No abstract

Existing groundwater table (GWT) class maps, available at full coverage for the Netherlands at 1:50,000 scale, no longer satisfy user demands. Groundwater levels have changed due to strong human impact, so the maps are partially outdated. Furthermore, a more dynamic description of groundwater table dynamics representative for the current climate is needed. A mapping method to obtain a large set of parameters describing groundwater table dynamics was developed. The method uses time series analysis and well-timed phreatic head measurements to obtain a data set at point support. This point data set is correlated to groups of exhaustive high-resolution ancillary data by stratified multiple linear regression. Finally, simple kriging is applied to interpolate the residuals of the regression model. The method was applied in a 1,790,000 ha area and its performance was measured in 10,000 and 179,000 ha test areas. The relation between higher sampling density, mapping cost and map quality was explored. Validation results show that reasonable to good quality maps of various aspects of groundwater dynamics can be obtained by this method, at much lower cost than traditional survey-based mapping methods. The method includes the quantification of uncertainty at the actual sampling density and allows the a priori estimation of uncertainty at other sampling densities. Future research aims at identification of the effect of sources of error in ancillary data and how to diminish these. D

Here we report that chiral Mn­(I) complexes are capable of H–P bond activation. This activation mode enables a general method for the hydrophosphination of internal and terminal α,β-unsaturated nitriles. Metal−ligand cooperation, a strategy previously not considered for catalytic H–P bond activation, is at the base of the mechanistic action of the Mn­(I)-based catalyst. Our computational studies support a stepwise mechanism for the hydrophosphination and provide insight into the origin of the enantioselectivity.

This study compared the efficiency of geostatistical digital soil mapping (DSM) with conventional soil mapping (CSM) for updating soil class and property maps of a cultivated peatland in the Netherlands. For digital soil class mapping, the generalized linear geostatistical model was used. Digital mapping of the soil organic matter (SOM) content and peat thickness was done by universal kriging. The conventional soil class map was created by free survey, while the property maps were created with the representative profile description (RPD) and map unit means (MUM) methods. For each method, we computed the effort invested in the mapping in terms of the sampling and cost densities. The accuracies of the created soil maps were estimated from independent probability sample data. The results showed that for DSM, the cost density could be reduced by a factor of three compared with CSM without compromising accuracy. The map purity of both maps was around 55%. For conventional soil property mapping, the MUM maps were more accurate than the RPD maps. For SOM, CSM-MUM (RMSE 7.5%) performed better than DSM (RMSF 12.1%), although accuracy differences were not significant. For peat thickness, DSM (RMSE 23.3 cm) performed slightly better than CSM-MUM (RMSE 24.9 cm). Despite the differences in accuracy being small, the digital soil property maps were produced more efficiently. The cost density was a factor of 3.5 smaller. We conclude that for updating conventional soil maps in the Dutch peatlands, geostatistical DSM can be more efficient, although not necessarily more accurate, than CSM.

The transition between spin states in d-block metal complexes has important ramifications for their structure and reactivity, with applications ranging from information storage materials to understanding catalytic activity of metalloenzymes. Tuning the ligand field (Δ O ) by steric and/or electronic effects has provided spin-crossover compounds for several transition metals in the periodic table, but this has mostly been limited to coordinatively saturated metal centers in octahedral ligand environments. Spin-crossover complexes with low coordination numbers are much rarer. Here we report a series of four-coordinate, (pseudo)tetrahedral Fe(II) complexes with formazanate ligands and demonstrate how electronic substituent effects can be used to modulate the thermally induced transition between S = 0 and S = 2 spin states in solution. All six compounds undergo spin-crossover in solution with T 1/2 above room temperature (300–368 K). While structural analysis by X-ray crystallography shows that the majority of these compounds are low-spin in the solid state (and remain unchanged upon heating), we find that packing effects can override this preference and give rise to either rigorously high-spin ( 6 ) or gradual spin-crossover behavior ( 5 ) also in the solid state. Density functional theory calculations are used to delineate the empirical trends in solution spin-crossover thermodynamics. In all cases, the stabilization of the low-spin state is due to the π-acceptor properties of the formazanate ligand, resulting in an “inverted” ligand field, with an approximate “two-over-three” splitting of the d-orbitals and a high degree of metal–ligand covalency due to metal → ligand π-backdonation. The computational data indicate that the electronic nature of the para -substituent has a different influence depending on whether it is present at the C–Ar or N–Ar rings, which is ascribed to the opposing effect on metal–ligand σ- and π-bonding.