Various methods are available to estimate reference evapotranspiration (ET 0 ) from standard meteorological observations. The Penman-Monteith method is considered to be the most physical and reliable method and is often used as a standard to verify other empirical methods. This study estimates and compares the monthly ET 0 calculated by 3 methods at 580 Chinese stations over the last 50 yr. The Penman-Monteith method is used here as a reference, and its spatial and temporal differences with the Thornthwaite method and pan measurement are evaluated. The results show that: (1) in terms of spatial difference, the Thornthwaite estimates show different regional patterns, while pan measurements display a consistent regional pattern; (2) the temporal variability of ET 0 is much better represented by pan measurements than by the Thornthwaite estimates. Overall, pan measurements are more useful than the Thornthwaite estimates if appropriate pan coefficients are determined. The Thornthwaite method only considers the temperature and latitude and gives unreliable results under dry conditions, e.g. in NW China. With reference to the Penman-Monteith estimates, the correction factors (pan coefficients) of pan measurements for the whole of China, and the regional averages over the 10 major drainage basins are determined. The average value lies between 0.6 and 0.8, although a seasonal and regional difference is present.KEY WORDS: Reference evapotranspiration · Water evaporation · Penman-Monteith · Thornthwaite · Pan · China Resale or republication not permitted without written consent of the publisherClim Res 28: [123][124][125][126][127][128][129][130][131][132] 2005 Brutsaert 1982). Since then, many methods have been developed, which can be grouped into 6 categories (e.g. Xu & Singh 2002): (1) water budget methods (e.g. Guitjens 1982); (2) mass-transfer methods (e.g. Harbeck 1962); (3) combination methods (e.g. Penman 1948, Monteith 1965, for the FAO Penman-Monteith method see Allen et al. (1998); (4) radiation-based methods (e.g. Priestley & Taylor 1972); (5) temperature-based methods (e.g. Thornthwaite 1948, BlaneyCriddle 1950; and (6) pan evaporation methods (e.g. Allen et al. 1998). In general, techniques for estimating ET 0 are based on one or more atmospheric variables, such as air temperature, solar or net radiation and humidity, or on some measurements related to these variables, like pan evaporation. Certain of these methods are accurate and reliable; others provide only a rough approximation. Most of the methods were developed for use in specific studies and are most appropriately applied to climates similar to that where they were developed (Chattopadhyay & Hulme 1997).The Penman-Monteith method is recommended as the sole standard by the FAO (Allen et al. 1998). The classic Penman-Monteith method combines both energy and mass balances to model ET 0 . It is based on fundamental physical principles, which guarantee the universal validity of the method. However, it needs a number of meteorological variable...

Four cyano-bridged 1D bimetallic polymers have been prepared by using the paramagnetic building block trans-[Ru(acac)(2)(CN)(2)](-) (Hacac=acetylacetone): {[{Ni(tren)}{Ru(acac)(2)(CN)(2)}][ClO(4)].CH(3)OH}(n) (1) (tren=tris(2-aminoethyl)amine), {[{Ni(cyclen)}{Ru(acac)(2)(CN)(2)}][ClO(4)].CH(3)OH}(n) (2) (cyclen=1,4,7,10-tetraazacyclododecane), {[{Fe(salen)}{Ru(acac)(2)(CN)(2)}]}(n) (3) (salen(2-)=N,N'-bis(salicylidene)-o-ethyldiamine dianion) and [{Mn(5,5'-Me(2)salen)}(2){Ru(acac)(2)(CN)(2)}][Ru(acac)(2)(CN)(2)].2CH(3)OH (4) (5,5'-Me(2)salen=N,N'-bis(5,5'-dimethylsalicylidene)-o-ethylenediimine). Compounds 1 and 2 are 1D, zigzagged NiRu chains that exhibit ferromagnetic coupling between Ni(II) and Ru(III) ions through cyano bridges with J=+1.92 cm(-1), zJ'=-1.37 cm(-1), g=2.20 for 1 and J=+0.85 cm(-1), zJ'=-0.16 cm(-1), g=2.24 for 2. Compound 3 has a 1D linear chain structure that exhibits intrachain ferromagnetic coupling (J=+0.62 cm(-1), zJ'=-0.09 cm(-1), g=2.08), but antiferromagnetic coupling occurs between FeRu chains, leading to metamagnetic behavior with T(N)=2.6 K. In compound 4, two Mn(III) ions are coordinated to trans-[Ru(acac)(2)(CN)(2)](-) to form trinuclear Mn(2)Ru units, which are linked together by pi-pi stacking and weak Mn...O* interactions to form a 1D chain. Compound 4 shows slow magnetic relaxation below 3.0 K with phi=0.25, characteristic of superparamagnetic behavior. The Mn(III)...Ru(III) coupling constant (through cyano bridges) and the Mn(III)...Mn(III) coupling constant (between the trimers) are +0.87 and +0.24 cm(-1), respectively. Compound 4 is a novel single-chain magnet built from Mn(2)Ru trimers through noncovalent interactions. Density functional theory (DFT) combined with the broken symmetry state method was used to calculate the molecular magnetic orbitals and the magnetic exchange interactions between Ru(III) and M (M=Ni(II), Fe(III), and Mn(III)) ions. To explain the somewhat unexpected ferromagnetic coupling between low-spin Ru(III) and high-spin Fe(III) and Mn(III) ions in compounds 3 and 4, respectively, it is proposed that apart from the relative symmetries, the relative energies of the magnetic orbitals may also be important in determining the overall magnetic coupling in these bimetallic assemblies.

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A novel polyanionic ligand (LaAs4W400140) 25-and its derivatives (LaAs4W40Ol,oM2) "-(M = Mn 2+, Fe 2+, Fe 3+, Cr 3+, Co 2+, Ni 2+, Cu 2+ or Zn 2+) have been prepared and characterized by elemental analyses, i.r., u.v.-vis. and emission spectra, 183W-n.m.r. and polarography. There is evidence that lanthanide occupies the central S 1 site, whereas the transition metal cations occupy the $2 site, in the complexes.

Heavy metal ions are increasingly being released into environment, leading to serious pollution and significant health problems to human being. To address the adverse effects posed by them, in the present study, a remediation method by magnetic nanoparticles was proposed. The magnetic particles were synthesized by a solvothermal process first. Then they were derivatized with dual functional moieties of amino- and mercapto- by reacting with aminopropyl-triethoxysilane and mercaptopropyl-triethoxysilane simultaneously. The prepared material was characterized by infrared spectrometry and elemental analysis. Both functional groups of amino- and mercapto- were present within the material. Since amino- and mercapto- have high affinity for heavy metal ions, the material can be used to retrieve these ions from water samples. Pb2+ and Mn2+ were used as model analytes to evaluate the effectiveness of the material. It is found that, after 60 min adsorption, the ions were almost total removed from the sample solution.