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19941. 题目: Spatial distribution of soil organic carbon stocks in Masson pine (Pinus massoniana) forests in subtropical China
文章编号: N19031901
期刊: CATENA
作者: Xiong Yao, Kunyong Yu, Yangbo Deng, Qi Zeng, Zhuangjie Lai, Jian Liu
更新时间: 2019-03-19
摘要: Masson pine (Pinus massoniana) is a typical reforestation species in subtropical China, which plays a key role in soil and water conservation. Site-specific forest management requires an accurate estimation of the soil organic carbon (SOC) stocks, and information about the spatial distribution of SOC stocks is essential for improving the soil quality and ecosystem productivity. We examined the spatial distribution of SOC stocks using 91 soil samples from Masson pine forests in subtropical China. Ordinary kriging (OK) and inverse distance weighting (IDW) methods were used to compare the spatial patterns of the SOC stocks. A moderate spatial dependence of the SOC stocks suggested that extrinsic and intrinsic factors affected the SOC stocks. Similar spatial distributions but different cross-validation accuracies indicated that OK outperformed IDW. The soil pools at a depth of 0–60 cm were 774.06 Gg and 761.61 Gg as determined by the OK and IDW methods, respectively, which were higher than that measured by the conventional method (CM, 734.22 Gg). This highlights the need to apply different methods when studying the regional SOC pools. On the basis of the comparison of OK, IDW, and CM methods, OK is recommended for determining nonhomogeneous sampling point distributions. The present results enhance our understanding of method selection when studying the spatial distribution of SOC stocks.

19942. 题目: Mineral elements uptake and physiological response of Amaranthus mangostanus (L.) as affected by biochar
文章编号: N19031811
期刊: Ecotoxicology and Environmental Safety
作者: Weili Jia, Cuiping Wang, Chuanxin Ma, Jicheng Wang, Hongwen Sun, Baoshan Xing
更新时间: 2019-03-18
摘要: Amaranthus mangostanus L. (amaranth) was hydroponically grown in different concentrations of biochar amended nutrient solution to investigate the mineral elements migration and physiological response of amaranth as affected by biochar. Our results showed that exposure to 26.6 g/L of biochar greatly increased the root and shoot K, Na and Al content, while 2.6 g/L of biochar greatly increased the root Ca and Mg content. The uptake of K and Al notably altered other elements' accumulation in shoots and roots upon the biochar exposure. The ratio of Ca: K in shoots and Mg: K in roots were negatively correlated to the biochar concentrations, while the ratio of Al: Ca and Al: Mg in roots were positively related to the biochar concentrations. The Al: Fe ratio was also polynomial correlated to the concentrations of biochar. The addition of biochar beyond 2.6 g/L resulted in the cell membrane and DNA damages in roots. The activity of SOD and CAT in 6.7 g/L biochar treated roots was significantly elevated as compared to the ones in other biochar treatments and was almost 2-fold of the control. The photosynthetic Fv/Fm intensity and subcellular structure in leaves were also compromised upon exposure to 26.6 g/L biochar. Taken together, biochar could significantly alter the mineral migration in amaranth and physiologically damage in the plants. It is essential to study the effect of biochar within appropriate concentrations on plants prior to wide application in agriculture.

19943. 题目: Plant presence reduces root and shoot litter decomposition rates of crops and wild relatives
文章编号: N19031810
期刊: Plant and Soil
作者: Janna M. Barel, Thomas W. Kuyper, Wietse de Boer, Gerlinde B. De Deyn
更新时间: 2019-03-18
摘要: Aims: Roots contribute greatly to carbon cycling in agriculture. Measuring aboveground litter decomposition could approximate belowground turn-over if drivers of decomposition, f.e. litter traits and plant presence, influence shoot and root decomposition in a comparable manner. We tested coordination of above- and belowground litter traits and decomposition rates for six pairs of crops and closely related wild plants and studied the influence of plant presence on decomposition. Methods: Above- and belowground traits were measured, compared and related to decomposition rates. Shoot and root litters were incubated in presence of the same plant species as the litter species (own) or in presence of two other plant species (a grass or forb). Results: Shoots decomposed 1.43–1.98 times faster than (resp.) wild plant and crop roots. Decomposition correlated negatively with litter carbon and lignin concentrations, except crop root decomposition which correlated negatively with nitrogen concentration. Unexpectedly, plant presence reduced litter decomposition, with strongest effects for root litters in presence of forbs. Conclusions: Carbon cycling might be slower than predicted solely based on shoots decomposition rates, especially in presence of growing plants. While root decomposition of wild plants can be approximated by shoot decomposition, crop shoots are a poor proxy for crop root decomposition.

19944. 题目: Anthropogenic influence on the sediment chemistry and diatom assemblages of Balamtetik Lake, Chiapas, Mexico
文章编号: N19031809
期刊: Environmental Science and Pollution Research
作者: Margarita Caballero, Lucy Mora, Esperanza Muñoz, Oscar Escolero, Roberto Bonifaz, Carolina Ruiz, Blanca Prado
更新时间: 2019-03-18
摘要: Balamtetik is the receiving body of the Rio Grande de Comitán and is located just at the outskirts of the Montebello National Park, Chiapas, México. Multi-elemental, infrared spectra, 137Cs, 210Pb, and diatom analyses in a 75-cm sediment core were used to reconstruct the recent disturbance history of the lake. The sequence chronology, based mostly on 137Cs profiles, allowed to infer high sedimentation rates in Balamtetik (~ 7 mm/year) and a nearly cyclic series of disturbance events that can be related to anthropogenic causes such as deforestation and increased development of agriculture and urban areas at local and regional scale. These disturbance events show high local and regional erosion (high Ca, TIC, and Ti), soil organic matter (IR spectra), eutrophication (high P and diatoms), and anoxic bottom water conditions (low Mn) and can be dated to the early 1950s, the late 1950s, and from the 1980s until the 2000s. The entrance of wastewaters is related with an increase in salinity inferred by the diatom record and the organic matter type. The first two disturbance events are related to changes in land use during the agrarian reform that started during the 1940s; the last event is related with the increase in local population and the introduction of intensive agriculture. This last phase of disturbance corresponds with the reports of fish mortality events around 2003; however, high lake turbidity and anoxic bottom waters seem to have been established since the 1980s. The record from Lake Balamtetik also shows that during the intermediate periods, there was a recovery of the lake and its catchment; however, the future trends might be different, as the increase in the speed of organic matter and nutrients arrival to the lake reduces its resilience.

19945. 题目: Long-term soil biological fertility, volatile organic compounds and chemical properties in a vineyard soil after biochar amendment
文章编号: N19031808
期刊: Geoderma
作者: Laura Giagnoni, Anita Maienza, Silvia Baronti, Francesco Primo Vaccari, Lorenzo Genesio, Cosimo Taiti, Tania Martellini, Roberto Scodellini, Alessandra Cincinelli, Corrado Costa, Stefano Mancuso, Giancarlo Renella
更新时间: 2019-03-18
摘要: The agronomic management of vineyards, aimed at the maximization of grape yields, is intensive and includes repeated tillage, crop residues removal, strict weed and pest control treatments. In viticulture, healthy soils and a suitable climate are the key factors that influence the quality of the produced wine. Even under intensive agronomic practices, typical of conventional viticulture, the choice of appropriate soil management strategies can preserve soil quality in the long term. The use of biochar as soil amendment has been suggested as a potential practice that allows restoration of the functionality of degraded soils in terms of water retention, chemical and biological fertility. In this paper we report the results of a long field trial on biochar amendment of a vineyard, assessing the impact on soil functionality, VOC emission and fertility. Our results show that biochar effects on soil functions and fertility are maintained in the long term (seven years) after a one-time application.

19946. 题目: Topographic influences on soil properties and aboveground biomass in lucerne-rich vegetation in a semi-arid environment
文章编号: N19031807
期刊: Geoderma
作者: Zi-Qiang Yuan, Chao Fang, Rong Zhang, Feng-Min Li, Muhammad Mansoor Javaid, Ivan A. Janssens
更新时间: 2019-03-18
摘要: Lucerne (Medicago sativa L.) is widely planted on the semi-arid Loess Plateau in China to control soil erosion, yet the extent to which topography affects the productivity of lucerne still remains poorly understood. This study aimed to evaluate how topographic position influences soil properties and aboveground biomass in lucerne-rich vegetation. A total of 112 quadrats were established in 28 fields covered with 11-year-old lucerne vegetation. In each quadrat, the slope, slope position, slope aspect, altitude, soil properties (soil moisture content, organic carbon, total nitrogen [N] and phosphorus [P], available P and inorganic N), and aboveground biomass were measured. Redundancy and multiple regression analyses were performed to determine the relationships among topographic factors, soil properties and aboveground biomass. A modest proportion of variation in soil variables was explained by topographic variables. The altitude, slope and slope position, rather than the slope aspect, were the key factors that influencing soil variables. Soil organic carbon, total N, inorganic N, the ratio of organic carbon to available P (C/P), and the ratio of total N to available P were positively correlated with altitude, whereas available P was negatively correlated with altitude. The soil moisture content was primarily affected by the slope and slope position. The topographic factors did not directly affect the total and lucerne aboveground biomass. The total and lucerne aboveground biomass were positively correlated to soil moisture content, inorganic N and C/P. Therefore, the aboveground biomass of lucerne-rich vegetation could be indirectly regulated by the slope and slope position through the effect on the soil moisture content and by altitude through the effect on soil inorganic N and C/P. This work highlighted the importance of soil properties such as soil moisture and P dynamics in the revegetation process of lucerne in this semi-arid region. As soil properties can be directly governed by topography, considering topography could enhance the quality of vegetation restoration in the large hilly region of the Loess Plateau.

19947. 题目: Collapse and failure of ancient agricultural stone terraces: On-site geomorphic processes, pedogenic mechanisms, and soil quality
文章编号: N19031806
期刊: Geoderma
作者: Ilan Stavi, Yulia Gusarov, Rares Halbac-Cotoara-Zamfir
更新时间: 2019-03-18
摘要: Water is the major limiting factor for primary productivity in drylands. In ancient times, stone terraces aimed at runoff harvesting and soil erosion control were established, allowing agricultural crop production. Land abandonment and cease of maintenance have led to the collapse and failure of terraces in the hinterlands of the Roman/Byzantine city of Avdat in the arid Negev Desert, Israel. The objective of this study was to assess the geomorphic processes and pedogenic mechanisms related to terrace collapse, and their on-site impact on soil quality. We studied key properties of the top 10 cm of soil in intact-terrace plots and partially-collapsed terrace plots, as well as in ‘natural’ lands. Unexpectedly, the soil texture was finer in the partially collapsed-terrace plots (clay loam) than that in the intact-terrace plots (loam). This was attributed to transportation of mineral material by rolling, which sorts out the large primary particles. This process, which characterizes rill erosion of high erosive power, is probably the predominant surface process in this study. The soil penetration resistance was significantly greater in the partially-collapsed terrace plots, and was attributed to the continuous removal of recently deposited loose sediments and exposure of the underlying, compacted older sediments. Soil stoniness, which was 16-fold greater in the partially-collapsed terrace plots, was also attributed to soil erosion. Unexpectedly, the total organic carbon was similar in both terrace states. Yet, labile organic carbon was 41% lower in soil of the partially-collapsed terrace plots, suggesting greater susceptibility of this fraction to erosional processes. The low electrical conductivity in the soil of the intact-terrace plots, was attributed to the better leaching of salts. The soil's calculated available water capacity was 42% greater in the intact-terrace plots. The study suggests that these processes and mechanisms strengthen each other through a chain of feedbacks, resulting in accelerated degradation of the collapsed-terrace lands.
图文摘要:

19948. 题目: Exploring sediment porewater dissolved organic matter (DOM) in a mud volcano: Clues of a thermogenic DOM source from fluorescence spectroscopy
文章编号: N19031805
期刊: Marine Chemistry
作者: Simona Retelletti Brogi, Ji-Hoon Kim, Jong-Sik Ryu, Young Keun Jin, Yun Kyung Lee, Jin Hur
更新时间: 2019-03-18
摘要: Mud volcanoes (MVs) are potential conduit migration pathways for deep thermogenic DOM. In this study, we investigated the dissolved organic matter (DOM) of porewater in a MV in the Canadian Beaufort Sea and compared dissolved organic carbon (DOC) and fluorescent DOM (FDOM) between the MV and a reference site (RS). The chemical and isotopic compositions (Cl, δ18O and δD) of porewater from the MVs indicated that these fluids are derived from a mixture of seawater, meteoric water, and clay dehydration, causing a freshening of the porewaters. Interestingly, the porewaters in the MV exhibited DOC concentrations up to 14 times higher than those in the RS. This high DOC concentration was attributed to a higher concentration in the deep fluid moving upwards through the MV, and in minor part to processes such as particulate organic matter sulfate reduction, anaerobic oxidation of methane and higher biological activity in the MV sediments. The fluorescence results showed the presence of four components in both MV and RS sites, which included two humic-like, one microbial humic-like, and a protein-like component. All the four fluorescent components increased with depth, showing a good linear relationship with DOC. However, the DOC-normalized fluorescence in the porewater DOM was on average 3 to 7 times lower in the MV, suggesting that the DOM molecules have undergone thermogenic processes in the deep sediments, and that shallow processes do not affect significantly to FDOM composition. Our results highlight that fluids migrating from the deep sediment through the MV can be an important source of thermogenically altered DOM to the shallow sediments and overlaying water column.

19949. 题目: A new software of calculating the pH values of coastal seawater: Considering the effects of low molecular weight organic acids
文章编号: N19031804
期刊: Marine Chemistry
作者: Li-Na Lyu, Daoming Lu, Chengjun Sun, Haibing Ding, Liang-Min Yu, Gui-Peng Yang
更新时间: 2019-03-18
摘要: Effects of low molecular weight organic acids (LMWOAs) on the pH value of seawater were investigated in the surface seawater of the Jiaozhou Bay, China. The new software of Org·TCO2TA was developed to calculate the pH values of seawater based on the alkalinity (Alk) equation where organic acid Alk (Org-Alk) was separated into LMWOA Alk (LMWOA-Alk) and humic acid Alk (HA-Alk). In the calculations, all dissociation constants of organic acids were from previous literature. In our study, the average concentration of total LMWOAs was 14.5 ± 11.2 μmol·kg−1 SW. pH values from the Org·TCO2TA software were closer to the pH values from spectrophotometric measurement than those from the CO2SYS program, indicating pH values can be influenced by high concentrations of LMWOAs in coastal seawater of the Jiaozhou Bay. Although the differences still existed between the pH values from the spectrophotometric method and the calculated pH values from the Org·TCO2TA software due to the influence of various factors, including the analytical errors of dissolved inorganic carbon and nutrients, the new software can calculate the pH values of coastal seawater more accurately by considering the effects of LMWOAs.

19950. 题目: Diagenetic transformation of organic matter in sapropel sediments of small lakes (southern West Siberia and eastern Transbaikalia)
文章编号: N19031803
期刊: Quaternary International
作者: G.A. Leonova, A.E. Maltsev, V.N. Melenevsky, S.K. Krivonogov, L.M. Kondratyeva, V.A. Bobrov, M.Y. Suslova
更新时间: 2019-03-18
摘要: Sapropels, biogenic lake sediments, are characterized by a reduction type of diagenesis, during which decomposition of organic compounds, modification of the pore water chemical composition and precipitation of authigenic minerals, mostly pyrite, occur. Pyrolysis data indicate that organic matter undergoes radical transformations already in the uppermost sapropel layers, and composition of the organic matter in the sediments is principally different from the composition of the organic matter of live organisms, which produce the sediments. The sapropels lose labile protein–carbohydrate compounds in the horizon of unconsolidated sediment (0–5 cm), and kerogen appears, whose macromolecular structures start to develop in the very early stages of diagenesis. Various physiological groups of microorganisms provide diagenetic transformations of the organic matter, where heterotrophic, ammonifying and sulfate-reducing bacteria play key role. Their effect is well-seen from the pore water transformation: a decrease in concentrations of SO42– and consequent increase of reduced Fe and S as pyrite in the solid phase of the sediment. Comparative analysis shows that, unlike in lakes of the Baikal area, sapropels in southern West Siberia are affected by more active sulfate reduction, which can depend on both the composition of the organic matter and the SO42– concentration in the pore waters.

19951. 题目: Long-term impact of no-till conservation agriculture and N-fertilizer on soil aggregate stability, infiltration and distribution of C in different size fractions
文章编号: N19031802
期刊: Soil and Tillage Research
作者: Nkanyiso J. Sithole, Lembe S. Magwaza, Guy R. Thibaud
更新时间: 2019-03-18
摘要: Soil degradation associated with the loss of soil organic carbon (SOC) has been a major concern in sub-Saharan Africa because of the subsequent yield reduction. It is not fully understood how long-term additional C through biomass and N-fertilizers impact on C distribution in soil aggregates and its effects on soil aggregate stability and infiltration in sub-tropical maize monocropping system. The study, therefore, assessed long-term changes in total SOC (TSOC), aggregate-associated C, particulate organic C (POC), aggregate stability and infiltration in the 0–10, 10–20 and 20–30 cm depths under different tillage systems after 13 years of implementation of the trial. The three tillage systems were no-till (NT), rotational tillage (RT) both with permanent residue cover and conventional tillage (CT) with residue removed. N-fertilizer was applied at a rate of 0, 100 and 200 kg/ha. On average TSOC did not vary (p > 0.05) across the tillage treatments, 27.1 t/ha NT vs 26.0 t/ha RT and 26.6 t/ha CT, but varied with depth where it was stratified in the 0–10 cm depth in NT and RT. Particulate organic C, however, varied significantly (p < 0.05) across the treatments where it decreased with increase in tillage intensity but only in the 0–10 cm depth. Carbon associated with large aggregates (>2000 μm) differed marginally (p = 0.085) with tillage treatment with NT having 38.0 t/ha, RT 36.6 t/ha and CT 29.7 t/ha. However, differences (p < 0.05) were observed in small macroaggregates (250–2000 μm) with NT having 37.8 t/ha, RT 33.5 t/ha and CT 30.4 t/ha in the surface depth. Fertilizer application rate did not seem to affect soil aggregate stability & SOC. The results found a strong effect of residue retention in NT and RT in the soil surface with aggregate stability which, was correlated with the high rate of infiltration rate in these treatments. The results of this study indicate that reduced soil disturbance improves physical protection of SOC, soil structure and infiltration, however, it also indicated that TSOC takes time to improve in maize continuous monocrop system in the studied soil.

19952. 题目: Effects of pH on redox proxies in a Jurassic rift lake: Implications for interpreting environmental records in deep time
文章编号: N19031801
期刊: Geochimica et Cosmochimica Acta
作者: Eva E. Stüeken, Aaron Martinez, Gordon Love, Paul E. Olsen, Steve Bates, Timothy W. Lyons
更新时间: 2019-03-18
摘要: It is widely agreed that the Earth’s atmosphere and oceans have undergone major redox changes over the last 2.5 billion years. However, the magnitude of these shifts remains a point of debate because it is difficult to reconstruct concentrations of dissolved O2 from indirect proxies in sedimentary archives. In this study, we show that an additional complicating factor that is rarely considered may be the pH of the water column. We analyzed rock samples from the early Jurassic Towaco Formation in the Newark basin (eastern USA), comprising deposits of a rift lake that became temporarily redox stratified. New biomarker evidence points to increasingly saline aquatic conditions during the second half of the lake’s history, with a salinity stratification that induced redox stratification, including evidence for water column anoxia, and that state may also explain the disappearance of macrofauna at this time. Distinctive lipid biomarker assemblages and stable nitrogen isotope data support previous mineralogical indications that the lake was alkaline (pH ≥ 9) during its saline episode. Despite the biomarker and macrofaunal evidence for anoxia, ratios of Fe/Al and FeHR/FeT show only small to no enrichments in the anoxic horizon compared to oxic facies in the same section – counter to what is commonly observed in anoxic marine settings. Molybdenum, As, V, U and to some degree Cd show enrichments in the anoxic interval, whereas Co, Ni, Cu, Zn and Cr do not. These patterns are most parsimoniously explained by differential pH effects on the solubility of these elements. Extrapolating from these observations in lacustrine strata, we speculate that a secular increase in seawater pH over Earth’s history as recently proposed may have helped modulate the magnitude of trace metal enrichments in marine shales, although other factors such as atmospheric and oceanic redox likely dominated the observed enrichment patterns. Further, a decrease in the solubility of ferrous iron, a major O2 sink, with increasing pH may have contributed to ocean oxygenation. In summary, our results highlight the potential importance of pH in influencing global biogeochemical cycles for multiple elements and for the interpretation of ancient nitrogen isotope signatures.

19953. 题目: Distribution of carbon and nitrogen along hillslopes in three valleys on Herschel Island, Yukon Territory, Canada
文章编号: N19031708
期刊: CATENA
作者: Justine L. Ramage, Daniel Fortier, Gustaf Hugelius, Hugues Lantuit, Anne Morgenstern
更新时间: 2019-03-17
摘要: Thermokarst results from the thawing of ice-rich permafrost and alters the biogeochemical cycling in the Arctic by reworking soil material and redistributing soil organic carbon (SOC) and total nitrogen (TN) along uplands, hillslopes, and lowlands. Understanding the impact of this redistribution is key to better estimating the storage of SOC in permafrost terrains. However, there are insufficient studies quantifying long-term impacts of thaw processes on the distribution of SOC and TN along hillslopes. We address this issue by providing estimates of SOC and TN stocks along the hillslopes of three valleys located on Herschel Island (Yukon, Canada), and by discussing the impact of hillslope thermokarst on the variability of SOC and TN stocks. We found that the average SOC and TN 0–100 cm stocks in the valleys were 26.4 ± 8.9 kg C m-2 and 2.1 ± 0.6 kg N m-2. We highlight the strong variability in the soils physical and geochemical properties within hillslope positions. High SOC stocks were found at the summits, essentially due to burial of organic matter by cryoturbation, and at the toeslopes due to impeded drainage which favored peat formation and SOC accumulation. The average carbon-to‑nitrogen ratio in the valleys was 12.9, ranging from 9.7 to 18.9, and was significantly higher at the summits compared to the backslopes and footslopes (p < 0.05), suggesting a degradation of SOC downhill. Carbon and nitrogen contents and stocks were significantly lower on 16% of the sites that were previously affected by hillslope thermokarst (p < 0.05). Our results showed that lateral redistribution of SOC and TN due to hillslope thermokarst has a strong impact on the SOC storage in ice-rich permafrost terrains.

19954. 题目: Organic carbon mineralization in soils of a natural forest and a forest plantation of southeastern China
文章编号: N19031707
期刊: Geoderma
作者: Jinxue Huang, Teng-Chiu Lin, Decheng Xiong, Zhijie Yang, Xiaofei Liu, Guangshui Chen, Jinsheng Xie, Yiqing Li, Yusheng Yang
更新时间: 2019-03-17
摘要: Understanding soil organic carbon (SOC) mineralization under different temperature regimes is critical for predicting SOC responses to climate change. Yet, the effects of altering temperature regimes on SOC mineralization remain poorly understood in forest plantations converted from natural forests. Forest conversion is extensive and could have major impact on SOC dynamics, so that this knowledge limits our ability of predicting the consequences of such land use change on carbon cycling. To fill this knowledge gap, we conducted a 360-day incubation experiment under constant and varying temperature regimes for soils of a natural forest and a Chinese fir (Cunninghamia lanceolata) plantation. Results showed that SOC mineralization was greater in the forest plantation soil than in the natural forest soil in both temperature treatments, possibly due to greater labile SOC in the forest plantation soil by 27–28%. The results suggested that replacing natural forests with forest plantations may increase CO2 emission via the mineralization of SOC. In the natural forest soil, SOC mineralization was greater in the varying temperature treatment relative to the constant temperature treatment but no difference was found in the forest plantation soil. Moreover, temperature sensitivity (Q10) of SOC mineralization was greater in the natural forest soil than the Chinese fir soil for the 0–180 day of the incubation. The difference in the response to the two temperature treatments between the two forest soils which was accompanied by difference in soil microbial communities. It was likely that soil microbes of the closed-canopy natural forest were less adapted to temperature fluctuations than soil microbes of the forest plantation soil as the canopy was rarely closed. Our results highlight that soil incubation experiments need to take temperature fluctuations into consideration to more accurately reflect SOC dynamics in the field, especially when evaluating the impacts of replacing natural forests with forest plantations on soil carbon dynamics.

19955. 题目: Application of denitrifying bioreactors for the removal of atrazine in agricultural drainage water
文章编号: N19031706
期刊: Journal of Environmental Management
作者: Bahareh Hassanpour, Larry D. Geohring, Annaleise R. Klein, Shree Giri, Ludmilla Aristilde, Tammo S. Steenhuis
更新时间: 2019-03-17
摘要: Atrazine and nitrate NO3N are two agricultural pollutants that occur widely in surface and groundwater. One of the pathways by which these pollutants reach surface water is through subsurface drainage tile lines. Edge-of-field anaerobic denitrifying bioreactors apply organic substrates such as woodchips to stimulate the removal of NO3N from the subsurface tile waters through denitrification. Here we investigated the co-removal of NO3N and atrazine by these bioreactors. Laboratory experiments were conducted using 12-L woodchips-containing flow-through bioreactors, with and without the addition of biochar, to treat two concentrations of atrazine (20 and 50 μg L−1) and NO3N (1.5 and 11.5 mg L−1), operated at four hydraulic retention time, HRT, (4 h, 8 h, 24 h, 72 h). Additionally, we examined the effect of aerating the bioreactors on atrazine removal. Furthermore, we tested atrazine removal by a field woodchip denitrifying bioreactor. The removal of both NO3N and atrazine increased with increasing HRT in the laboratory bioreactors. At 4 h, the woodchip bioreactors removed 65% of NO3N and 25% of atrazine but, at 72 h, the bioreactors eliminated all the NO3N and 53% of atrazine. Biochar-amended bioreactors removed up to 90% of atrazine at 72-h retention time. We concluded that atrazine removal was primarily via adsorption because neither aeration nor NO3N levels had an effect. At 4-h retention time, the field bioreactors achieved 2.5 times greater atrazine removal than the laboratory bioreactors. Our findings thus highlighted hydraulic retention time and biochar amendments as two important factors that may control the efficiency of atrazine removal by denitrifying bioreactors. In sum, laboratory and field data demonstrated that denitrifying bioreactors have the potential to decrease pesticide transport from agricultural lands to surface waters.
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19956. 题目: Macroaggregates as biochemically functional hotspots in soil matrix: Evidence from a rice paddy under long-term fertilization treatments in the Taihu Lake Plain, eastern China
文章编号: N19031705
期刊: Applied Soil Ecology
作者: Zichuan Li, Zhipeng Rui, Dengxiao Zhang, Xiao Feng, Haifei Lu, Shengyuan Shen, Jufeng Zheng, Lianqing Li, Zhaoliang Song, Genxing Pan
更新时间: 2019-03-17
摘要: Abundance and allocation of organic matter, microbial community and their extracellular enzyme activities in soil aggregates had been increasingly concerned for mediating biogeochemical cycle and biodiversity provided by soil. In this study, the variations of soil organic carbon (SOC) accumulation and extracellular enzyme activities in aggregate size fractions of a rice paddy with long-term fertilization treatments were analyzed. These treatments included no fertilizer application (NF) as a control, chemical fertilizer only (CF), chemical fertilizer combined with swine manure (CFM), and with straw residue return (CFS). Hereby, size fractions of soil aggregates respectively of >2000 μm (large macroaggregates), 250–2000 μm (macroaggregates), 53–250 μm (microaggregates), 2–53 μm (fine aggregates), and <2 μm (fine clay) were obtained from undisturbed soil cores following water-dispersion and subsequent wet-sieving using a low energy separation protocol. Of these aggregate fractions, SOC and total nitrogen (N) contents were determined with wet digestion and soil enzyme activities were analyzed with substrate-induction incubation assays. Contents of SOC and total N were both highest in macroaggregates, followed by large macroaggregates and microaggregates, but depleted in fine microaggregates. Activities of carbon-degrading enzymes and N-acetyl-glucosaminidase were markedly enriched in soil aggregate fractions in size >53 μm. Whereas, activity of phenol oxidase was generally concentrated in soil aggregate fractions in size between 2 and 2000 μm while that of peroxidase in size between 53 and 2000 μm. Activity of β-glucosidase and cellobiohydrolase was both significantly elevated under CFS and that of peroxidase under CF, CFM and CFS treatments, but phenol oxidase activity was suppressed under CFS treatment. The enzyme activities of β-xylosidase, β-glucosidase, cellobiohydrolase and N-acetyl-glucosaminidase varied greatly (CVs up to 50%), rather with size fractions than with treatments, while those of α-Glucosidase and phenol oxidase varied moderately (CVs up to 35%), rather with treatments than with size fractions. However, those of acid phosphatase and peroxidase changed slightly (CVs up to 20%), regardless of both size fractions and fertilization treatments. Thus, abundance and enrichment of all the soil enzyme activities analyzed depended not on SOC although the overall extracellular enzyme activity was generally well correlated to SOC abundance, among aggregate size fractions. Only activities of carbon-degrading enzymes were greatly enriched in macroaggregates, which were seen reduced under combined organo/mineral fertilization. This study highlighted macroaggregates as biochemically active micro- hotspots and lower activities of carbon-degrading enzymes with SOC accumulation under long-term rational fertilization in the rice paddy.
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19957. 题目: Storage, patterns and controls of soil organic carbon in the alpine shrubland in the Three Rivers Source Region on the Qinghai-Tibetan Plateau
文章编号: N19031704
期刊: CATENA
作者: Xiuqing Nie, Lucun Yang, Fan Li, Feng Xiong, Changbin Li, Guoying Zhou
更新时间: 2019-03-17
摘要: Alpine shrubland ecosystems in the Three Rivers Source Region (TRSR) store substantial soil organic carbon (SOC), but the storage, patterns and control of SOC in those ecosystems have rarely been investigated. In this study, using data from 66 soil profiles surveyed from 22 sites between 2011 and 2013, we estimated the storage and patterns of SOC, and their relationships with climatic factors, elevation, ground cover and slope. Our results showed that SOC storage in the top 100 cm across the TRSR shrubland was 0.68 ± 0.38 Pg C, with an average SOC density (soil carbon storage per area) of 26.21 ± 14.58 kg m−2. Spatially, SOC density increased with longitude and latitude. Vertically, SOC in the topsoil at 30 cm and 50 cm accounted for 56% and 75%, respectively, of the total at 100 cm. SOC density showed a decreasing trend with increasing elevation, but it was greater in regions of higher ground cover. The density had no relationship with either mean annual precipitation or slope. Increasing mean annual temperature had positive effects on SOC density, which is inconsistent with the global trend. With increasing soil depth, however, the effects of temperature on SOC density were not significant. Therefore, in a global warming scenario, increasing temperature gives shrubland considerable C sink potential on the topsoil, and the regions of C sequestration differ as a result of uneven increases in temperature. Hence, further monitoring of dynamic changes is necessary to provide a more accurate assessment of potential C sequestration in TRSR shrubland.

19958. 题目: Long-term organic matter application reduces cadmium but not zinc concentrations in wheat
文章编号: N19031703
期刊: Science of The Total Environment
作者: Roman Grüter, Benjamin Costerousse, Jochen Mayer, Paul Mäder, Cécile Thonar, Emmanuel Frossard, Rainer Schulin, Susan Tandy
更新时间: 2019-03-17
摘要: Wheat is a staple food crop and a major source of both the essential micronutrient zinc (Zn) and the toxic heavy metal cadmium (Cd) for humans. Since Zn and Cd are chemically similar, increasing Zn concentrations in wheat grains (biofortification), while preventing Cd accumulation, is an agronomic challenge. We used two Swiss agricultural long-term field trials, the “Dynamic-Organic-Conventional System Comparison Trial” (DOK) and the “Zurich Organic Fertilization Experiment” (ZOFE), to investigate the impact of long-term organic, mineral and combined fertilizer inputs on total and phytoavailable concentrations of soil Zn and Cd and their accumulation in winter wheat (Triticum aestivum L.). “Diffusive gradients in thin films” (DGT) and diethylene-triamine-pentaacetic acid (DTPA) extraction were used as proxies for plant available soil metals. Compared to unfertilized controls, long-term organic fertilization with composted manure or green waste compost led to higher soil organic carbon, cation exchange capacity and pH, while DGT-available Zn and Cd concentrations were reduced. The DGT method was a strong predictor of shoot and grain Cd, but not Zn concentrations. Shoot and grain Zn concentrations correlated with DTPA-extractable and total soil Zn concentrations in the ZOFE, but not the DOK trial. Long-term compost fertilization led to lower accumulation of Cd in wheat grains, but did not affect grain Zn. Therefore, Zn/Cd ratios in the grains increased. High Zn and Cd inputs with organic fertilizers and high Cd inputs with phosphate fertilizers led to positive Zn and Cd mass balances when taking into account atmospheric deposition and fertilizer inputs. On the other hand, mineral fertilization led to the depletion of soil Zn due to higher yields and thus higher Zn exports than under organic management. The study supports the use of organic fertilizers for reducing Cd concentrations of wheat grains in the long-term, given that the quality of the fertilizers is guaranteed.
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19959. 题目: Local habitat heterogeneity determines the differences in benthic diatom metacommunities between different urban river types
文章编号: N19031702
期刊: Science of The Total Environment
作者: Shan Chen, Wei Zhang, Jiahui Zhang, Erik Jeppesen, Zhaoying Liu, J. Patrick Kociolek, Xiaoying Xu, Liqing Wang
更新时间: 2019-03-17
摘要: Benthic diatoms are useful indicators of the ecological state of river systems. To understand the factors determining benthic diatom metacommunity composition in urban rivers, we studied in situ surface sediment diatom communities from 23 rivers in Shanghai City. Based on our study results on the metacommunity structure of benthic diatoms and hierarchical cluster analysis (HCA), we found substantial differences between restored (G1) and unrestored rivers (G2–G4) in taxa richness, relative abundances, and dominant and indicator taxa of benthic diatoms. The epiphytic diatoms Cocconeis placentula and Amphora libyca var. baltica were representative of the restored rivers (G1), where aquatic macrophytes were more abundant and the water was clearer. The motile epipelic diatoms Navicula recens and Navicula germainii dominated the moderately polluted rivers (G2). The eutrophic taxa Cyclotella meneghiniana, Aulacoseira granulata, and Cyclostephanos tholiformis dominated in G3, which comprised relatively heavily polluted rivers with low organic matter sediment and high disturbance. The polysaprobic taxon Nitzschia palea and the halophilous taxon Fallacia pygmaea represented relatively heavily polluted rivers with a comparatively higher sedimentary salinity (SSal) (G4). Redundancy analysis (RDA) revealed that total phosphorus (TP), dissolved organic carbon (DOC), silicon dioxide (SiO2), dissolved oxygen (DO), Secchi depth (SD), SSal, and the ratio of carbon to nitrogen (C/N) in the sediment were important environmental factors explaining variation among benthic diatom metacommunity composition. Partial RDA (pRDA) implied that the relative importance of environmental factors in structuring benthic diatom metacommunity was much higher than spatial factors. Classification and regression trees (CART) further indicated that DOC, the sediment C/N ratio, and SSal were the key local environmental factors affecting grouping patterns of benthic diatom metacommunities. Our study proposes that benthic diatom metacommunities respond to the complex characteristics of local environment in urban rivers and provides useful knowledge for consideration in the ecological monitoring of urban river systems.
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19960. 题目: Effects of tillage, crop establishment and diversification on soil organic carbon, aggregation, aggregate associated carbon and productivity in cereal systems of semi-arid Northwest India
文章编号: N19031701
期刊: Soil and Tillage Research
作者: H.S. Jat, Ashim Datta, M. Choudhary, A.K. Yadav, V. Choudhary, P.C. Sharma, M.K. Gathala, M.L. Jat, A. McDonald
更新时间: 2019-03-17
摘要: Intensive tillage based management practices are threatening soil quality and systems sustainability in the rice-wheat belt of Northwest India. Furthermore, it is accentuated with puddling of soil, which disrupts soil aggregates. Conservation agriculture (CA) practices involving zero tillage, crop residue management and suitable crop rotation can serve as better alternative to conventional agriculture for maintaining soil quality. Soil organic carbon is an important determinant of soil quality, playing critical role in food production, mitigation and adaptation to climate change as well as performs many ecosystem functions. To understand the turnover of soil carbon in different forms (Total organic carbon-TOC; aggregate associated carbon-AAC; particulate organic carbon- POC), soil aggregation and crop productivity with different management practices, one conventional agriculture based scenario and three CA based crop management scenarios namely conventional rice-wheat system (Sc1), partial CA based rice-wheat-mungbean system (Sc2), full CA-based rice-wheat-mungbean system (Sc3) and maize-wheat-mungbean system (Sc4) were evaluated. TOC was increased by 71%, 68% and 25% after 4 years of the experiment and 75%, 80% and 38% after 6 years of the experiment in Sc4, Sc3 and Sc2, respectively, over Sc1 at 0–15 cm soil depth. After 4 years of the experiment, 38.5% and 5.0% and after 6 years 50.8% and 24.4% improvement in total water stable aggregates at 0–15 and 15–30 cm soil depth, respectively was observed in CA-based scenarios over Sc1. Higher aggregate indices were associated with Sc3 at 0–15 cm soil depth than others. Among the size classes of aggregates, highest aggregate associated C (8.94 g kg−1) was retained in the 1-0.5 mm size class under CA-based scenarios. After 6 years, higher POC was associated with Sc4 (116%). CA-based rice/maize system (Sc3 and Sc4) showed higher productivity than Sc1. Therefore, CA could be a potential management practice in rice-wheat cropping system of Northwest India to improve the soil carbon pools through maintaining soil aggregation and productivity.

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