施用液态家畜废物的水稻田土壤中硝酸盐异化还原成铵过程的研究

Most studies on dissimilatory nitrate reduction to ammonium (DNRA) in paddy soils were conducted in the laboratory and in situ studies are in need for better understanding of the DNRA process.In this study,in situ incubations of soil DNRA using 15 N tracer were carried out in paddy fields under conventional water (CW) and low water (LW) managements to explore the potential of soil DNRA after liquid cattle waste (LCW) application and to investigate the impacts of soil redox potential (Eh) and labile carbon on DNRA.DNRA rates ranged from 3.06 to 10.40 mg N kg 1 dry soil d 1,which accounted for 8.55%-12.36% and 3.88%-25.44% of consumption of added NO 3-15 N when Eh at 5 cm soil depth ranged from 230 to 414 mV and 225 to 65 mV,respectively.DNRA rates showed no significant difference in paddy soils under two water managements although soil Eh and/or dissolved organic carbon (DOC) were more favorable for DNRA in the paddy soil under CW management 1 d before,or 5 and 7 d after LCW application.Soil DNRA rates were negatively correlated with soil Eh (P < 0.05,n=5) but positively correlated with soil DOC (P < 0.05,n=5) in the paddy soil under LW management,while no significant correlations were shown in the paddy soil under CW management.The potential of DNRA measured in situ was consistent with previous laboratory studies;and the controlling factors of DNRA in paddy soils might be different under different water managements,probably due to the presence of different microfloras of DNRA.     

pH与石灰性水稻土铁氧化还原过程的关系

光照和pH是调控土壤铁氧化物厌氧生物氧化还原的关键环境因素。本文采用恒温厌氧培养试验研究了黑暗、光照条件下土壤pH的变化及pH对铁氧化还原的影响,探索了pH与Fe(II)和水溶性无机碳的关系。结果表明,光照可改变土壤厌氧培养过程中pH的变化趋势,避光培养时土壤pH呈降低趋势,光照时呈先降低后增加趋势。pH介于4~9之间均可发生铁的还原反应,pH=7时还原量最大,128.5μmol g-1,pH调至4和9均可抑制避光条件下的铁还原。光照条件下pH 6~8时可发生Fe(II)的再氧化,控制初始pH为7时可使其再氧化量增加77.13%,达49.17μmol g-1。厌氧培养过程中Fe(II)与水溶性无机碳在避光时存在显著线性正相关关系,pH与Fe(II)和水溶性无机碳之间均存在显著线性负相关关系。     

水稻土中铁氧化还原循环的光照水分效应

水稻土中铁的氧化还原循环与CO2和CH4排放关系密切。采用恒温厌氧培养试验分别在黑暗、光照条件下研究了不同水分状况对水稻土中铁氧化还原过程、水溶性碳含量及CO2和CH4排放的影响。结果表明,水分和光照是调控土壤铁氧化还原过程及其耦合的碳转化过程的关键环境因子。避光时增加含水量缩短铁还原最大速率出现的时间,促进CH4排放。光照条件下含水量小于50%时增加含水量可促进亚铁的再氧化,大于50%时则抑制了亚铁的再氧化。避光时增加含水量可增加体系的水溶性无机碳含量(WSIC),WSIC与CH4的排放存在显著正相关关系。光照可显著降低体系的WSIC,降低幅度随含水量的增加而增大。在含水量25%～200%范围内,光照可使CO2和CH4排放量分别降低95.80%和96.08%。     

Mineralogy and Arsenic Mobility in Arsenic-rich Brazilian Soils and Sediments (11 pp)

Background   Soils and sediments in certain mining regions of Brazil contain an unusually large amount of arsenic (As), which raises concerns that mining could promote increased As mobility, and thereby increase the risks of contaminating water supplies. Objectives   The purpose of this study was to identify the most important factors governing As mobility in sediments and soils near three gold-mining sites in the State of Minas Gerais, Brazil. Methods   Surface and sub-surface soil samples were collected at those sites and characterized by chemical and mineralogical analyses. Oxalate (Feo) and citrate-bicarbonate-dithionite (Fed) iron contents were determined by atomic absorption spectroscopy (AAS). Arsenic mobilization was measured after incubating the samples in a 2.5 mM CaCl2 solution under anaerobic conditions for 1, 28, 56, 84, or 112 days. The solution concentrations of As, Fe, and Mn were then measured by inductively coupled plasma-mass spectrometry (ICP-MS) and AAS, respectively. Results and Discussion   Results indicated that As mobilization is largely independent of both the total As and the Feo/Fed ratio of the solid phase. Soluble As is roughly controlled by the Fe (hydr)oxide content of the soil, but a closer examination of the data revealed the importance of other highly weathered clay minerals and organic matter. Large amounts of organic matter and a low iron oxide content should favor As leaching from soils and sediments. Under reducing conditions, As is mobilized by the reductive dissolution of Fe and/or Mn oxides. However, released As may be readsorbed depending on the sorptive properties of the soil. Gibbsite is particularly effective in adsorbing or readsorbing As, as is the remaining unreduced fraction of the iron (hydr)oxides. Conclusion and Outlook   In general, low soluble As is related to the presence of gibbsite, a large amount of iron oxides, and a lack of organic matter in the solid phase. This has environmental significance because gibbsite is thermodynamically more stable than Fe oxides under anaerobic conditions, such as those found in waterlogged soils and lake sediments.     

In situ long‐term redox potential measurements in a dyked marsh soil

The long‐term measurement of soil redox potential (E_H) by permanently installed Pt electrodes may be restricted by electrode breakdown (electrode rupture and resin leakage) and contamination, especially under wet and strongly reducing soil conditions. The E_H of a slightly alkaline (pH 7.1 to 7.3) Calcaric Gleysol developed from marine sediment in the dyked marsh of Schleswig‐Holstein, Northern Germany, was monitored weekly during a 4‐year period using permanently installed Pt electrodes. Measurements were performed in fivefold at 10, 30, 60, 100, and 150 cm. Furthermore, water table level was recorded. Sulfide occurred in 150 cm as a heritage of the previous marine environment. Mean water table level was 84 cm below the soil surface but was characterized by both short‐term and seasonally strong fluctuations. Levels of water table ranged from 33 to >200 cm below soil surface. In consistence with water table level, the E_H continually decreased with soil depth. Mean redox conditions were oxidizing at 10 (550 mV) and 30 cm (430 mV), weakly reducing at 60 cm (230 mV), and moderately reducing at 100 (120 mV) and 150 cm depth (–80 mV). Soil hydrology differed markedly during the study as expressed by periods of water saturation for each depth. This was reflected by Pt electrodes response, since period of water saturation and E_H were significantly negatively correlated as calculated for each year and depth (r_s = –0.971; n = 20; P < 0.01). The 60‐cm depth was most frequently influenced by water table fluctuations, showed the largest E_H range (920 mV) and the most distinct seasonal pattern in E_H. Good function of the electrodes in this depth can be concluded even after long time of installation in soil. Although established in a sulfide‐bearing environment, three of five electrodes at 150 cm showed a substantial increase (+500 mV) in E_H during summer of the third and fourth years of investigation, which had low water tables. It is not clear whether the non‐response of two electrodes was due to electrode contamination or spatial variation in E_H. When operating in reducing systems, this problem can be circumvented by installing a large number of electrodes or by a regular replacement of electrodes. Using properly constructed and permanently installed Pt electrodes, soil E_H can be monitored for extended periods under wet and reducing soil conditions.     

氧化势影响下的滇池沉积物孔隙水磷浓度变化

The sediment redox potential was raised in the laboratory to estimate reduction of internal available phosphorus loads, such as soluble reactive phosphorus （SRP） and total phosphorus （TP）, as well as the main elements of sediment extracts in Dianchi Lake. Several strongly reducing substances in sediments, which mainly originated from anaerobic decomposition of primary producer residues, were responsible for the lower redox potential. In a range of -400 to 200 mV raising the redox potential of sediments decreased TP and SRP in interstitial water. Redox potentials exceeding 320 mV caused increases in TP, whereas SRP maintained a relatively constant minimum level. The concentrations of Al, Fe, Ca^2＋, Mg^2＋, K^＋, Na^＋ and S in interstitial water were also related to the redox potential of sediments, suggesting that the mechanism for redox potential to regulate the concentration of phosphorus in interstitial water was complex.     

Effects of soil redox potential (Eh) and pH on growth of sunflower and wheat

ABSTRACT

Soil redox potential (Eh) and pH are fundamentals parameters for plants growth. Measuring soil Eh is essential but complex due to the lack of measurement reliability resulting from high temporal variability and metrological challenges. This paper proposes practical advancements for measuring Eh in aerobic soils using combined electrodes (improvements in methodology specific to cleaning electrodes, measurement time, cleaning the dataset). The study of soil Eh and pH on sunflower and wheat in pot experiments has highlighted the relationship between Eh_cumul (Eh associated with a dimension of time) and the portion of porosity that is accessible to air. For reduced soil conditions, sunflower positively reacts to better aeration. Strong correlations exist between the duration of each potential range and the growth of sunflower. The study of sunflower growth in soil reveals extremely harmful impact resulting from too high and/or too low Eh values.     

Dietary taurine supplementation enhances antioxidative capacity and improves breast meat quality of broiler chickens

ABSTRACT

1. The aim of this study was to determine the effect of dietary taurine supplementation on growth performance, meat quality and antioxidant responses in breast muscle of broiler chickens.

2. A total of 72 Arbor Acres broiler chickens (28-day-old) with similar body weight were randomly allocated into two groups, and fed either 0 g/kg (control; C) or 5 g/kg taurine-supplemented diets (TS) for 14 days.

3. The results showed that TS had no effect on growth performance or chemical composition of breast muscle in broilers. The drip and cooking losses were significantly decreased (P < 0.05), and the pH_24h of breast muscle were increased (P < 0.05) in the TS group. Meanwhile, broilers in the TS group exhibited significantly higher (P < 0.05) scavenging activities of superoxide and 2,2-diphenyl-1-picrylhydrazyl radicals, and lower (P < 0.05) contents of carbonyl, malondialdehyde, and 4-hydroxynonenal. TS increased (P < 0.05) total antioxidant capacity and superoxide dismutase activities. Moreover, TS significantly upregulated (P < 0.05) the mRNA expressions of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1, NAD(P)H quinone dehydrogenase 1, superoxide dismutase, catalase, and glutathione peroxidase.

4. These findings suggested that TS enhanced antioxidative capacity and improved breast meat quality of broilers via activating the Nrf2 pathway.     

The effect of the source and dosage of dietary Cu on redox status in rat tissues

The aim of this experiment was to investigate whether the amount of Cu added to the diet of rats can be reduced without adversely affecting the antioxidant status of tissues and growth, and whether copper nanoparticles can be used for this purpose. For four weeks, four experimental groups of rats were fed diets with two dosages of added Cu (standard—6.5 or 3.25 mg/kg) in two forms (standard—CuCO₃ or copper nanoparticles). Replacing the CuCO₃ supplement with CuNPs resulted in a decreased lung weight and an increased Cu content in brain, kidney and lung, intensification of lipid peroxidation processes, and weakened antioxidant defence in the lungs and kidneys. This treatment also reduced the Cu content in heart, level of lipid oxidation in the liver and testes and improved antioxidant defence in the brain. Reducing the addition of Cu to the diet from 6.5 to 3.25 mg/kg reduced lung weight and increased lipid peroxidation in the liver, heart and lungs, and also weakened antioxidant defence in the lungs and testes. This treatment also weakened the lipid peroxidation process in the spleen, small intestine and brain and strengthened the antioxidant defence of the brain and kidneys. In conclusion, replacing CuCO₃ with CuNPs and reducing the level of Cu in the diet of rats has a particularly unfavourable effect on the respiratory system, causing adverse changes in the lungs. However, these treatments have a clearly positive effect on the redox status of the liver and brain.