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The policy-driven “Grain for Green Programme” (GGP) has resulted in large-scale land conversion from agricultural land to natural land in the karst area. One research surrounding the GGP is focused on evaluating its ecological implications for total mercury (THg) enrichment. In Yinjiang County, our study area, the THg content and distribution are investigated, and the controlling factors and potential ecological risk for THg in soil are explored for different land-use types. Results show that: (1) THg content in agricultural land (201.85 ± 57.23 μg kg–-1) is lower compared to the forest (1048.62 ± 306.19 μg kg–-1) and shrub (2582.60 ± 614.76 μg kg–-1). (2) The THg content shows a good correlation with Fe (agricultural land: R = 0.75, p < 0.01; shrub: R = 0.88, p < 0.01), pH (shrub: R = 0.87, p < 0.01), and sand proportion (forest: R = –0.65, p < 0.01), rather than soil organic carbon. In the shrub, the increased pH and Fe content correspond to THg content between 1804 and 3743 μg kg–-1; below the depth of 80 cm of the forest soil, the increased sand proportion correlates to THg content between 1223 and 748 μg kg–-1. (3) The risk index of the THg exceeds 320 in the soil and imposes a very high ecological risk to this area. This article is protected by copyright. All rights reserved
Rui Qu; Guilin Han; Man Liu; Qian Zhang. Vertical Distribution and Contamination of Soil Mercury in Karst Catchment, Southwest China: Land‐Use Type Influence. CLEAN – Soil, Air, Water 2021, 2100061 .
AMA StyleRui Qu, Guilin Han, Man Liu, Qian Zhang. Vertical Distribution and Contamination of Soil Mercury in Karst Catchment, Southwest China: Land‐Use Type Influence. CLEAN – Soil, Air, Water. 2021; ():2100061.
Chicago/Turabian StyleRui Qu; Guilin Han; Man Liu; Qian Zhang. 2021. "Vertical Distribution and Contamination of Soil Mercury in Karst Catchment, Southwest China: Land‐Use Type Influence." CLEAN – Soil, Air, Water , no. : 2100061.
The dynamics of soil organic carbon (SOC) during agricultural abandonment mainly depend on the balance between input from new vegetation type and loss caused by microbial decomposition and soil erosion at an eroded site. However, there is still a challenge to quantify the amount of SOC loss caused by erosion and decomposition. In the Mun River basin of Northeast Thailand, the agricultural lands converted from C3 wood forest before 60 years ago were studied, in which four soil profiles from paddy land and abandoned paddy lands for 1, 3, and 5 years were selected to analyze SOC contents and their stable carbon isotope composition (δ13C). The SOC in the agricultural soils was mainly derived from past C3 wood (δ13C: –28.4‰) and modern rice (δ13C: –20.2‰). In the paddy land, the average content of C3 wood-derived SOC was 2.38 g kg–1 while that of rice-derived SOC was 4.80 g kg–1. The C3 wood-derived SOC decreased by 1.3–1.6 times, while the rice-derived SOC decreased by 7.1–12.6 times with the continuous consumption through decomposition and erosion during the short-term (1–5 years) paddy land abandonment. Total SOC contents decreased by about 70% after paddy land abandonment, in which 25.2–36.3% of SOC loss was associated with soil erosion, while 33.2–44.8% of SOC was lost through microbial decomposition. These results suggest that both microbial decomposition and soil erosion play key roles in SOC loss during short-term paddy land abandonment in tropical sandy soils.
Man Liu; Guilin Han; Xiaoqiang Li. Contributions of soil erosion and decomposition to SOC loss during a short-term paddy land abandonment in Northeast Thailand. Agriculture, Ecosystems & Environment 2021, 321, 107629 .
AMA StyleMan Liu, Guilin Han, Xiaoqiang Li. Contributions of soil erosion and decomposition to SOC loss during a short-term paddy land abandonment in Northeast Thailand. Agriculture, Ecosystems & Environment. 2021; 321 ():107629.
Chicago/Turabian StyleMan Liu; Guilin Han; Xiaoqiang Li. 2021. "Contributions of soil erosion and decomposition to SOC loss during a short-term paddy land abandonment in Northeast Thailand." Agriculture, Ecosystems & Environment 321, no. : 107629.
Dissolved heavy metals (HMs), derived from natural and anthropogenic sources, are an important part of aquatic environment research and gain more international concern due to their acute toxicity. In this study, the geochemistry of dissolved HMs was analyzed in the upper Three Gorges Reservoir (TGR) of the Yangtze River (YZR) watershed to explore their distribution, status, and sources and further evaluate the water quality and HM-related risks. In total, 57 water samples were collected from the main channel and tributaries of the upper TGR. The concentrations of eight HMs, namely V, Ni, Cu, Zn, As, Mo, Cd, and Pb, were measured by ICP-MS. The mean concentrations (in μg/L) of eight HMs decreased in the order: As (1.46), V (1.44), Ni (1.40), Mo (0.94), Cu (0.86), Zn (0.63), Pb (0.03), and Cd (0.01). The concentrations of most HMs were 1.4~8.1 times higher than that in the source area of the YZR, indicating a potential anthropogenic intervention in the upper TGR. Spatially, the concentrations of V, Cu, As, and Pb along the main channel gradually decreased, while the others were relatively stable (except for Cd). The different degrees of variations in HM concentrations were also found in tributaries. According to the correlation analysis and principal component (PC) analysis, three PCs were identified and explained 75.1% of the total variances. combined with the concentrations of each metal, PC1 with high loadings of V, Ni, As, and Mo was considered as the main contribution of human inputs, PC2 (Cu and Pb) was primarily attributed to the contribution of mixed sources of human emissions and natural processes, and Zn and Cd in PC3 were controlled by natural sources. Water quality assessment suggested the good water quality (meeting the requirements for drinking purposes) with WQI values of 14.1 ± 3.4 and 11.6 ± 3.6 in the main channel and tributaries, respectively. Exposure risk assessment denoted that the health effects of selected HMs on the human body were limited (hazard index, HI < 1), but the potential risks of V and As with HI > 0.1 were non-negligible, especially for children. These findings provide scientific support for the environmental management of the upper TGR region and the metal cycle in aquatic systems.
Jie Zeng; Guilin Han; Mingming Hu; Yuchun Wang; Jinke Liu; Shitong Zhang; Di Wang. Geochemistry of Dissolved Heavy Metals in Upper Reaches of the Three Gorges Reservoir of Yangtze River Watershed during the Flood Season. Water 2021, 13, 2078 .
AMA StyleJie Zeng, Guilin Han, Mingming Hu, Yuchun Wang, Jinke Liu, Shitong Zhang, Di Wang. Geochemistry of Dissolved Heavy Metals in Upper Reaches of the Three Gorges Reservoir of Yangtze River Watershed during the Flood Season. Water. 2021; 13 (15):2078.
Chicago/Turabian StyleJie Zeng; Guilin Han; Mingming Hu; Yuchun Wang; Jinke Liu; Shitong Zhang; Di Wang. 2021. "Geochemistry of Dissolved Heavy Metals in Upper Reaches of the Three Gorges Reservoir of Yangtze River Watershed during the Flood Season." Water 13, no. 15: 2078.
Purpose Post-agricultural restoration affects soil organic carbon (SOC) sequestration and ecosystem nitrogen (N) cycle. However, the control mechanism of SOC sequestration and alteration of ecosystem N status following post-agricultural restoration are not well understood in karst regions. Methods Croplands, abandoned croplands, and native vegetation forests were selected to represent three stages following post-agricultural restoration using a space for time substitution approach in a karst critical zone in Guizhou province, Southwest China. The variations of soil aggregate associated SOC and relationships between soil Ca and SOC were analyzed to identify SOC sequestration potential. Foliar δ15N composition and soil to plant 15N enrichment factor (EF = δ15Nlitter − δ15Nsoil) were analyzed to determine ecosystem N status. Results Macro-aggregate proportions and their SOC concentrations significantly increased following post-agricultural restoration. Soil Ca concentrations non-linearly increased with increasing SOC concentrations of bulk soils and aggregates. Foliar δ15N values and EF values significantly decreased following post-agricultural restoration, mainly attributed to the increasing plant uptake of 15N-depleted inorganic N, which was produced from soil organic nitrogen (SON) mineralization and nitrification. During post-agricultural restoration, the increasing plant biomass and slow SON mineralization led to more inorganic N uptake and less N loss, i.e., a more closed N cycle. Conclusion Soil aggregates and Ca play important roles in promoting SOC sequestration, and ecosystem N cycles are towards closed during post-agricultural restoration in the karst ecosystem.
Man Liu; Guilin Han; Qian Zhang. Increasing SOC sequestration and closing N cycle during post-agricultural restoration in karst region, Southwest China. 2021, 1 .
AMA StyleMan Liu, Guilin Han, Qian Zhang. Increasing SOC sequestration and closing N cycle during post-agricultural restoration in karst region, Southwest China. . 2021; ():1.
Chicago/Turabian StyleMan Liu; Guilin Han; Qian Zhang. 2021. "Increasing SOC sequestration and closing N cycle during post-agricultural restoration in karst region, Southwest China." , no. : 1.
The sulfate pollution in water environment gains more and more concerns in recent years. The discharge of domestic, municipal, and industrial wastewaters increases the riverine sulfate concentrations, which may cause local health and ecological problems. To better understand the sources of sulfate, this study collected water samples in a typical agricultural watershed in East Thailand. The source apportionment of sulfide was conducted by using stable isotopes and receptor models. The δ34SSO4 value of river water varied from 1.2‰ to 16.4‰, with a median value of 8.9‰. The hydrochemical data indicated that the chemical compositions of Mun river water were affected by the anthropogenic inputs and natural processes such as halite dissolution, carbonate, and silicate weathering. The positive matrix factorization (PMF) model was not suitable to trace source of riverine sulfate, because the meaning of the extracted factors seems to be vague. Based on the elemental ratio and isotopic composition, the inverse model yielded the relative contribution of sulfide oxidation (approximately 46.5%), anthropogenic input (approximately 41.5%), and gypsum dissolution (approximately 12%) to sulfate in Mun river water. This study indicates that the selection of models for source apportionment should be careful. The large contribution of anthropogenic inputs calls an urgent concern of the Thai government to establish effective management strategies in the Mun River basin.
Jinke Liu; Guilin Han. Tracing riverine sulfate source in an agricultural watershed: Constraints from stable isotopes. Environmental Pollution 2021, 288, 117740 .
AMA StyleJinke Liu, Guilin Han. Tracing riverine sulfate source in an agricultural watershed: Constraints from stable isotopes. Environmental Pollution. 2021; 288 ():117740.
Chicago/Turabian StyleJinke Liu; Guilin Han. 2021. "Tracing riverine sulfate source in an agricultural watershed: Constraints from stable isotopes." Environmental Pollution 288, no. : 117740.
Human agricultural activities have resulted in widespread land degradation and soil contamination in the karst areas. However, the effects of reforestation after agricultural abandonment on the mobility risks and contamination of heavy metals have been rarely reported. In the present study, six soil profiles were selected from cropland and abandoned cropland with reforestation in the Puding karst regions of Southwest China. The Community Bureau of Reference (BCR) sequential extraction method was used to evaluate the compositions of different chemical fractions of soil heavy metals, including Fe, Mn, Cr, Zn, Ni, and Cd. The total contents of Cr, Ni, Zn, Cd, and Mn in the croplands were significantly higher than those in the abandoned croplands. For all soils, Cr, Ni, Zn, and Fe were mainly concentrated in the residual fractions (>85%), whereas Mn and Cd were mostly observed in the non-residual fractions (>65%). The non-residual fractions of Cd, Cr, Ni, and Zn in the croplands were higher than those in the abandoned croplands. These results indicated that the content and mobility of soil heavy metals decreased after reforestation. The individual contamination factor (ICF) and risk assessment code (RAC) showed that Cd contributed to considerable contamination of karst soils. The global contamination factor (GCF) and potential ecological risk index (RI) suggested low contamination and ecological risk of the investigated heavy metals in the croplands, moreover they can be further reduced after reforestation.
Qian Zhang; Guilin Han; Xingliang Xu. Reforestation Impacted Soil Heavy Metal Fractionation and Related Risk Assessment in the Karst Area, Southwest China. Forests 2021, 12, 891 .
AMA StyleQian Zhang, Guilin Han, Xingliang Xu. Reforestation Impacted Soil Heavy Metal Fractionation and Related Risk Assessment in the Karst Area, Southwest China. Forests. 2021; 12 (7):891.
Chicago/Turabian StyleQian Zhang; Guilin Han; Xingliang Xu. 2021. "Reforestation Impacted Soil Heavy Metal Fractionation and Related Risk Assessment in the Karst Area, Southwest China." Forests 12, no. 7: 891.
Zinc (Zn) is an essential micronutrient released into soils during rock weathering, and Zn isotope composition has been emerging as a powerful tracer involved in the Earth’s surface processes. To explore the soil development in dry tropical regions and evaluate the influence on the global Zn cycles, stable Zn isotope data were presented for the two pristine low-humic gleysol profiles from the Mun River Basin (MRB), northeast Thailand. The samples exhibit the δ66Zn (relative to JMC 3-0749L standard) from −0.69‰ to 0.32‰. Therein, the Fe nodule-containing soils exhibit a light shift of δ66Zn relative to parent red siltstones (Δ66Znnodule-containing soil–p of S1 = −0.60‰) and the other soils (Δ66ZnII-other zones = −0.66‰ – −0.50‰), indicating that the preferential retention of light Zn isotopes in residual soils is attributed to the adsorption of heavy Zn isotopes onto the surface of secondary Fe oxides. Due to the water insufficiency in the MRB, the redox conditions to control the oxide precipitation are driven by the seasonal alteration of groundwater levels. With the recession of groundwater, Fe oxides precipitate and adsorb heavy Zn isotopes. Besides, heavy Zn isotopes are also incorporated in clay fraction. On the contrary, the saturated water is likely to disrupt the interactions of Zn with Fe phases and clay minerals. In addition, low content of organic matter and Mn oxides and the absence of sulfides limitedly contribute to the light Zn pool in soils. Conclusively, the isotopic signature of Zn indicates that Fe oxide-rich soils are likely to control the heavier Zn isotope composition of dissolved load in rivers relative to continental rocks in dry tropical regions.
Bin Liang; Guilin Han; Man Liu; Xiaoqiang Li. Zn isotope fractionation during the development of low-humic gleysols from the Mun River Basin, northeast Thailand. CATENA 2021, 206, 105565 .
AMA StyleBin Liang, Guilin Han, Man Liu, Xiaoqiang Li. Zn isotope fractionation during the development of low-humic gleysols from the Mun River Basin, northeast Thailand. CATENA. 2021; 206 ():105565.
Chicago/Turabian StyleBin Liang; Guilin Han; Man Liu; Xiaoqiang Li. 2021. "Zn isotope fractionation during the development of low-humic gleysols from the Mun River Basin, northeast Thailand." CATENA 206, no. : 105565.
The geochemistry of rare earth elements (REEs, La to Lu) in suspended sediments (SS) is generally controlled by weathering processes and the water environment. Although the concentrations and fractionations of REEs in SS have been reported in the Zhujiang River, China, their variations and controlling factors have not been researched. Thus, the objective of this study was to identify the REE controlling factors in SS through their variations of concentrations and fractionations during 14 years (from 2000 to 2014). The concentrations of REEs, light REE (LREE, La to Nd), middle REE (MREE, Sm to Ho), and heavy REE (HREE, Er to Lu) in the SS of the Zhujiang River were investigated, and REE fractionation proxies including ∑LREE/∑HREE, ∑MREE/∑HREE, and Ce and Eu anomalies were calculated. Furthermore, the Pearson correlation relationships between physicochemical parameters, REE concentrations, and REE fractionation proxies were analyzed. The ∑REE concentrations of SS in the Zhujiang River varied from 35.9 to 396.4 mg kg−1 (mean 229.6 mg kg−1), higher than the world’s rivers (mean 174.8 mg kg−1). Moreover, ∑REE, ∑LREE, ∑MREE, and ∑HREE concentrations increased along the flow direction. PAAS-normalized REE ratios showed that MREE in SS were enriched relative to LREE and HREE. The concentrations of all REEs in SS significantly correlated with Fe, Al, and K concentrations positively, while significantly correlating with Ca and Na concentrations in a negative trend. These correlation relationships between the concentrations of REEs and major metal elements were attributed to the spatial variation of rock distribution based on the same source (weathering processes and soil erosion) of REEs and major metal elements in SS. The physicochemical properties affected REE fractionation in SS, such as clay minerals, water pH, and dissolved oxygen (DO). During 14 years from 2000 to 2014, the decrement of soil erosion reduced the REE concentrations of SS in the upper reaches. Meanwhile, river water acidification resulted in the weakening negative Ce anomaly and positive Eu anomaly of SS. These results suggested that the variations of REE concentrations and fractionations in SS were mainly controlled by soil erosion and water pH in the Zhujiang River from 2000 to 2014. The concentrations of REEs in SS mainly depend on weathering processes, while REE fractionations are closely associated with river water physicochemical properties in the Zhujiang River.
Guilin Han; Kunhua Yang; Jie Zeng. Distribution and fractionation of rare earth elements in suspended sediment of the Zhujiang River, Southwest China. Journal of Soils and Sediments 2021, 1 -13.
AMA StyleGuilin Han, Kunhua Yang, Jie Zeng. Distribution and fractionation of rare earth elements in suspended sediment of the Zhujiang River, Southwest China. Journal of Soils and Sediments. 2021; ():1-13.
Chicago/Turabian StyleGuilin Han; Kunhua Yang; Jie Zeng. 2021. "Distribution and fractionation of rare earth elements in suspended sediment of the Zhujiang River, Southwest China." Journal of Soils and Sediments , no. : 1-13.
Understanding the environmental iron cycle influenced by natural and anthropogenic processes is significant to obtain the key information on earth-surface evolution. Iron isotope compositions and elemental compositions of the suspended particulate matter (SPM) in Zhujiang River were investigated to provide key insights for the earth-surface iron cycle. The δ56Fe values of SPM display the range from −0.05‰ to 0.34‰ (averaged 0.19‰) while the iron contents range from 0.73 wt% to 7.63 wt% (averaged 4.15 wt%). The Chemical Index of Alteration (CIA) shows that the main weathering type of SPM is intermediate weathering (mean CIA value: 79.12). While the main chemical weathering types are similar, the δ56Fe values vary dramatically, indicating that chemical weathering is not the governing factor of δ56Fe values of SPM. Furthermore, evidence from the enrichment factors (EF, 0.78 to 1.29) of iron and Zinc isotopes reveals that the iron input from anthropogenic activities is quite limited. The significant correlation between (Fe/Ca)SPM and (Na/Ca)SPM, (Mg/Ca)SPM, (Al/Ca)SPM and (K/Ca)SPM (0.73 < r < 0.99, p < 0.01, n = 22) and the A–CN–K diagram could confirm that clay minerals (especially smectite and illite) are important components of SPM. Meanwhile, the higher enrichment rates of La, Pr and Nd with the increasing iron contents denote heavy minerals (mainly Fe oxides/oxy-hydroxides) are also important compositions of SPM. Based on the isotopic mass balance, it shows that the iron flux of SPM to the oceans during the wet season would reduce the δ56Fe values of the bulk ocean by 0.3%. The present study reports the iron isotope and elemental compositions of Zhujiang SPM and identifies its influencing factors (weathering, anthropogenic inputs, and minerals effect), and also provides a quantitative reference for the intriguing question on the distinct δ56Fe values of oceans, which is beneficial for understanding iron cycle in earth-surface system.
Guilin Han; Jie Zeng. Iron isotope of suspended particulate matter in Zhujiang River, Southwest China: Characteristics, sources, and environmental implications. Science of The Total Environment 2021, 793, 148562 .
AMA StyleGuilin Han, Jie Zeng. Iron isotope of suspended particulate matter in Zhujiang River, Southwest China: Characteristics, sources, and environmental implications. Science of The Total Environment. 2021; 793 ():148562.
Chicago/Turabian StyleGuilin Han; Jie Zeng. 2021. "Iron isotope of suspended particulate matter in Zhujiang River, Southwest China: Characteristics, sources, and environmental implications." Science of The Total Environment 793, no. : 148562.
Background Soil erosion can affect the distribution of soil nutrients, which restricts soil productivity. However, it is still a challenge to understand the response of soil nutrients to erosion under different soil types. Methods The distribution of soil nutrients, including soil organic carbon (SOC), soil organic nitrogen (SON), and soil major elements (expressed as Al2O3, CaO, Fe2O3, K2O, Na2O, MgO, TiO2, and SiO2), were analyzed in the profiles from yellow soils, red soils, and lateritic red soils in an erosion region of Southeast China. Soil erodibility K factor calculated on the Erosion Productivity Impact Calculator (EPIC) model was used to indicate erosion risk of surface soils (0∼30 cm depth). The relationships between these soil properties were explored by Spearman’s rank correlation analysis, further to determine the factors that affected the distribution of SOC, SON, and soil major elements under different soil types. Results The K factors in the red soils were significantly lower than those in the yellow soils and significantly higher than those in the lateritic red soils. The SON concentrations in the deep layer of the yellow soils were twice larger than those in the red soils and lateritic red soils, while the SOC concentrations between them were not significantly different. The concentrations of most major elements, except Al2O3 and SiO2, in the yellow soils, were significantly larger than those in the red soils and lateritic red soils. Moreover, the concentrations of major metal elements positively correlated with silt proportions and SiO2 concentrations positively correlated with sand proportions at the 0∼80 cm depth in the yellow soils. Soil major elements depended on both soil evolution and soil erosion in the surface layer of yellow soils. In the yellow soils below the 80 cm depth, soil pH positively correlated with K2O, Na2O, and CaO concentrations, while negatively correlated with Fe2O3 concentrations, which was controlled by the processes of soil evolution. The concentrations of soil major elements did not significantly correlate with soil pH or particle distribution in the red soils and lateritic red soils, likely associated with intricate factors. Conclusions These results suggest that soil nutrients and soil erodibility K factor in the yellow soils were higher than those in the lateritic red soils and red soils. The distribution of soil nutrients is controlled by soil erosion and soil evolution in the erosion region of Southeast China.
Man Liu; Guilin Han. Distribution of soil nutrients and erodibility factor under different soil types in an erosion region of Southeast China. PeerJ 2021, 9, e11630 .
AMA StyleMan Liu, Guilin Han. Distribution of soil nutrients and erodibility factor under different soil types in an erosion region of Southeast China. PeerJ. 2021; 9 ():e11630.
Chicago/Turabian StyleMan Liu; Guilin Han. 2021. "Distribution of soil nutrients and erodibility factor under different soil types in an erosion region of Southeast China." PeerJ 9, no. : e11630.
Iron (Fe) is an essential element for bio-physiological functioning terrestrial organisms, in particular of aquatic organisms. It is therefore crucial to understand the aquatic iron cycle and geochemical characteristics, which is also significant to obtain the key information on earth-surface evolution. The stable iron isotopic composition (δ56Fe) of the dissolved fraction is determined in the Mun River (main tributary of Mekong River), northeast Thailand to distinguish the human and nature influenced riverine iron geochemical behavior. The results show that dissolved Fe concentration ranges from 8.04 to 135.27 μg/L, and the δ56Fe ranges from −1.34‰ to 0.48‰, with an average of 0.23‰, 0.14‰ and −0.15‰ in the upper, middle and lower reaches, respectively. The δ56Fe values of river water are close to that of the bulk continental crust and other tropical rivers. The correlations between δ56Fe and Fe, Al, and physicochemical parameters show mixing processes of different Fe end-members, including the rock weathering end-member (low Fe/Al ratio and high δ56Fe), the urban activities end-member (high Fe/Al ratio and moderate δ56Fe), and a third end-member with probable sources from the Chi River and reservoir. For the most river water samples, the primary contribution is attributed to rock weathering, and the second is urban activities (only a few samples are from the upper and middle reaches). Thus, Fe isotopes could be employed as a proxy to identify and quantify the natural and anthropogenic contributions, respectively. These findings also provide data support for the scientific management of water resources in the Mun River catchment and other large tropical rivers.
Guilin Han; Kunhua Yang; Jie Zeng; Ye Zhao. Dissolved iron and isotopic geochemical characteristics in a typical tropical river across the floodplain: The potential environmental implication. Environmental Research 2021, 200, 111452 .
AMA StyleGuilin Han, Kunhua Yang, Jie Zeng, Ye Zhao. Dissolved iron and isotopic geochemical characteristics in a typical tropical river across the floodplain: The potential environmental implication. Environmental Research. 2021; 200 ():111452.
Chicago/Turabian StyleGuilin Han; Kunhua Yang; Jie Zeng; Ye Zhao. 2021. "Dissolved iron and isotopic geochemical characteristics in a typical tropical river across the floodplain: The potential environmental implication." Environmental Research 200, no. : 111452.
The Fe isotopic composition of the riverine suspended particulate matter (SPM) in the Mun River was found to improve the knowledge of the Fe isotope behaviors in the surface environment. The δ56Fe varies from −0.25 to 0.29‰ with an average value of 0.02‰. Most Fe (on average 76.1%) exists in suspended phases rather than dissolved phases in the Mun River, highlighting the significance of investigating the Fe isotopic compositions of riverine SPM. The close relationship between the chemical index of alteration (CIA) value and the δ56Fe value (r = 0.56, P < 0.01), as well as the increasing trend of the δ56Fe value along the weathering trend line (A–CN–K diagram), confirm that the types and intensities of weathering are essential for regulating Fe isotopic fractionation. Evidence from the high enrichment factor (EF, 0.62–3.97) and the significant correlation between (Fe/Al)SPM and (Zn/Al)SPM indicate the important role of the anthropogenic Fe contribution. To decipher the origin of Fe in SPM, the natural and anthropogenic end-members were investigated further. The Fe contents display a clear correlation with Na, Mg, Al, K, and rare earth elements (REE), indicating that clay and heavy minerals are important containers for riverine particulate Fe. A binary mixing model was adopted and the results showed that the relative anthropogenic Fe contribution varies from 5.79 to 97.70% (average 48.46%) for most SPM (excluding high-Mn samples). The spatial distribution characteristics of relative anthropogenic contribution suggest agricultural activities as a likely source of anthropogenic particulate Fe in SPM.
Kunhua Yang; Guilin Han; Jie Zeng; Man Liu; Xiaoqiang Li; Ye Zhao. Tracing Fe Sources in Suspended Particulate Matter (SPM) in the Mun River: Application of Fe-Stable Isotopes Based on a Binary Mixing Model. ACS Earth and Space Chemistry 2021, 5, 1613 -1621.
AMA StyleKunhua Yang, Guilin Han, Jie Zeng, Man Liu, Xiaoqiang Li, Ye Zhao. Tracing Fe Sources in Suspended Particulate Matter (SPM) in the Mun River: Application of Fe-Stable Isotopes Based on a Binary Mixing Model. ACS Earth and Space Chemistry. 2021; 5 (6):1613-1621.
Chicago/Turabian StyleKunhua Yang; Guilin Han; Jie Zeng; Man Liu; Xiaoqiang Li; Ye Zhao. 2021. "Tracing Fe Sources in Suspended Particulate Matter (SPM) in the Mun River: Application of Fe-Stable Isotopes Based on a Binary Mixing Model." ACS Earth and Space Chemistry 5, no. 6: 1613-1621.
In order to better constrain calcium cycling in natural soil and in soil used for agriculture, we present the δ44/40Ca values measured in rainwater, groundwater, plants, soil, and bedrock samples from a representative karst forest in SW China. The δ44/40Ca values are found to differ by ≈3.0‰ in the karst forest ecosystem. The Ca isotope compositions and Ca contents of groundwater, rainwater, and bedrock suggest that the Ca of groundwater primarily originates from rainwater and bedrock. The δ44/40Ca values of plants are lower than that of soils, indicating the preferential uptake of light Ca isotopes by plants. The distribution of δ44/40Ca values in the soil profiles (increasing with soil depth) suggests that the recycling of crop-litter abundant with lighter Ca isotope has potential effects on soil Ca isotope composition. The soil Mg/Ca content ratio probably reflects the preferential plant uptake of Ca over Mg and the difference in soil maturity. Light Ca isotopes are more abundant in mature soils than nutrient-depleted soils. The relative abundance in the light Ca isotope (40Ca) is in the following order: farmland > burnt grassland > forests > grassland > shrubland. Our results further indicate that biological fractionation in a soil–plant system is a vital factor for Ca–geochemical transformations in soil surface systems.
Guilin Han; Anton Eisenhauer; Jie Zeng; Man Liu. Calcium Biogeochemical Cycle in a Typical Karst Forest: Evidence from Calcium Isotope Compositions. Forests 2021, 12, 666 .
AMA StyleGuilin Han, Anton Eisenhauer, Jie Zeng, Man Liu. Calcium Biogeochemical Cycle in a Typical Karst Forest: Evidence from Calcium Isotope Compositions. Forests. 2021; 12 (6):666.
Chicago/Turabian StyleGuilin Han; Anton Eisenhauer; Jie Zeng; Man Liu. 2021. "Calcium Biogeochemical Cycle in a Typical Karst Forest: Evidence from Calcium Isotope Compositions." Forests 12, no. 6: 666.
Soil erosion has threatened food security by decreasing the area of arable lands and disturbing soil nutrient cycling, especially nitrogen (N) cycling. However, there is still a challenge to indicate soil N dynamics by N stable isotope composition (δ15N) under an erodible environment. In the present study, the six soil sites from forest lands and agricultural lands were selected to collect soil samples in the Mun River basin, the largest agricultural region in Thailand. The contents of soil organic nitrogen (SON), C/N ratios, and δ15N values of SON in soil profiles were analyzed to identify soil N transformation processes under agricultural soil erosion. Moreover, the relationships of SON and δ15N with soil erodibility K factor were determined by linear regression analysis. Fine particles in the paddy land were largely lost under intensive soil erosion during a short-term abandonment (1 ~ 5 years). Agricultural soil erosion has reduced SON content by 3.8 ~ 4.9 times. The δ15N values of SON in the paddy soils ranged from –5‰ to 5‰, which was attributed to the application of manure and synthetic fertilizer and the δ15N fractionations in the alteration processes of the redox environment. In the abandoned paddy lands, δ15N values of SON in the soils above the illuvial horizon were 4‰ higher than those in the soils below the horizon. The results indicated the discrepant soil N processes at the two soil layers, i.e., soil N mineralization in the upper layer produces 15N-depleted inorganic N and leads to 15N enrichment in organic residues; the inorganic N was leached into the lower layer and re-assimilated by microbes, resulting in 15N-depleted SON. The results suggest that agricultural soil erosion significantly reduces soil N level. However, microbial re-assimilation of inorganic N in the deep soils can mitigate soil N loss.
Man Liu; Guilin Han; Xiaoqiang Li. Using stable nitrogen isotope to indicate soil nitrogen dynamics under agricultural soil erosion in the Mun River basin, Northeast Thailand. Ecological Indicators 2021, 128, 107814 .
AMA StyleMan Liu, Guilin Han, Xiaoqiang Li. Using stable nitrogen isotope to indicate soil nitrogen dynamics under agricultural soil erosion in the Mun River basin, Northeast Thailand. Ecological Indicators. 2021; 128 ():107814.
Chicago/Turabian StyleMan Liu; Guilin Han; Xiaoqiang Li. 2021. "Using stable nitrogen isotope to indicate soil nitrogen dynamics under agricultural soil erosion in the Mun River basin, Northeast Thailand." Ecological Indicators 128, no. : 107814.
Global carbon cycle is closely related to the earth's energy budget, because CO2 plays an active role in the global climate change. The higher CO2 partial pressure (pCO2) in inland water in comparison with atmosphere, causing a CO2 evasion from water to the air. However, the relationship between CO2 evasion, riverine carbon export, and hydrochemistry in watershed has remained largely unknown. This study collected 84 river water samples in Jiulongjiang River, to further address this subject on a small watershed scale. Water temperature fluctuation, riverine photosynthesis, and acidic matter input could not account for the seasonal variation of pCO2 in Jiulongjiang River. The spatial shifts of pCO2 were derived from the mixing process between headwater and soil influx. The soil influx with high pCO2 compensated the CO2 lost from evasion and caused pCO2 in Jiulongjiang River higher than the atmospheric level. The seasonal variation of pCO2 was caused by the precipitation difference between the wet season and dry season. The addition of rainwater significantly decreased the riverine pCO2 and HCO3− concentration in the wet season. The CO2 evasion rate in Jiulongjiang River was clearly higher than that in most worldwide large rivers. The annual CO2 evasion flux in Jiulongjiang River Basin was estimated about 2.48 × 105 T C/year, which was higher than the riverine total carbon export. The CO2 evasion rate exhibited significantly positive relationship with water surface area, indicating that the global CO2 evasion flux may be roughly estimated based on the observed regression relationship. Overall, our study indicated that it still requires collaborative effects to investigate the carbon dynamics in river water, more estimations of CO2 outgassing flux from river water under different hydrologic and geologic conditions are necessary.
Jinke Liu; Guilin Han. Controlling factors of seasonal and spatial variation of riverine CO2 partial pressure and its implication for riverine carbon flux. Science of The Total Environment 2021, 786, 147332 .
AMA StyleJinke Liu, Guilin Han. Controlling factors of seasonal and spatial variation of riverine CO2 partial pressure and its implication for riverine carbon flux. Science of The Total Environment. 2021; 786 ():147332.
Chicago/Turabian StyleJinke Liu; Guilin Han. 2021. "Controlling factors of seasonal and spatial variation of riverine CO2 partial pressure and its implication for riverine carbon flux." Science of The Total Environment 786, no. : 147332.
Trace metal pollution is one of the most concerning issues in Yunnan province, where red soil is the dominant soil. To investigate the sources of trace metals and assess their pollution level and potential ecological and health risk, trace metal concentrations were measured in two red soil profiles (S1 and S2) from Yunnan province. Results show that Cr, As, and Zn are the most abundant trace metals in both soil profiles. However, As and Cr might be pollutants because their concentrations are higher than the local background values and the average concentrations in soils from other countries such as China, Japan, the UK, and the USA. Based on the correlation matrix and principal component analysis, As and Cr in red soils were affected by mining activities. Based on the single factor index and Nemero pollution index, the enrichment of As and Cr in Yunnan province can lead to light pollution in red soils. The RI values of trace metals exhibit a low ecological risk, of which the RI values of As and Cd in S1 are higher than those of Cr, Cu, Ni, Pb, and Zn in both profiles, implying a higher soil pollution level in south Yunnan. Furthermore, the HI results indicate that As can cause non‐carcinogenic risk on human health and should be paid more attention to. This study is aimed to help developing the ecological management of red soils and providing scientific evidence for preventing the hazardous contamination of trace metals in soils. This article is protected by copyright. All rights reserved
Bin Liang; Guilin Han; Jie Zeng; Rui Qu; Man Liu; Jinke Liu. Source and Risk Assessment of Trace Metals in Red Soils from Yunnan Province, Southwest China. CLEAN – Soil, Air, Water 2021, 2000288 .
AMA StyleBin Liang, Guilin Han, Jie Zeng, Rui Qu, Man Liu, Jinke Liu. Source and Risk Assessment of Trace Metals in Red Soils from Yunnan Province, Southwest China. CLEAN – Soil, Air, Water. 2021; ():2000288.
Chicago/Turabian StyleBin Liang; Guilin Han; Jie Zeng; Rui Qu; Man Liu; Jinke Liu. 2021. "Source and Risk Assessment of Trace Metals in Red Soils from Yunnan Province, Southwest China." CLEAN – Soil, Air, Water , no. : 2000288.
The rainwater chemistry and related air contaminants are used to investigate the rainwater ions sources, variations, and influence factors from 2012 to 2014 in Guiyang city (the typical karst urban area of Southwest China). According to temporal rainwater ion concentrations, the obvious variations were presented in the study period, such as Ca2+ (125∼6,652 μeq L−1) and SO4 2− (11∼4,127 μeq L−1). Consequently, Ca2+, Mg2+, SO4 2− and Cl− are considered as the leading ions. Three critical influencing factors of rainwater ions concentrations, including sources variations, rainfall amount and long-distance migration (rainfall amount > 100 mm) are identified. Based on the typical ionic ratios, source identification suggested that anthropogenic inputs mainly contributed to F−, NO3 − and SO4 2−, while the dusts (crustal sources) are the primary sources of Mg2+, Ca2+ and K+. Cl− Enrichment in long-distance transport is the main contributor of Cl−. According to the observation of high level of total wet acid deposition, the more detailed spatio-temporal monitoring of rainfall-related acid deposition (particularly sulfur deposition) is required to understand its potential environmental effects in the aquatic ecosystem of the earth surface.
Jie Zeng; Guilin Han. Rainwater chemistry observation in a karst city: variations, influence factors, sources and potential environmental effects. PeerJ 2021, 9, e11167 .
AMA StyleJie Zeng, Guilin Han. Rainwater chemistry observation in a karst city: variations, influence factors, sources and potential environmental effects. PeerJ. 2021; 9 ():e11167.
Chicago/Turabian StyleJie Zeng; Guilin Han. 2021. "Rainwater chemistry observation in a karst city: variations, influence factors, sources and potential environmental effects." PeerJ 9, no. : e11167.
Rainwater is an essential pathway to remove fine particulate matter and dissolved atmospheric pollutants (e.g., SO2, HNO3, and NH3). Acid rain (pH < 5.6) has been a severe environmental issue in China since the 1970s, adversely impacting ecosystem health. This study focuses on the influence of anthropogenically induced anions (SO42– and NO3–) and alkaline cations (Ca2+ and NH4+) on acid rain in Chinese cities. In this review, cities with high population density east of the Hu Huanyong Line that divides China geographically according to its uneven economic development were studied. Coastal and central areas of China to the east of the line are characterized by a much faster developing economy and rapid urbanization. The observed trends and spatial variability of acidity and chemical composition in rainwater are discussed in relation to industrialization and environmental changes in China. Over the past 3½ decades, the precipitation pH in the urban regions has exhibited reduced acidity. A mixed nitric–sulfuric acid rain type has become prominent due to the significant decrease in SO42– via desulfurization. Ca2+ levels have decreased, while NH4+ has increased slightly due to more vehicular transportation. In addition, the neutralization capacity of Ca2+ and NH4+ has decreased from north to south. Overall, the acid rain problem in Chinese cities has been alleviated in recent years.
Rui Qu; Guilin Han. A critical review of the variation in rainwater acidity in 24 Chinese cities during 1982–2018. Elementa: Science of the Anthropocene 2021, 9, 1 .
AMA StyleRui Qu, Guilin Han. A critical review of the variation in rainwater acidity in 24 Chinese cities during 1982–2018. Elementa: Science of the Anthropocene. 2021; 9 (1):1.
Chicago/Turabian StyleRui Qu; Guilin Han. 2021. "A critical review of the variation in rainwater acidity in 24 Chinese cities during 1982–2018." Elementa: Science of the Anthropocene 9, no. 1: 1.
Forty-eight suspended particulate matter (SPM) samples were collected from the Mun River, northeast Thailand and its junction with the Mekong River, to investigate the relationship between the distribution of rare earth elements (REE) in SPM and the soils in the watershed. The total REE contents (∑REE) in SPM in the Mun River ranged from 78.5 to 377.8 mg/kg with the average of 189.3 mg/kg, which was lower than ∑REE of 222.3 mg/kg at the Mekong River (one sample at junction). The Post Archean Australia Shale (PAAS)-normalized ratios of light REE (LREE), middle REE (MREE) and heavy REE (HREE) were averaged to 1.0, 1.3 and 1.0, which showed a clear enrichment in MREE. In short, along the Mun River, the REE contents in SPM were decreasing, and the PAAS-normalized patterns of REE showed gradually flat. The REE content in SPM and soils are highest in the upper catchment, indicating that soil/bedrock is the most important source of REE in SPM. Additionally, the positive Eu anomaly was enhanced by the higher Ca content in SPM (R = 0.45), which may be caused by more feldspars or carbonates with Ca and Eu substituting Ca. The results present the REE behaviors of SPM in the Mun River and relationship between REE in SPM and soil/bedrock, the findings may support the other studies in catchment weathering.
Kunhua Yang; Guilin Han; Jie Zeng; Wenxiang Zhou. Distribution, fractionation and sources of rare earth elements in suspended particulate matter in a tropical agricultural catchment, northeast Thailand. PeerJ 2021, 9, e10853 .
AMA StyleKunhua Yang, Guilin Han, Jie Zeng, Wenxiang Zhou. Distribution, fractionation and sources of rare earth elements in suspended particulate matter in a tropical agricultural catchment, northeast Thailand. PeerJ. 2021; 9 ():e10853.
Chicago/Turabian StyleKunhua Yang; Guilin Han; Jie Zeng; Wenxiang Zhou. 2021. "Distribution, fractionation and sources of rare earth elements in suspended particulate matter in a tropical agricultural catchment, northeast Thailand." PeerJ 9, no. : e10853.
This study presents a method for one-step chromatographic separation of K–Ca–Sr from matrix elements, and the purification procedure is based on AG50W-X12 cation exchange resin without any intervening evaporation step.
Xiaoqiang Li; Guilin Han. One-step chromatographic purification of K, Ca, and Sr from geological samples for high precision stable and radiogenic isotope analysis by MC-ICP-MS. Journal of Analytical Atomic Spectrometry 2021, 36, 676 -684.
AMA StyleXiaoqiang Li, Guilin Han. One-step chromatographic purification of K, Ca, and Sr from geological samples for high precision stable and radiogenic isotope analysis by MC-ICP-MS. Journal of Analytical Atomic Spectrometry. 2021; 36 (3):676-684.
Chicago/Turabian StyleXiaoqiang Li; Guilin Han. 2021. "One-step chromatographic purification of K, Ca, and Sr from geological samples for high precision stable and radiogenic isotope analysis by MC-ICP-MS." Journal of Analytical Atomic Spectrometry 36, no. 3: 676-684.