Institute of Earth Environment
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Hydrochemistry and source apportionment of boron, sulfate, and nitrate in the Fen River, a typical loess covered area in the eastern Chinese Loess Plateau
No full textFen River Basin (FRB) is water-deficient and strongly influenced by human activities in the eastern Chinese Loess Plateau. The spatio-temporal variation and controlling factors of hyrochemistry and quality, sources of high boron, sulfate, and nitrate of surface waters in FRB were unclear. Major ions, delta 11B, delta 15N, and delta 18O in surface waters in dry season and wet season of FRB were analyzed and correlation analysis (CA), principal component analysis (PCA), self-organizing map (SOM), forward model, and Bayesian isotope mixing model (MixSIAR) were used to solve above problems. Results showed that average riverine delta 11B, delta 15N, and delta 18O of FRB was 7.8%o, 11.2%o, and 1.3%o (1SD), respectively. Dissolved solutes ranked midstream > downstream > upstream with water type of Na +-Cl-, Ca2+-Mg2+-Cl-, and Ca2+-HCO3-, respectively. Low dissolved solutes were in forest areas while high values were in cropland and city areas. SOM analysis indicated that hydrochemistry was both influenced by natural (upstream) and pollutional input (midstream and downstream) and variation between dry season and wet season was minor. The abnormally high boron concentrations were mainly from silicate weathering (43%) and evaporites dissolution of loess (32%), urban and industrial input contributed 15% of riverine boron. High SO42- (207 +/- 267 mg/L, 1SD) was mainly from sulfates. delta 15N and delta 18O analysis indicated that nitrification was the primary N cycling process. Further, MixSIAR showed that NO3- was mainly from municipal sewage (-67%) and the total contribution of chemical fertilizer and soil nitrogen was -30% with slightly higher values in upstream and wet season. Influenced by land-use types, evaporite dissolution, and anthropogenic input, water quality below midstream was worse and strict sewage reduction policies must be developed. This study highlights the significant influence of evaporite dissolution of loess and anthropogenic input (urban and industrial input for B and sewage for NO3- ) on hydrochemistry and water quality
Asynchronized erosion effects due to climate and human activities on the central Chinese Loess Plateau during the Anthropocene and its implications for future soil and water management
No full textVariations and regional differences in land surface processes during the Anthropocene have directly impacted local economic development and social stability. Nevertheless, little is known about the historical erosion effects and human-environment interactions at annual and decadal scales on the central Chinese Loess Plateau (CLP) over the past 200 years, when human activities and annual sediment discharge both reached historical peaks. Located in the northcentral hilly-gully and southcentral plateau-gully regions, respectively, the Jingbian and Heshui landslide-dammed reservoirs were ideal settings to reconstruct the erosion flux and precipitation over A.D. 1850-2000 due to vertical stacking of interannual couplets. During this period, the mean annual specific sediment yield reached 1.17 x 10(4) t/(km(2) a) in the Jingbian catchment (precipitation threshold of 30 mm), while it reached 1.13 x 10(4) t/(km(2) a) in the Heshui catchment (precipitation threshold of 40 mm) according to sediment yield with frustum and extrapolation of historical precipitation. Interannual El Nino-Southern Oscillation (ENSO) events were deemed a primary climatic factor inducing soil erosion over the central CLP. This should remind decision-makers that it is necessary to prevent large-scale floods and severe erosion before future ENSO events. Changes in population, policies, and human activities also affected land surface processes on the central CLP during 1850-2000. In addition, the results revealed that abandoned farmlands in the southcentral regions with 600 mm and more precipitation had a strong ecological resilience, while this was weak in the northcentral drier region. These findings imply that future ecological restoration of the central CLP should consider the ecological resilience of farmlands that have been recently abandoned due to urbanization. These novel results provide new insights into regional soil and water management under China's development agenda of 'Ecological Conservation and High-quality Development of the Yellow River Basin'
Asynchronized erosion effects due to climate and human activities on the central Chinese Loess Plateau during the Anthropocene and its implications for future soil and water management
No full textVariations and regional differences in land surface processes during the Anthropocene have directly impacted local economic development and social stability. Nevertheless, little is known about the historical erosion effects and human-environment interactions at annual and decadal scales on the central Chinese Loess Plateau (CLP) over the past 200 years, when human activities and annual sediment discharge both reached historical peaks. Located in the northcentral hilly-gully and southcentral plateau-gully regions, respectively, the Jingbian and Heshui landslide-dammed reservoirs were ideal settings to reconstruct the erosion flux and precipitation over A.D. 1850-2000 due to vertical stacking of interannual couplets. During this period, the mean annual specific sediment yield reached 1.17 x 10(4) t/(km(2) a) in the Jingbian catchment (precipitation threshold of 30 mm), while it reached 1.13 x 10(4) t/(km(2) a) in the Heshui catchment (precipitation threshold of 40 mm) according to sediment yield with frustum and extrapolation of historical precipitation. Interannual El Nino-Southern Oscillation (ENSO) events were deemed a primary climatic factor inducing soil erosion over the central CLP. This should remind decision-makers that it is necessary to prevent large-scale floods and severe erosion before future ENSO events. Changes in population, policies, and human activities also affected land surface processes on the central CLP during 1850-2000. In addition, the results revealed that abandoned farmlands in the southcentral regions with 600 mm and more precipitation had a strong ecological resilience, while this was weak in the northcentral drier region. These findings imply that future ecological restoration of the central CLP should consider the ecological resilience of farmlands that have been recently abandoned due to urbanization. These novel results provide new insights into regional soil and water management under China's development agenda of 'Ecological Conservation and High-quality Development of the Yellow River Basin'
A method of the determination nitrate nitrogen (NO3--N) in high-salinity water samples
No full textThe determination of nitrate nitrogen (NO3--N) is a key step in the pretreatment of nitrogen isotope determination, but how to determine NO3--N in high-salinity water samples simply and efficiently is always a difficult problem. A spectrophotometric method for the determination of nitrate is presented and verified in this paper. Samples with different salinity were added to determine the known concentration gradient of NO3--N. The results show that the nitrate content can be determined between 0.2 similar to 2.8 mg/L by ultraviolet-visible spectrophotometer (hereafter as UVS), and the relative error is about 10%. A standard curve of the same salinity should be attempted for a water sample with known salinity. Precon-Isotope Mass Spectrometry (hereafter as Precon-MS) was used to verify the determination of sample concentration by UVS, and the relative error was less than 8%. This paper presents a simple and efficient method for the determination of NO3--N in high-salinity water samples, which has made great progress in the determination of nitrate nitrogen in samples and provides a theoretical basis for the determination of nitrogen isotopes in the pretreatment process of water samples
The Seasonally Altered Atmosphere Moisture Circulations With Rainfall and Rainfall Isotopes in Southwest China
No full textTo interpret the climatic signals of precipitation/speleothem delta O-18, it is critical to identify the importance of the factors affecting the precipitation delta O-18. This study presents new stable isotope data for precipitation delta O-18 and delta D in the site of Shenqi cave, southwest China, from November-2015 to October-2016 (the "Super-El Nino " event), to investigate the regional-scale climate forcing on precipitation delta O-18. The precipitation delta O-18, delta D and d-excess have an obvious seasonality, relatively low values in the wet season and high in the dry season. The further analysis of seasonally altered LMWL and moisture circulations suggested that changes in atmosphere moisture circulations would be the key factor underlying the precipitation/speleothem delta O-18 fluctuations in our study area at least on seasonal timescales. Combined with the seasonal-monthly variations of the IsoGSM delta O-18, GPCP/CRU rainfall and NCEP/NCAR moisture fluxes, we detected that the super-El Nino of 2016 have changed the distributions of monthly rainfall in wet season through the Western Pacific Subtropical High, but not mainly the precipitation isotopic compositions and moisture circulations in our study area
Multiple-Year Changes (2014-2018) in Particulate Vanadium Linked to Shipping Regulations in the World's Largest Port Region
No full textChina introduced an emission control area (ECA) along the coastline of the Yangtze River Delta (YRD) region in 2016 in a bid to reduce its shipping emissions. Performed at a costal site in the YRD region from 2014 to 2018, we found a significant reduction (16-22%, p < 0.01) in vanadium concentrations, the exclusive marker for heavy fuel oil combustion, after the full-scale implementation of lower sulfur fuel change for marine ships. Another site closer to the coastline showed a larger reduction (24- 30%, p < 0.01) during the corresponding period. The reduction of vanadium was consistent with an overall decrease rate of 17% in the annual SO2 concentrations of 10 sites across the region from 2016 to 2017. We thus provide a robust assessment of the positive effects of regulating shipping emissions on air quality in coastal China. The future trajectories of shipping-related emissions are also discussed
Nonlinear Responses of Droughts Over China to Volcanic Eruptions at Different Drought Phases
No full textPrevious studies show that volcanic eruptions can intensify and extend drought events triggered by internal variability over Eastern China. However, it has remained unclear whether volcanic eruptions occurring in different drought phases have different impacts. Here, based on multiple reconstructions, simulations, as well as volcanic sensitivity experiments with volcanic forcing imposed in the early and late phases of droughts, we propose a nonlinear effect of volcanic eruptions on drought events. Late-phase volcanic eruptions exert greater impact on drought persistence and intensity while early-phase volcanic eruptions induce modest and weaker impacts. The evolutions of drought differ substantially from the typical volcanic-only influence or the linear combination of the drought triggered by internal variability and volcanic-only influences, which are hypothesized to be associated with positive feedbacks of soil moisture to precipitation, as well as its interaction with the evolution of the East Asia Summer monsoon
Concentration, optical characteristics, and emission factors of brown carbon emitted by on-road vehicles
No full textAtmospheric brown carbon (BrC) is a light-absorbing component that affects radiative forcing; however, this effect requires further clarification, particularly with respect to BrC emission sources, chromophores, and optical properties. In the present study, the concentrations, optical properties, and emission factors of organic carbon (OC), water-soluble OC (WSOC), and humic-like substances (HULIS) in fine particulate matter (PM2.5) emitted from vehicles in three road tunnels ( the Wucun, Xianyue, and Wenxing tunnels in Xiamen, China) were investigated. The mass concentrations and light absorption of OC, WSOC, and HULLS were higher at the exits of each tunnel than at entrances, demonstrating that vehicle emissions were a BrC source. At each tunnel's exit, the average light absorption contributed by HULIS-BrC to water-soluble BrC (WS-BrC) and total BrC at 365 nm was higher than the corresponding carbon mass concentration contributed by HULIS (HULIS-C) to WSOC and OC, indicating that the chromophores of HULIS emitted from vehicles had a disproportionately high effect on the light absorption characteristics of BrC. The emission factors (ER) of HUUS-C and WSOC mass concentrations were highest at the Xianyue tunnel; however, the EFs of HULIS-BrC and WS-BrC light absorption were highest at the Wenxing tunnel, indicating that the chromophore composition of BrC was different among the tunnels and that the mass concentration EFs did not correspond directly to the light absorption EFs. (C) 2021 Elsevier B.V. All rights reserved
Exceptional terrestrial warmth around 4200-2800 years ago in Northwest China
No full textOne of the Holocene abrupt events around 4200 years ago, lasting for -200 years, is thought to have caused cultural disruptions, yet terrestrial climatic status right after the cold/dry event remains poorly defined and is often presumed that a generally cool condition prevailed during the Bronze Age (4000-2200 years ago). Here we report an alkenone-based summer temperature record over the past -12,000 years, in addition to two updated alkenone records, from Northwest China, providing new insights into the climatic status right after the event. Our results indicate that exceptional terrestrial warmth, up to -6 degrees C, occurred around 4200-2800 years ago during the Bronze Age, superimposed on the long-term Holocene cooling trend. The exceptional warmth in Northwest China, together with other climate anomalies elsewhere, suggests an unusual large-scale climatic reorganization at 4200-2800 years ago when solar activity remained high, with important implications to the climate background for cultural developments during the Bronze Age. (c) 2021 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved
Chemical characteristics and sources of nitrogen-containing organic compounds at a regional site in the North China Plain during the transition period of autumn and winter
No full textOrganic nitrogen constitutes a significant fraction of the nitrogen budget in particulate matter (PM). However, the composition and sources of nitrogen-containing organic compounds (NOCs) in PM remain unclear currently in North China Plain (NCP), China. Rare local or regional studies on NOCs were conducted. In this study, ambient fine particles (PM2.5) were collected in Xianghe, a regional background site in NCP, from 26 October to 26 December 2017. The insights from this study include NOC molecule identification, concentration level, and NOC sources and origins. Specifically, we have identified and quantified >90 NOC species, with urea being the most abundant, accounting for 39.7 +/- 4.7% of the total NOC followed by free amino acids (FAAs; 21.9 +/- 1.5%), cyclic NOCs (15.3 +/- 4.5%), amines (14.8 +/- 1.5%), alkyl amides (5.8 +/- 0.5%), isocyanates (1.7 +/- 0.2%), and nitriles (1.1 +/- 0.2%). The time series of FAAs was well correlated (r = 0.51-0.68, p < 0.01) with the organic marker of levoglucosan and was moderately correlated with O-x (r = 0.29-0.41, p < 0.01), suggesting biomass burning and secondary formation were important FAAs sources. We also show that amines can be oxidized and/or reacted by aqueous-phase processing to form secondary aerosols, which are further enhanced by the involvement of iron in the catalytic process. Using the receptor model of positive matrix factorization (PMF), six factors were identified including coal combustion, crustal sources, biomass burning, industry-related sources, traffic emissions, and secondary aerosols. Source apportionment of NOC shows biomass burning was the dominant factor, accounting for 31.8% of the total NOCs. This study provides a unique dataset of NOCs at this regional background site in the NCP, with the insights of NOC chemical composition and sources gained in this study being important for future NOC modeling as well as NOC health effects studies