Effect of organic amendments on arsenic solubilization in soils during long-term flooded incubation

Rice consumption is considered an important arsenic source for the population in Asian countries. Previous studies showed increase in arsenic solubility in flooded soils and arsenic uptake by rice plants with the application of organic amendments, while contrasting results were also reported. Here, we comprehensively examined the effect of three types of organic amendments on arsenic solubility during long-term flooded soil incubation. The amendments examined were categorized as (1) plant-based composts, (2) cattle manures, and (3) fermented livestock (swine and poultry) droppings. The dissolved arsenic in all soils with fermented livestock dropping was significantly greater than that in control soils at 10 and 39 days after incubation. The soils with two cattle manures also contained significantly greater amounts of dissolved arsenic than control soils at day 39, while the rest of the amendments did not increase arsenic solubility. At day 80, the amount of dissolved arsenic in all soils became comparable. Tukey’s test demonstrated that the relative ratio of dissolved arsenic in soils with fermented livestock droppings to control soils was significantly greater than those with the plant-based composts and cattle manures at days 10 and 39. Furthermore, the solubilizing effect of some organic amendments was mostly explained by promotion of decrease in soil Eh, rather than increase in dissolved organic carbon. Thus, it could be concluded that fermented livestock droppings potentially have a greater risk of solubilizing As than plant-based composts and cattle manures, because of their greater ability for accelerating soil reduction, associated with their higher bio-decomposability.     

Size of the hard X-ray source in the Crab Nebula

The size of the hard X-ray source in the Crab Nebula was observed with scintillation counters on board two balloons at a lunar occulatation on 24 January, 1975. The Gaussian width of the source is 34 (+17, –14) and the center thereof is offset from the pulsar by 6±4 at position angle 102°. The observed time profile can also be fitted to an alternative model of two line sources whose intensities are 48% at 11 and 25.5% at 7 on both sides of the pulsar.Paper presented at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.     

Sixth- and eighth-order Hermite integrator for N-body simulations

We present sixth- and eighth-order Hermite integrators for astrophysical N-body simulations, which use the derivatives of accelerations up to second-order (snap) and third-order (crackle). These schemes do not require previous values for the corrector, and require only one previous value to construct the predictor. Thus, they are fairly easy to implement. The additional cost of the calculation of the higher-order derivatives is not very high. Even for the eighth-order scheme, the number of floating-point operations for force calculation is only about two times larger than that for traditional fourth-order Hermite scheme. The sixth-order scheme is better than the traditional fourth-order scheme for most cases. When the required accuracy is very high, the eighth-order one is the best. These high-order schemes have several practical advantages. For example, they allow a larger number of particles to be integrated in parallel than the fourth-order scheme does, resulting in higher execution efficiency in both general-purpose parallel computers and GRAPE systems.     

Estrogen equivalent concentration of individual isomer-specific 4-nonylphenol in Ariake sea water, Japan

Concentrations of 4-nonylphenol (NP) were determined by isomer-specific quantification of individual NP isomers based on relative response factor (RRF) quantification with GC–MS in combination with steam distillation extraction. Concentrations of NP in the Ariake Sea decreased with distance from the river mouth (St.A; 49 ng NP/l) to offshore areas (St.C; 11 ng NP/l). Even the least concentration in water from St.C in Ariake Sea was sufficient to have adverse effects on barnacles. The isomers, NP1–NP14 were separated by GC–PFC and identified structurally with NMR. The isomers varied in estrogenic activity with NP7 exhibiting the greatest estrogenic activity with a potency that was approximately 1.9 × 10⁻³ that of 17β-estradiol (E2) in recombinant yeast screen system. The coefficient of variation (CV) of NP isomer’s concentrations among three samples at St.A, B and C were 4–75%. This suggests that NP isomers might be independently degraded in aquatic environmental samples. The predicted estrogenic activity of measured concentrations of NP in Ariake Sea was 2.7–3.0-fold greater than the measured estrogen agonist activity.