Simulated nitrogen load promoted mineralization of N2P1 compounds and accumulation of N4S2 compounds in soil dissolved organic matter in a typical subtropical estuarine marsh.

Soil dissolved organic matter (DOM) is the most reactive pool in estuarine marshes, playing an important role in the biogeochemical processes of biogenetic elements. To investigate the impacts of enhanced nitrogen (N) load on DOM molecular composition and its interactions with microbes in typical Cyperus malaccensis mashes of the Min River estuary, a field N load experiment with four N levels (0, 37.50, 50 and 100 g exogenous N m-2 yr-1, respectively; applied monthly for a total of seven months) was performed. DOM molecular composition was characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), the microbial community compositions (MCC, including fungi and bacteria) were determined by high-throughput sequencing technique, and their relationships were presented by co-occurrence network analysis. The results indicated that enhanced N load had significant impacts on soil DOM molecular composition, with N/C and P/C of DOM decreasing but S/C increasing markedly. Meanwhile, enhanced N load decreased the percentages of N2P1 compounds (primarily lipids) but increased those of N4S2 compounds (mainly lignins and lipids). The relative abundances of lignins significantly increased with increasing N load levels, whereas the proportions of lipids decreased. The abundance of N2P1 and N4S2 compounds was primarily positively correlated with eutrophic and oligotrophic microorganisms, respectively. Therefore, mineralization of N2P1 compounds might act as a source to replenish inorganic P, while enrichment of N4S2 compounds may make great contribution to organic S accumulation. Overall, enhanced N load promoted P depletion and S enrichment via altering plant growth, litter decomposition and MCC.

[Effects of different regeneration patterns on soil dissolved organic matter degradation in Castanopsis carlesii forests of subtropical China]. / äºšçƒ­å¸¦ç±³æ§ æž—ä¸åŒæ›´æ–°æ–¹å¼å¯¹åœŸå£¤å¯æº¶æ€§æœ‰æœºè´¨é™è§£æ€§çš„å½±å“.

Biodegradability of dissolved organic matter (DOM) affects stabilization and mineralization of soil organic matter, which is of great significance to soil nutrient cycling. In order to explore the effects of forest regeneration on soil DOM degradation, soil DOM solution was sampled in a natural Castanopsis carlesii forest (NF), a secondary forest of C. carlesii (SF), and an artificial-assisted regeneration forest of C. carlesii (AR) in a sub-tropical area and conducted 42-day laboratory incubation. The results showed that: 1) both the degradation rate of soil dissolved organic carbon (DOC) and the ratio of labile DOC were as follows: SF>AR>NF; dissolved organic nitrogen (DON) and microbial biomass carbon (MBC) are the factors significantly affecting the ratio of labile DOC; 2) stable DOC accounted for the majority of soil DOC in all the three forest types (72.3%-94.6%), which had long turnover time and contributed to the formation of stable soil organic matter (SOC); 3) the initial humification index in emission mode (HIXem) of soil DOM would affect the turnover time of labile DOC. The spectral structure of DOM changed dynamically during the degradation process, indicating that microorganism would turn to degrade aromatic and hydrophobic fractions for carbon source after the depletion of labile DOM. Overall, the transformation from NF of C. carlesii into SF and AR could increase the proportion of the easily degradable DOC, and enhance the biodegradability of soil DOM, which were not conducive to the accumulation of SOC.

Effects of short-term warming and nitrogen addition on the quantity and quality of dissolved organic matter in a subtropical Cunninghamia lanceolata plantation.

Increasing temperature and nitrogen (N) deposition are two large-scale changes projected to occur over the coming decades. The effects of these changes on dissolved organic matter (DOM) are largely unknown. This study aimed to assess the effects of warming and N addition on the quantity and quality of DOM from a subtropical Cunninghamia lanceolata plantation. Between 2014 and 2016, soil solutions were collected from 0-15, 15-30, and 30-60 cm depths by using a negative pressure sampling method. The quantity and quality of DOM were measured under six different treatments. The spectra showed that the DOM of the forest soil solution mainly consisted of aromatic protein-like components, microbial degradation products, and negligible amounts of humic-like substances. Warming, N addition, and warming + N addition significantly inhibited the concentration of dissolved organic carbon (DOC) in the surface (0-15 cm) soil solution. Our results suggested that warming reduced the amount of DOM originating from microbes. The decrease in protein and carboxylic acid contents was mostly attributed to the reduction of DOC following N addition. The warming + N addition treatment showed an interactive effect rather than an additive effect. Thus, short-term warming and warming + N addition decreased the quantity of DOM and facilitated the migration of nutrients to deeper soils. Further, N addition increased the complexity of the DOM structure. Hence, the loss of soil nutrients and the rational application of N need to be considered in order to prevent the accumulation of N compounds in soil.

[Soil microbial community structure of two types of forests in the mid-subtropics of China].

Soil microbial community structures were analyzed by biomarker method of phospholipid fatty acid (PLFA) for a natural forest dominated by Castanopsis fabri (CF) and an adjacent plantation of Cunninghamia lanceolata (CL) in the mid-subtropics of China. The results showed that the amounts of total PLFAs, bacterial PLFAs, fungal PLFAs, gram-positive bacterial PLFAs and gramnegative bacterial PLFAs in the 0-10 cm soil layer were higher than in the 10-20 cm soil layer, and each type of PLFAs in CF were higher than in CL. In either soil layer of the two forest types, the contents of bacterial PLFAs were significantly higher than those of fungal PLFAs. In the two forests, the contents of bacterial PLFAs accounted for 44%-52% of total PLFAs, while the contents of fungal PLFAs just accounted for 6%-8%, indicating the bacteria were dominant in the soils of the two vegetation types. Principal component analysis showed that the influence of vegetation types was greater than soil depth on the microbial community structures. Correlation analysis showed that gram-negative bacterial PLFAs, gram-positive bacterial PLFAs and bacterial PLFAs were significantly negatively correlated with pH, positively with water content, and the PLFAs of main soil microorganism groups were significantly positively correlated with soil total nitrogen, organic carbon, C/N and ammonium.

[Fractionation of dissolved organic carbon along soil profiles during the leaching process].

Two distinct soil types in mid-subtropical China were selected for soil sampling at the depth of 0-10, 10-20, 20-40, 40-60, 60-80, 80-100 cm for soil cores preparation. Dissolved organic carbon (DOC) extracted from recently fallen litters of Castanopsis carlesii with ultrapure water was leached through such soil cores to investigate the fractionation and retention pattern when migrating along the soil layers. The results showed the leachates out of deeper soil cores had lower concentrations and were chemically simpler, the hydrophobic pools contributed to the majority of the retention, but the proportion of retained hydrophilic materials gradually increased with the increasing soil depth. The infrared spectrum suggested that the hydrophobic materials containing aromatic rings could be easily absorbed by soils, but alkanes and simple carbohydrates would transport into subsoils with soil solution. Proportional decrease in the highly sorptive DOC restricted C sorption by subsoils, and thus the adsorption occurred mainly in 0-40 cm soil layers, suggesting that the chemical nature of DOC had a greater influence on sorption capacity of the soils than soil physicochemical properties. The retention amounts of DOC by different soil types differed significantly, which were significantly positively correlated with the contents of clay, iron and aluminum oxides.

Bis(acetato-κO)bis-(pyridine-2-aldoxime-κ(2)N,N')nickel(II).

In the mononuclear title compound, [Ni(CH(3)COO)(2)(C(6)H(6)N(2)O)(2)], the Ni(II) atom is coordinated by two pyridine-2-aldoxime (PaoH) ligands and two acetate groups, with cis coordination for the pairs of identical ligands. While each acetate group binds to the Ni(II) atom by one O atom, each PaoH chelates the Ni(II) atom through two N atoms. The O atom on PaoH is not deprotonated and does not participate in bonding to the Ni(II) atom. Thus, the Ni(II) atom exhibits an octa-hedral environment. Intra-molecular O-H⋯O hydrogen-bonding inter-actions and inter-molecular C-H⋯O hydrogen-bonding inter-actions are present in the structure. Adjacent mol-ecules pack along [100] through van der Waals forces.

Dipyridinium diaqua-bis-(pyrazole-3,5-di-carboxyl-ato-κ(2) N,O)cuprate(II) dihydrate.

In the mononuclear title salt, (C5H6N)2[Cu(C5H2N2O4)2(H2O)2]·2H2O, the Cu(II) ion is located on an inversion centre and is coordinated by two chelating pyrazole-3,5-dicarboxyl-ate anions and two water mol-ecules, forming a Jahn-Teller-distorted CuN2O4 octa-hedron. O-H⋯O and N-H⋯O hydrogen bonds are formed between water mol-ecules, complex anions and the pyridine counter-cations, leading to the formation of layers parallel to (100). The layers are held together by weak C-H⋯O hydrogen bonds.

A triclinic polymorph of bis-(µ(2)-ethane-thiol-ato)-1:2κS:S;3:4κS:S-(µ(4)-disulfido-1:2:3:4κS:S:S':S')tetra-kis-[tricarbonyl-iron(II)](2 Fe-Fe).

Next to the monoclinic polymorph [Cheng et al. (2005 ▶). Acta Cryst. E61, m892-m894], the triclinic title compound, [Fe(4)(C(2)H(5)S)(2)(S(2))(CO)(12)], is the second known form of this composition. The structure is composed of an [Fe(2)(C(2)H(5)S)(S)(CO)(6)] subcluster, which is linked to its counterpart by an inversion centre located at the mid-point of the central disulfide bond. The Fe(2)S(2) core of each subcluster exhibits a butterfly-like shape, with two S atoms bridging two Fe atoms. In the subcluster, each Fe atom is coordinated in a distorted octa-hedral coordination by three terminal carbonyl C atoms, two S atoms and one Fe atom. The crystal packing is accomplished through van der Waals inter-actions.

[1,2-Bis(diphenyl-phosphan-yl)ethane-2κP,P']tetra-carbonyl-1κC,2κC-(µ-2-cyclo-pentyl-2-aza-propane-1,3-dithiol-ato-1:2κS,S':S,S')diiron(II)(Fe-Fe).

In the title compound, [Fe(2)(C(7)H(13)NS(2))(C(26)H(24)P(2))(CO)(4)], the Fe(2)S(2) core exhibits a butterfly-like shape, with two S atoms bridging the Fe-Fe dumbbell. Each of the two Fe atoms exhibits a distorted octa-hedral environment. One Fe atom is additionally bonded to three carbonyl C atoms, whereas the other Fe atom is additionally bonded to one carbonyl C atom and two P atoms of the chelating dppe [dppe = 1,2-bis-(diphenyl-phosphan-yl)ethane] ligand. Non-classical intra-molecular C-H⋯S hydrogen-bonding inter-actions are present in the structure. The packing of adjacent mol-ecules along [100] is accomplished mainly through van der Waals forces.

Non-innocent bma ligand in a dissymetrically disubstituted diiron dithiolate related to the active site of the [FeFe] hydrogenases.

The purpose of the present study was to evaluate the use of a non-innocent ligand as a surrogate of the anchored [4Fe4S] cubane in a synthetic mimic of the [FeFe] hydrogenase active site. Reaction of 2,3-bis(diphenylphosphino) maleic anhydride (bma) with [Fe(2)(CO)(6)(mu-pdt)] (propanedithiolate, pdt=S(CH(2))(3)S) in the presence of Me(3)NO-2H(2)O afforded the monosubstituted derivative [Fe(2)(CO)(5)(Me(2)NCH(2)PPh(2))(mu-pdt)] (1). This results from the decomposition of the bma ligand and the apparent C-H bond cleavage in the released trimethylamine. Reaction under photolytic conditions afforded [Fe(2)(CO)(4)(bma)(mu-pdt)] (2). Compounds 1 and 2 were characterized by IR, NMR and X-ray diffraction. Voltammetric study indicated that the primary reduction of 2 is centered on the bma ligand.

Diiron models for the active site of Fe-only hydrogenase with terminal organosulfur ligation: synthesis, structures and electrochemistry.

Diiron model complexes (micro-SCH(2)CH(2)CH(2)S)Fe(2)(CO)(5)L with thioether-substitution, L=S(CH(2)CH(3))(2) (2), S(CH(2)CH(3))(CH(2)CH(2)Cl) (3), S(CH(2)CH(3))(C(6)H(5)) (4), or sulfoxide-substitution, L=SO(CH(2)CH(2)CH(3))(2) (5), SO(CH(3))(2) (6), were synthesized as active site analogues of Fe-only hydrogenase. The organosulfur ligands were introduced into the diiron centers via moderately stable intermediates following two routes. The X-ray crystallographic structures of complexes 2-6 show the apical positions of terminal organosulfur ligands. The electrochemical behaviors of the model complexes were investigated, especially for the interesting properties of the derivative of 6 which is proposed to be the first model with weak donor ligand similar to CO.

Bis(acetyl-acetonato)oxido(triphenyl-phosphine oxide)vanadium(IV).

In the structure of the title compound, [V(C(5)H(7)O(2))(2)O(C(18)H(15)OP)], the V atom adopts a slightly distorted octa-hedral geometry with its coordination completed by four O atoms of two acetyl-acetonate (acac) ligands, one oxo group and one O atom of the triphenyl-phosphine oxide (OPPh(3)) ligand.