[Influencing Factors of Cadmium Bioaccumulation Factor in Crops].

The Cd bioaccumulation factor (BCF) of crops is affected by many aspects. In order to clarify the differences in the Cd bioaccumulation factor characteristics of different crops under field conditions and the influence of soil properties, point-to-point samples of soil and crop grains were collected during crop harvesting on plots with varying pollution levels in the primary production areas of rice, wheat, and maize in China. The characteristics of the Cd bioaccumulation factors of rice, wheat, summer maize, and spring maize and the effects of soil properties on the Cd bioaccumulation factors of different crops were studied, and the quantitative relationship between the Cd bioaccumulation factors and soil properties was established through multiple regression equations. The results revealed that the average BCF values of Cd in rice, wheat, summer maize, and spring maize were 0.915, 0.155, 0.113, and 0.102, respectively, with the Cd content in the field soil of 0.15-2.66 mg·kg-1. Rice is significantly higher than wheat and maize, and spring maize has the lowest Cd bioaccumulation factor. The Cd content in the soil is extremely negatively correlated with the BCF of wheat, summer maize, and spring maize. The relationship between soil organic matter (SOM) and the BCF of wheat and summer maize demonstrated a significant negative correlation. The soil pH and cation exchange capacity (CEC) also affect the BCF of crops. Introducing the soil Cd content, pH, SOM, CEC, and other factors, the Cd bioaccumulation factor prediction equations of rice, wheat, summer maize, and spring maize were established. The correlation coefficients of the BCF prediction equations for rice, wheat, summer maize, and spring maize are 0.423*, 0.796**, 0.826**, and 0.551**, respectively. The above models reached significant or extremely significant levels, which can better predict the BCF value of different crops under varying soil conditions.

Cadmium accumulation in wheat and maize grains from China: Interaction of soil properties, novel enrichment models and soil thresholds.

The cadmium (Cd) activity in soil has been widely studied. However, the interactive effects of soil properties (e.g. soil pH, CEC, and SOM) on Cd transfer from soil to grain are generally overlooked. In total 325 datasets including soil pH, CEC, SOM, and soil Cd content were used in this study. The descriptive statistics indicated that Cd content in wheat and maize soils ranged from 0.05 to 10.31 mg/kg and 0.02-13.68 mg/kg, with mean values of 0.87 and 1.14 mg/kg, respectively. Cd contents in wheat and maize grains were 0.01-1.36 mg/kg and 0.001-1.08 mg/kg with average values of 0.15 and 0.10 mg/kg, respectively. The results of SEM demonstrated that the interactive effects of soil properties contributed more to Cd transfer from soil to wheat grain than the soil Cd content. Subsequently, CITs-MLR indicated that the critical factors, including soil pH and total soil Cd content, could mask the contribution of other soil properties on Cd accumulation in grain; soil CEC may prevent Cd from leaching and therefore improve grain Cd level of wheat especially at acidic soil condition. The result of derived Cd thresholds revealed that current Cd thresholds are not completely suitable to wheat and maize grain at different soil conditions. This study provides a new model for further investigation on relationships between soil properties, soil Cd content and grain Cd level.

[Characteristics of Heavy Metal Absorption by Winter Wheat and Its Quantitative Relationship with Influencing Factors].

Winter wheat is one of the main food crops in China, and ensuring the quality and safety of agricultural products is an important component in agricultural production. The absorption of heavy metals by winter wheat is affected by many factors. To clarify the characteristics of heavy metal absorption by winter wheat under field conditions, and the quantitative relationship between the content of heavy metals in wheat grains and the physical and chemical properties of soil and its content of heavy metals, point-to-point sampling was carried out from 50 fields with different levels of heavy metal pollution in the main wheat-producing areas of North China. The pH, organic matter (OM), cation exchange capacity (CEC), and contents of heavy metals in soil, wheat grain, and straw were analyzed. In addition, the characteristics of heavy metals absorbed by wheat and the effects of the physical and chemical properties of soil on the absorption of heavy metals by wheat were studied, and the quantitative relationship between heavy metals and physical and chemical properties of soil and heavy metals in wheat grain was studied by multivariate regression analysis. The results showed that the Cd content in soil in the wheat field ranged from 0.150 to 2.66 mg·kg-1, and the Cd content of the corresponding wheat grain ranged from 0.033 to 0.39 mg·kg-1. The range of Pb content in soil was 4.68-371 mg·kg-1, and the corresponding wheat Pb content range was 0.27-2.4 mg·kg-1. The soil As content range was 3.00-21.3 mg·kg-1, and the corresponding wheat grain As content range was 0.044-0.18 mg·kg-1. The over-standard rates of wheat Cd, Pb, and As were 55%, 100%, and 0, respectively, and those of soil Cd, Pb, and As were 52%, 13%, and 0, respectively. Soil Cd content was positively correlated with wheat grain Cd content (P<0.01), with correlation coefficient r=0.663 (n=50). There was a significant positive correlation between soil Pb content and wheat Pb content (P<0.05), with correlation coefficient r=0.348 (n=50). There was no significant correlation between soil As content and wheat As content. The mean enrichment coefficients of wheat grains on Cd, Pb, and As were 0.17, 0.027, and 0.0089, respectively, and the mean transfer coefficients were 0.52, 0.27, and 0.22, respectively. The enrichment and transfer coefficients of heavy metals in wheat were Cd > Pb > As. The content of heavy metals in wheat straw was 2-5 times higher than that in corresponding grains. Soil pH, OM, and CEC also affect Cd content in wheat grains. Soil Cd content, soil pH, OM, CEC, and wheat grain Cd content were analyzed by multiple regression analysis, and four prediction equations of wheat grain Cd content were obtained. The correlation coefficient r reached a very significant level (P<0.01), and the correlation coefficient of the prediction equation including all variables was highest at r=0.810 (n=50), showing that it could predict the Cd content in wheat grains well.

[Quantitative Relationship Between Paddy Soil Properties and Cadmium Content in Rice Grains].

Rice is a crop with the potential for high accumulation of Cd, which can be affected by many factors. Sixty pairs of soil and rice samples from different plots were collected and analyzed, in order to understand the quantitative relationships between the Cd content in soil and the properties of soil and the Cd content in rice grains under field conditions, by simple and multiple regression analyses. The results showed that the Cd contents in soil and rice grains ranged from 0.15-2.54 mg·kg-1 and 0.02-2.00 mg·kg-1, respectively. According to the result of simple regression analysis, there were significantly positive correlations (P<0.01) between the Cd contents in soil and rice grains (r=0.392); the pH, SOM, and CEC in soil also had certain effects on Cd accumulation in rice grains, which were not significant, however. When the soil pH was<6.5, the Cd content in rice grains increased with increasing soil pH, but decreased with increasing soil pH when the soil pH was>6.5. The Cd content, pH, SOM, and CEC in the soil and the Cd content in rice grains were analyzed by multiple regression analysis, and five equations, which all reached extremely significant levels (P<0.01), were obtained. The equation that included the four variables (Cd content, pH, SOM, and CEC in soil) had the most r, and it could predict the Cd content in rice grains better, given the conditions of the present study.

[Effects of Continuous Application of Sewage Sludge Compost on Heavy Metals Accumulation and Mobility Characteristics in Soil Profile and on Heavy Metals Uptake of Wheat].

The use of sewage sludge compost(SSC)as fertilizer may cause increased leaching due to its high content of heavy metals and thus pose a threat to groundwater quality. The effect of SSC application on heavy metals leaching in calcareous soils has been studied in field trials, which provides basis for determining heavy metals environmental capacity and preventing metal pollution in farmland soil scientifically. The results indicated that the contents of Cu, Zn elevated obviously with the increase of the age and the dosage of SSC utilization in the topsoil(0-15 cm) under 4-year continuous application of SSC. Under higher levels of the compost treatment, the heavy metals Cu and Zn were found to migrate into the 15-30 cm soil and 60-90 cm soil under the experimental condition. Nevertheless, the majority of Cu and Zn from SSC accumulated in topsoil and the highest accumulation rates could reach 75.3% for Cu and 85.9% for Zn. The contents of Cd, Pb increased significantly in topsoil after 4-year continuous application of SSC, and their increases could reach 57.2%-165.2% for Cd and 13%-34% for Pb compared with CK. At 60-90 cm soil, the contents of Cr, As and Pb were also significantly higher than those in CK treatment. Application of SSC not only caused accumulation of some heavy metals in topsoil but also leached heavy metals located in the subsurface soil down in this experiment. Continuous utilization of SSC increased Zn concentration of wheat grain, and the increase could reach 13.3%-47.9%. For the concentrations of Cr and Pb in wheat grain, the values exceeded the national food and healthy standards value (GB 2762-2012) in part of compost treatments. The cumulative ratio of heavy metals carried out by wheat were all below 10% after 4-year experiment, wheat grain carried much more Cu, Zn out than wheat straw, but it was opposite for Cr, As, Cd, Pb. The cumulative ratio of heavy metals carried by wheat decreased with the increasing level of SSC utilization. The amounts of heavy metals migrated to deeper soil should be considered when determining the environmental capacity of heavy metals in farmland soil.

[Distribution of Phosphorus in Soil Profiles after Continuous Application of Different Fertilizers].

This study clarifies the distribution and migration characteristics of phosphorus in the soil profile and discusses the phosphorus load of farmland after continuous application of different organic fertilizers. The distribution and migration characteristics of phosphorus in soil profiles were studied through a field experiment lasting four consecutive years. The results showed that total phosphorus and Olsen-P are mainly accumulated in the soil surface, and their contents decrease with the deepening of soil depth after the continuous application of different fertilizers. With a four-year application of higher levels of organic fertilizer, the total phosphorus was found to migrate into the 15-30 cm soil layer. Olsen-P was found to migrate into the 60-90 cm soil layer under higher levels of pig manure. The ratio of available phosphorus to total phosphorus in the soil surface increased, and there were significant differences after the application of different amounts of organic fertilizers. The amount of Olsen-P as a proportion of total phosphorus in the soil profile decreased as pig manure treatment > chicken manure treatment > sludge treatment > phosphate fertilizer treatment. After the application of chicken manure, pig manure, sludge, and phosphate fertilizer, the value of Olsen-P in the soil surface increased with an increase in phosphorus input and then remained stable. When applying the same phosphorus onto the soil, the contribution of different organic fertilizers to Olsen-P in the surface soil was quite different. The bioavailability and mobility of phosphorus from pig manure was significantly higher than that of chicken manure, sludge, and phosphate fertilizer.

[Accumulation and Migration Characteristics in Soil Profiles and Bioavailability of Heavy Metals from Livestock Manure].

The long term and high dosage application of livestock manure may result in heavy metal accumulation and migration in the soil, which may endanger food security and affect the top soil heavy metal environmental capacity. Thus, one of the most important tasks for prevention of soil heavy metal pollution is scientific determination of the safe use load of heavy metals in livestock manure. A 4-year field plot experiment was carried out to quantitatively study the accumulation and migration characteristics of heavy metals from pig and chicken manure in soil profiles and the differences of bioavailability. The results showed that the contents of Cu and Cd increased significantly by 43.8%-118.6% and 28.2%-44.9% in topsoil(0-15 cm) after 4-consecutive year application of pig manure, and the contents of Cu, Zn, Cd, Cr, As, Pb also increased by 29.7%-48.5%, 239%-456%, 19.9%-80.8%, 40.4%-163%,11.8%-22.0% and 80.3%~95.0% obviously after application of chicken manure. The accumulation rates of Cu and Zn in topsoil were 76.4%-119% and 14.2%-20.4% with pig manure, 72.1%-88.7% and 63.9%-78.9% with chicken manure. Under a high dosage of pig and chicken manure, Cu and Zn migrated to a deeper soil evidently. Applying 60 t·hm-2 of pig manure after 4-consecutive year, Cu could migrate to 15-30 cm soil layer, Zn migrated to 30-60 cm soil layer with chicken manure. Except topsoil, the contents of Cr, Cd, As, Pb did not significantly increase in other soil layers. 4-year continuous application of chicken manure significantly decreased the contents of Cu and Cd, but increased the contents of Zn and Cr in wheat grain and the content of Zn in wheat straw. Pig manure significantly decreased the content of Zn in wheat grain, but increased As content with 60 t·hm-2, the contents of Cu and As in wheat straw also increased significantly. Besides, the cumulative rate of heavy metals in wheat was no more than 6%, wheat grain carried out more Cu, Zn than straw, but the Cd, Cr, As, Pb were opposite. The cumulative rate of heavy metals in wheat decreased with the increasing application of manure. This research has an important significance in scientific determination of the heavy metal loads of plow layer, ensuring the quality and safety of agricultural production, and providing a scientific basis for the source control of soil heavy metal pollution and the safety production of agricultural goods.

[Form tendency and bio-availability dynamics of Cu and Zn in different farm soils after application of organic fertilizer of livestock and poultry manures].

Soil incubation experiments were conducted with different sources of manures containing heavy metals to evaluate the bioavailability of heavy metals (Cu and Zn) and their form transformation in different soils. This study may assist in developing strategies to ascertain the loads of heavy metals which entered into soils together with manures, and promote policies to evaluate the ecological risk in agriculture soils. The results showed that, during the six months of soil incubation, the pH value of acidic soil increased and the pH value of calcareous soil reduced. After adding chicken manures, the contents of available Cu in both calcareous and acid soils were significant lower than those in the equivalent inorganic salt treatments, but there was no significant difference between the treatments in the contents of available Zn in both calcareous and acid soils. Furthermore, there were also no significant differences between pig matures and the equivalent inorganic salt treatments in the contents of available Cu and Zn in both calcareous and acid soils. The results of form tendency showed that the main forms of Cu and Zn in both calcareous and acid soils, which entered into soils together with manures, were exchangeable, carbonate, Fe-Mn oxides, and organic. And the proportions of different heavy metals species in calcareous and acid soils were different with different manures sources. After six months of incubation, the contents of exchangeable and Fe-Mn oxides Cu, Zn were lower than those in the equivalent inorganic salt treatments, the contents of organics Cu and Zn were higher than those in the equivalent inorganic salt treatments, and other Cu and Zn forms in soils showed no difference with inorganic salt treatments.

[Application of ICP-mS and AFS to detecting heavy metals in phosphorus fertilizers].

In order to investigate heavy metals in phosphorus fertilizers in China, 159 samples of phosphorus fertilizers including imported fertilizers and domestic fertilizers were collected from fertilizer markets, and the contents of heavy metals were determined by ICP-MS and AFS after microwave digestion. The results showed that the phosphorous fertilizers contained certain amount of heavy metals, and there was great variability in the contents of heavy metals. The mean contents of Cd, Cu, Zn, Cr, Pb, Ni, As and Hg were 0. 77, 35.6, 102.7, 24. 1, 16.6, 15.4, 19.4 and 0. 08 mg kg-1 fertilizer, respectively; based on the calculation of P2O5, the mean contents of above heavy metals were 4. 48, 258. 4, 767. 4, 190. 0, 151.3, 134. 5, 155. 8 and 8. 79 mg kg-1 P2 O5, respectively. The contents of heavy metals Cd, Cr, Pb, As and Hg in the tested samples accord with the ecological index of arsenic, cadmium, lead, chromium and mercury for fertilizers (GB/T 23349-2009), with the exception of Cd in one imported sample of diammonium phosphate and As in one sample of mono-ammonium phosphate. Analyzing the contents of heavy metals in imported fertilizers, the Cd contents in imported fertilizers was ranged from 0. 02 to 27. 2 mg kg-1 fertilizer, the mean and median Cd contents in imported fertilizers were 3. 20 and 0. 41 mg kg-1 fertilizer, respectively. And the Cu, Cr and Hg contents in the imported fertilizers were higher than that of domestic fertilizers, the mean contents of Cu, Cr and Hg in imported fertilizers were 39. 4, 26. 6 and 0. 47 mg kg-1 fertilizer, respectively.

[Phytoavailability and chemical speciation of cadmium in different Cd-contaminated soils with crop root return].

Pot experiments were conducted under greenhouse condition to investigate the effects of crop root return on succeeding crops growth, Cd uptake and soil Cd speciation in Cd-contaminated soil and artificial Cd-contaminated soil. The results showed that the amount of root residue returned to soil by corn and kidney bean growth successive for 3 times was 0.4%-1.1%. The Cd returned to soil by root residue was 1.3%-3.5% to the total soil Cd. There was no significant difference in the shoot dry weights of winter wheat and Chinese cabbage grown on the 2 Cd-contaminated soils with and without root return. While Cd concentration of Chinese cabbage increased significantly in the Cd-contaminated soil with corn or kidney bean root return. Light fraction of soil organic matter increased with root return in both of the Cd-contaminated soils. The percentage of Cd in the light fraction of soil organic matter increased with root return in the artificial Cd-contaminated soil. Soil carbonates-bound Cd concentration decreased significantly with corn root return in the Cd-contaminated soil. Soil exchangeable Cd concentration decreased and soil Fe-Mn oxide-bound Cd concentration increased significantly with kidney bean root return in the artificial Cd-contaminated soil.

[Physicochemical properties of Guanting Reservoir sediment and its land application].

Surface sediment of Guanting Reservoir was dredged up and dewatered in field, and pollutant and physicochemical characterizations were mensurated. The stabilization and agricultural land use of the sediment was also studied in the field. Results showed that the sediments have a higher clay content, bulk density (1.89 g x cm(-3)) and lower porosity (23.8%), higher deoxidize material and available nitrogen, phosphorus concentration. Heavy metal and organochlorinated pesticides concentration was lower than the class II of national standard for soil. Stabilized the sediment with sand soil and straw could improve the physical property and decrease the concentration of deoxidize material and available nitrogen, phosphorus. Stabilized sediment could be a suitable medium for alfalfa, tree and corn growth and used for agricultural land.

[The effects of various beta-blockers on myocardial gap junction structure in rat with myocardial ischemia-reperfusion injury].

OBJECTIVE: To compare the effects of carvedilol, metoprolol and propranolol on myocardial gap junction (GJ) structure in rat with myocardial ischemia and reperfusion injury. METHODS: Rats were divided randomly into five groups: sham operation group (SO), myocardial ischemia and reperfusion group (IR), IR + carvedilol group (CV), IR + metoprolol group (MT), and IR + propranolol group (PP). The left anterior descending branch was ligated for 30 minutes and reperfused for 4 hours (IR). After 4 h reperfusion, the distribution and composition of gap junctional connexin 43 (CX43) were observed by immunofluorescence and laser scanning confocal microscopy (LSCM), and the quantification of CX43 was measured by LSCM. RESULT: Compared with SO group, IR resulted in abnormal distribution and composition of CX43-GJ and the impairment of CX43-GJ was significantly attenuated by CV, MT and PP treatments with the best effect observed in CV group (P<0.05 vs. MT and PP). CONCLUSION: These results suggest that beta-blockers, especially, carvedilol, could significantly attenuate IR induced CX43-GJ impairment.

[Role of gap junction in ischemic preconditioning].

OBJECTIVE: To investigate the role of gap junction in ischemic preconditioning (IPC). METHODS: Sprague-Dawley rats were subjected to a 30 min coronary artery occlusion followed by 4 h of reperfusion (I/R). Rats were divided into seven groups: I/R, IPC/R, IPC/R + 5-hydroxydecanoic acid (mitochondrial ATP sensitive potassium channel antagonist), I/R + diazoxide (mitochondrial ATP sensitive potassium channel agonist), I/R + 5-hydroxydecanoic acid + diazoxide, I/R + 18beta-glycyrrhetinic acid (gap junction blocker) and I/R + 18beta-glycyrrhetinic acid + 5-hydroxydecanoic acid. Hemodynamics and myocardial infarct size were measured and connexin43 phosphorylation and subcellular distribution were determined by quantitative immunoblotting and confocal immunofluorescence. RESULTS: Infarct size was reduced in IPC/R, I/R + diazoxide and I/R + 18beta-glycyrrhetinic acid group (13.34% +/- 7.87%, 11.02% +/- 2.24%, and 15.03% +/- 11.35%, respectively; P < 0.001 vs. I/R group: 45.81% +/- 7.91%). 5-hydroxydecanoic acid abolished the cardioprotective effects of IPC and diazoxide (46.57% +/- 5.36% and 47.36% +/- 3.17%; P > 0.05 vs. I/R) but not the effects of glycyrrhetinic acid (14.60% +/- 7.36%; P < 0.001 vs. I/R). Phosphorylation of connexin43 was significantly increased, dephosphorylation and connexin43 intracellular redistribution significantly decreased (Cx43 size in the cellular membrane 1.00% +/- 0.35% and 0.83% +/- 0.31%, P < 0.001 vs. I/R: 0.19% +/- 0.06%) by IPC and diazoxide and these effects could be abolished by 5-hydroxydecanoic acid. CONCLUSION: Ischemic preconditioning could reduce myocardial infarction size by activating mitochondrial ATP sensitive potassium channel and modulating connexin43 phosphorylation and internalization.

Distribution of cadmium in oilseed rape and Indian mustard grown on cadmium contaminated soil.

Heavy metal distribution in the specialized accumulating plants was important for phytoextraction technique. Hydroponic and pot experiment were conducted to investigated Cd phytoextraction ability and Cd distribution in the plant of oilseed rape species. The results showed that oilseed rape Chuanyou II-10 was more effective in phytoexetraction Cd among 21 varieties of oilseed rape and indicator plant Indian mustard. Cd concentration in the shoot of Chuanyou 11-10 and Indian mustard gradually decreased with an increase in growth period, while the amount of Cd uptake increased with the increase of growth period. There was constantly decrease in Cd concentration from the base leaves to the top leaves of Chuanyou II-10 and Indian mustard, the percentages of Cd uptake in older leaves were higher than those of younger leaves. Older leaves of Chuanyou 11-10 and Indian mustard extracted more Cd for the Cd contamination soil, leaves should as far as possible develop before they reached the soil and the older leaves were harvested in priority.

Characteristics of Cd uptake and accumulation in two Cd accumulator oilseed rape species.

Two pot experiments were conducted under greenhouse conditions to investigate the characteristics of Cd uptake and accumulation by two Cd accumulator oilseed rape varieties and one Indian mustard grown on a loamy soil that had been artificially contaminated by different amounts of CdSO4 (0, 20, 40, 60, 80, 100 mg/kg soil). The relationship between shoot Cd uptake of the two oilseed rape cultivars and the soil Cd concentrations could be simulated via quadratic equations. The curve showed that maximum shoot Cd uptake of Indian mustard was 314.7 microg/pot at soil Cd concentration of 87.8 mg/kg, while maximum uptake of the variety Xikou Huazi was 543.3 microg/pot at soil Cd concentration of 69.1 mg/kg and that of the variety Zhongyou Za-1hao was 576.7 microg/pot at soil Cd concentration of 84.0 mg/kg, suggesting that shoot Cd uptake ability of the two Cd accumulator oilseed rapes was significantly higher than that of the Indian mustard. Xikou Huazi had higher phytoremediation potential for Cd contaminated soil. Shoot Cd accumulation ability of the two Cd accumulator oilseed rapes was correspond and Cd was easier translocated to the shoot than hyperaccumulator Indian mustard as comparation plant. Shoot Cd distribution pattern showed consistent and significant reduction from older leaves to younger ones of two oilseed rapes and Indian mustard. Cd uptake by oilseed rapes in growth prophase was higher than that of growth anaphase.