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1.
Purpose
This study aims to verify the performances of Water Erosion Prediction Project (WEPP) rill erosion equation using loess material by investigating the variations of soil detachment rate with sediment load by rill flow, quantifying the response of soil detachment rate to sediment load, and comprehensively examining WEPP rill erosion equation, so as to provide scientific basis for the application of WEPP model on the loess plateau and to sufficiently understand the response of soil detachment rate to sediment load.Materials and methods
The experiment was conducted in a rill flume with a soil-feeding hopper and was specifically designed to isolate the effect of sediment load on detachment rate. Loess material was collected from a typical hilly region of the Loess Plateau, Ansai, Shaanxi, China. The test soil was quantitatively fed into rill flow by a soil-feeding hopper to produce different sediment loads. Seven unit flow discharges (1.11, 1.56, 2.00, 2.44, 2.89, 3.33, and 3.78?×?10?3 m2 s?1) were combined with six slopes (10.51, 15.84, 21.26, 26.79, 32.49, and 38.39 %). The sediment transport capacity was measured for each combination. The detachment rate was measured for each combination under seven sediment loads, which were 0, 10, 25, 50, 75, 90, and 100 % of the sediment transport capacity.Results and discussion
Soil detachment rate decreased with the increase of sediment load. Levels of sediment load in 0, 10, 25, 50, 75, 90, and 100 % reduced detachment rate in rates of 0, 18.93, 36.36, 56.28, 70.15, 83.42, and 92.19 %, respectively. The response relationship of detachment rate to sediment load by rill flow was described well by a negative linear equation (R 2 range from 0.8489 to 0.9982, P?<?0.01), and the vertical and horizontal intercepts of the linear equation represented the detachment and transport capacities, respectively (R 2?=?0.9955, NSE?=?0.9788 for D c ; R 2?=?0.9957, NSE?=?0.9635 for T c ), as expressed by the WEPP rill erosion equation. The WEPP rill erosion equation predicted the soil detachment rate very well (R 2?=?0.9667, NSE?=?0.9611).Conclusions
Sediment load transported by rill flow has a negative influence on soil detachment rate in rills. Introducing sediment load as a factor in model equation of detachment is essential for developing an accepted erosion model. The WEPP rill erosion equation could correctly reflect the response relationship of detachment rate to sediment load in this flume experiment and has a good applicability to loess material.2.
Vincenzo Bagarello Vito Ferro Vincenzo Pampalone Paolo Porto Francesca Todisco Lorenzo Vergni 《Journal of Soils and Sediments》2018,18(12):3365-3377
Purpose
The USLE-MM estimates event normalized plot soil loss, Ae,N, by an erosivity term given by the runoff coefficient, QR, times the single-storm erosion index, EI30, raised to an exponent b1?>?1. This modeling scheme is based on an expected power relationship, with an exponent greater than one, between event sediment concentration, Ce, and the EI30/Pe (Pe = rainfall depth) term. In this investigation, carried out at the three experimental sites of Bagnara, Masse, and Sparacia, in Italy; the soundness of the USLE-MM scheme was tested.Materials and methods
A total of 1192 (Ae,N, QREI30) data pairs were used to parameterize the model both locally and considering all sites simultaneously. The performances of the fitted models were established by considering all erosive events and also by distinguishing between events of different severity.Results and discussion
The b1 exponent varied widely among the three sites (1.05–1.44) but using a common exponent (1.18) for these sites was possible. The Ae,N prediction accuracy increased in the passage from the smallest erosion events (Ae,N?≤?1 Mg ha?1, median error =?3.35) to the largest ones (Ae,N?>?10 Mg ha?1, median error =?1.72). The QREI30 term was found to be usable to predict both Ae,N and the expected maximum uncertainty of this prediction. Soil erodibility was found to be mainly controlled by the largest erosion events.Conclusions
Development of a single USLE-MM model appears possible. Sampling other sites is advisable to develop a single USLE-MM model for a general use.3.
An investigation of the effect of aquic conditions on Fe-oxides distribution and magnetic susceptibility (χlf) was conducted on selected soils from Southern Iran. Seven pairs of adjacent soil pedons with different soil moisture regimes (aquic and non-aquic), were selected. The average concentrations of poorly crystalline Fe (Feo) and total free Fe (Fed) in aquic soils were 0.2 and 0.07% respectively, and 0.45 and 0.9% in non-aquic soils, respectively. The ratio of Feo/Fed varied from 0.03 to 0.64. χlf ranged from 1.8 to 113 × 10?8 m3 kg?1 in the soil studied. The variation of χfd ranged from 0.0 to 9.65%. The χfd values observed in non-aquic soils were larger than in aquic soils (4.00% vs. 1.37%). Positive correlations were observed between χ and clay contents in both aquic and non-aquic soils; however, non-aquic soil samples showed a larger coefficient of determination. A positive correlation existed between χfd and χ in aquic and non-aquic soils. Higher values of χfd were observed at the soil surface of non-aquic soil samples than at deeper levels, suggesting a greater proportion of ultrafine grains. Of the soil properties that were assessed, clay, cation exchangeable capacity (CEC), Fed, Feo/Fed ratio, χlf and χfd contents, changed significantly in response to the aquic condition. 相似文献
4.
Purpose
The intensive development of nanotechnology raises a question of the potential consequences of the presence of nanoparticles (NPs) in the different components of the environment, including sediments. The aim of this study was to evaluate the toxicity of nanoparticles of ZnO and Ni and their bulk counterparts in bottom sediments (SD1, SD2) with different properties collected from the Vistula River in Poland.Materials and methods
Sediment samples with NPs at a concentration of 100 mg kg?1 were incubated for 17 months in the dark or under a photoperiod of 12 h light/12 h dark. The Microtox® (bacteria, Vibrio fischeri) and OSTRACODTOXKIT F? (ostracods, Heterocypris incongruens) tests were used to evaluate toxicity. In addition, the contents of Zn and Ni were determined in extracts (H2O and CaCl2) of the bottom sediments.Results and discussion
The Zn concentration was much lower in the SD1 sediment with the addition of NPs/bulk particles (30–230 μg kg?1) compared to the SD2 sediment (280–1140 μg kg?1). The toxicity of ZnO and Ni was determined by the type of bottom sediment and the parameter studied. Both nano- and bulk-ZnO and Ni caused the mortality of H. incongruens at a level of 13.3–53.3 %. The influence of ZnO and Ni on the growth of H. incongruens was observed to be the opposite. ZnO resulted in growth stimulation, while Ni resulted in growth inhibition of H. incongruens. Both ZnO and Ni stimulated V. fisheri luminescence. In most cases, the incubation of ZnO and Ni under the photoperiod increased the toxicity or decreased the stimulation of V. fisheri bioluminescence and H. ingongruens growth compared to the dark-incubated sediments.Conclusions
The study provides new and important information on the ecotoxicological effects of ZnO and Ni nanoparticles in different sediments and under various environmental conditions that may be useful for the risk assessment of this new group of contaminants.5.
Changes in the soil microbial communities and networks were monitored after planting the cover crop for 9 years. The field experiment included plots with a cover crop and without a cover crop but with weed control, and two subplots with or without chemical fertilizer (192 kg N ha?1, 108 kg P2O5 ha?1, and 168 kg K2O ha?1 each year). After applying the cover crop and chemical fertilizer for 9 years, the composition and activity of bacterial and fungal communities changed significantly (p?<?0.05), with the cover crop had greater effects than the chemical fertilizer on the composition of the soil microbial community. The relative abundances of 22 selected genera (in Firmicutes and Bacteroidetes) and two selected classes (Ascomycota) related to cover crop residue degradation increased significantly in the presence of the cover crop (p?<?0.05). Network analysis showed that the cover crop decreased the number of positive links between bacterial and fungal taxa by 25.33%, and increased the negative links by 22.89%. The positive links among bacterial taxa increased by 16.63% with the cover crop, mainly among Proteobacteria (increase of 39), Firmicutes (16), Actinobacteria (five), and Bacteroidetes (10). The links among fungal taxa were less than among bacterial taxa and were not significantly affected by cover crop. Taxa such as Thaumarchaeota, unidentified_Nitrospiraceae, unidentified_Nitrosomonadaceae, Faecalibacterium, Coprococcus_3, and Ruminococcaceae_NK4A214_group dominated the network without the cover crop but they were not dominant with the cover crop. The relative abundances of potential genes involved with the degradation of cellulose, hemicellulose, and cello-oligosaccharides increased significantly with the cover crop. Therefore, the SOC and TN contents were enhanced by the cover crop with the increase of the soil enzyme activities. Thus, the apple yield was improved by the cover crop. 相似文献
6.
Nataša Mori Barbara Debeljak David Kocman Tatjana Simčič 《Journal of Soils and Sediments》2017,17(7):1939-1947
Purpose
Increased sedimentation due to land use intensification is increasingly affecting carbon processing in streams and rivers around the globe. This study describes the design of a laboratory-scale flow-through incubation system as a tool for the rapid estimation of sediment respiration. The measurements were compared with those obtained using an in situ closed chamber respiration method. The influence of sediment size on respiration rates was also investigated.Materials and methods
Measurements were conducted on a pre-alpine gravel-bed river sediment separated into the following grain size fractions: > 60 mm (14.3%), 60–5 mm (60.2%), 5–2 mm (13.7%), 2–0.063 mm (11.1%) and <0.063 mm (0.6%). Concurrently, in situ and laboratory measurements were carried out on a naturally heterogeneous sediment. In situ respiration was determined in closed chambers as O2 consumption over time, while in the laboratory, respiration was determined using flow-through respiration chambers. Oxygen concentrations were measured using a fibre-optic oxygen meter positioned at the inflow and outflow from the chamber.Results and discussion
The mean respiration rates within naturally mixed riverbed sediments were 1.27 ± 0.3 mg O2 dm?3 h?1 (n = 4) and 0.77 ± 0.1 mg O2 dm?3 h?1 (n = 3) for the flow-through chamber system and closed chamber system, respectively. Respiration rates were statistically significantly higher in the flow-through chamber system (t test, p < 0.05), indicating that closed chamber measurements underestimated the oxygen consumption within riverbed sediments. Sediment grain size was found to significantly affect respiration rates in both systems (ANOVA, p < 0.001) with the fine sediment fraction (particle size <0.063 mm) having the highest respiration rate (rflow-through = 51 ± 23 mg O2 dm?3 h?1). The smallest fractions (2–0.063 and <0.063 mm), which represent approximately 12% of total sediment volume, contributed 60% of total respiration.Conclusions
The study demonstrated that flow-through respiration chambers more accurately estimate the respiration rate within riverbed sediments than in situ closed chambers, since the former experiment imitates the natural conditions where continuous interstitial flow occurs in the sediments. We also demonstrated that fine sediments (<5 mm) substantially contribute to heterotrophic respiration in the studied gravel-bed river.7.
Diying Xiang Gang Zhang Ruijuan Gong Bao Di Yaran Tian 《Water, air, and soil pollution》2018,229(8):279
The use of plants for ecological remediation is an important method of controlling heavy metals in polluted land. Cotinus coggygria is a landscape plant that is used extensively in landscaping and afforestation. In this study, the cadmium tolerance level of C. coggygria was evaluated using electrical impedance spectroscopy (EIS) to lay a theoretical foundation for broad applications of this species in Cd-polluted areas and provide theoretical support to broaden the application range of the EIS technique. Two-year-old potted seedlings of C. coggygria were placed in a greenhouse to analyse the changes in the growth, water content and EIS parameters of the roots following treatment with different Cd concentrations (50, 100, 200, 500, 1000 and 1500 mg kg?1), and soil without added Cd was used as the control. The roots grew well following Cd treatments of 50 and 100 mg kg?1. The Cd contents increased with the increase in Cd concentration in the soil. However, the lowest root Cd content was found at 4 months of treatment. The extracellular resistance re and the intracellular resistance ri increased first overall and then decreased with the increasing Cd concentration, and both parameters increased with a longer treatment duration. The water content had a significant negative correlation with the Cd content (P?<?0.01) and the re (P?<?0.05). C. coggygria could tolerate a soil Cd concentration of 100 mg kg?1. There was a turning point in the growth, water content and EIS parameters of the C. coggygria roots when the soil Cd concentration reached 200 mg kg?1. The root water content and re could reflect the level of Cd tolerance in C. coggygria. 相似文献
8.
Qing Teng Xue-Feng Hu Chang Cheng Zhiqing Luo Fan Luo Yong Xue Yijun Jiang Zhen Mu Liming Liu Minyong Yang 《Journal of Soils and Sediments》2016,16(10):2395-2407
Purpose
This paper aims to study the ecological effects of rice-duck integrated farming on soil fertility and weed and pest control.Materials and methods
A field experiment was carried out in the suburb of Shanghai in 2014, which included a rice-duck integrated treatment and non-duck treatment (CK) under organic management. Each treatment was in triplicate, and the experiment included six plots in total, with each plot 667 m2 in area.Results and discussion
(1) The number of weeds in the plots with the duck treatment was significantly lower than that with CK (p?<?0.01). (2) The incidence of stem borers (Chilo suppressalis) with the duck treatment was significantly lower than that with CK (p?<?0.05). The incidences of rice leaf rollers (Cnaphalocrocis medinalis), rice sheath blight (Rhizoctonia solani), and planthoppers with the duck treatment were extremely significantly lower than those with CK (p?<?0.01). (3) The contents of NH4 +-N, alkali-hydrolyzable N, available P, and available K in the soils with the duck treatment were higher than those with CK, and the activities of urease, phosphatase, sucrase, and catalase in the soils with the duck treatment were also much higher than those with CK. The grain yield with the duck treatment was 1.9 times that with CK. (4) The number of soil nematodes with the duck treatment was significantly higher than that with CK in the late rice growing stage (p?<?0.01).Conclusions
Raising ducks in the paddy fields not only showed a potential of controlling weed hazards and reducing rice pests and diseases but also raised soil fertility, improved soil biodiversity, and increased grain yield effectively. Implementing the rice-duck integrated farming could highly reduce the amount of pesticides and herbicides and was beneficial to develop the organic rice farming in the suburbs of Shanghai, Southeast China.9.
Hai-Yan Yuan Long-Jun Ding Ning Wang Song-Can Chen Ye Deng Xiao-Ming Li Yong-Guan Zhu 《Journal of Soils and Sediments》2016,16(12):2657-2665
Purpose
Geobacteraceae are important dissimilatory Fe (III)-reducing microorganisms, influencing the cycling of metals, nutrients as well as the degradation of organic contaminants. However, little is known about their distribution, diversity, and abundance of Geobacteraceae and the effects of environment factors and geographic distance on the distribution and diversity of Geobacteraceae in paddy soils remain unclear. Therefore, the objectives of this study were to investigate the distribution, diversity, and abundance of Geobacteraceae in paddy soils and to determine key factors in shaping the Geobacteraceae distribution, environmental factors, geographic distance, or both and to quantify their contribution to Geobacteraceae variation.Materials and methods
Illumina sequencing and quantitative real-time PCR using a primer set targeting 16S rRNA genes of bacteria affiliated with the family Geobacteraceae were employed to measure the community composition, diversity, and abundance patterns of 16S rRNA genes of Geobacteraceae in 16 samples collected from north to south of China. MRT, Mantel test, and VPA were used to analyze the relationship between communities of Geobacteraceae and environmental factors and geographic distance.Results and discussion
Quantitative PCR showed that the abundance of 16S rRNA genes of Geobacteraceae ranged from (1.20?±?0.18)?×?108 to 1.13?×?109?±?2.25?×?108 copies per gram of soil (dry weight) across different types of soils. Illumina sequencing results showed Geobacter was the dominant genus within the family of Geobacteraceae. Multivariate regression tree (MRT) analysis showed that soil amorphous iron contributed more (22.46 %) to the variation of dominant species of Geobacteraceae than other examined soil chemical factors such as pH (14.52 %), ammonium (5.12 %), and dissolved organic carbon (4.74 %). Additionally, more geographically distant sites harbored less similar communities. Variance partitioning analysis (VPA) showed that geographic distance contributed more to the variation of Geobacteraceae than any other factor, although the environmental factors explained more variation when combined. So, we detected the uneven distribution of Geobacteraceae in paddy soils of China and demonstrated that Geobacteraceae community composition was strongly associated with geographic distance and soil chemical factors including aFe, pH, Fe, DOC, C:N, and NO3 ?-N. These results greatly expand the knowledge of the distribution of Geobacteraceae in environments, particularly in terrestrial ecosystems.Conclusions
Our results showed that geographic distance and amorphous iron played important roles in shaping Geobacteraceae community composition and revealed that both geographic distance and soil properties governed Geobacteraceae biogeography in paddy soils. Our findings will be critical in facilitating the prediction of element cycling by incorporating information on functional microbial communities into current biogeochemical models.10.
Hassana Ibrahim Mustapha J. J. A. van Bruggen P. N. L. Lens 《Water, air, and soil pollution》2018,229(4):137
Typha latifolia-planted vertical subsurface flow constructed wetlands (VSSF CWs) can be used to treat petroleum refinery wastewater. This study evaluated if the removal efficiency of VSSF CWs can be improved by changing the plant species or coupling horizontal subsurface flow constructed wetlands (HSSF CWs) to the VSSF CW systems. The VSSF CWs had a removal efficiency of 76% for biological oxygen demand (BOD5), 73% for chemical oxygen demand (COD), 70% for ammonium-N (NH4+-N), 68% for nitrate-N (NO3?-N), 49% for phosphate (PO43?-P), 68% for total suspended solids (TSS), and 89% for turbidity. The HSSF CWs planted with T. latifolia further reduced the contaminant load of the VSSF CW-treated effluent, giving an additional removal efficiency of 74, 65, 43, 65, 58, 50, and 75% for, respectively, BOD5, COD, NH4+-N, NO3?-N, PO43?-P, TSS, and turbidity. The combined hybrid CW showed, therefore, an improved effluent quality with overall removal efficiencies of, respectively, 94% for BOD5, 88% for COD, 84% for NH4+-N, 89% for NO3?-N, 78% for PO43?-P, 85% for TSS, and 97% for turbidity. T. latifolia strived well in the VSSF and HSSF CWs, which may have contributed to the high NH4 +-N, NO3?-N, and PO43?-P removal efficiencies. T. latifolia-planted VSSF CWs showed a higher contaminant removal efficiency compared to the unplanted VSSF CW. T. latifolia is thus a suitable plant species for treatment of secondary refinery wastewater. Also a T. latifolia-planted hybrid CW is a viable alternative for the treatment of secondary refinery wastewater under the prevailing climatic conditions in Nigeria. 相似文献
11.
Tongbin?Zhu Cheng?Yang Jun?Wang Siman?Zeng Manqiang?Liu Jinling?Yang Bing?Bai Jianhua?Cao Xiaoyun?Chen
We conducted a microcosm experiment with soil being sterilized, reinoculated with native microbial community and subsequently manipulated the bacterivorous nematodes, including three treatments: without (CK) or with introducing one species of the two bacterivores characterized with different body size but similar c-p (colonizer-persister) value (Rhabditis intermedia and Protorhabditis oxyuroides, accounted for 6 and 59% of bacterivores in initially undisturbed soil, respectively). We monitored the N2O and CO2 emissions, soil properties, and especially quantified gross N transformation rates using 15N tracing technique after the 50 days incubation. No significant differences were observed on soil NH4 + and NO3 ? concentrations between the CK and two bacterivores, but this was not the case for gross N transformation rates. In comparison to CK, R. intermedia did not affect soil N transformation rates, while P. oxyuroides significantly increased the rates of mineralization of organic N to NH4 +, oxidation of NH4 + to NO3 ?, immobilization of NO3 ? to organic N and dissimilatory NO3 ? reduction to NH4 +. Furthermore, the mean residence time of NH4 + and NO3 ? pool was greatly lowered by P. oxyuroides, suggesting it stimulated soil N turnover. Such stimulatory effect was unrelated to the changes in abundance of bacteria and ammonia-oxidizing bacteria (AOB). In contrast to CK, only P. oxyuroides significantly promoted soil N2O and CO2 emissions. Noticeably, bacterivores increased the mineralization of recalcitrant organic N but decreased soil δ13C-TOC and δ15N-TN values, in particular for P. oxyuroides. Combining trait-based approach and isotope-based analysis showed high potential in moving forward to a mechanistic understanding of bacterivore-mediated N cycling. 相似文献
12.
Qing-Long Fu Jian-Zhou He Hua Gong Lee Blaney Dong-Mei Zhou 《Journal of Soils and Sediments》2016,16(5):1557-1568
Purpose
The application of roxarsone (ROX), an arsenic-containing compound, as a feed additive in the animal production industry results in elevated soil levels of ROX and its metabolites, namely, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenate (As(V)), and arsenite (As(III)). This study was conducted to study the extraction and speciation analysis of ROX-related arsenicals in soils with different physicochemical properties and the possible effects of soil properties on the extraction of ROX and its metabolites.Materials and methods
Analytical method based on high-performance liquid chromatography (HPLC)-inductively coupled plasma–mass spectrometry (ICP-MS) was employed to determine the concentrations of As(III), DMA, MMA, As(V), and ROX extracted by different extraction solvents from different soils spiked by arsenicals. Validity of the developed method was assessed by the recovery efficiencies of arsenic species in soil-dissolved matter solutions containing 20 μg As?·?L?1 of each arsenic species. Effects of soil properties on the extraction of ROX and its metabolites were analyzed by Pearson’s correlation.Results and discussion
Arsenic species were separated using gradient elution of water and 20 mmol?·?L?1 (NH4)2HPO4 + 20 mmol?·?L?1 NH4NO3 + 5 % methanol (v/v) within 27 min. The linear ranges of all arsenicals were 0–200 μg As?·?L?1 with R 2?>?0.9996. The developed method provided lower limits of detection for As(III), DMA, MMA, As(V), and ROX (0.80, 0.58, 0.35, 0.24, and 1.52 μg As?·?L?1, respectively) and excellent recoveries (92.52–102.2 %) for all five species. Arsenic speciation was not altered by 0.1 mol?·?L?1 NaH2PO4 + 0.1 mol?·?L?1 H3PO4 (9:1, v/v), which offered better average extraction efficiencies for As(III), As(V), DMA, MMA, and ROX (32.49, 92.50, 78.24, 77.64, and 84.54 %, respectively). Extraction performance of arsenicals was influenced by soil properties, including pH, cation exchange capacity (CEC), total Fe, and amorphous Fe.Conclusions
ROX and its metabolites from soils could be satisfactorily separated by the developed method for the studied arsenicals. To extract arsenic species from soils, 0.1 mol?·?L?1 NaH2PO4 + 0.1 mol?·?L?1 H3PO4 (9:1, v/v) was recommended. Extraction efficiencies of arsenicals were influenced more by solvent composition than soil physicochemical properties. The present study provides a valuable tool and useful information for determining the concentrations of ROX and its metabolites in contaminated soils.13.
Soil components from different environments (forest (OF), semiarid (SZ), and sand (AS)) were separated from fulvic and humic substances, characterized by DRX, EDS(SEM), and zero-charge points were determined. The sorption of U(VI) by these materials was determined considering contact time, concentration of U(VI), pH, ionic strength, and presence of sodium chloride and humic acids. The time to reach the kinetic sorption equilibrium was ca. 1 min for the components of the SZ and AS soils, whereas those from OF required longer times. The zero-charge points of the materials indicate that in the experimental conditions, the surfaces of the materials are positively charged, as are uranyl ions. The sorption kinetic data were well fitted to the pseudo-second-order model, which indicates chemical sorption. The maximum sorption capacities for U(VI) obtained from data fitted to the Langmuir model of OF and SZ were 49 and 19.8 mg g?1 respectively. Sorption isotherm data for AS were best fitted to the Freundlich model (qe?=?5.4 mg g?1). The maximum values of distribution coefficients (Kd) were 23?±?7 L kg?1, 545?±?64 L kg?1, and 1178?±?229 L kg?1 for AS, SZ, and OF, respectively; these values may depend on pH, contact time, initial concentration of U(VI), and the composition of the materials. Sodium chloride in the aqueous solutions affects U(VI) sorption by the materials SZ and AS. The effect of humic acids depends on pH, only in acid media soluble humate complexes may be formed. 相似文献
14.
Purpose
Input of N as NH4 + is known to stimulate nitrification and to enhance the risk of N losses through NO3 ? leaching in humid subtropical soils. However, the mechanisms responsible for this stimulation effect have not been fully addressed.Materials and methods
In this study, an acid subtropical forest soil amended with urea at rates of 0, 20, 50, 100 mg N kg?1 was pre-incubated at 25 °C and 60 % water-holding capacity (WHC) for 60 days. Gross N transformation rates were then measured using a 15N tracing methodology.Results and discussion
Gross rates of mineralization and nitrification of NH4 +-N increased (P?<?0.05), while gross rate of NO3 ? immobilization significantly decreased with increasing N input rates (P?<?0.001). A significant relationship was established between the gross nitrification rate of NH4 + and the gross mineralization rate (R 2?=?0.991, P?<?0.01), so was between net nitrification rate of NH4 + and the net mineralization rate (R 2?=?0.973, P?<?0.05).Conclusions
Stimulation effect of N input on the gross rate of nitrification of NH4 +-N in the acid soil, partially, resulted from stimulation effect of N input on organic N mineralization, which provides pH-favorable microsites for the nitrification of NH4 + in acid soils (De Boer et al., Soil Biol Biochem 20:845–850, 1988; Prosser, Advan Microb Physiol 30:125–181, 1989). The stimulated gross nitrification rate with the decreased gross NO3 ? immobilization rate under the elevated N inputs could lead to accumulation of NO3 ? and to enhance the risk of NO3 ? loss from humid forest soils.15.
Goal, Scope and Background
Distribution of hydrophobic organic contaminants in abiotic compartments is essential for describing their transfer and fate in aquatic ecosystems. Taihu Lake is the third largest freshwater lake in China. Water quality of Taihu Lake has deteriorated greatly during the last decades and has threatened the water supply. The aim of the present study was to investigate the partitioning of polycyclic aromatic hydrocarbons (PAHs) among overlying water, suspended particulate matter (SPM), sediments, and pore water in Meiliang Bay, Taihu Lake and to provide useful information for the ecological engineering in this area.Materials and Methods
Overlying water and surface sediment were sampled from six sites in Meiliang Bay, Taihu Lake, China. Within 72 h of sampling, sediments were centrifuged to obtain the pore water. Overlying water samples were filtered to separate dissolved and SPM samples. After extraction, samples were purified following a clean-up procedure. PAH fraction was obtained by elution with a mixture of hexane: DCM (7:3, V/V) and analyzed by GC/MS.Results
PAHs concentrations in overlying water varied from 37.5 ng/L to 183.5 ng/L. Concentrations of PAHs in pore water were higher than those in overlying water. The total concentrations of 16 priority PAHs in sediments ranged from 2091.8 ng/g-dw to 4094.4 ng/g-dw. PAHs concentrations on SPM were decreased with suspended solid concentrations (SSC). Total PAHs concentrations on SPM varied in the range of 3369.6 ng/g-dw to 7531.1 ng/g-dw. The partition coefficients between sediment and overlying water (log K oc) for PAHs with log K ow<5 were positively correlated with their octanol-water partition coefficients (log K ow) (n=39, r=0.79, p<0.0001). Partition coefficients between sediment and pore water (log K oc′) for all PAHs were also significantly correlated with their log K ow values (n=48, r=0.82, p<0.0001).Discussion
In general, PAHs derived from combustion sources tend to bind strongly to soot particles in natural sediment. Consequentially, K oc values observed in the natural environment could be orders of magnitude higher than those predicted by linear correlation relationships under laboratory conditions. In the present study, the ratio of log K oc values to log K ow values falls consistently above 1, indicating that the sediment soot carbon in the bay was more attractive for PAHs than n-octanol. The log K oc′ was also higher than that predicted under laboratory conditions, suggesting that the measured pore water PAH concentrations were lower than those predicted. That is to say, not all the sediment PAHs can be available to partition rapidly into sediment pore waters. A variation in soot content is a possible reason. Furthermore, concentrations of PAHs on SPM were higher than those in sediments. The compositions of PAHs on SPM and in sediments were similar, indicating the importance of re-suspension process of sediments in the partitioning process of the shallow lake.Conclusions
The results indicated the equilibrium partitioning model could be used to predict PAHs distribution in various phases of a shallow lake in the stagnation period, but re-suspension processes should be considered to modify the relationship between log K ocs and log K ows.Recommendations and Perspectives
Concentration, particle size and composition of resuspended particles could affect the relationship between log K ocs and log K ows. Further work should be done under field conditions, especially where a steady thermodynamic equilibrium state could be assumed.16.
J. S. Penha A. C. A. Lopes R. L. F. Gomes J. B. Pinheiro J. R. Assunção Filho E. A. Silvestre J. P. G. Viana J. Martínez-Castillo 《Genetic Resources and Crop Evolution》2017,64(6):1355-1364
Lima bean (Phaseolus lunatus L.) is an important food source in Brazil, especially in the northeast region, where its production and consumption are high. The goals of the present study were to estimate natural outcrossing rates and genetic diversity levels of Lima bean from Brazil, using ten microsatellite loci to obtain information for their conservation and breeding. Fourteen accessions were selected from an experiment in field with open-pollinated and with the presence of pollinating insects. Twelve seeds of each of the 14 selected accessions were grown in screenhouse for tissue harvest and DNA extraction. The multilocus model was used to determine the reproductive system. The outcrossing rate was 38.1 % (tm = 0.381; ts = 0.078), and the results indicated a mixed mating system with a predominance of selfing (1 ? tm = 61.9 %). The biparental inbreeding rate was high (t m ? t s = 0.303) and the multilocus correlated paternity was quite high (r p(m) = 0.889), indicating that the progeny was mostly composed of full sibs. The average effective number of pollen donors per maternal plant (N ep ) was low (1.12), and the fixation index for maternal genotypes (F m ) was 0.945, indicating that most genitors resulted from inbreeding. The studied families presented considerable genetic variability: A = 6.10; %P = 30; H e = 0.60 and H o = 0.077. Total diversity was high (H T = 0.596), and a portion was distributed within families (H S = 0.058). In addition, diversity was higher between families (D ST = 0.538), and genetic differentiation was high (G ST = 0.902). The results presented here can be used in the implementation of Lima bean conservation and breeding programs in Brazil. 相似文献
17.
Hai-Ming?Zhao Rui-Wen?Hu He-Biao?Huang Hong-Fei?Wen Huan?Du Yan-Wen?Li Hui?Li Quan-Ying?Cai Ce-Hui?Mo
The widely used plastic film containing di(2-ethylhexyl) phthalate (DEHP) in agriculture has caused serious soil pollution and poses risks to human health through the food chain. An effective DEHP degradation bacteria, Microbacterium sp. J-1, was newly isolated from landfill soil. Response surface methodology was successfully employed for optimization resulting in 96% degradation of DEHP (200 mg L?1) within 5 days. This strain degraded DEHP by hydrolysis of the ester bond and hydroxylation of the aromatic ring to form 2-ethyl hexanol, mono-(2-ethylhexyl) phthalate, phthalate acid, and protocatechuic acid, and subsequently transformed these compounds with a maximum specific degradation rate (q max), half-saturation constant (K s ), and inhibition constant (K i ) of 1.46 day?1, 180.2 mg L?1, and 332.8 mg L?1, respectively. Bioaugmentation of DEHP-contaminated soils with the strain J-1 greatly enhanced the DEHP dissipation rate (~88%). Moreover, this strain could efficiently colonize the rhizosphere soil of inoculated vegetables and further enhanced DEHP degradation (~97%), leading to a significant decrease (>70%) in DEHP accumulation in shoots and roots of the inoculated vegetables compared to uninoculated vegetables. The results highlighted the roles of the inoculated exogenous bacteria in simultaneously bioremediating contaminated soils and reducing bioaccumulation of DEHP in the edible part of the vegetable for food safety. 相似文献
18.
Xueping Chen Hao Ma Yu Zheng Jiamiao Liu Xia Liang Chiquan He 《Journal of Soils and Sediments》2017,17(1):181-189
Purpose
The dynamics and uncertainties in wetland methane budgets affected by the introduction of Alnus trabeculosa H. necessitate research on production of methane by methanogenic archaea and consumption by methane-oxidizing microorganisms simultaneously.Materials and methods
This study investigated methane emission in situ by the closed chamber method, and methanogenic and methanotrophic communities using denatured gradient gel electrophoresis (DGGE) and quantitative PCR based on mcrA (methyl coenzyme M reductase), pmoA (particulate methane monooxygenase) genes in the rhizosphere and non-rhizosphere soils in the indigenous pure Phragmites australis T., and A. trabeculosa–P. australis mixed communities in Chongxi wetland.Results and discussion
Methane flux rate from the pure P. australis community was 2.4 times larger than that of A. trabeculosa–P. australis mixed community in the rhizosphere and 1.7 times larger in the non-rhizosphere, respectively. The abundance of methanogens was lower in the mixed community soils (3.56?×?103–6.90?×?103 copies g?1 dry soil) compared with the P. australis community (1.47?×?104–1.89?×?104 copies g?1 dry soil), whereas the methanotrophs showed an opposite trend (2.08?×?106–1.39?×?106 copies g?1 dry soil for P. australis and 6.20?×?106–1.99?×?106 copies g?1 dry soil for mixed community soil). A liner relationship between methane emission rates against pmoA/mcrA ratios (R 2?=?0.5818, p?<?0.05, n?=?15) was observed. The community structures of the methane-cycling microorganism based on mcrA and pmoA suggested that acetoclastic methanogens belonging to Methanosarcinaceae and a particular type II methanotroph, Methylocystis, were dominant in these two plant communities.Conclusions
The introduction of A. trabeculosa would promote the proliferation of methanotrophs, especially the dominant Methylocystis, but not methanogens, ultimately diminishing methane emission in the wetland.19.