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This study evaluated the effects of vegetation restoration on soil organic carbon (SOC) and its fractions, by exploring the SOC, particulate organic C (POC), mineralizable organic C (MOC), and light fraction organic C (LFOC) of three sloping land-use types (sloping farmland, forestland and grassland) and at four locations along each hillslope (30, 60, 90 and 120 m from the hilltop). Soil 137Cs was measured to calculate the soil erosion rate. The SOC, POC, MOC, and LFOC were significantly higher (p < 0.05) in the forestland and grassland than the sloping farmland. The SOC, LFOC, MOC, and POC of the grassland and forestland were higher in the lower than in the upper parts of the hillslope. The 137Cs activity was associated with soil loss rate and related to the redistribution of soil carbon fractions along the hillslope. The distribution of the soil carbon fractions and soil erosion in the forestland and grassland showed opposing trends. The soil labile organic carbon distribution and erosion of sloping farmland displayed a consistent distribution trend. Land-use changes and erosion were the most important factors that governed soil labile organic carbon: accounting for 21.7% and 25.7% of the observed variances, respectively. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is an important endogenous signaling molecule with a variety of biological functions. Development of fluorescent probes for highly selective and sensitive detection of H2S is necessary. We show here that dual-reactable fluorescent H2S probes could react with higher selectivity than single-reactable probes. One of the dual-reactable probes gives more than 4000-fold turn-on response when reacting with H2S, the largest response among fluorescent H2S probes reported thus far. In addition, the probe could be used for high-throughput enzymatic assays and for the detection of Cys-induced H2S in cells and in zebrafish. These dual-reactable probes hold potential for highly selective and sensitive detection of H2S in biological systems. [ABSTRACT FROM AUTHOR]

Soil salinization is currently an important limiting factor on agriculture development in irrigation areas all over the world. Electrical conductivity (EC) is one of the main indicators which are used to determine whether the irrigation water will cause soil salinization. It is of important significance to study the temporal and spatial variation of groundwater EC for agricultural irrigation in irrigation districts. This study was conducted to examine the temporal stability and periodicity of groundwater EC in irrigation districts. To accomplish this, 51 observation wells were selected for analysis of groundwater EC in Luohuiqu irrigation district which was an important agricultural production base in Shaanxi Province, China. The 51 observation wells belonged to 3 different terraces which were Terrace 1, 2 and 3. The altitudes of the 3 terraces were >342-360, >360-369 and >370-388 m, respectively. The numbers of observation wells in Terrace 1, 2 and 3 were 26, 13 and 12, respectively. Water samples were collected from 2 m below the well water surface to measure the groundwater EC and temperature at each site. Well 36 (high EC) and 43 (low EC) were selected for long-term observation. A CTD-Diver (USA) groundwater level data logger was adopted for measuring and recording the groundwater EC, temperature and level. According to the long sequence monitoring results of groundwater EC for the 51 observation wells, relative difference analysis and non-parametric Spearman's rank correlation test were used to check for temporal stability of groundwater EC, while Morlet wavelet analysis was applied to study the periodic variation of groundwater EC and groundwater level of high and low salinity wells. The results indicated that the order of mean groundwater EC values of the 3 terraces at different time instants was Terrace 3 > Terrace 1 > Terrace 2. Significant difference existed among the mean groundwater EC values of the 3 terraces (P<0.01). The groundwater EC values of the 3 terraces at different time instants all indicated moderate spatial variability, with coefficient of variation (CV) values ranging from 44% to 75%. Based on the mean EC value of each observation well, 21 wells were slightly saline and 30 wells were moderately saline. The ranges of minimum and maximum value of groundwater EC were 0.08-0.14 and 0.50-1.00 S/m, respectively. The most of Spearman rank correlation coefficients for groundwater EC were close to 1 (P< 0.01), which indicated that the groundwater EC of the 3 terraces exhibited strong temporal stability. But the temporal stability of groundwater EC had little relationship with the terraces which the corresponding well sites belonged to. The representative locations of mean groundwater EC for Terrace 1, 2 and 3 were Well 40, 38 and 45, respectively. The representative location of mean groundwater EC for the entire study area was Well 2. Based on the Morlet wavelet analysis of the groundwater EC and water level of Well 36 (high EC) and 43 (low EC), both of the groundwater EC and water level showed periodic variations. The groundwater EC and water level indicated different vibration periods on different time scales for both Well 36 and 43. The change in groundwater EC on small time scales was mainly affected by lateral recharge sources. The groundwater EC and water level showed an obviously inverse phase on large time scales. In conclusion, the groundwater EC has strong temporal stability and periodicity in Luohuiqu irrigation district. The representative location with mean groundwater EC can be used to monitor the mean groundwater EC of the study area. Irrigation time should be fully considered in irrigation districts to avoid soil salinization. The representative location with mean groundwater EC can provide great guidance to determine the irrigation time quickly and accurately to reduce the risk of soil salinization. [ABSTRACT FROM AUTHOR]

The sediment problem is a globally occurring problem that has long been a focus of research. The sediment-reducing effect of check dams and the safety problem after check dam breaks have always been a common concern of the society. This study analyzed the runoff change and sediment source during rainstorms in a small watershed using a multivariate mixed model and a comparative analysis of watersheds. The problem of sediment loss from dammed farmland after check dam break during rainstorms was evaluated. The results showed that the flood peak lag time (PLT) was significantly influenced by pre-soil moisture in case of small amounts of rainfall but not during rainstorms. Ecological construction significantly reduced the linear correlation between rainfall and runoff modulus (RM). The reduction of sediment delivery modulus (SDM) by check dam was stronger than that of the RM. The reduction in RM and SDM under rainstorm conditions were 16%~74% and 53%~93%, respectively. The contributions of inter-gully and gully lands to the sediment deposited in dammed farmland during the large rainstorm on July 26, 2017 were 38.07% and 61.93%, respectively. The increase in vegetation coverage in hillslope increased the proportion of sediment from gully lands. Check dam breaches have accounted for a loss of only 1.2% of the total area of the dammed farmland, and thus have not caused a large loss of sediment. However, the breaches of the check dams clearly increased the coefficient of variation of RM and SDM. Therefore, Check dams have a critical effect on controlling sediment delivery in watershed scale. Dam break will not result in a large percentage of sediment loss from the dammed farmland. [ABSTRACT FROM AUTHOR]

The influence of land use patterns on stream water quality is scale-dependent in space and time. Understanding the relationship between landscape characteristics and water quality is of great importance to improve water contamination prediction in unmonitored watersheds and for providing guidelines for watershed land use planning. In this study, five water sampling sites in the upper Dan River basin were established to monitor seasonal water chemical contamination over the period of 2000 to 2008. The relationships between land use patterns and water quality were analyzed across multiple-scales using redundancy analysis. The results showed that stream water quality variables displayed highly temporal variations, with electrical conductivity (EC), ammonium nitrogen (NH 4 + -N), nitrate nitrogen (NO 3 − N), and total suspended solids (TSS) all generally displaying higher levels in the wet season, while there were higher concentrations of biochemical oxygen demand (BOD 5 ), chemical oxygen demand (COD cr ), and dissolved oxygen (DO) in the dry season. The total contribution of land use patterns on overall water quality was stronger at the riparian scale than at the catchment and reach scales during the wet season. However, different land use metrics had different scale effects. Urban land had a higher positive relationship with degraded water quality at small scales than at large scales, whereas agricultural land displayed the opposite scale effects. Forest and grassland explained more water quality variations at the riparian scale than at other scales. Analyses of spatial development patterns suggested that size, density, aggregation, and diversity of landscape patterns were important factors impacting on stream water quality. The results provide important information regarding sustainable land use and landscape planning at multiple-scales that can be used to improve water quality. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2 S) is an important endogenous signaling molecule with multiple biological functions. New selective fluorescent turn-on probes based on fast thiolyling of NBD (7-nitro-1,2,3-benzoxadiazole) amine were explored for sensing H2 S in aqueous buffer and in living cells. The syntheses of both probes are simple and quite straightforward. The probes are highly sensitive and selective toward H2 S over other biologically relevant species. The fluorescein-NBD-based probe showed 65-fold green fluorescent increase upon H2 S activation. The rhodamine-NBD-based probe reacted rapidly with H2 S (t1/2 ≈1 min) to give a 4.5-fold increase in red fluorescence. Moreover, both probes were successfully used for monitoring H2 S in living cells and in mice. Based on such probe-based tools, we could observe H2 O2 -induced H2 S biogenesis in a concentration-dependent and time-dependent fashion in living cells., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hydrogen sulfide (H2 S) is an important endogenous signaling molecule with a variety of biological functions. Development of fluorescent probes for highly selective and sensitive detection of H2 S is necessary. We show here that dual-reactable fluorescent H2 S probes could react with higher selectivity than single-reactable probes. One of the dual-reactable probes gives more than 4000-fold turn-on response when reacting with H2 S, the largest response among fluorescent H2 S probes reported thus far. In addition, the probe could be used for high-throughput enzymatic assays and for the detection of Cys-induced H2 S in cells and in zebrafish. These dual-reactable probes hold potential for highly selective and sensitive detection of H2 S in biological systems., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)