[Spatial Distribution and Risk Assessment of Heavy Metals in Sediments of the Ruxi Tributary of the Three Gorges Reservoir].

Sediment column and soil samples collected from 12 sampling sites in four regions of the Ruxi River, a typical tributary of the Three Gorges Reservoir, were analyzed for eight selected heavy metals including Cr, Ni, Cu, Mn, Zn, Cd, Pb, and Hg to evaluate their spatial and vertical distribution, source, and biological toxic effects. The results showed that the average concentrations of heavy metals were (79.60±11.

[Response of Soil CO Emissions to Straw-returning in Citrus/Mushroom Intercropping Systems].

Based on the pattern of citrus tree/stropharia mushrooms intercropping, returning-straw was used as the raw material for the stropharia mushrooms, and an in-situ experiment was conducted to monitor soil CO emissions under different dosage of straw application during the stropharia growth period. Soil CO emissions and the influencing factors were analyzed under different treatments of cultivated (HSM, ASM, and DSM) and uncultivated stropharia mushrooms (HS, AS, and DS). The mushroom yield and soil carbon emission efficiency (CEE) were used to provide a theoretical basis for improving the use of land under citrus orchards.

[Comparison of Relationship Between Conduction and Algal Bloom in Pengxi River and Modao River in Three Gorges Reservoir].

Pengxi River is the largest tributary in the northern bank of Yangtze River in the Three Gorges Reservoir (TGR) region, and serious algal bloom has been reported since 2003 when the TGR dam started impounding water. On the other hand, Modao River, a tributary in TGR locating in the same county with Pengxi River, was rarely reported with algal bloom in the same time period. In this study, water samples were collected on the same day in both rivers in spring and summer, the most likely blooming seasons in TGR, to compare the water quality parameters and Chlorophyll-a(Chl-a) concentration dynamics in order to understand the mechanism of algal bloom in TGR.

[Influence of Spatial Pattern of Paddy Field on the Losses of Nitrogen and Phosphorus in Three Gorges Reservoir Area].

This paper used three plots of paddy field in Wangjiagou small catchment in Fuling District, Chongqing Municipality as a case study. Wangjiagou, located in Three Gorges Reservoir Area, provided a good case in terms of its closeness of surface runoff. The samples of individual rainfall of twelve times and process of two typical individual rainfalls on three plots of sloping paddy field were collected from 2014 to 2015.

[Effect of Nano Zeolites on pH, CEC in Soil and Cd Fractions in Plant and Soil at Different Cadmium Levels].

Soil incubation experiment and pot experiment were carried out to investigate the influence of nano zeolite (NZ) and ordinary zeolite (OZ) on the soil pH, cation exchange capacity, concentration of soil Cd, soil Cd fraction and Cd uptake by Chinese cabbage when exposed to different Cd pollution levels(1, 5, 10 and 15 mg·kg). The results of soil incubation experiment showed that the nano zeolite and ordinary zeolite dose(5, 10 and 20 g·kg) increased the soil pH and cation exchange capacity, and decreased the concentration of soil exchangeable Cd, while increased the concentration of Cd in carbonate, Fe-Mn oxide, organic matter and residual fraction. The lowest EX-Cd was observed in the high nano zeolite (20 g·kg) treatment.

[Effect of Nano Zeolite on Growth, Activity of Antioxidant Enzyme, and Chemical Fractions and Concentration of Cd in Chinese Cabbage].

Pot experiment was carried out to investigate the influence of nano zeolite (NZ) and ordinary zeolite (OZ) on the growth, activities of antioxidant enzyme, Cd fraction and Cd concentration in two varieties of Chinese cabbage. The results showed that the activities of SOD, CAT and POD in the shoot and root of two varieties increased, and the dry weight of shoot and the total dry weight of Chinese cabbage increased by 4.5%-96.

[Effect of Nano Zeolite on Chemical Fractions of Cd in Soil and Uptake by Chinese Cabbage at Different Soil pH and Cadmium Levels].

Incubation experiments were carried out to investigate the influence of different nano zeolite(NZ) and ordinary zeolite(OZ) levels(0, 5, 10 and 20 g·kg) on the fraction distribution coefficient (FDC) of Cd and soil CEC at different soil pH (4, 5, 6, 7 and 8) when exposed to different cadmium(Cd) levels(1, 5, 10 and 15 mg·kg), and pot experiment were carried out to investigate the effects of nano zeolite(NZ) and ordinary zeolite(OZ) on the growth, Cd concentration and Cd accumulation of Chinese cabbage. The results showed that nano zeolite and ordinary zeolite decreased the concentration and FDC of exchangeable Cd (EX-F), and increased the concentration and FDC of carbonate(CAB-F), Fe-Mn oxide(FMO-F), organic matter (OM-F) and residual fraction(RES-F) in incubation experiments. At the end of incubation, the FDC of soil exchangeable Cd decreased from 72.

[Nitrogen Losses Under the Action of Different Land Use Types of Small Catchment in Three Gorges Region].

As an independent water-collecting area, small catchment is the source of non-point source pollution in Three Gorges Region. Choosing 3 kinds of the most representative land-use types and using them to lay monitoring points of overland runoff within the small catchment of Wangjiagou in Fuling of Three Gorges Region, the author used the samples of surface runoff collected through the twelve natural rainfalls from May to December to analyze the feature of spatial-temporal change of Nitrogen's losses concentrations under the influence of different land use types and the hillslopes and small catchments composed by those land use types, revealing the relation between different land-use types and Nitrogen's losses of small catchments in Three Gorges Region. The result showed: the average losses concentration of TN showed the biggest difference for different land use types during the period of spring crops, and the average value of dry land was 1.

[Reduction Effect of Reduced Phosphorus Fertilizer and Combining Organic Fertilizers on Phosphorus Loss of Purple Soil Sloping Field].

In order to better understand the effect of reduced phosphorus fertilizer and combining organic fertilizers on phosphorus loss of purple soil sloping field, three rainfall-runoff events were monitored using field runoff observation method in the purple soil sloping field in 2014. There were six treatments in this research, including optimized fertilization (P), optimized fertilization+pig manure application (MP), optimized fertilization+straw return (SP), optimized fertilization which was reduced by 20%+pig manure application (MDP), optimized fertilization which was reduced by 20%+straw return (SDP), without phosphate (P0). The results indicated that the interflow was the main pathway of runoff for purple soil sloping field.

[Effects of Soil Moisture and Temperature Variations on Organic Carbon Mineralization of Purple Soil in the Hydro-fluctuation Belt of the Three Gorges Reservoir].

Soil sampling in the field and an incubation experiment in the laboratory was conducted to investigate the effects of soil moisture and temperature on soil organic carbon (SOC) mineralization of purple soil in the hydro-fluctuation belt of the Three Gorges Reservoir. Three incubation temperatures (10, 20 and 30℃) and four moisture levels (40% water holding capacity (WHC), 70% WHC, 100% WHC and submerged condition) were used in the experiment. In the entire incubation period (66 d), the SOC cumulative mineralization reached the maximum at 100% WHC, but there was no significant difference between 100% WHC and submerged condition (>0.

[Variation Characteristics of Inorganic Phosphorus in Purple Soil Profile Under Different Conservation Tillage Treatments].

In this study the effects of tillage methods (rice-winter paddy field conventional farming, CF; rice-winter paddy field combing ridge with no-tillage, RNT1; rice-wheat or rape combing ridge with no-tillage, RNT2; rice-wheat or rape conventional paddy-upland rotation tillage, CR) on purple soil profile of different forms of inorganic phosphorus distribution characteristics were investigated in a long-term experimental site established in 1990, Chongqing City, China. The results showed that compared to the status before the experiment, the total phosphorus, available phosphorus and various morphologies of inorganic phosphorus all increased to a certain degree in the soils with different long-term tillage treatments,and the contents of different forms of inorganic phosphorus in soil size ranked as RNT2> CF> CR> RNT1. Except that the contents of Fe-P in the lower layer were higher than those in the upper layer, contents of Ca-P, Ca-P, Al-P, Ca-P and O-P in the arable layers were all higher than those in the lower layers.

[Effect of Nano Zeolite on Chemical Fractions of Cd in Soil and Its Uptake by Cabbage].

Incubation experiments were carried out to investigate the influence of different nano zeolite (NZ) and ordinary zeolite (OZ) levels(0, 5, 10 and 20 g · kg⁻¹) on the change trends in fraction distribution coefficient (FDC) of Cd when exposed to different Cadmium (Cd) levels (1, 5, 10 and 15 mg · kg⁻¹), and pot experiments were carried out to investigate their influence on soil Cd fraction and Cd uptake by cabbage. The results in incubation experiments showed that the application of nano zeolite as well as ordinary zeolite effectively decreased the FDC of exchangeable Cd and increased the FDC of Fe-Mn oxide fraction. The FDC of soil Cd from 0 d to 28 d was deceased at first, then increased and tended to be stable, and finally increased.

[Characterization of phosphorus forms in different organic materials].

The existing forms of phosphorus in seven organic waste materials including biogas residues of swine manure (ZZ), biogas residues of cattle manure (NZ), compost of cattle manure and corn straw (NJD), compost of sewage sludge (WD) and compost of rural daily garbage (NSLD) were characterized according to phosphorus fractionation procedures developed by DOU et al. The result showed that there was a great difference in the total phosphorus (TP) and the total phosphorus of various forms (P(t)) among different organic materials. ZZ had the highest content of TP with the value of 23.

[Effect of exogenous selenium on accumulation and chemical forms of cadmium in cucumber (Cucumis satiuus L.)].

Pot experiments were carried out to investigate the influence of different selenium (Se) levels (0, 0.5 and 1.0 mg x L(-1)) on the plant growth, concentration of malonaldehyde (MDA), activities of antioxidant enzymes, accumulation and chemical forms of cadmium (Cd) in cucumber when exposed to Cd (20 mg x kg(-1)).

[Effects of variable temperature on organic carbon mineralization in typical limestone soils].

Soil sampling in the field and incubation experiment in the laboratory were conducted to investigate the responses of soil organic carbon (SOC) mineralization to variable temperature regimes in the topsoil of limestone soils from forest land and dry land. Two incubated limestone soils were sampled from the 0-10 cm layers of typical forest land and dry land respectively, which were distributed in Tianlong Mountain area of Puding county, Guizhou province. The soils were incubated for 56 d under two different temperature regimes including variable temperature (range: 15-25 degrees C, interval: 12 h) and constant temperature (20 degrees C), and the cumulative temperature was the same in the two temperature treatments.

[Effects of ryegrass and arbuscular mycorrhiza on activities of antioxidant enzymes, accumulation and chemical forms of cadmium in different varieties of tomato].

Pot experiments were carried out to investigate the effects of ryegrass and arbuscular mycorrhiza on the plant growth, malondialdehyde (MDA), antioxidant enzyme activities of leaf and root, accumulation and chemical forms of cadmium (Cd) in tow varieties of tomato when exposed to Cd (20 mg x kg(-1)). The results showed that dry weights of fruit and plant, and contents of malondialdehyde (MDA) and antioxidant enzyme activities of leaf and root, and concentrations and accumulations of Cd significantly differed between two varieties of tomato. Dry weights of fruit, roots, stem, leaf and plant were increased by single or combined remediation of ryegrass and arbuscular mycorrhiza, while MDA contents and antioxidant enzyme activities of leaf and root reduced.

[Composition and stability of soil aggregates in hedgerow-crop slope land].

Based on a long-term experiment of using hedgerow to control soil and water loss, this paper studied the composition and stability of soil aggregates in a hedgerow-crop slope land. Compared with those under routine contour cropping, the contents of > 0.25 mm soil mechanical-stable and water-stable aggregates under the complex mode hedgerow-crop increased significantly by 13.

[Prediction of total nitrogen and total phosphorus concentrations in purple soil using hyperspectral data].

Hyper-spectral remote sensing is one of the effective means for prediction of soil nutrients. Taking Wangjiagou small watershed of Three Gorges Reservoir Area as researching zone, based on the soil physicochemical properties, reflective spectrum analysis and measurement, were built predictive models for total phosphorous and total phosphorus concentrations in purple soil. Meanwhile, 33 soil samples from paddy soil were used to validate the prediction models for soil nutrients in purple soil.

[Cd uptake in rice cultivars and Cd fractions in soil treated with organic acids and EDTA].

A pot experiment was conducted to examine the yield, quality and cadmium (Cd) uptake in different rice cultivars, and Cd speciation in soil after exposing to Cd (0, 1 and 5 mg x kg(-1)) in the presence of organic acids and ethylenediamine tetraacetic acid (EDTA). The results showed that general increase in the yield for cultivars Xiushui63 and II you527 was observed. Yield of two rice cultivars were in order of organic acids treatment or organic acids + 1/2EDTA treatment > EDTA treatment.

[Seasonal variation characteristics of phosphorus speciation in the sediment of Changshou Lake].

To further know the seasonal variation characteristics of phosphorus species in lake sediment, the contents of different phosphorus species in the surface sediment sampling from Changshou Lake were determined by using the SMT sequential extraction method in July and November, 2009, and March, 2010. The contents of total phosphorus (TP) basically show an order of the low-water period, high-water period, and normal-water period from high to low, and the maximum appeared in Shoudao (2960.29 mg/kg) while the minimum in Guanjiakou (586.

Spatial variability of soil heavy metals in the three gorges area: multivariate and geostatistical analyses.

There is a growing concern about environmental contamination in the three gorges area. The objectives of this study were to investigate the spatial variability and the possible influence factors of seven heavy metals (As, Cd, Cr, Cu, Hg, Pb, and Zn) in the center of this area based on multivariate and geostatistical approaches. All analyzed heavy metals were below their background levels, except Cd.

[Effects of conservational tillage on aggregate composition and organic carbon storage in purple paddy soil].

A 13 year experiment was conducted to study the effects of conservational tillage on the aggregate composition and organic carbon storage in purple paddy soil of Sichuan Basin. The results showed that under no-tillage and ridge culture (rice-rape) (NR-RR), no-tillage and plain culture (rice-rape) (NP-RR), no-tillage and ridge culture (rice-green manure) (NR-RGM), tillage and ridge culture (rice-rape) (TR-RR), and tillage and plain culture (rice-rape) (TP-RR), the proportion of macroaggregates in 0-10 cm soil layer was 23%, 69%, 9%, 36%, and 28% higher than that under conventional tillage (CT) (12%), respectively, while in 10-20 cm soil layer, this proportion under conservational tillage was 9%-38% lower than that under CT. The organic carbon storages in the macroaggregates at the depth of 0-10 cm were 13%, 31% and 32% higher under no-tillage and ridge culture (rice-fallow) (NR-RF), NR-RR and NR-RGM than under CT, respectively, while that at the depth of 10-20 cm was 28%-54% lower.

Response of CH4 emission of paddy fields to land management practices at a microcosmic cultivation scale in China.

The terrestrial ecosystem may be either a source or a sink of CH4 in rice paddies, depending, to a great extent, on the change of ecosystem types and land use patterns. CH4 emission fluxes from paddy fields under 4 cultivation patterns (conventional plain culture of rice (T1), no-tillage and ridge culture of rice (T2), no-tillage and ridge culture of rice and wheat (T3), and rice-wheat rotation (T4)) were measured with the closed chamber technique in 1996 and 1998 in Chongqing, China. The results showed that differences existed in CH4 emission from paddy fields under these land management practices.