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As endocrine-disrupting chemicals, a few frequently used phthalate plasticizers were banned or restricted for use as additives in food in some countries. The interaction mechanisms between three phthalate plasticizers with human serum albumin (HSA) were studied by fluorescence (quenching, synchronous, and three-dimensional), UV-vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy, in combination with molecular modeling under simulative physiological conditions, respectively. The results obtained from fluorescence quenching data revealed that the plasticizers-HSA interaction altered the conformational strcture of HSA. Meanwhile, the alterations of HSA secondary structure in the presence of phthalate plasticizers were investigated. The binding distances for the plasticizers-HSA system were provided by the efficiency of fluorescence resonance energy transfer. Furthermore, the thermodynamic analysis implied that hydrophobic forces were the main interaction for the plasticizers-HSA system, which agreed well with the results from the molecular modeling study.

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The effects of near soil surface characteristics on the soil detachment process might be different at different stages of vegetation restoration. This study was performed to investigate the effects of near soil surface factors on the soil detachment process by overland flow. Soil samples were collected from two natural grasslands of different ages and subjected to flow scouring. The results indicated that the effects of near soil surface characteristics on soil detachment were substantial during vegetation restoration. The total reduction in soil detachment capacity of the 1-yr-old grassland was 98.1%, and of this total, 7.9, 30.0, and 60.2% was attributed to the litter, biological soil crusts (BSCs), and plant roots, respectively. In the 24-yr-old grassland, the soil detachment capacity decreased by 99.0%, of which 13.2, 23.5, and 62.3% were due to litter, BSCs, and plant roots, respectively. Combined with previously published data for a 7-yr-old grassland, the influence of plant litter on soil detachment was demonstrated to increase with restoration time, but soil detachment was also affected by the litter type and composition. The role of BSCs was greater than that of plant litter during the early stages of vegetation recovery. However, its contribution weakened with time. The influence of plant roots accounted for half to two-thirds of the total near soil surface factors, of which >72.6% was attributed to the physical binding effects of roots. The correction coefficients of near soil surface characteristics for rill erodibility were determined for the Water Erosion Prediction Project model.

No abstract

Determination of rates of mineralization of organic nitrogen (N) into ammonium-N (NH4+-N) and nitrification of NH4+-N into nitrate-N (NO3−-N) could be used to evaluate inorganic N supply capacity, which, in turn, could guide N fertilizer application practices in crop cultivation systems. However, little information is available on the change of mineralization and nitrification in soils under fruit cultivation systems converted from forestlands in karst regions. In a 15N-tracing study, inorganic N supply capacity in forest soils and three typical fruit crop soils under long-term cultivation was investigated, in addition to factors influencing the supply, in calcareous soils in the karst regions in southwestern China. Long-term fruit crop cultivation decreased soil organic carbon (SOC), total N, and calcium concentrations, cation exchange capacity (CEC), water holding capacity (WHC), pH, and sand content, significantly, but increased clay content. Compared to that of forests, long-term fruit crop cultivation significantly decreased mineralization and nitrification rates to 0.61–1.34 mg N kg−1 d−1 and 1.95–5.07 mg N kg−1 d−1, respectively, from 2.85–6.49 mg N kg−1 d−1 and 8.17–15.5 mg N kg−1 d−1, respectively, but greatly increased the mean residence times of NH4+-N and NO3−-N. The results indicate that long-term fruit crop cultivation could decrease soil inorganic N supply capacity and turnover in karst regions. Both mineralization and nitrification rates were significantly and positively correlated with SOC and total N concentrations, CEC, and WHC, but negatively correlated with clay content, suggesting that decreased soil organic matter and increased clay content were responsible for the decline in mineralization and nitrification rates in soils under long-term cultivation of fruit crops. The results of the present study highlight the importance of rational organic fertilizer application in accelerating soil inorganic N supply and turnover under long-term cultivation of fruit crops in karst regions.

Core Ideas Runoff simulation was conducted on different sides of rock outcrops. Rock outcrops shaped the water flow paths differently on their three sides. Outcrop runoff will contribute greatly to soil loss, rock dissolution, and biodiversity. Rock outcrops (ROCs), a widespread surface component in a karst landscape, play a unique, hydrological role in the infiltration and redistribution of precipitation. This experiment aimed to explore water pathways of outcrop runoff and their ecological functions in epikarst by applying the dye tracer Brilliant Blue FCF on three sides of rocks—the uphill sides, the downhill sides, and the lateral sides—to simulate the outcrop runoff under a rainfall intensity of 100 mm h−1, combined with a soil loss survey and soil property measurements. Our results showed that the outcrop runoff infiltration in three directions (i.e., lateral flow into the soil, vertical flow, and lateral spread at the soil–rock interface) differed greatly on the three sides of the ROCs. Deep but narrow vertical flow was the most common infiltration pattern on the uphill sides; long but shallow lateral flow toward downslope dominated outcrop runoff movement on the lateral sides. However, on the downhill sides, the vertical flow at the soil–rock interface was quantitatively equal to the lateral flow to soil. The difference in outcrop runoff infiltration at the three sides of ROCs may help to reveal the mechanisms of soil erosion as well as rock dissolution and biodiversity in a karst environment.

An in-depth understanding of the dominant factors controlling soil respiration is important to accurately estimate carbon cycling in forest ecosystems. However, information on variations in soil respiration at different soil depths and the influencing factors in forest is limited. This study examined the variations in soil respiration at two soil depths (0–10 and 10–20 cm) as well as the effects of soil temperature, soil water content, litter removal, and root cutting on soil respiration in three typical forest types (i.e., Pinus tabulaeformis Carrière, Platycladus orientalis (L.) Franco, and Quercus variabilis Bl.) in the mountainous area of north China from March 2013 to October 2014. The obtained results show that soil respiration exhibited strong seasonal variation and decreased with soil depth. Soil respiration was exponentially correlated to soil temperature, and soil respiration increased with soil water content until reaching threshold values (19.97% for P. tabulaeformis, 16.65% for P. orientalis, and 16.90% for Q. variabilis), followed by a decrease. Furthermore, interactions of soil temperature and water content significantly affected soil respiration at different soil depths of forest types, accounting for 68.9% to 82.6% of the seasonal variation in soil respiration. In addition to soil temperature and water content, aboveground litter and plant roots affected soil respiration differently. In the three forest types, soil respiration at two soil depths decreased by 22.97% to 29.76% after litter removal, and by 44.84% to 53.76% after root cutting. The differences in soil respiration reduction between the two soil depths are largely attributed to variations in substrate availability (e.g., soil organic content) and soil carbon input (e.g., litter and fine root biomass). The obtained findings indicate that soil respiration varies at different soil depths, and suggest that in addition to soil temperature and water content, soil carbon input and dissolved organic substances may exert a strong effect on forest soil respiration.