt to 12.3 ± 0.14 ppt during sampling period which is about a half of typical seawater. The aquifer systems at the lake shoreline have obvious saline water and freshwater mixing zones with similar hydrogeological and biogeochemical settings to coastal aquifers. This study aims to estimate lacustrine groundwater discharge (LGD) and the associated chemical loadings to western Qinghai Lake. Naturally occurring radium isotopes (223Ra, 224Ra, 226Ra and 228Ra), nutrients, heavy metals and dissolved inorganic carbon (DIC) were systematically investigated in different water endmembers of western Qinghai Lake. LGD was estimated with radium inventory model and radium eddy diffusion model, leading to a LGD estimate of 7.67 × 106 m3 d−1 and 8.52 × 106 m3 d−1, respectively. The fresh groundwater discharge obtained based on regional water budget is about 5.97 × 106 m3 d−1 during sampling period, accounting for 73.74% (ranging from 53.22 to 80.43%) of total LGD. This study reveals that the fresh groundwater component is dominant in LGD of Qinghai Lake, which is quite different from most coastal scenarios. Furthermore, the chemical loadings derived from fresh-LGD and recirculated-LGD are evaluated. The preliminary results indicate that fresh-LGD is an important source of nutrient, barium, strontium, uranium, and DIC to the lake, and may significantly impact biogeochemical and ecological processes in the lake. This study presents the first LGD estimate in the largest QTP saline lake in China, and would be instructive to further similar studies in saline lakes in QTP and elsewhere in the world.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
First continuous observations of
7
Be and
210
Pb monthly total depositional fluxes were performed from December 2014 to November 2017 in Xining, a typical city on the Qinghai-Tibet Plateau, China. ...The depositional fluxes showed a clear seasonal variation, with peak depositional fluxes in summer for
7
Be and in summer or fall for
210
Pb, and minimum values in winter for both
7
Be and
210
Pb. These are ascribed to the seasonal variability in precipitation and the stratosphere-troposphere exchange of atmosphere. The annual depositional fluxes were 1555 Bq m
−2
year
−1
for
7
Be and 284 Bq m
−2
year
−1
for
210
Pb. The annual volume-weighted activities and depositional fluxes of
7
Be increased with altitude.
The establishment of field test site in Batang alpine meadow, Yushu County, Tibetan Autonomous Prefecture of Yushu, hinterland of the Qinghai-Tibet Plateau, soil temperature and moisture dynamic were ...monitoried. Using the field every 10min monitoring data of soil temperature and moisture, and meteorological data, we are analysis the varitaions of soil temperature and moisture by linear trend method. Analysis of daily and yearly variations of soil temperature and moisture characteristics, the results showed that: daily soil temperature began to rise from around 10:00, to 17:00, 18:00 reached the highest value, and then began to decline, at about 9:00 to reach the lowestpoint; the soil moisture reaches a minimum value at about 10:00, reached a maximum at about 18:00, with the increase of soil depth, the soil moisture decreased; soil temperature and moisture showed a different trend in different seasons, two different soil showed a relatively uniform change, with the increase of soil depth.
Radionuclides are widely used to perform geochronologic investigations of the trace sediment deposition process in aquatic environments on different temporal scales. This study presents the ...activities of radionuclides to select a reasonable geochronologic dating method and study the sediment depositional environment in Lake Qinghai on the Qinghai-Tibet Plateau. The range of activities (Bq.kg−1) of 137Cs, 226Ra, 238U, 228Ra, 228Th, and 40K were 2–103, 24–49, 33–156, 20–49, 30–50, and 403–664, respectively. The sedimentation flux was calculated as 1.66 × 106 ton.a−1 based on the summary sedimentation rate in Lake Qinghai, and the sediment contributions from rivers, authigenic carbonates, lacustrine organisms, and atmospheric deposition were 45.18%, 22.44%, 3.02%, and 29.36%, respectively. The decreased 226Ra/238U radioactivity ratios from the catchment to the lake centre indicated that the removal of uranium relative to its daughter products occurs during erosion processes. The positive 228Thex (excess 228Th) values in the upper 1 cm of the sediment suggested that the sediment in the top 1 cm have been resuspended, mixed and/or transported. The distribution of 137Cs in the sediments indicated that the maximum activity of 137Cs in the sediments corresponds to the 1963 peak in the global fallout from atmospheric nuclear weapons testing; moreover, the 1986 Chernobyl accident signal was difficult to identify. The use of 137Cs as a chronologic tool must be performed carefully due to its migration process in sediments.
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•The vertical distribution of radionuclides was investigated.•Sedimentary depositional flux is 1.66 × 106 ton.a−1 in Lake Qinghai.•Sediment have been resuspended or/and mixed in the top 1 cm by the 228Thex result.•The diffusion of 137Cs in the sediment column was significant.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
First continuous observations of .sup.7Be and .sup.210Pb monthly total depositional fluxes were performed from December 2014 to November 2017 in Xining, a typical city on the Qinghai-Tibet Plateau, ...China. The depositional fluxes showed a clear seasonal variation, with peak depositional fluxes in summer for .sup.7Be and in summer or fall for .sup.210Pb, and minimum values in winter for both .sup.7Be and .sup.210Pb. These are ascribed to the seasonal variability in precipitation and the stratosphere-troposphere exchange of atmosphere. The annual depositional fluxes were 1555 Bq m.sup.-2 year.sup.-1 for .sup.7Be and 284 Bq m.sup.-2 year.sup.-1 for .sup.210Pb. The annual volume-weighted activities and depositional fluxes of .sup.7Be increased with altitude.
Sediment sequences in Lake Qinghai spanning the past 100 years were explored to assess the effects of changes in local land desertification, dust input and agriculture on sediment deposition in ...different parts of Lake Qinghai. Three short sediment cores (QH01, QH02, QH07) were collected from the main lake and one sediment core (Z04) from a sublake (Lake Gahai) of Lake Qinghai, China, during 2012 and 2013. The concentrations of Fe, Mn, Al, Rb, Ti, Ca, and Sr were analysed to determine the effects of historical and regional anthropogenic activities in the Lake Qinghai catchment from 1910 to 2010. The elemental concentrations in the sediment cores ranged from 1.85 to 2.79% for Fe, 397 to 608 μg/g for Mn, 3.04 to 5.64% for Al, 13.5 to 19.7 μg/g for Rb, 0.171 to 0.268% for Ti, 9.43 to 13.9% for Ca, 652 to 1020 μg/g for Sr, and 0.049 to 0.075% for P. Good correlations were found between the concentrations of Fe, Mn, Al, and Rb, and the Ti/Al ratios in the sediments suggest that these elements share a similar source. The enrichment factors (EFs) of Ti EF(Ti) and P EF(P) in each core were utilized to reflect variations in anthropogenic activities from 1950 to 2010. EF(Ti) ranged from 1 to 1.17 in QH01 and QH02, reflecting the variation of land desertification areas in the Buha River catchment from 1950 to 2010. The EF(Ti) showed positive linear correlations with the variation in cropland area in Gangcha County, suggesting that agricultural activity in the Quanji River and Shaliu River catchments was enhanced from 1950 to 2010. The sediment records showed similar biogeochemical changes in most lakes and bays in China, indicating that the intensity of changes in anthropogenic activities was caused by national policy enforcement from the 1950s to 2010. EF(Ti) can serve as a tracer for anthropogenic activities in Lake Qinghai, with the anthropogenic activities in different parts of the Lake Qinghai catchment represented in the homologous sediments from parts of Lake Qinghai over the past 100 years. The variation of EF(P) increased from 1 to 1.55 from deep layer to upper layer in all sediment cores, reflecting the increased fertilizer input and tourism activity from 1980 to 2010, a period during which the lake was evolved into a eutrophic lake.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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