Erosion and covered zones altered by surface coverage effects on soil nitrogen and carbon loss from an agricultural slope under laboratorysimulated rainfall events

Soil erosion,one of the most serious environmental concerns,might remove topsoil and essential element from terrestrial land.However,few attentions have been given to investigating how soil erosion regimes affect soil carbon and nitrogen loss.Therefore,this study investigated the effects of surface coverage rates(83%,67%,50%,33%,17%and 0%)and two positions(up-and downslope)on erosion regimes and its associated soil nitrogen and carbon loss under a sequence of six rainfalls(R1-R6).These results showed that the sediment concentrations with 33%(R4)and 17%(R5)coverage downslope were significantly lower than those with coverage upslope,whereas there was no significant difference between the runoff rates of the two slopes.Thus,surface coverage at different positions induced two soil erosion regimes(deposition-and transport-dominated processes).Dynamics of the DON and DIN concentrations indicated different release processes of soil nitrogen into runoff.The DON contributed to a substantial amount of soil nitrogen loss,which accounted approximately 81%of the organic form.The SBOC is significantly correlated with sediment-enriched clay particles from the deposition-dominated processes and is higher than that from the transport-dominated processes.The DOC is significantly correlated with Rr for transport-dominated processes.These results illustrated the critical role of erosion regimes in soil organic carbon loss in dissolved or sediment-bound form.It is concluded that erosion/covered zones altered by surface coverage could produce transport-and deposition-dominated erosion regimes and consequently affect soil carbon and nitrogen loss.In addition,these results demonstrated that surface coverage pattern may efficiently control soil erosion and soil carbon and nitrogen loss.

Synthesis of π-extended dibenzo[d,k]ullazines by a palladium-catalyzed double annulation using arynes

An efficient Pd-catalyzed double annulation reaction of 1-(2,6-dibro mophenyl)-1 H-pyrroles with arynes is developed to synthesizeπ-extended dibenzo[d,k]ullazines in good to excellent yields.For the first time,the parent dibenzo[d,k]ullazine core is obtained and characterized.

A prototype of benzobis(imidazolium)-embedded conjugated polyelectrolyte: Synthesis by direct C–H arylation and fluorescent responses to anions

We report the convenient synthesis of a benzobis(imidazolium)-embedded conjugated polyelectrolyte pBBI by a Cu-catalyzed direct C–H arylation of a cationic benzobis(imidazolium)monomer with a di-iodide comonomer.pBBI shows weak fluorescence in solution due to rotation of the repeat units in the conjugated backbone,and enhanced fluorescence when electrostatically interacting with a variety of an-ions to form aggregates.Specially,pBBI responds to the bisulfite anion with intensified unique deep-blue fluorescence easily discriminated by naked eye.