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1.
Junna Sun Runya Yang Wenxue Li Yinghua Pan Mengzhu Zheng Zhenhua Zhang 《Journal of Soils and Sediments》2018,18(11):3271-3279
Purpose
Increasing data have shown that biochar amendment can improve soil fertility and crop production, but there is little knowledge about whether biochar amendment can improve water infiltration in saline soils. We hypothesized that biochar amendment could promote water infiltration in saline soil. The aims of this study were to evaluate the effects of biochar amendment on water infiltration and find the suitable amendment rate and particle size of biochar as a saline soil conditioner.Materials and methods
We measured water infiltration parameters in a coastal saline soil (silty loam) amended with non-sieved biochar at different rates (0.5, 1, 2, 5, and 10%, w/w) or sieved biochar of different particle sizes (≤?0.25 mm, 0.25–1 mm, and 1–2 mm) at 1 and 10% (w/w).Results and discussion
Compared with the control, amending non-sieved biochar at 10% significantly decreased water infiltration into the saline soil (P?<?0.05). In contrast, sieved biochar of ≤?0.25 mm significantly improved water infiltration capacity, irrespective of the amendment rate. Sieved biochar of 1–2 mm was less effective to improve soil porosity and when amended at 10%, it even reduced the water infiltration capacity. The Philip model (R2?=?0.983–0.999) had a better goodness-of-fit than the Green-Ampt model (R2?=?0.506–0.923) for simulation of cumulative infiltration.Conclusions
Amending biochar sieved to a small particle size improved water infiltration capacity of the coastal saline soil compared with non-sieved biochar irrespective of the amendment rate. This study contributes toward improving the hydrological property of coastal saline soil and rationally applying biochar in the field.2.
Purpose
Quarrying activities in areas with serpentinized rocks may have a negative impact on plant growth. Quarry soils generally offer hostile environments for plant growth due to their low-nutrient availability, low organic matter, and high-trace metal content.Materials and methods
In order to determine the factors that can limit plant revegetation, this study was carried out in two serpentine quarries in Galicia (NW Spain): one abandoned in 1999 and the other still active.Results and discussion
The results show that in soils developed in the abandoned quarry, the limitations for revegetation were: moderate alkaline pH (7.87–8.05), strong Ca/Mg (<1) imbalance, low N (<0.42 mg kg?1) and P (<2 mg kg?1) content, and high total heavy-metal content (Co 76–147 mg kg?1; Cr 1370–2600 mg kg?1; and Ni 1340–2040 mg kg?1). The limitations were much less intense in the soils developed in the substratum in the active quarry, which were incipient soils poorly developed and permanently affected by the quarrying activity.Conclusions
Restoration work should be geared toward establishing a stable diverse vegetation cover, including serpentinophile species, which would provide the necessary modifications to correct nutritive imbalances and improve soil quality.3.
Yao Feng Chaojun Wei Wenjuan Zhang Yuanwang Liu Zhaojun Li Haiyan Hu Jianming Xue Murray Davis 《Journal of Soils and Sediments》2016,16(9):2242-2251
Purpose
A simple and highly efficient economic method for the analysis of 11 antibacterial drugs including two tetracyclines, three quinolones, four sulfonamides, chloramphenicol and tylosin, in livestock manure, was developed using solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC).Materials and methods
The analytes were successively extracted by EDTA-McIlvaine solution and organic solvent mixture. The extracts were degreased with n-hexane and cleaned through SPE on a hydrophile-lipophile balance (HLB) cartridge. All compounds were determined on a C18 reverse phase column with gradient elution.Results and discussion
Recoveries calculated from spiked samples of animal manures ranged from 62.65 to 99.16 % for 11 antibiotics with relative standard deviations of less than 10.0 %. Limits of detection ranged from 0.1 to 1.9 μg kg?1, and limits of quantification ranged from 0.3 to 5.9 μg kg?1.Conclusions
The results show that SPE-HPLC is an inexpensive and practical method for rapid detection of multiple antibiotics in animal manure.4.
Xiaodong Zhang Zhaoliang Song Kim McGrouther Jianwu Li Zimin Li Ning Ru Hailong Wang 《Journal of Soils and Sediments》2016,16(2):461-466
Purpose
Occlusion of carbon in phytoliths is an important biogeochemical carbon sequestration mechanism and plays a significant role in the global biogeochemical carbon cycle and atmospheric carbon dioxide (CO2) concentration regulation at a millennial scale. However, few studies have focused on the storage of phytolith and phytolith-occluded carbon (PhytOC) in subtropical forest soils.Materials and methods
Soil profiles with 100-cm depth were sampled from subtropical bamboo forest, fir forest, and chestnut forest in China to investigate the variation of phytoliths and PhytOC storage in the soil profiles based on amass-balance assessment.Results and discussion
The storage of phytoliths in the top 100 cm of the bamboo forest soil (198.13?±?25.08 t ha?1) was much higher than that in the fir forest (146.76?±?4.53 t ha?1) and chestnut forest (170.87?±?9.59 t ha?1). Similarly, the storage of PhytOC in the bamboo forest soil (3.91?±?0.64 t ha?1) was much higher than that in the fir forest soil (1.18?±?0.22 t ha?1) and chestnut forest soil (2.67?±?0.23 t ha?1). The PhytOC percentage in the soil organic carbon pool increased with soil depth and was the highest (4.29 %) in the bamboo forest soil. Our study demonstrated that PhytOC in soil was significantly influenced by forest type and the bamboo forest ecosystem contributed more significantly to phytolith carbon sequestration than other forest ecosystems.Conclusions
Different forest types have a significant influence on the soil PhytOC storage. Optimization of bamboo afforestation/reforestation in future forest management plans may significantly enhance the biogeochemical carbon sink in the following centuries.5.
Xinzhang Song Mark O. Kimberley Guomo Zhou Hailong Wang 《Journal of Soils and Sediments》2017,17(9):2250-2256
Purpose
The purpose of this study was to better understand how both the content and flux of soil carbon respond to forest succession and anthropogenic management practices in forests in subtropical China.Materials and methods
We assembled from the literature information on soil organic carbon (SOC) and soil respiration (Rs) covering the forest successional chronosequence from pioneer masson pine (Pinus massoniana) forest (MPF) to medium broadleaf and needleleaf mixed forest (BNMF) and the climax evergreen broadleaf forest (EBF), along with the two major forest plantation types found in subtropical China, Chinese fir (Cunninghamia lanceolata) forest (CFF) and Moso bamboo (Phyllostachys pubescens) forest (MBF).Results and discussion
Both SOC and Rs increased along the forest successional gradient with the climax EBF having both the highest SOC content of 33.1?±?4.9 g C kg?1(mean?±?standard error) and the highest Rs rate of 46.8?±?3.0 t CO2?ha?1 year?1. It can be inferred that when EBF is converted to any of the other forest types, especially to MPF or CFF, both SOC content and Rs are likely to decline. Stand age did not significantly impact the SOC content or Rs rate in either types of plantation.Conclusions
Forest succession generally increases SOC content and Rs, and the conversion of natural forests to plantations decreases SOC content and Rs in subtropical China.6.
Xia Hu Yan-Li Lyu Yong Liu Xiao-Yan Li Zhen-Ting Sun Zong-Chao Li Ya-Qian Cheng Lan-Lan Guo Lian-You Liu 《Journal of Soils and Sediments》2018,18(3):718-726
Purpose
Grassland exclosure is a widely-used option to prevent from grazing in degraded grasslands for restoration. However, the influence of exclosure on soil macropore of grassland remain scarce. The objective of this study was to quantify the pore architecture of grassland soils under exclosure.Materials and methods
Two treatments, 9E (grassland enclosed for 9 years) and 5E (grassland enclosed for 5 years), were designed, with grazing as a control in the experiment. Nine soil columns (0–50 cm deep) were taken at the three sites with three replicates. At each site, three soil columns were from the grassland, and cores were scanned with a Philips Brilliance ICT Medical Scanner. Numbers of macropores, macroporosity, network density, length density, and node density within the 50-cm soil profile were interpreted from X-ray computed tomography to analyze soil pore architecture.Results and discussion
The results indicated that exclosure significantly influenced CT-measured soil macroporosity in the Inner Mongolia grassland of northern China. Soils under enclosed grassland had greater macroporosity, length density, total volume, and node density than that of under freely grazed grassland. Macroporosity increased as the enclosure age increased. For soils under enclosed grassland, macropores were concentrated at 0–300-mm soil layers, and macropores were mainly present at 0–100-mm soil depth under freely grazed grassland. The large number of macropores found in soil under enclosed grassland can be attributed to greater root development.Conclusions
Exclosure increases soil macroporosity and improve soil structure.7.
Analy Quiñonez-Plaza Fernando Toyohiko Wakida Juan Temores-Peña Diana Dolores Rodriguez-Mendivil Enrique Garcia-Flores Miguel Angel Pastrana-Corral Samuel Guillermo Melendez-Lopez 《Journal of Soils and Sediments》2017,17(12):2873-2886
Purpose
A study was carried out to evaluate the concentration of heavy metals (Pb, Cu, Cr, Cd, and Hg) and total petroleum hydrocarbons (TPH) in road-deposited sediments (RDS) from Tijuana, Mexico, and identify their possible sources.Materials and methods
Thirty RDS samples were randomly collected during the dry season using a brush and dustpan and classified according to construction material, traffic intensity, and land use. Soil samples were collected from a nonurban area and their concentrations were used as background values. For TPH, the samples were quantified gravimetrically after Soxhlet extraction, whereas heavy metals were extracted by acid digestion and their concentrations were measured by atomic absorption spectrometry.Results and discussion
The mean TPH concentrations for RDS were 4208 mg kg?1 and ranged from 1186 to 9982 mg kg?1. For heavy metals, mean concentrations were 31.8, 50.2, 17.1, 0.1, and 0.1 mg kg?1 for Pb, Cu, Cr, Cd, and Hg, respectively. The Igeo results showed that RDS from Tijuana are moderately to strongly polluted with Pb and Cu and moderately polluted with Cr. Principal component analysis (PCA) showed that Pb, Cu, and Cr could have their origin in tire wear, brake pads, bearings, and bushings.Conclusions
The findings of this study revealed that RDS from Tijuana are polluted with TPH and heavy metals and that their principal sources are anthropogenic activities.8.
Anushka Upamali Rajapaksha Meththika Vithanage Sang Soo Lee Dong-Cheol Seo Daniel C. W. Tsang Yong Sik Ok 《Journal of Soils and Sediments》2016,16(3):889-895
Purpose
Sulfamethazine (SMT) is increasingly detected in environmental matrices due to its versatile use as antibiotics. We aimed to investigate the benefits and roles of steam activation of biochars with respect to SMT sorption kinetics and equilibrium sorption.Materials and methods
Biochars were produced from burcucumber plant and tea waste using a pyrolyzer at a temperature of 700 °C for 2 h. The biochar samples were treated with 5 mL min?1 of steam for an additional 45 min for post-synthesis steam activation. The SMT sorption on the unmodified and steam activated biochars were compared.Results and discussion
The time taken to reach equilibrium was significantly less for steam activated biochars (~4 h) than non-activated biochars (>24 h). Up to 98 % of SMT could be removed from aqueous solutions by steam activated biochars. The sorption kinetic behaviors were well described by the pseudo-second model and SMT sorption rates of steam activated biochars (k 2?~?1.11–1.57 mg g?1 min?1) were significantly higher than that of the unmodified biochars (k 2?~?0.04–0.11 mg g?1 min?1) because of increased availability of accessible porous structure with averagely larger pore diameters. Moreover, the equilibrium sorption on the unmodified biochars was significantly influenced by increasing solution pH (~30–50 % reduction) because of speciation change of SMT, whereas steam activated biochars manifested much stronger sorption resilience against pH variation (~2–4 % reduction only) because the enhanced porosity offset the effect of unfavorable electrostatic repulsion.Conclusions
The observed features of steam activated biochars would render their applications more versatile and reliable in field throughout changeable environmental conditions.9.
Wenjie Pan Zhaoliang Song Hongyan Liu Lukas Van Zwieten Yutong Li Xiaomin Yang Yue Han Xu Liu Xiaodong Zhang Zijuan Xu Hailong Wang 《Journal of Soils and Sediments》2017,17(10):2420-2427
Purpose
A better understanding of the role of grassland systems in producing and storing phytolith-occluded carbon (PhytOC) will provide crucial information in addressing global climate change caused by a rapid increase in the atmospheric CO2 concentration.Materials and methods
Soil samples of typical steppe, meadow steppe, and meadow in Inner Mongolia, China, were taken at 0–10-, 10–20-, 20–40-, and 40–60-cm depths in July and August of 2015. The soil phytoliths were isolated by heavy liquid (ZnBr2), and the soil PhytOC was determined by the traditional potassium dichromate method.Results and discussion
The results of our study showed that the storage of soil phytoliths was significantly higher in the meadow (33.44 ± 0.91 t ha?1) cf. meadow steppe (26.8 ± 0.98 t ha?1) and typical steppe (21.19 ± 4.91 t ha?1), which were not different. The soil PhytOC storage was significantly different among grassland types, being: meadow (0.39 ± 0.01 t ha?1) > meadow steppe (0.29 ± 0.02 t ha?1) > typical steppe (0.23 ± 0.02 t ha?1). PhytOC storage in typical steppe soil within the 0–60-cm soil layer is the lowest and that in meadow soils is the highest. The grassland type and the soil condition play significant roles in accumulation of phytoliths and PhytOC in different grassland soils. We suggest that the aboveground net primary productivity (ANPP) is important in soil phytolith accumulation and PhytOC content.Conclusions
Phytolith and PhytOC storages in grassland soil are influenced by factors such as grass type, local climate and soil conditions, and management practices. Management practices to increase grass biomass production can significantly enhance phytolith C sequestration.10.
Manuel Carrillo Christina Siebe Philipp Dalkmann Jan Siemens 《Journal of Soils and Sediments》2016,16(9):2186-2194
Purpose
The increasing reuse of wastewater for irrigation introduces surfactants and antibiotics into the environment. How these two kinds of compounds interact with regard to their sorption processes in soil is not clear.Materials and methods
We performed batch experiments to investigate the sorption of linear alkylbenzene sulfonates (LAS) and its effect on sorption of sulfamethoxazole and ciprofloxacin in irrigated and non-irrigated soils with different organic matter (OM) contents.Results and discussion
LAS sorption was non-linear in the presence of the antibiotics, and as general trend, it increased with rising OM content of soils. Free LAS was also removed from solution by complexation with Ca2+. Dissolved organic compounds released from soils with OM contents ≥18.4 g kg?1 further reduced LAS sorption. Sorption of sulfamethoxazole was reduced by LAS sorption only in one soil with a small OM content of 9.5 g kg?1.Conclusions
The strong sorption of ciprofloxacin is not affected by LAS. Sulfamethoxazole sorption only competes with LAS sorption in organic matter-poor soils. Accumulation of organic matter in soils, for example due to long-term wastewater irrigation, provides extra sorption capacity for LAS and sulfamethoxazole so that competition for sorption sites is reduced.11.
Borui Liu Qing Huang Yuefeng Su Mengyuan Wang Yufei Ma Ryan M. Kelly 《Journal of Soils and Sediments》2018,18(3):669-679
Purpose
Cobalt (Co) is a toxic metal to the environment and human’s health. The purpose of the study is to achieve an investigation into the efficacy of calcium carbonate and cow dung for Co immobilization in fluvo-aquic soil, as well as their effects on the antioxidant system in plants.Materials and methods
Calcium carbonate and cow dung were incorporated with the Co-polluted fluvo-aquic soil where pakchois (Brassica chinensis L.) were grown. Co concentration, superoxide dismutase (SOD) activity, catalase (CAT) activity, and malondialdehyde (MDA) concentration in the shoots of the mature plants were inspected.Results and discussion
As calcium carbonate concentration rose (0 to 12 g kg?1), Co concentration in shoots of the plants decreased firstly and then increased again (P < 0.05), while the accumulation level of Co kept decreasing with cow dung concentration rising (P < 0.05). Under the amendment treatments, the SOD activity, CAT activity, and MDA concentration in the shoots were all positively correlated to the Co concentration in the plant tissue (r = 0.792, 0.904, and 0.807, P < 0.01), indicating the antioxidant system receptivity to the Co accumulation. The amendments in soil can alleviate the oxidative stress in pakchois owing to Co pollution. As calcium carbonate concentration ranged from 5.64 to 7.86 g kg?1, the parameters reached a maxima (minimum), respectfully.Conclusions
Calcium carbonate and cow dung in fluvo-aquic soil are effective for Co immobilization and mitigating any pertinent oxidative stress in pakchoi plants. Calcium carbonate concentration within a range of 5.64 to 7.86 g·kg?1 will achieve optimum efficacy.12.
Xingchao Qi Yanli Liu Min Zhang Bin Gao Chengliang Li 《Journal of Soils and Sediments》2017,17(10):2438-2448
Purpose
With the increase of surfactant usages, more and more concerns were paid on their effects on the physicochemical characteristics of soils. Up to now, only few researches have examined the effects of ionic surfactants on the stability of soil structure and soil water repellency.Materials and methods
Cetyltrimethyl ammonium bromide (CTAB) as cationic surfactant and sodium dodecyl sulfate (SDS) as anionic surfactant were adopted to investigate their effects on the aggregate stability and water repellency of a silt loam soil which was sampled in Corn High-Tech Park, Huang-Huai-Hai region, China. (1) Aggregate stability: 50 g soil was mixture with 100 mL surfactant solution in a beaker. The concentrations of surfactant solutions were 0 (the blank), 200, 400, 600, 800, 1000, and 2000 mg L?1, respectively. After 30 min, the soil was sieved and divided into four fraction aggregates. (2) Soil water repellency: the concentrations of surfactant solutions were the same as experiment 1. Forty grams of soil was blended with 80 mL surfactant solution in an aluminum specimen. Drying the water by oven of 40 °C firstly and then by air, the whole period was about 1 week. After that, soil water infiltration and sorptivity were measured.Results and discussion
Compared to the blank, surfactants increased the amounts of 2–0.25 and <0.053 mm aggregates of the soil and decreased the amounts of 0.25–0.053 mm aggregates of the soil. Surfactants also increased the mean weight diameter (MWD) of the soil. Except the 200 mg L?1 treatment, CTAB promoted the soil water infiltration. All SDS treatments impeded the soil water infiltration. The soil repellency factor (R) value of the blank was 1.22, lower than the critical value of 1.95, which implied that the soil of blank treatment was free of soil water repellency. For CTAB, only 200 and 400 mg L?1 treatment’s R were higher than 1.95 while for SDS, all the treatment’s R were higher than 1.95.Conclusions
Surfactants improved the stability of soil aggregates. Soil treated with CTAB did not show the repellency, whereas SDS treatment resulted in intense water repellency compared with the wettable blank soil. Findings of this study can be used to explain the role of ionic surfactants on soil structure stability as well as on the development of water repellency in lower soil depths.13.
Hyuck Soo Kim Kwon-Rae Kim Seung-Heon Lee Anitha Kunhikrishnan Won-Il Kim Kye-Hoon Kim 《Journal of Soils and Sediments》2018,18(2):336-341
Purpose
A reclaimed tidal land along the shore has poor soil properties such as high exchangeable sodium percentage (ESP), and electrical conductivity (EC) due to excess sodium (Na) content. Therefore, Na content should be decreased to improve the land productivity, and for this, gypsum has been widely used. The objective of this study was to determine the changes in ESP and EC of the gypsum-treated reclaimed tidal soil in a field scale.Materials and methods
For this, gypsum was applied to Daeho reclaimed tidal land (500 ha) in Korea for 5 years (2006 to 2010). The Daeho reclaimed tidal land has been used as reclaimed paddy fields since 1993. The application rate of gypsum was calculated based on exchangeable calcium (Ca) contents and soil cation exchange capacity (CEC) to maintain 60 % exchangeable calcium percentage (ECP) of CEC in soil and the average amount treated was 1570 kg ha?1 year?1. The changes in ESP and EC were monitored from 2006 to 2010, and 2013.Results and discussion
The ESP dropped from 80 % in 2006 to 34 % in 2013. The EC of the soil was decreased by 73 %, from 11.5 dS m?1 in 2006 to 3.1 dS m?1 in 2013. Eventually, it was estimated that the ESP will be lowered below 15 % in 2023 with continuous treatment of gypsum according to ECP calculation, and EC will be declined to reach at 0.5 dS m?1 in 2035, the average EC level of Korean rice paddy.Conclusions
This field scale study evidenced that gypsum application effectively improves the soil properties of reclaimed tidal soil by decreasing ESP and EC.14.
Tingru Chen Xiaoyan Liu Xinying Zhang Yunyun Hou Xiao Chen Kaiyun Tao 《Journal of Soils and Sediments》2016,16(8):2090-2096
Purpose
This study aimed to evaluate the effect of combination of alkyl polyglucoside (APG) and nitrilotriacetic acid (NTA) on improving the efficiency of phytoremediation for pyrene and lead (Pb) co-contaminated soil by Scirpus triqueter.Materials and methods
Seedlings of S. triqueter with a similar size and biomass (3 g/pot) were grown on 2-month aged soil contaminated with 184.5 mg kg?1of pyrene and 454.3 mg kg?1 of Pb at pH?=?8.3. After growth for 10 days, different doses of APG and NTA were added into the soil. After 60 days, the height of plants, Pb concentrations in plants, and pyrene amounts in soil were determined.Results and discussion
Combined application of NTA and APG with lower dosage (1 + 1 g kg?1 soil and 1 + 2 g kg?1 soil) had no notable negative influence on the growth of S. triqueter. Moreover, significant synergy on Pb accumulation in S. triqueter was achieved with APG and NTA combined application. Besides, the dissipation of pyrene from soil after 60-day planting was increased in APG and NTA treatments when compared with the control treatments. Application of APG alone or combined with NTA had greater effect on enhancing dissipation of pyrene from soil than NTA alone.Conclusions
This study demonstrated that the remediation of Pb and pyrene co-contaminated soil by S. triqueter can be enhanced by combined application of APG and NTA. Long-term evaluation of this strategy is needed in co-contaminated field sites.15.
Thi Thu Nhan Nguyen Helen M. Wallace Cheng-Yuan Xu Zhihong Xu Michael B. Farrar Stephen Joseph Lukas Van Zwieten Shahla Hosseini Bai 《Journal of Soils and Sediments》2017,17(12):2763-2774
Purpose
Organo-mineral biochar fertiliser has the potential to replace conventional biochar and organic fertiliser to improve soil quality and increase plant photosynthesis. This study explored mechanisms involved in nitrogen (N) cycling in both soil and ginger plants (Zingiber officinale: Zingiberaceae) following different treatments including organic fertiliser, commercial bamboo biochar fertiliser, and organo-mineral biochar fertiliser.Materials and methods
Soil received four treatments including (1) commercial organic fertiliser (5 t ha?1) as the control, (2) commercial bamboo biochar fertiliser (5 t ha?1), (3) organo-mineral biochar fertiliser at a low rate (3 t ha?1), and (4) organo-mineral biochar fertiliser at a high rate (7.5 t ha?1). C and N fractions of soil and plant, and gas exchange measurements were analysed.Results and discussion
Initially, organo-mineral biochar fertiliser applied at the low rate increased leaf N. Organo-mineral biochar fertiliser applied at the high rate significantly increased N use efficiency (NUE) of the aboveground biomass compared with other treatments and improved photosynthesis compared with the control. There was N fractionation during plant N uptake and assimilation since the 15N enrichment between the root, leaf, and stem were significantly different from zero; however, treatments did not affect this N fractionation.Conclusions
Organo-mineral biochar fertiliser has agronomic advantages over inorganic and raw organic (manure-based) N fertiliser because it allows farmer to put high concentrations of nutrients into soil without restricting N availability, N uptake, and plant photosynthesis. We recommend applying the low rate of organo-mineral biochar fertiliser as a substitute for commercial organic fertiliser.16.
Manyun Zhang Ying Teng Zhihong Xu Jun Wang Peter Christie Yongming Luo 《Journal of Soils and Sediments》2016,16(6):1754-1763
Purpose
Chlorothalonil (CTN) has received much attention due to its broad-spectrum antifungal function and repeated applications in agriculture production practice. An incubation experiment was conducted to study the accumulating effects of CTN repeated application on soil microbial activities, biomass, and community and to contrast the discrepancy of effects in contrasting soils.Materials and methods
Different dosage CTN (5 mg kg?1, T1, and 25 mg kg?1, T5) was applied into two contrasting soils at 7-day intervals. Soil samples were taken 7 days after each application to assess soil enzyme activities and gene abundances. At the end of incubation, the soil samples were also taken to analyze microbial communities in the two test soils.Results and discussion
Soil fluorescein diacetate hydrolysis (FDAH) and urease activities were inhibited by CTN repeated applications. After 28 days of incubation, bacterial 16S rRNA gene abundances in T1 and T5 treatments were significantly lower than those in the CK treatments (46.4 and 36.6 % of the CK treatment in acidic red soil, 53.6 and 37.9 % of the CK treatment in paddy soil). Archaeal 16S rRNA gene abundances of T1 and T5 treatments were observed the similar trends (56.1 and 40.8 % of the CK treatment in acidic red soil, 45.6 and 43.7 % of the CK treatment in paddy soil). Repeated applications at 25 mg kg?1 exerted significantly negative effects on the Shannon-Weaver, Simpson and McIntosh indices.Conclusions
Microbial activity, biomass, and functional diversity were significantly inhibited by repeated CTN application at the higher dosage (25 mg kg?1), but the inhibitory effects by the application at the recommended dosage (5 mg kg?1) were erratic. More emphasis needs to be placed on the soil type and cumulative toxicity from repeated CTN application when assessing environmental risk.17.
Qidong Wang Jinming Song Lei Cao Xuegang Li Huamao Yuan Ning Li 《Journal of Soils and Sediments》2017,17(1):11-22
Purpose
Soil organic carbon (SOC) stock is one of the most important carbon reservoirs on the earth and plays a vital role in the global climate change. However, research on the carbon sequestration and storage of coastal wetland soil is very scarce. Therefore, a study in the coastal wetland was conducted to investigate the SOC distribution, storage, and variation under the influence of human activities.Materials and methods
Surface soil samples in different seasons and profile soil samples were collected in the Changyi coastal wetland. SOC content, soil physicochemical properties, and sedimentation rate were determined. Organic carbon storage and burial flux were calculated. On the basis of correlation analysis and comparative study, factors affecting the distribution and storage of SOC were investigated.Results and discussion
The average SOC content of the surface soil in June and November was 4.65 and 6.13 g kg?1, respectively. The distribution of surface SOC content was consistent with the distribution of vegetation and was affected by the soil particle size. In plant-covered area, the relationship between SOC content and depth could be expressed by the power function y?=?ax b . The contribution of plants to SOC was only significant in the shallow layer. As for the deep layer, the SOC content was higher in the mudflat. The organic carbon storage in the upper 1 m soil was estimated at 1.795 kg m?2 in average and the total organic carbon storage of Changyi wetland was estimated at 6.373?×?107 kg. The sedimentation rate was very low and the average organic carbon burial flux of the whole wetland was 17.5 g m?2 a?1.Conclusions
Low sedimentation rate, weak downward migration, and high decomposition rate of organic matter caused by poor hydrological condition were the reasons why the SOC storage in Changyi wetland was low. Under intensive human activities, the Changyi wetland was drying and the organic carbon storage was reducing. Strategies were proposed to be taken urgently to restore the wetland for the long-term benefit.18.
Nitrogen transformation rates and N<Subscript>2</Subscript>O producing pathways in two pasture soils
Ting Lan Helen Suter Rui Liu Xuesong Gao Deli Chen 《Journal of Soils and Sediments》2018,18(9):2970-2979
Purpose
Better understanding of N transformations and the regulation of N2O-related N transformation processes in pasture soil contributes significantly to N fertilizer management and development of targeted mitigation strategies.Materials and methods
15N tracer technique combined with acetylene (C2H2) method was used to measure gross N transformation rates and to distinguish pathways of N2O production in two Australian pasture soils. The soils were collected from Glenormiston (GN) and Terang (TR), Victoria, Australia, and incubated at a soil moisture content of 60% water-filled pore space (WFPS) and at temperature of 20 °C.Results and discussion
Two tested pasture soils were characterized by high mineralization and immobilization turnover. The average gross N nitrification rate (ntot) was 7.28 mg N kg?1 day?1 in TR soil () and 5.79 mg N kg?1 day?1 in GN soil. Heterotrophic nitrification rates (nh), which accounting for 50.8 and 41.9% of ntot, and 23.4 and 30.1% of N2O emissions in GN and TR soils, respectively, played a role similar with autotrophic nitrification in total nitrification and N2O emission. Denitrification rates in two pasture soils were as low as 0.003–0.004 mg N kg?1 day?1 under selected conditions but contributed more than 30% of N2O emissions.Conclusions
Results demonstrated that two tested pasture soils were characterized by fast N transformation rates of mineralization, immobilization, and nitrification. Heterotrophic nitrification could be an important NO3?–N production transformation process in studied pasture soils. Except for autotrophic nitrification, roles of heterotrophic nitrification and denitrification in N2O emission in two pasture soils should be considered when developing mitigation strategies.19.
Purpose
The Al forms on maize and soybean roots were investigated to determine the main factors affecting the distribution of Al forms and its relationship with Al plant toxicity.Materials and methods
Solution culture experiments were conducted to obtain the fresh roots of maize and soybean. KNO3, citric acid, and HCl were used to extract the exchangeable, complexed, and precipitated forms of Al on the roots.Results and discussion
The complexed Al was higher than the exchangeable and precipitated Al. Root CECs of soybean and maize were 77 and 55 cmol kg?1, and functional groups on the soybean roots (262.4 cmol kg?1) were greater than on maize roots (210.8 cmol kg?1), which resulted in more exchangeable and complexed Al on soybean roots than on maize roots, and was one of the reasons for the increased Al toxicity to soybean. The total and exchangeable Al were the highest on the plant root tips and decreased gradually with increasing distance from the tips. Ca2+, Mg2+, and NH4 + cations reduced the exchangeable Al on the roots. Oxalate and malate also reduced the adsorption and absorption of Al by roots, and the effect of oxalate was greater than malate.Conclusions
Higher exchangeable and complexed Al on plant roots led to increased Al plant toxicity. Ca2+, Mg2+, and NH4 + and oxalate and malate can effectively alleviate Al plant toxicity.20.