Heavy Metals in a Sulfldic Minespoil: Fractions and Column Leaching

Fractions of various heavy metals in a sulfidic minespoil were investigated. Column leaching experimentwas also conducted to simulate 'acid mine drainage' (AMD) from the minespoil. The results show thatleaching of heavy metals from the minespoil was extremely significant during the initial water flushing.The amounts of heavy metals leached out dramatically reduced after leaching twice. It is worthwhile tonote that in this study, Zn, Mn, Fe, As and Ni in the first leachate exceeded the total amount of eachcorresponding water-extractable (1:5, soil:water) metal contained in the minespoil sample. This appears tosuggest that 1:5 water extraction did not allow accurate estimation of water-leachable concentrations of theabove heavy metals. This work has implications for the management of sulfidic minespoils. Acid drainageof great environmental concerns is likely to occur only during heavy rainfall events after substantial solubleand readily exchangeable acid and metals are accumulated in the minespoils. The slow-reacting fractionsother than water-soluble and readily exchangeable fractions may pose little environmental hazards. This isparticularly true for Pb, As and Ni.

Characteristics of Soluble and Exchangeable Acidity inan Extremely Acidified Acid Sulfate Soil

An extremely acidified acid sulfate soil (ASS) was investigated to characterize its soluble and exchangeableacidity. The results showed that soluble acidity of a sample determined by titration with a KOH solutionwas much significantly greater than that indicated by pH measured using a PH meter, particularly for theextremely acidic soil samples. This is because the total soluble acidity of the extremely acidic soil sampleswas mainly composed of various soluble Al and Fe species, possibly in forms of Al sulfate complexes (e.g.,AISO4) and ferrous Fe (Fe2+). It is therefore suggested not to use pH alone as an indicator of soluble acidityin ASS, particularly for extremely acidic ASS. It is also likely that AISO4+ actively pericipated in cationexchange reactions. It appears that the possible involvement of this Al sulfate canon in the canon adsorptionhas significant effect on increasing the amount of acidity being adsorbed by the soils.

Acid Release from an Acid Sulfate Soil Sample Under Successive Extractions with Different Extractants

An acid sulfate soil sample was successively extracted with deionized water, 1 mol L-1 KCl and 0.000 5 mol L-l Ca(OH)2 solutions. The results showed that only very small amounts of acidity were extracted by deionized water, possibly through slow jarosite hydrolysis. Acid release through jarosite hydrolysis was greatly enhanced by Ca(OH)2 extraction at the expense of the added OH- being neutralized by the acid released. Successive extraction of the sample with KCl removed the largest amounts of acidity from the sample. However, it is likely that the major form of acidity released by KCl extraction was exchangeable acidity. The results also show the occurrence of low or non charged Al and Fe species in water and Ca(OH)2 extracts after first a few extractions. It appears that such a phenomenon was related to a decreasing EC value with increasing number of extractions.

Factors Controlling Deoxygenation of "Floodwater" Overlying an Acid Sulfate Soil: Experimental Modeling

An incubation experiment was conducted to simulate the effect of flooding onwater deoxygenation in acid sulfate soil floodplain systems. The originally oxygenated 'floodwater'could be deoxygenated immediately following 'flooding' and it is likelythat this was caused mainlyby decomposition of organic debris from the inundated plants. Deoxygenation eventually led to thedepletion of dissolved oxygen (DO) in the 'floodwater' and it is highly possible that this resultedin the transformations of ferric Fe to ferrous Fe, sulfate to hydrogen sulfide. and organic nitrogento ammonia (ammonification). The accumulation of these reduced substances allows the 'floodwater'to develop DO-consuming capacity (DOCC). When the 'floodwater' is mixed with the introducedoxygenated water, apart from the dilution effects, the reduced substances contained in the'floodwater' oxidize to further consume DO carried by the introduced water. However, it appears thatthe DO drop in the mixed water can only last for a few hours if no additional DO-depleted'floodwater' is added. Entry of atmospheric oxygen into the water can raise the DO level of themixed water arid lower water pH through the oxidation of the reduced substances.

Impeded Acidification of Acid Sulfate Soils in an Intensively Drained Sugarcane Land

Recent research results suggest that acidification of acid sulfate soils may be inhibited in well-drained estuarine floodplains in eastern Australia by the absence of natural creek levees. The lack of natural levees has allowed the inundation of the land by regular tidal flooding prior to the construction of flood mitigation work. Such physiographical conditions prevent the development of pre-drainage pyrite-derived soil acidifica- non that possibly occurred at many levee-protected sites in eastern Australian estuarine floodplains during extremely dry spells. Pre-drainage acidification is considered as an important condition for accumulation of soluble Fe and consequently, the creation of favourable environments for catalysed pyrite oxidation. Under current intensively drained conditions, the acid materials produced by ongoing pyrite oxidation can be rapidly removed from soil pore water by lateral leaching and acid buffering, resulting in low concentrations of soluble Fe in the Pyretic layer, which could reduce the rate of pyrite oxidation.

Proton beams from intense laser-solid interaction:Effects of the target materials

We report systematic studies of laser-driven proton beams produced with micrometer-thick solid targets made of aluminum and plastic,respectively.Distinct effects of the target materials are found on the total charge,cutoff energy,and beam spot of protons in the experiments,and these are described well by two-dimensional particle-in-cell simulations incorporating intrinsic material properties.It is found that with a laser intensity of 8×10^(19) W/cm^(2),target normal sheath acceleration is the dominant mechanism for both types of target.For a plastic target,the higher charge and cutoff energy of the protons are due to the greater energy coupling efficiencies from the intense laser beams,and the larger divergence angle of the protons is due to the deflection of hot electrons during transport in the targets.We also find that the energy loss of hot electrons in targets of different thickness has a significant effect on the proton cutoff energy.The consistent results obtained here further narrow the gap between simulations and experiments.

Search for the doubly heavy baryon Ξ_(bc)^(+)→ decaying to J/ψΞ_(c)^(+)

A first search for the Ξ_(bc)^(+)J/ψΞ_(c)^(+) decay is performed by the LHCb experiment with a data sample of proton-proton collisions, corresponding to an integrated luminosity of 9 fb−1 recorded at centre-of-mass energies of 7, 8, and 13 TeV. Two peaking structures are seen with a local (global) significance of 4.3(2.8) and 4.1(2.4) standard deviations at masses of 6571 and 6694 MeV/c2, respectively. Upper limits are set on the Ξ+bc baryon production cross-section times the branching fraction relative to that of the B+c→J/ψD+s decay at centre-of-mass energies of 8 and 13 TeV, in the Ξ+bc and in the B+c rapidity and transverse-momentum ranges from 2.0 to 4.5 and 0 to 20GeV/c, respectively. Upper limits are presented as a function of the Ξ+bc mass and lifetime.

Microwave dielectric properties of CaCu_(3)Ti_(4)O_(12) ceramics:A clue to its intrinsic dielectric response

CaCu_(3)Ti_(4)O_(12)(CCTO)is a potential dielectric material with giant permittivity,good stability over the wide temperature and frequency range.However,the dielectric responses of CCTO-based ceramics are mainly investigated in the frequency of 102-106 Hz,which is far low to clarify the intrinsic dielectric feature.So,microwave dielectric properties have been investigated for the CCTO porous ceramics sintered at low temperature(≤1000°C).Good microwave dielectric properties of permittivityε=62.7,quality factor Qf=3062 GHz and temperature coefficient of the resonant frequencyτf=179 ppm/°C are achieved for the CCTO ceramics sintered at 1000°C,the dielectric loss significantly decreases two orders to 0.002 compared to that of CCTO ceramics sintered at critical temperature of 1020°C confirmed by differential scanning calorimetry(DSC).This clue indicates that giant permittivity and high loss is not intrinsic for CCTO ceramics,but derives from composition segregation,liquid phase and defects associated with internal barrier layer capacitor(IBLC).It suggests that CCTO-based ceramics is a promising microwave dielectric materials with high permittivity.

Search for the rare decays W^(+)→D_(s)^(+)γ and Z→D^(0)γ at LHCb

A search for the rare decays W^(+)→D_(s)^(+)γ and Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity of 2.0fb−1.No significant signal is observed for either decay mode and upper limits on their branching fractions are set using W^(+)→D_(s)^(+)γ and Z→μ+μ−decays as normalization channels.The upper limits are 6.5×10^(−4) and 2.1×10^(−3) at 95% confidence level for the W^(+)→D_(s)^(+)γ and Z→D^(0)γ decay modes,respectively.This is the first reported search for the Z→D^(0)γ decay,while the upper limit on the W+→D+sγbranching fraction improves upon the previous best limit.

A high specific Young's modulus steel reinforced by spheroidal kappa-carbide

1.Introduction High strength steels continue to be developed for automotive applications to increase safety and reduce lightweight by downgauging[1,2].In addition,reducing density is another solution for the lightweight of automotive components[3,4].Aluminum addition could effectively reduce the density of steels,since it has a low atomic mass and invokes a lattice expansion[5].