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Background: Nanoparticle albumin-bound paclitaxel (nab-PTX) has exhibited clinical efficacy in breast cancer treatment, but toxicities can be yielded more at the same time. We did this meta-analysis aiming to unambiguously compare nab-PTX with conventional solvent-based paclitaxel (sb-PTX) in breast cancer patients of all stages. Method: Pubmed, Embase and Cochrane Library were searched for head-to-head randomized controlled trials of nab-PTX and sb-PTX in breast cancer. Risk ratio (RR) with 95% confidence interval was used for dichotomous variables while Hazard ratio (HR) was used for time-to-event outcomes. Results: Our review finally included 9 studies with 3508 patients. Nab-PTX showed a benefit on objective response rate (ORR) (RR=1.22 [1.04-1.43], P=0.01) as well as non-inferiority compared with sb-PTX in disease control rate (DCR) (RR=1.01 [0.98-1.04], P=0.44), overall survival (OS) (HR=0.99 [0.93-1.05], P=0.81) and disease free survival/progression free survival (DFS/PFS) (HR=0.92 [0.81-1.05], P=0.21). However, when it comes to toxicities (fatigue, nausea or vomiting, peripheral sensory neuropathy and adverse event related discontinuation), results favored sb-PTX (RR=2.89 [1.07-7.8], 3.15 [1.78-5.59], 2.11 [1.32-3.37], 2.02 [1.61-2.53]; P

The removal of organic matter and iron oxides could increase and decrease soil CEC in tropical and subtropical regions, but the quantitative information is insufficient so far about the change of soil CEC, the influence factors and their contribution. In this study, the subhorizon soils of 24 soil series in the tropical and subtropical China were used, pH, particle size composition, organic matter, iron oxides of these samples were measured, and also CECs were measured and compared for the original soils and after the removal of organic matter and iron oxides. The results showed that, compared with CEC of the original soil, the eliminating organic matter increased soil CEC significantly by 2.28% - 56.50% with a mean of 24.02%, but the further obliterating iron oxides decreased soil CEC significantly by 0.75% - 20.30% with a mean of 7.73%. CEC after the removal of organic matter and iron oxides had positive correlation with iron oxides (p − 0.546pH − 0.024OM + 0.053FexOy − 0.001Silt + 0.007Clay + 0.972CECoriginal (R2 was 0.923, RSME was 1.55 cmol(+)∙kg−1, p − 0.546pH − 0.024OM + 0.053FexOy − 0.001Silt + 0.007Clay + 0.972CECoriginal (R2 was 0.923, RMSE was 1.55 cmol(+)∙kg−1, p < 0.01). Further research is needed in the future as for exploring internal functional mechanism in view of soil electrochemistry and mineralogy.

Purple paddy soils cover about 66% of the paddy soils in Sichuan Basin. Complex interactions made the effects of potassium fertilizer application on NH4+ adsorption more complicated and the behavior of NH4+ and K+ interaction in purple paddy soils has rarely been evaluated. We hypothesize that correct management of these soils can enhance the efficiency of ammonium and potassium fertilizers. In order to determine correct management methods, it is important to understand the interaction of main nutrient cations NH4+ and K+ and maturation hydroponics in purple paddy soils with different paddy cultivation times. A purple paddy soil chronosequence with cultivation history from 0 to 300 years was studied to understand the respective effects of SOM and mineralogy on NH4+ and K+ sorption behavior by adsorption experiments using samples both before and after H2O2 oxidation. The study shows that maturation hydroponics influenced NH4+ and K+ adsorption mainly through changing clay mineralogy and enhancing SOM accumulation. SOM and smectite play positive effects for NH4+ adsorption. The K+ adsorption, however, is mainly affected by the smectite changes. The adsorption percentages are obviously higher at 25–50 mg L−1 for each NH4+ solution and higher at 50–100 mg L−1 for each K+ solution. When ammonium and potassium were applied together, NH4+ and K+ adsorption are mutually weakened. In addition, the percentage of K+ adsorption increased from 49.7–57.7% for the 100 mg L−1 K+ solution to 50.9–58.5% for the 200 mg L−1 K+ solution at 200 mg L−1 of added NH4+. SOM enrichments could be a positive way to improve the ammonium fertilizer utilization efficiency in purple paddy soils. Potassium may be more vulnerable to loss at low K+ concentrations given that ammonium and potassium fertilizers were applied together and it should be separately applied to enhance the utilization efficiency of applied fertilizer.

Nitrate accumulation has been reported in the top 1 m and subsurface soil (> 1 m) across arid to semi-humid regions, but not in humid regions. Nitrate inventories through the whole regolith, referred to collectively as soil and saprolite, in humid regions have received little attention to date, likely due to previously assumed low nitrification rates and large nitrogen (N) losses by severe surface runoff and erosion. In order to understand if and how reactive N exists in the below ground (soil and saprolite) in humid environment, the amount of NO3--N, NH4+-N and dissolved organic N (DON) present in the regolith to a depth of 9 m in a typical red soil Critical Zone was investigated under different land uses (upland, woodland and paddy field). The Red Soil Critical Zone Observatory is located in the subtropical Jiangxi Province, China, with a mean annual precipitation of 1795 mm and mean annual potential evapotranspiration of 1229 mm. The examined regoliths were acidic, highly weathered, and mainly clay loam in texture. Results showed that on average 92% (827 ± 97 kg N ha-1) of NO3--N and 82% (521 ± 153 kg N ha-1) of DON were stored at depth (from a depth of 1 m to the bedrock surface) in the upland regolith, while 92% (283 kg N ha-1) of NO3--N and 78% (820 kg N ha-1) of DON were stored at depth in the woodland regolith. Nitrate N significantly accumulated with depth in the upland regolith from the 1- to 4-m depth interval (p < 0.01), while the inventory (632 ± 75 kg N ha-1) in the top 3-m zone accounted for on average 71% of the total. Dissolved organic N significantly accumulated with depth in the upland regolith from the 0- to 3-m depth interval (p < 0.01), while the inventory (408 ± 75 kg N ha-1) in the top 3-m zone accounted for on average 64% of the total. There was no significant accumulation for NH4+-N throughout the upland regolith (p = 0.35). No substantial accumulation of dissolved N was measured at depth in paddy field regoliths with different cultivation ages. The finding that large reservoirs of reactive N can exist in deep regolith rather than in the routinely investigated solum of subtropical regions shows a missing part of the terrestrial N budget and raises concerns about potential 34 groundwater nitrate pollution.

Nitrate (NO3−) loss and enrichment in water bodies caused by fertilization are a major environmental problem in agricultural areas. However, the quantitative contribution of different NO3− sources, especially chemical fertilizers (CF) and soil organic nitrogen (SON), to NO3− runoff loss remains unclear. In this study, a systematic investigation of NO3− runoff and its sources was conducted in a subtropical agricultural watershed located in Yujiang County, Jiangxi Province, China. A semi-monthly sampling was performed at the inlet and outlet from March 2018 to February 2019. Hydrochemical and dual NO3− isotope (15 N and 18O) approaches were combined to estimate the NO3− runoff loss and quantify the contribution of different sources with a Bayesian isotope mixing model. Source apportionment by Stable Isotope Analysis in R (SIAR) suggested that NO3− in runoff was mainly derived from nitrification of ammonium (NH4+) mineralized from SON (37–52%) and manure/sewage (M&S) (25–47%), while the contribution of CF was relatively small (14–25%). The contribution of various sources showed seasonal variations, with a greater contribution of CF in the wet growing season (March to August). Compared with the inlet which contributed 37–40% to runoff NO3−, SON contributed more at the outlet (49–52%). Denitrification in the runoff was small and appeared to be confined to the dry season (September to February), with an estimated NO3− loss of 2.73 kg N ha−1. The net NO3− runoff loss of the watershed was 34.5 kg N ha−1 yr−1, accounting for 15% of the annual fertilization rate (229 kg N ha−1 yr−1). Besides M&S (22%), fertilization and remineralization of SON (CF + SON) were the main sources for the NO3− runoff loss (78%), suggesting accelerated nitrification of NH4+ from CF (24%) and SON mineralization (54%). Our study indicates that NO3− runoff loss in subtropical agricultural watersheds is dominated by nonpoint source pollution from fertilization. SON played a more important role than CF. Besides, the contribution of sewage should not be neglected. Our data suggest that a combination of more rational fertilizer N application (CF), better management of SON, and better treatment of domestic sewage could alleviate NO3− pollution in subtropical China.

Plant root-derived carbon (C) inputs (Iroot) are the primary source of C in mineral bulk soil. However, a fraction of Iroot may lose directly (Iloss, e.g., via rhizosphere microbial respiration, leaching and fauna feeding) without contributing to bulk soil C pool. This loss has never been quantified, particularly at global scale, inhibiting reliable estimation of soil C dynamics. Here we integrate three observational global datasets including radiocarbon content, allocation of photosynthetically assimilated C, and root biomass distribution in 2,034 soil profiles to quantify Iroot and its contribution to the bulk soil C pool. We show that global average Iroot in the 0-200 cm soil profile is 3.5 Mg ha-1 yr-1, ~80% of which (i.e., Iloss) is lost rather than entering bulk soil. If ignoring Iloss, bulk soil C turnover will be incorrectly estimated to be four times faster. This can explain why Earth system models (in which all Iroot enters bulk soil C pools) predict much faster soil C turnover than radiocarbon-constrained estimates. Iroot decreases exponentially with soil depth, and the top 20 cm soil contains >60% of total Iroot. Actual C input to bulk soil (i.e., Iroot – Iloss) shows a similar depth distribution to Iroot. We also map Iloss and its depth distribution across the globe. Our results demonstrate the global significance of direct C losses which limit the contribution of Iroot to bulk soil C storage; and provide spatially explicit data to facilitate reliable soil C predictions via separating direct C losses from total root-derived C inputs.

Nitrate accumulated deep (>100 cm) in the regolith (soil and saprolite) threatens groundwater quality, but most studies focus only on nitrate nearer the surface (

Nitrogen (N)-induced soil acidification has received much attention worldwide. Nitrification and soil N mineralization are two key N cycle processes that affect soil acidification. However, the seasonal dynamics of soil pH under their combined influence is unclear. We studied the effect of N fertilization on soil pH and N transformations using 15N tracing in field lysimeters with soils developed from different parent materials (Quaternary red clay, sandstone, and basalt). Maize was planted with 200 kg N ha−1 yr−1 15N-labeled urea addition. During 7–45 days after fertilization, proton (H+) production due to nitrification of fertilizer N, nitrate (NO3−) leaching, and plant uptake exceeded H+ consumption by base cations mobilization and leaching, resulting in a significant soil pH decline. When nitrification activity decreased (after 45 days), due to exhausted ammonium (NH4+) availability, soil pH rose again. During the fallow period, acid neutralization due to base cation mobilization, and ammonification of soil organic N (SON) offset H+ production caused by nitrification of mineralized SON, leading to a sustained rise in soil pH. After the one-year experiment, no significant soil pH decrease was observed in any of the soils. Parent material had little effect on the seasonal dynamics of soil acidification, which appeared to be controlled by fertilization, environmental factors (temperature and moisture), and plant uptake. In subtropical regions, monitoring of soil pH on an annual basis may mask the effect of N fertilization on soil acidification.

A paddy soil chronosequence consisting of four profiles derived from Quaternary red clay (QRC) in Southern China with cultivation history from 0 to 300 years was studied to understand the underlying mechanisms and processes controlling the centennial scale Fe evolution during anthropedogenesis. We evaluated the chronosequencial changes in depth distribution of Fe oxides and Fe isotopic compositions. Results showed that paddy soil development on QRC over a centennial time scale caused increasing profile differentiation of Fe oxides and measurable Fe isotope fractionation. Total Fe and oxide bound Fe as well as the maximum Fe illuviation depth decreased as paddy soils age, leading to significant differences in morphological properties between paddy and non-paddy soils with the same parent material. Selective extractions showed that the weakly-bound, oxide-bound and silicate bound Fe corresponded to 4–18%, 49–81%, and 11–40% of the total Fe, respectively, and these proportions varied with both time and depth due to the redox-related Fe transformation and redistribution. δ56Fe values in the studied paddy soil chronosequence ranged from 0.05‰ to 0.26‰ and exhibited a strong negative correlation with the logarithm of total Fe concentrations, suggesting mass-dependent Fe isotope fractionation occurred as a result of the preferential removal of lighter Fe isotopes during Fe leaching loss under the predominant reducing conditions. However, the Fe isotopic ratio of a specific paddy soil horizon was a result of a complex interaction of different processes, which were summarized and interpreted in our proposed conceptual model of Fe evolution in terraced paddy soils. Further investigations of Fe isotope signatures in the soil-plant-water system with a combination of laboratory simulation and prediction of Fe isotope fractionation under different pedogenic processes are needed to evaluate the relative contribution of multiple processes to Fe isotope fractionation during anthropedogenesis of paddy soils.

Nitrate (NO3−) leaching in agroecosystems has caused much concern worldwide due to its negative environmental and health impacts. To evaluate the effect of fertilization on NO3− leaching and soil N accumulation, a two-year 15N tracing study was conducted in subtropical China with field lysimeters packed with non-destructive sampling red soil. 200 kg N ha−1 yr−1 urea (15N abundance of 10%) was applied for maize crops. Fertilization promoted NO3− leaching by 91.5 ± 6.1 and 57.9 ± 15.2 kg N ha−1 yr−1 at 20 and 100 cm depth, respectively. Soil organic nitrogen (SON) pool was the main NO3− source (>60%), especially at surface soil. Fertilizer contributed 19.4 ± 2.0 and 32.8 ± 1.9% to NO3− leaching. At 20 cm depth, besides NO3− leaching accelerated by fertilization during the crop growth period (51.8%), mineralization of SON also resulted in abundant NO3− leaching during the fallow period (48.2%). At 100 cm depth, NO3− leaching significantly increased with the fertilization year due to the continuous NO3− leaching and the delay of NO3− leaching by soil NO3− adsorption. After two-year fertilization, 55.3 ± 2.2% of the applied N accumulated in the soil, leading to a soil N pool increase of 110.0 ± 10.1 kg N ha−1 yr−1. If the fertilization was maintained, the continuous N accumulation poses a potential threat to groundwater quality or drinking water safety. In subtropical red soil regions, to reduce NO3− leaching, NO3− leaching during both the crop growth and fallow period should be taken seriously, and effective management practices, such as cover crops and intensive tile drainage systems, should be carried out to reduce the fertilizer N accumulation and the contribution of SON.

A paddy soil chronosequence consisting of five profiles derived from calcareous marine sediments with cultivation history from 0 to 1000 years was studied to understand the underlying mechanisms and processes controlling the millennial scale Fe evolution. We evaluated the chronosequencial changes in depth distribution of Fe oxide contents and Fe isotopic compositions. Results showed that paddy soil evolution under the influence of periodic flooding and groundwater fluctuation resulted with time in variations of soil moisture regime and redox condition that control Fe mobilization, translocation and redistribution, leading to enhanced profile differentiation of Fe oxides and measurable Fe isotope fractionation. Total Fe and oxide bound Fe as well as their differentiation between surface and subsurface horizons increased as paddy soils age, leading to the formation of diagnostic horizons and features characterizing Fe distribution and redistribution. Selective extractions showed that the weakly-bound, oxide-bound and silicate bound Fe corresponded to 1–16%, 8–46%, and 52–91% of the total Fe, respectively, and these proportions varied with both time and depth due to the redox-related Fe transformation and translocation. δ56Fe values in the studied paddy soil chronosequence ranged from − 0.01‰ to 0.18‰ and exhibited a strong negative correlation with the logarithm of total Fe concentrations, suggesting mass-dependent Fe isotope fractionation occurred as a result of the preferential removal of lighter Fe isotopes during long-term paddy soil evolution under the predominant reducing conditions. However, the Fe isotopic ratio of a specific paddy soil horizon was a result of a complex interaction of different processes, which were summarized and interpreted in our proposed conceptual model. Comparison of Fe isotopic compositions in the worldwide soils demonstrated that Fe isotopes can evidence Fe transfer and pinpoint the factors and processes that control Fe mobilization and redistribution particularly in soils with changing moisture regimes and redox conditions. Our findings provide new insights into the behavior and geochemical cycle of Fe at the Earth's surface strongly affected by human activities and contributes to an improved understanding of how anthropedogenesis affects Fe evolution in the Earth's Critical Zone.

This paper was oriented to characterise spatio-temporal variation of soil organic carbon (SOC) over a 30-year period and to explore its driving forces in East China. A comparative study was done of data obtained during 1980 and 2010 in Anhui Province. Spatio-temporal changes of SOC density and storage in the surface (0–30 cm) and 0–100 cm layers were analysed using geographic information system (GIS) spatial analysis techniques. Relationships between soil erosion, land use change, agricultural management, and changes in SOC are discussed. Results show: (1) over 30 years, the average SOC density decreased by 0.59 kg C m−2 in the surface layer and 1.63 kg C m−2 in 0–100 cm layer. The average SOC density increased in Calcaric Cambisols and Haplic Fluvisols, and decreased in other soil types.The average SOC density in upland increased but decreased as a result of other land use practices. (2) SOC density in the surface layer increased to the north but decreased to the south in Anhui. SOC density in the 0–100 cm layer increased in the central area and decreased to the south. About 59% of all soil increased in SOC density. (3) SOC storage decreased by 117.91 Tg C in the surface layer and decreased by 237.65 Tg C in the 0–100 cm layer. The SOC storage increased mainly in the northern and central areas. (4) Severe soil erosion was a main reason for the large reduction in SOC storage in western and southern Anhui. Cultivated land use that changed to paddy field from upland improved SOC more than changes to other land use types. SOC storage change in farmland was significantly and positively related to organic matter content in crop roots.

Calcareous soils are those soils containing layers of carbonate accumulation formed by either secondary accumulation or inheritance of CaCO 3 from calcareous parent materials. These soils are widely distributed in arid, semi-arid and even some humid climate environments. However, in the Chinese Soil Taxonomy (CST, 3rd version), the soils that contain large amounts of CaCO 3 but do not meet requirements of Aridosols are classified as Hapli-Ustic Cambosols. This group also includes many non-calcareous soils and those soils strongly affected by secondary carbonate accumulation together with quite dissimilar soils in terms of their morphology and properties. This study was conducted to determine calcification patterns and calcic processes occurring in representative pedons of calcareous soils in northwestern Henan Province, China and to classify these soils in CST. A Calcic subgroup was proposed to add within the Hapli-Ustic Cambosols. A diagnostic key was also provided to separate this subgroup from the Typic subgroup. In this way the different calcification degrees of soils were better reflected in the classification, which should lead to more uniform interpretive groups for better soil management.

Soil organic phosphorus transformation during ecosystem development exerts a crucial influence on soil fertility and ecosystem properties. This paper reviews the use of solution 31P NMR spectroscopy for characterizing organic phosphorus speciation in soil chronosequence and long-term field experiments in order to improve our understanding of the temporal changes, fundamental processes, and associated natural and anthropogenic controls of organic phosphorus transformation during long-term ecosystem evolution. Published soil chronosequence studies show that organic phosphorus compounds under aerobic conditions are dominated by phosphate monoesters (occurred mainly as inositol phosphates) followed by phosphate diesters (occurred mainly as DNA) and phosphonates, irrespective of the different parent materials, vegetation covers and climatic conditions. This contrasted markedly with wetland soils in which phosphate monoesters and diesters maintained approximately equal proportions, which is attributed to the limited reactive clay surfaces for stabilization and/or decomposition of myo-inositol hexakisphosphate under frequent anaerobic conditions. Most organic phosphorus compounds in soil chronosequences increase with age to reach a maximum and then decline with time, although the apex varies significantly among different organic phosphorus compounds and chronosequences. Variations of the potential for phosphorus stabilization resulting from mineralogical transformation, changes in phosphorus sources due to shifts in plant and microbial communities, and differences in the biological utilization of various phosphorus compounds have been suggested as three main mechanisms controlling the temporal changes in organic phosphorus species, abundance and availability during natural ecosystem development. In agricultural soils, the amounts, forms, and dynamics of organic phosphorus are determined by internal soil properties, external environmental conditions and managements, including the history and intensity of land use, different tillage practices and fertilizer treatments. These mechanisms are interlinked and more research is required to isolate both internal and external factors that regulate organic phosphorus transformation in agricultural ecosystems. Given the universal dependence on organic phosphorus for life and its critical roles in biogeochemical cycling, we put forward several open questions that need to be resolved in the future studies by emphasizing the multidisciplinary collaborations, the use of multiple analytical techniques and the establishment of quantitative organic phosphorus transformation models.

Increasing acid deposition and intense nitrogen (N) fertilization have resulted in severe soil acidification in many regions of the world. However, the soil acidification rate, especially quantitative contributions of different proton (H+) sources remain unclear in various cropping systems. In this study, a two-year field lysimeter experiment was conducted with a set of different N fertilization treatments (0, 100, 200 and 400 kg N ha−1 yr−1) for maize crop in typical red soil in subtropical China. The pathways and budgets of different H+ sources were quantified by calculating the input–output balance of major elements. Results showed that fertilization significantly accelerated soil acidification by increasing the leaching of NO3– and base cations (K+, Ca2+, Na+, and Mg2+) as well as increasing the cation removals by plant uptake and harvest. Unbalanced plant uptake of anions and cations was the primary H+ source (64.4–80.5%) to soils. Plants have an important effect on soil acidification by redistributing cations in soils. Due to cation removals by plant uptake and harvest, there were significant decreases of soil exchangeable base cations under high urea-N treatments (200 and 400 kg N ha−1 yr−1) and significant increases of soil exchangeable H+ and Al3+ under three fertilization treatments. Of course, N transformation also plays an important role (12.1% to 38.8%). However, the effect of direct H+ deposition is minor in this area comparatively (5.78% to 7.34%). Quantification of acidification contribution of different sources is useful for the establishment of further soil remediation practices. The field management is considered very important to alleviate soil acidification, including increasing straw return and controlling fertilizer application.

Nitrate contamination of water bodies is a serious concern in regions with intensive agriculture. Previous studies, which only considered surface water and groundwater but not the regolith, do not provide a comprehensive accounting of nitrate sources and their proportional contributions in the Critical Zone, which extends from the top of the vegetation canopy down to the bottom of the fresh groundwater. In this study, dual nitrate isotopes, hydrochemical compositions and a Bayesian isotope mixing model were used to investigate nitrate sources, processes and individual source contributions across surface water, regolith and groundwater at the Red Soil Critical Zone Observatory of China. Denitrification was found to be weak in the Critical Zone. Dilution processes were important in eliminating nitrate from streamflow and groundwater. More than 90% of the nitrate inventory was stored at depths from 1 m to the bedrock surface in the upland regolith. Nitrate with light nitrogen (14N) isotopes was preferentially adsorbed by the variable charge soils with the help of weak electrostatic attraction. The contribution of soil organic N (SON) to the nitrate in the upland catchment streamflow was found to be highest with a mean of 56%, followed by manure and sewage (MS, 26%), NH4+ in chemical fertilizers (CF, 17%). For the paddy subcatchment streamflow, the contribution of SON (68%) was highest, followed by CF (19%) and MS (13%). In contrast, for the groundwater, the contributions of CF and SON were 60% and 36%, respectively. For the regolith, the contributions of CF and SON were 72% and 25%, respectively. Thus the most important sources of nitrate were SON for the streamflow and CF for the groundwater and regolith. These findings show that the different partitioning and isotopic fractionation within the regolith strongly affect the sources of nitrate reaching groundwater, compared to the sources reaching surface water.

Nitrate accumulation at depth in variable charge soils in humid tropics and subtropics affects nitrogen (N) leaching to groundwater. However, the mechanisms on the nitrate accumulation in relation to regolith (soil and saprolite) properties are poorly understood. In this study, four upland regoliths were selected in a typical red soil Critical Zone of humid subtropical China. These regoliths with a thickness of 6–8 m, which developed from Quaternary red clay underlain by sandstone bedrock, were acidic, highly weathered, and clay loam to clay in texture. We analyzed the relationships between nitrate concentrations and the regolith physiochemical properties. The results showed that regolith pH was negatively correlated with nitrate concentrations, whereas crystalline iron (Fe) and aluminum (Al) and anion exchange capacity (AEC) were positively correlated with nitrate concentrations at depths below both soil surface and 1 m. Bulk density (BD) was significantly related to nitrate concentrations only at depths below soil surface, while depth, clay, amorphous Fe and Al, total organic carbon (C), and total N were significantly related to nitrate concentrations only at depths below 1 m. There was no significant correlation between nitrate concentrations and sand, silt, silicate bound Fe or Al, C/N, or moisture at depths below both soil surface and 1 m. Based on the random forest analysis, the relative contributions of pH, crystalline Fe, depth, AEC, BD, crystalline Al and amorphous Fe to explaining nitrate concentration variations were 28.3%, 9.5%, 4.3%, 3.4%, 2.9%, 2.8% and 2.6%, respectively. The concentration of crystalline Fe was ten times that of crystalline Al, which would account for its larger contribution to the nitrate variations. Nitrate accumulation at depth was most likely controlled both by electrostatic adsorption on crystalline Fe and Al oxides and low hydraulic conductivity of the regolith at depth, which appeared to be largely influenced by regolith pH and competitive anions. Our findings shed light on regolith internal property controls on nitrate legacy in the subtropical vadose zone and may help control nitrate contamination of groundwater in intensified agricultural regions.

There is evidence that high levels of nitrate are stored in Earth’s Critical Zone between the land surface and impermeable bedrock. While nitrate in the upper layers of the soil ( 1 m). To study controls on nitrate accumulation in a subtropical monsoon area, a total of 728 regolith samples, taken from land surface to fresh bedrock, were collected from 21 drillings in a typical red soil Critical Zone in southern China. We characterized the variation of nitrate in these deep horizons and investigated the effect of land use, slope position and regolith physiochemical properties. The results showed that the amount of nitrate at 240-380 cm depth was more stable than at 100-240 cm or 380-500 cm depth, and accumulated at that depth in the upland and orchard regoliths. Nitrate contents in the deep horizons of upland and orchard regoliths were significantly larger than that in the paddy fields or woodland (p

Fisetin, a natural flavonoid found in a variety of edible and medical plants, has been suggested to inhibit the proliferation of various tumor cells and to induce apoptosis. However, the effects of fisetin on breast cancer have rarely been reported and the underlying mechanism is still undefined. The present study explored the anti-cancer effects of fisetin on mammary carcinoma cells and the underlying mechanisms. Following treatment with fisetin, viability of 4T1, MCF-7 and MDA-MB-231 cells were measured by MTT assay. The inhibitory effects of fisetin on proliferation, migration and invasion were evaluated in 4T1 cells using proliferation array, wound-healing assay, and HUV-EC-C-cell barrier based on electrical cell-substrate impedance sensing platform. Cell apoptosis was analyzed by flow cytometry, and western blotting analysis was performed to identify target molecules. A 4T1 orthotopic mammary tumor model was used to assess the fisetin-inhibition on tumor growth in vivo. Test kits were used to examine the liver and kidney function of tumor-bearing mice. The results suggest that fisetin suppressed the proliferation of breast cancer cells, suppressed the metastasis and invasiveness of 4T1 cells, and induced the apoptosis of 4T1 cells in vitro. The potent anti-cancer effect of fisetin was associated with the regulation of the phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin pathway. In vivo experiments demonstrated that fisetin suppressed the growth of 4T1 cell-derived orthotopic breast tumors and enhanced tumor cell apoptosis, and the evaluated alanine amino transferase and aspartate amino transferase levels in serum of tumor-bearing mice suggested that fisetin may lead to side effects on liver biochemical function. The present study confirms that fisetin exerted an anti-mammary carcinoma effect. However, in vivo experiments also revealed that fisetin had low solubility and low bioavailability. Further investigation is required to determine the clinical value of fisetin.

Soil organic matter (SOM) is a key property determining soil functions and a major form of carbon stored in soil. Understanding the spatial and temporal variability of SOM and the driving forces responsible for spatial and temporal changes is important to assess regional soil quality and carbon sequestration potential and, particularly, to establish better practices for land use and management. We evaluated the spatio-temporal change in SOM content from 1979–1982 to 2006 and its driving forces in Jiangsu Province, East China, using geostatistics. The results showed that mean SOM content increased from 16.60 ± 8.50 to 18.31 ± 8.32 g/kg over a 26-yr period. The maps of SOM generated by ordinary kriging represented the increasing trend from north to south across the province in the two periods. The level of SOM in 1979–1982 affected the pattern of change: the SOM increasing in areas initially with a small content while decreasing in areas having a large content. The map of SOM change showed that the rate of increase decreased from north to south within the province. Increased fertilizer application promoted crop production with more residual biomass being retained in the soil, which resulted in increased SOM content. Land use changes to paddy, upland or forest improved SOM content, whereas abandoning land reduced SOM content.

Dynamic changes in Fe oxides and magnetic properties during natural pedogenesis are well documented, but variations and controls of Fe and magnetism changes during anthropedogenesis of paddy soils strongly affected by human activities remain poorly understood. We investigated temporal changes in different Fe pools and magnetic parameters in soil profiles from two contrasting paddy soil chronosequences developed on calcareous marine sediment and acid Quaternary red clay in Southern China to understand the directions, phases and rates of Fe and magnetism evolution in Anthrosols. Results showed that paddy soil evolution under the influence of artificial submergence and drainage caused changes in soil moisture regimes and redox conditions with both time and depth that controlled Fe transport and redistribution, leading to increasing profile differentiation of Fe oxides, rapid decrease of magnetic parameters, and formation of diagnostic horizons and features, irrespective of the different parent materials. However, the initial parent material characteristics (pH, Fe content and composition, weathering degree and landscape positions) exerted a strong influence on the rates and trajectories of Fe oxides evolution as well as the phases and rates of magnetism changes. This influence diminished with time as prolonged rice cultivation drove paddy soil evolving to common pedogenic features.

article i nfo Chronosequencesand associated space-for-time substitutionsare animportant and fruitful means for investigat- ing the rates and directions of soil and ecosystem evolution across multiple time-scales ranging from decades to millions of years. Thispaperreviews the useof chronosequencesfor studying biogeochemistry of paddy soil evo- lution to improve our understanding of the fundamental processes, the dynamic changes in soil properties and the associatedenvironmentalthresholdsatdifferentstagesofpaddysoilevolutionundertheintensiveanthropo- genic managements. Rice paddy cultivation results in accumulations of various nutrients (e.g. organic carbon, ni- trogen, and phosphorus) over a much longer time period than predicted by typical long-term (b50 years) field experiments, although it is not clear how long it takes paddy soils with different origins to reach a steady-state of these important nutrients. Extensive investigations of a 2000-year paddy soil chronosequence derived from calcareous marine sediments in the coastal region of Zhejiang Province (P.R. China) illustrate three phases of paddy soil evolution and the associated pedogenic thresholds: an initial phase during the first few decades dom- inated by rapid desalinization, loss of magnetic susceptibility, accumulation of topsoil organic matter and forma- tion of a compacted plow pan due to extrinsic thresholds resulting from anthropogenic activities; the second phaselastsseveralcenturiescomprisingFeandclayenrichmentintheilluvialhorizon,andthelossofphosphorus

This study aims to understand how clay minerals change sequentially with paddy cultivation age and how parent materials (or original soils) affect the clay mineral behavior of paddy soils. Three paddy soil chronosequences in the hilly regions of South China, derived from purple sandy shale (PS), Quaternary red clays (RC), and red sandstone (RS), were selected to explore the dynamic changes in clay mineralogy, by comparing physical, chemical, and mineralogical properties of soil sequences. For RC and RS soils, both of which have a low K content, there was little change in the clay minerals. Long-term paddy cultivation can promote formation of illite-like minerals; however, this form of K storage was limited under present farming conditions. In PS soils, which are abundant in K-bearing minerals, the depotassication was strong, accompanied by marked transformation of clay minerals. Kaolinite-like minerals gradually decreased with paddy cultivation age; by contrast, derivative clay minerals such as secondary chlorite and halloysite gradually increased. Strong depotassication mainly occurred in the nonclay fractions. The rate of depotassication and the generation of clay fractions were much faster than in natural soils. The clay minerals of paddy soils mainly followed the feature of their original soils. Their evolutions could be distinguished based on their constituents, which are greatly affected by their parent materials. Moreover, paddy cultivation is able to modify clay mineralogy, according to the original mineralogy and paddy soil management.

Anaerobic ammonium oxidation coupled to iron(III) reduction (termed Feammox) with dinitrogen, nitrite, or nitrate as the end-product is a recently discovered process of nitrogen cycling. However, Feammox has not been described in paddy soils, which are rich in iron(III) oxides and subjected to intensive nitrogen fertilization. Here, evidence for Feammox in a paddy soil chronosequence with a gradient of microbially reducible iron(III) levels was obtained in Southern China using (15)N-labeled ammonium-based isotopic tracing and acetylene inhibition techniques. Our study demonstrated the occurrence of Feammox in the chronosequence, and direct dinitrogen production was shown to be the dominant Feammox pathway. Within the chronosequence, three paddy soils with higher microbially reducible iron(III) levels had higher Feammox rates (ranged from 0.17 to 0.59 mg N kg(-1) d(-1)) compared to an uncultivated soil (0.04 mg N kg(-1) d(-1)). It is estimated that a loss of 7.8-61 kg N ha(-1) year(-1) is associated with Feammox in the examined paddy soils. Overall, we discover that rice cultivation could enrich microbially reducible iron(III), accelerate Feammox reaction and thus fuel nitrogen loss from soils, and suggest that Feammox could be a potentially important pathway for nitrogen loss in paddy soils.

Information on the dynamics of phosphorus (P) fraction and sorption–desorption characteristics of paddy soils with long cultivation history is essential to improve our understanding of P transformation and transport in agro-ecosystems and critical for sustainable and environment-friendly soil management. We investigated changes in P fraction and sorption–desorption characteristics in topsoils from two contrasting paddy chronosequences developed on calcareous marine sediments at Cixi and acidic quaternary red clays at Jinxian, respectively, in subtropical China. Both chronosequences showed similar patterns and pedogenetic trends of their topsoil P status. Total P (PT) and various P fractions (calcium-associated P (PCa), organic P (Po), non-occluded and occluded P) accumulated to a maximum after 50-yrs and 150-yrs of cultivation, respectively, at Cixi and Jinxian due to P addition, consistent with the prior agronomic field studies on decadal time scales. However, rapid decrease of PT occurred in the older paddy soils at both sites, despite the continuous P additions, which we attributed to the decline of P sorption capacity since P sorbents (CaCO3, Fe- and Al-oxides, and clay) rapidly decreased. Compared with Walker and Syers’ model of gradual P depletion and decreasing bioavailabity in natural ecosystems, our results show that long-term paddy cultivation alters both the rate and trajectory of topsoil P transformations during agro-ecosystem development. The ability of the topsoil to sorb added P decreased with paddy cultivation history in both chronosequences, due to the decline in the maximum P sorption capacity (Smax); whereas the P release potential increased as a result of paddy cultivation at both sites, as indicated by the higher degree of P saturation (DPS) and greater P desorbability in the paddy soils than the uncultivated soils. Our study suggests that after long-term cultivation paddy soils are getting degraded by lowering their P holding capacity so may enhance the P release potential and lead to increasing environmental risk through P loss.

The biogeochemical cycles of nitrogen (N) and base cations (BCs), (i.e., K+, Na+, Ca2+, and Mg2+), play critical roles in plant nutrition and ecosystem function. Empirical correlations between large experimental N fertilizer additions to forest ecosystems and increased BCs loss in stream water are well demonstrated, but the mechanisms driving this coupling remain poorly understood. We hypothesized that protons generated through N transformation (PPRN)—quantified as the balance of NH4+ (H+ source) and NO3− (H+ sink) in precipitation versus the stream output will impact BCs loss in acid-sensitive ecosystems. To test this hypothesis, we monitored precipitation input and stream export of inorganic N and BCs for three years in an acid-sensitive forested watershed in a granite area of subtropical China. We found the precipitation input of inorganic N (17.71 kg N ha−1 year−1 with 54% as NH4+–N) was considerably higher than stream exported inorganic N (5.99 kg N ha−1 year−1 with 83% as NO3−–N), making the watershed a net N sink. The stream export of BCs (151, 1518, 851, and 252 mol ha−1 year−1 for K+, Na+, Ca2+, and Mg2+, respectively) was positively correlated (r = 0.80, 0.90, 0.84, and 0.84 for K+, Na+, Ca2+, and Mg2+ on a monthly scale, respectively, P

Alzheimer’s disease (AD) is the most common form of dementia, characterized by progressive loss of memory and cognitive dysfunctions. A central pathological event of AD is accumulation and deposition of cytotoxic amyloid-βpeptide (Aβ) in the brain parenchyma. Heparan sulfate proteoglycans (HSPGs) and the side chains heparan sulfate (HS) are found associated with Aβdeposits in the brains of AD patients and transgenic animal models of AD. A growing body of evidence fromin vitroandin vivostudies suggests functional roles of HSPG/HS in Aβpathogenesis. Although the question of “how and why HSPG/HS is codeposited with Aβ?” still remains, it is within reach to understand the mechanisms of the events. Recent progress by immunohistochemical examination with advanced antibodies shed light on molecular structures of HS codeposited with Aβ. Several recent reports have provided important new insights into the roles of HSPG in Aβpathogenesis. Particularly, experiments on mouse models revealed indispensible functions of HSPG in modulating Aβ-associated neuroinflammation and clearance of Aβfrom the brain. Application of molecules to interfere with the interaction between HS and Aβpeptides has demonstrated beneficial effects on AD mouse models. Elucidating the functions of HSPG/HS in Aβdeposition and toxicity is leading to further understanding of the complex pathology of AD. The progress is encouraging development of new treatments for AD by targeting HS-Aβinteractions.

Soil Sci. Soc. Am. J. 77:2078–2088 doi:10.2136/sssaj2013.01.0033 Received 23 Jan. 2013. *Corresponding author: (glzhang@issas.ac.cn). © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Pedogenic Transformation of Phosphorus during Paddy Soil Development on Calcareous and Acid Parent Materials Pedology

Elemene (ELE), a natural plant drug extracted from Curcumae Rhizoma, has been widely used for cancer treatment in China for more than 20 years. Although it is reported to be a broad‑spectrum anticancer drug, the mechanism underlying the action of ELE in the treatment of breast cancer remains to be fully elucidated. Heparanase, a mammalian endo‑D‑glucuronidase, is involved in degradation of the extracellular matrix (ECM), and thus promotes tumor progression and metastasis. The downregulation of heparanase can effectively reduce tumor malignant behaviors. In the present study, the inhibitory effects of ELE were evaluated in breast cancer cells using a Cell Counting kit 8 assay. The migratory and invasive capabilities of cancer cells were investigated using a wound healing assay, real‑time cell analysis and a Transwell assay. In addition, western blot analysis was used to assess alterations in the expression levels of key proteins. The present results confirmed the antiproliferative and antimetastatic effects of ELE, using low‑molecular weight heparin (LMWH) as a positive control. In addition, ELE was demonstrated to downregulate the expression of heparanase, and decrease the phosphorylation of extracellular signal‑regulated kinase and AKT. These findings suggested that ELE may be a promising agent targeting heparanase in the treatment of breast cancer.

Global nitrogen (N) emission and deposition have been increased rapidly due to massive mobilization of N which may have long-reaching impacts on ecosystems. Many agricultural and forest ecosystems have been identified as secondary N sources. In the present study, the input-output budget of inorganic N in a small forested watershed of subtropical China was investigated. Inorganic N wet deposition and discharge by stream water were monitored from March, 2007 to February, 2009. The concentrations and fluxes of inorganic N in wet precipitation and stream water and net retention of N were calculated. Global N input by dry deposition and biological fixation and N output by denitrification for forested watersheds elsewhere were reported as references to evaluate whether the studied forested watershed is a source or a sink for N. The results show that the inorganic N output by the stream water is mainly caused by NO3(-)-N even though the input is dominated by NH4(+)-N. The mean flux of inorganic N input by wet precipitation and output by stream water is 1.672 and 0.537 g N/(m2 x yr), respectively, which indicates that most of inorganic N input is retained in the forested watershed. Net retention of inorganic N reaches 1.135 g N/(m2 x yr) considering wet precipitation as the main input and stream water as the main output. If N input by dry deposition and biological fixation and output by denitrification are taken into account, this subtropical forested watershed currently acts as a considerable sink for N, with a net sink ranging from 1.309 to 1.913 g N/(m2 x yr) which may enhance carbon sequestration of the terrestrial ecosystem.

Soil ingestion is an important human exposure pathway of heavy metals in urban environments with heavy metal contaminated soils. This study aims to assess potential health risks of heavy metals in soils sampled from an urban environment where high frequency of human exposure may be present. A bioaccessibility test is used, which is an in vitro gastrointestinal (IVG) test of soluble metals under simulated physiological conditions of the human digestion system. Soil samples for assessing the oral bioaccessibility of arsenic (As) and lead (Pb) were collected from a diverse range of different land uses, including urban parks, roadsides, industrial sites and residential areas in Guangzhou City, China. The soil samples contained a wide range of total As (10.2 to 61.0 mg kg(-1)) and Pb (38.4 to 348 mg kg(-1)) concentrations. The bioaccessibility of As and Pb in the soil samples were 11.3 and 39.1% in the stomach phase, and 1.9 and 6.9% in the intestinal phase, respectively. The As and Pb bioaccessibility in the small intestinal phase was significantly lower than those in the gastric phase. Arsenic bioaccessibility was closely influenced by soil pH and organic matter content (r (2) = 0.451, p 0.01) in the stomach phase, and by organic matter, silt and total As contents (r (2) = 0.604, p 0.001) in the intestinal phase. The general risk of As and Pb intake for children from incidental ingestion of soils is low, compared to their maximum doses, without causing negative human health effects. The exposure risk of Pb in the soils ranked in the order of: industrial area/urban parks residential area/road side. Although the risk of heavy metal exposure from direct ingestion of urban soils is relatively low, the risk of inhalation of fine soil particulates in the air remains to be evaluated.

Energy use in urbanization has fundamentally changed the pattern and fluxes of carbon cycling, which has global and local environmental impacts. Here we have investigated organic carbon (OC) and black carbon (BC) in six soil profiles from two contrast zones in an ancient city (Nanjing) in China. BC in soils was widely variable, from 0.22 to 32.19 g kg(-1). Its average concentration in an ancient residential area (Zone 1) was, 0.91 g kg(-1), whereas in Zone 2, an industrial and commercial area, the figure was 8.62 g kg(-1). The ratio of BC/OC ranged from 0.06 to 1.29 in soil profiles, with an average of 0.29. The vertical distribution of BC in soil is suggested to reflect the history of BC formation from burning of biomass and/or fossil fuel. BC in the surface layer of soils was mainly from traffic emission (especially from diesel vehicles). In contrast, in cultural layers BC was formed from historical coal use. The contents of BC and the ratio of BC/OC may reflect different human activities and pollution sources in the contrasting urban zones. In addition, the significant correlation of heavy metals (Cu, Pb, and Zn) with BC contents in some culture layers suggests the sorption of the metals by BC or their coexistence resulted from the coal-involved smelting.

Magnetic susceptibility ( χ lf ) and other magnetic parameters of 11 typical profiles of Quaternary Red Clay (QRC) in subtropical China were measured. χ lf curves of the QRC profiles show similar vertical variations: χ lf of the uppermost yellow-brown earth (YBE) and uniform red clay (URC) of the profiles is high, mostly ranging from 50 to 150 × 10 − 8 m 3 kg − 1 ; that of the reticulate red clay (RRC) sharply decreases downwards. Especially in the Lower RRC (LRRC) with dense reticulate pattern, χ lf is often less than 10 × 10 − 8 m 3 kg − 1 . Grain-size characteristics and geochemical properties of the QRC suggest that the sharp decrease of χ lf in the RRC is not related to sudden change of parent materials, but to the formation of the reticulate pattern. Further study indicates that pedogenic fine ferrimagnetic minerals (FM) (superparamagnetic particles (SP) and/or stable single domain (SSD)) are the main magnetic carriers of the QRC. The YBE and URC, with higher χ lf , show low coercivity and magnetic soft behavior; the RRC, especially the LRRC, with weak magnetism, shows high coercivity and magnetic hard behavior. The temperature-dependent susceptibility (TDS) of the QRC suggests that the dominant type of FM in the YBE and URC is pedogenic maghemite; the RRC, especially the LRRC, however, contains little maghemite but a trace amount of lithogenic multi-domain (MD) magnetite inherited from the parent rock. During post-depositional hydromorphic processes, pedogenic maghemite was more easily dissolved than hematite, which caused the sharp decrease of χ lf in the RRC. As χ lf of the QRC was mainly controlled by the intensity of hydromorphic processes, rather than the weathering degree, χ lf of the QRC in subtropical China cannot accurately indicate the paleoclimate during the Quaternary period, when the red clay was initially formed.

Pedogenetic soil horizons are one of the fundamental building blocks of modern soil classiflcation; however, in soils of urban areas which are often strongly disturbed by human activities, horizons are difficult to distinguish but substitutive morphological layers may be identifled. To identify the characteristic soil layers in an urban environment, 224 soil layers of 36 in-situ pedons were examined and described in urban and suburban Nanjing, and 27 variables were extracted for multivariate analysis. Three groups and six subdivisions were identifled by TwoStep cluster analysis combined with hierarchical cluster analysis based on factor scores. Soil forming factors and soil forming processes could be interpreted from the principal component analysis (PCA) of variables, cluster analysis of soil layers, and discriminant analysis of soil layer groups and their subdivisions. Parent materials, moisture regimes, organic matter accumulation, and especially nutrient accumulation were the main causes of characteristic soil layer formations. The numerical approaches used in this study were useful tools for characteristic soil layer identiflcation of urban soils.

The vertical distribution and migration of Cu, Zn, Pb, and Cd in two forest soil proflles near an industrial emission source were investigated using a high resolution sampling method together with reference element Ti. One-meter soil proflle was sectioned horizontally at 2 cm intervals in the flrst 40 cm, 5 cm intervals in the next 40 cm, and 10 cm intervals in the last 20 cm. The migration distance and rate of heavy metals in the soil proflles were calculated according to their relative concentrations in the proflles, as calibrated by the reference element Ti. The enrichment of heavy metals appeared in the uppermost layer of the forest soil, and the soil heavy metal concentrations decreased down the proflle until reaching their background values. The calculated average migration rates of Cd, Cu, Pb, and Zn were 0.70, 0.33, 0.37, and 0.76 cm year −1 , respectively, which were comparable to other methods. A simulation model was proposed, which could well describe the distribution of Cu, Zn, Pb, and Cd in natural forest soils.

There is a need for accurate estimate of soil organic carbon (SOC) stocks for understanding the role of alpine soils in the global carbon cycle. We tested a method for mapping digitally the continuous distribution of the SOC stock in three dimensions in the northeast of the Tibetan Plateau. The approach integrated the spatial distribution of the mattic epipedon which is a special surface horizon widespread and rich in organic matter in Tibetan grasslands. Prediction models resulted in high prediction accuracy. An average SOC stock in the mattic epipedon was estimated to be 4.99 kg m−2 in a mean depth of 14 cm. The amounts of SOC in the mattic epipedon, the upper 30 cm and 50 cm accounted for about 21%, 80% and 89%, respectively, of the total SOC stock in the upper 1 m depth. Compared with previous estimates, our approach resulted in more reliable predictions. The mattic epipedon was proven to be an important factor for modelling the realistic distribution of the SOC stock in Tibetan grasslands. Vegetation-related covariates have the most important influence on the distribution of the mattic epipedon and the SOC stock in the alpine grassland soils of northeast Tibetan Plateau.

Potential toxic elements (PTEs) in urban soils are of great environmental concern because of their potential long-term effects on human health. A systematic soil geochemical survey was performed across central urban districts of Guangzhou, the largest city in southern China. Surface soil samples (0–10 cm) were collected from 426 sites in order to evaluate the environmental quality of this urban area. Geostatistical and multivariate analysis (principal component, clustering, and correlation) were applied to generate spatial distribution maps of PTEs concentrations as well as identify possible sources of metals. The results showed that PTEs ranged widely in value; Arsenic, Hg, Pb, Cu Zn, Cd, Ni, and Mn ranged from 1.4 to 144, 0.01 to 12.2, 18.5 to 4903, 5.0 to 417, 10.1 to 1795, 0.03 to 2.41, 2.5 to 77.6, and 21.2 to 1286 mg/kg, respectively. Iron ranged from 6.1 to 61.8 g/kg. Soils were enriched with Cd, Cu, Hg, Mn, Pb and Zn as compared with soil background values of Guangzhou. Spatial distribution maps indicated similar distribution patterns of Cd, Cu, Pb and Zn. Urbanization history and industrial activities affected the accumulation of PTEs. Relatively higher concentrations of As, Cd, Cu, Hg, Pb and Zn were found in districts with a longer history of urbanization and industrial activities, such as the Liwan district along the Pearl River in western Guangzhou. This area was the most highly contaminated, whereas the Tianhe, a district with a limited time of development, was the least contaminated. Multivariate statistical analysis showed distinctly different associations among the studied metals; suggesting that Fe, Ni and Mn were predominantly derived from a natural (geological) source; As, Cu, Hg, Pb and Zn from anthropogenic sources; and Cd from both sources. Present PTEs levels were also compared with those reported from other urban areas around world, and results indicate that further studies on assessing both the human and ecosystem risks associated with urban contaminated soils will be necessary.

Human activities can affect the biogeochemical cycling of phosphorus substantially. However, the relationship between P accumulation and urban development process is largely unknown. This study investigated the influence of urban development on the P accumulation in urban and suburban soils, using Nanjing (China) as a case. Based on its urban development history, Nanjing was divided into suburban and urban area, and the urban area was subdivided into urban north and urban south. Soil total P (TP) and available P (AP) of 578 samples from 68 pedons at different locations were measured. Thickness-weighted mean P content of each pedon (P w ), P content of the surface soil layer (P s ), the highest P content of each pedon (P h ), and the lowest P content (P l ) of each pedon were selected as statistical indices. Compared with the background value, urban and suburban soils were enriched in P. The highest TP content was up to 11.14 g P kg -1 , and the highest AP content was up to 360 mg P kg -1 . However, analysis of variance (ANOVA) and multiple comparisons of P w, P s, P h, P l showed that urban south with longest residential history had the highest TP w, TP s TP h, and AP w, AP l contents, and urbanizing suburban had the lowest TP w and AP w, AP l contents. For both APs and AP h, there was no significant difference between suburban and urban area. However, significant differences between urban south and urban north were observed. The results demonstrated that urban development process, including population quantity and level of urban infrastructure, could influence soil P accumulation and distribution in urban environment. A more detailed assessment is required to avoid the potential secondary eutrophication caused by excess P release from those anthropogenic high-P soils.

Soils in urban areas are often artificially formed and preserved as cultural layers in which soil materials are mixed with artifacts. The vertical change of soil properties denotes the historical change of human activities, and therefore, urban soil can be considered as a record of history of urban development. We studied a deep profile of urban soil (600 cm) in Nanjing, China, by intensively sampling at every 5 cm. Soil samples were analyzed for lead content. Charcoal from several layers was found and was dated using 14C to recognize archaeological cultural layers that might be formed in different Chinese dynasties. Pb isotope ratios were determined by thermal ionization mass spectrometry (TIMS) technology. The study found that artificial deposition, i.e., the formation of cultural layer started about 1700 years ago and lasted until recently. All cultural layers above the original loess were heavily contaminated by Pb with total content varying from 100 mg kg− 1 to more than 2000 mg kg− 1. There were several historical periods in which Pb content peaked, indicating significant contamination by human activities, such as ancient ore smelting for various purposes and use of Pb-containing materials for handicraft manufacture. Various Pb isotope ratios of the cultural layers differed substantially from that of the original undisturbed loess in the deepest position. 206Pb/207Pb value decreased gradually from the bottom layer to top layer, although with occasional exceptions, indicating a long-lasting mixing of extraneous sources of Pb during the entire history since ca. 300 A.D. In comparison with the isotope ratios of lead ores of different sources and that of aerosols, it was illustrated that the source of Pb in cultural layers might come from lead ores of southern China in the earlier dynasties, while Pb from north China might have contributed to the Pb source in the more recent years, suggested by the lowering of 206Pb/207Pb ratio in the near-surface cultural layers. However, the impact of petrol burning on cultural layers was basically excluded, considering the relatively short history of petroleum use in this area.

As a crucial factor of water eutrophication, nitrogen (N) discharge by agricultural non-point sources (NPS) has become a worldwide concern, and so has its relationship to land use. This study was aimed at the quantitative relationships between N discharge by stream and land use. It was conducted in the Meicun watershed of Xuancheng County, Anhui Province, in the subtropical low hilly area of China. The study integrated dynamic monitoring of nutrient discharge by stream water and Geographic Information Systems (GIS) analysis of land use of the watershed. Results showed that NO 3 − -N discharge ranged between 50 and 60% of the total nitrogen (T-N) and was 2.5–3.0 times as much as NH 4 + -N. There was a significant difference between forested and mixed sub-watersheds for NH 4 + -N, NO 3 − -N and T-N concentrations. Significant correlations existed between NH 4 + -N, NO 3 − -N and T-N concentrations in stream water and the area percentages of forest and paddy fields. The study found that the discharges of NH 4 + -N, NO 3 − -N and T-N decreased exponentially with forest area increase, but a steep decline for NO 3 − -N and T-N seemed to occur when the forest percentage surpassed 70% and then there was almost no change. Similarly, the discharges of NH 4 + -N, NO 3 − -N and T-N increased exponentially with the paddy fields increase, but a steep augmentation occurred for NO 3 − -N and T-N when the paddy percentage surpassed 20% and then it remained at a plateau. The study showed that in the subtropical hilly region, paddy fields could increase N discharge due to farming management practices. Thus, primary measures to reduce N in the receiving water body would include a change in farming management and building an ecological interception system for paddy fields.

Surface soil (0–10 cm) samples from 53 sampling sites including rural and urban areas of Hong Kong were collected and analyzed for 16 EPA priority polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations were in the range of 7.0–410 μg kg−1 (dry wt), with higher concentrations in urban soils than that in rural soils. The three predominant PAHs were Fluoranthene, Naphthalene and Pyrene in rural soils, while Fluoranthene, Naphthalene and Benzo(b + k)fluoranthene dominated the PAHs of urban soils. The values of PAHs isomer indicated that biomass burning might be the major origin of PAHs in rural soils, but vehicular emission around the heavy traffic roads might contribute to the soil PAHs in urban areas. A cluster analysis was performed and grouped the detectable PAHs under 4 clusters, which could be indicative of the PAHs with different origins and PAHs affected by soil organic carbon contents respectively.

About 150 soil samples from 20 urban and 3 non-urban soil profiles in Nanjing were analyzed for total concentrations of Cu, Zn, Pb and Cr using ICP spectrometry. The Cu, Zn, Pb and Cr of 23 urban and non-urban topsoils (A horizon soils) were sequentially extracted into 5 fractions according to the method of Tessier [Anal. Chem. 51 (1979) 844]. Total Cu, Zn, Pb and Cr concentrations of the urban soils were 84.7 (48.1–139.7), 66.1 (12.2–869.4), 162.6 (57.7–851.6) and 107.3 (36.3–472.6) mg kg−1, respectively. The soils were polluted with Cu, Zn and Cr to some extent and heavily polluted with Pb. For 20 urban topsoils, the Cu, Zn, Pb and Cr were dominated by the residual fraction and were least present in exchangeable fraction. On average, the order of Cr, Cu in each fraction was residual (92.9%, 66.1%)≫organic (4.2%, 23.4%)>Fe–Mn oxide (2.7%, 5.4%)>carbonate (0.2%, 4.7%)>exchangeable (0.04%, 0.38%), Zn followed the order residual (60.0%)≫Fe–Mn oxides (19.1%)>carbonate (11.6%)>organic (8.8%)>exchangeable (0.5%), Pb was residual (56.8%)>Fe–Mn oxide (30.9%)≫organic (6.3%)>carbonate (5.2%)>exchangeable (0.8%). The percentage of residual Cu and Zn decreased with the increase of total Cu and Zn concentrations. The proportion of residual Pb increased with the increase of total P. The mobility and bioavailability of heavy metals were Pb>Zn>Cu>Cr. Cu, Zn and Pb were more mobile and bioavailable in the urban than in the non-urban soils; however, Cr was similar.

Shan Liu,1,2 Wei Huang,1,2 Ming-Ji Jin,1,2 Qi-Ming Wang,1,2 Gan-Lin Zhang,3 Xiao-Min Wang,3 Shuai Shao,1,2 Zhong-Gao Gao1,2 1State Key Laboratory of Bioactive Substance and Function of Natural Medicines, 2Department of Pharmaceutics, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, People’s Republic of China; 3Beijing Hospital of Traditional Chinese Medicine affiliated to Capital Medical University, Beijing, People’s Republic of China Abstract: To our knowledge, the mechanism underlying the high transfection efficiency of ­alkylated low-molecular-weight polyethylenimine (PEI) is not yet well understood. In this work, we grafted branched PEI (molecular weight of 1,800 Da; bPEI1800) with lauryl chains (C12), and found that bPEI1800-C12was structurally similar to gemini surfactant and could similarly assemble into micelle-like particles. Stability, cellular uptake, and lysosome escape ability of bPEI1800-C12/DNA polyplexes were all greatly enhanced after C12grafting. bPEI1800-C12/DNA polyplexes exhibited significantly higher transfection efficiency than Lipofectamine™ 2000in the presence of serum. Bioluminescence imaging showed that systemic injection of bPEI1800-C12/DNA polyplexes resulted in intensive luciferase expression in vivo and bioluminescence signals that could be detected even in the head. Altogether, the high transfection efficacy of bPEI1800-C12was because bPEI1800-C12, being an analog of gemini surfactant, facilitated lysosome escape and induced the coil–globule transition of DNA to assemble into a highly organized micelle-like structure that showed high stability. Keywords: self-organization, alkylation, luciferase, bioluminescence imaging

This study was carried out in the Xujiawan watershed in Sichuan Province, China. The area is characterized by easy weathering of bedrock (sedimentary sandstone and shale) and vulnerability to erosion due to coarse soil texture and weak soil structure. The objective of this study was to understand the dynamics of nitrogen (N) and phosphorus (P) losses during typical storm events. The results showed that runoff generation was sudden and ephemeral, giving rise to flash floods with sharp, narrow hydrographs and short time lags in this type of agricultural ecosystems. The time lag effect of runoff formation depended on soil conditions before storm events. Suspended solids (SS) concentration peaks occurred at the beginning of the storm flow and decreased as rainfall progressed. Meanwhile, SS losses increased at the beginning of runoff flow, then decreased due to flow volume change. Concentrations of NO 3 − -N were four times higher than NH 4 + -N in runoff. NO 3 − -N concentrations first decreased as runoff volume increased until reaching relatively low concentrations, then increased again as runoff volume decreased. Both NH 4 + -N and dissolved phosphorus (DP) in runoff remained at low concentrations with a small magnitude of variation. Suspended particulate nitrogen (SN) was the dominant N form. Losses of NO 3 − -N were higher than NH 4 + -N in the dissolved nitrogen (DN). Suspended particulate nitrogen losses were several times higher than DN in the early period of runoff formation, but the ratio of SN/DN decreased gradually as rainfall progressed, and by the end of the storm event the rate was lower than 1, indicating DN took the main form after the early physical flush. In the early period of storm events, suspended particulate phosphorus (SP)/DP was above 70 and decreased as rainfall progressed, but remained higher than 1, which showed that SP was the main form of P loss. The transport of N, and particularly P, was intimately linked to sediment in the runoff, indicating an obvious soil erosion-associated nutrient transport, especially in relation to P loss.

Soil acidification rate is an essential parameter to assess the vulnerability and sustainability of various ecosystems to acid deposition. The acid-buffering mechanism of soil system includes two major proton (H + ) consumption pathways, i.e., mineral weathering and cation exchange in which the former consumes directly H + and does not lead to soil acidification while the latter would cause soil acidification by exporting base cations. However, no available method distinguishes between H + consumed by the two pathways, so soil acidification may have been overestimated as the bulk H + consumption. Here we establish a method to differentiate the two major H + consumption pathways quantitatively using the stoichiometric relations between silicon (Si) and base cations of rock, soil and stream water in a typical undisturbed forested watershed in subtropical China. The results showed that a large quantity of external H + was stored in soil from acid deposition, and the H + concentration in soil was further affected by the transformations and specific adsorptions of extraneous nitrogen (N) and sulfur (S) compounds. The net input of H + into the soil resulting from both wet and dry deposition was about 1395 mol ha − 1 yr − 1 . The base cations from weathering was about 46% of the total net output of cations as calculated using the net output of Si by stream and the release ratio of base cations over Si during the weathering reaction of plagioclase, the predominant weatherable mineral in the area. The remaining output of base cations was attributed to cation exchange. Based on the ratio of H + consumption by weathering and cation exchange, the actual soil acidification caused by cation exchange was estimated as 703 mol ha − 1 yr − 1 , only about half of the net input of protons, which was substantially lower than the previous results obtained with no distinction between H + consuming pathways. However, even taking the contribution of mineral weathering into account, the high net output of base cations indicates that the already acidic soil system is still depleting its base pools. This study provides a solution to estimate actual soil capacity to resist acid attack, which is crucial for reliable assessment of ecosystem resilience against external acid input.

Major, trace and organic elements of a laterite profile developed on Neogene basalt on Hainan Island, South China were reported to investigate elements mobilization and redistribution in tropical regions. The results indicate that strong acid environment and organic matter (OM) can remarkably improve the transfer of insoluble elements. Among all the elements, Th is the least mobile. As for the general conservative elements during incipient chemical weathering, such as Ti, Zr, Hf and Nb, the removals are up to 30%–40% in the upper profile. And for Fe, Al, Cu and Ni, that tend to be combined with secondary minerals and to be retained in temperate zone, they are removed from the upper profile, transferred downwards, and then precipitated in the lower profile. In addition, atmospheric inputs, including sea salt aerosols and dust, have a profound effect on the budgets of elements that are susceptible to leaching losses (e.g. K, Na and Sr). Excluding the possibilities of groundwater and erosion, the remarkable increase of K, Na and Sr concentrations in the upper profile, together with dramatically upward increasing trends of the percentage changes of Sr/Th, K/Th and Na/Th ratios, show that atmospheric inputs, especially sea salt aerosols, contribute much extraneous seawater derived elements, such as K, Na and Sr to the soils. The overall elemental behaviors in this profile suggest that organic matter and atmospheric inputs play a very important role in the mobilization and redistribution of elements during extreme weathering in tropical regions.