Xingyuan He

Accumulation and tolerance characteristics of cadmium in a potential hyperaccumulator-Lonicera japonica Thunb

Phytoremediation using hyperaccumulators is a promising technique of removing soil pollutants. In the study, growth responses, cadmium (Cd) accumulation capability and physiological mechanisms of Lonicera japonica Thunb. under Cd stress were investigated. Exposed to 5 and 10 mg L(-1) Cd, the plants did not show any visual symptoms, furthermore, the height, dry biomass of leaves, roots and total and the chlorophyll (CHL) content were obtained different grade increase. When the concentration of Cd was up to 50 mg L(-1), the height, dry biomass of leaves and roots had not significant differences compared with the control. The indexes of tolerance (IT) were all above 0.8. The maintenance of high superoxide dismutase (SOD) and catalase (CAT) activities was observed along with the increased Cd concentration, suggesting strong internal detoxification mechanisms inside plant cells. After 21 days exposure to 25 mg L(-1) Cd, stem and shoot Cd concentrations reached 344.49+/-0.71 and 286.12+/-9.38 microg g(-1) DW, respectively and the plant had higher bioaccumulation coefficient (BC) and translocation factor (TF). According to these results, it was shown L. japonica had strong tolerance and accumulation capability to Cd, therefore it is a potential Cd-hyperaccumulator.

Integrated assessment of heavy metal contamination in sediments from a coastal industrial basin, NE China.

The purpose of this study is to investigate the current status of metal pollution of the sediments from urban-stream, estuary and Jinzhou Bay of the coastal industrial city, NE China. Forty surface sediment samples from river, estuary and bay and one sediment core from Jinzhou bay were collected and analyzed for heavy metal concentrations of Cu, Zn, Pb, Cd, Ni and Mn. The data reveals that there was a remarkable change in the contents of heavy metals among the sampling sediments, and all the mean values of heavy metal concentration were higher than the national guideline values of marine sediment quality of China (GB 18668-2002). This is one of the most polluted of the world’s impacted coastal systems. Both the correlation analyses and geostatistical analyses showed that Cu, Zn, Pb and Cd have a very similar spatial pattern and come from the industrial activities, and the concentration of Mn mainly caused by natural factors. The estuary is the most polluted area with extremely high potential ecological risk; however the contamination decreased with distance seaward of the river estuary. This study clearly highlights the urgent need to make great efforts to control the industrial emission and the exceptionally severe heavy metal pollution in the coastal area, and the immediate measures should be carried out to minimize the rate of contamination, and extent of future pollution problems.

Changes in effects of ozone exposure on growth, photosynthesis, and respiration of Ginkgo biloba in Shenyang urban area

An open-top chamber experiment was carried out from April through October 2006 to examine the effects of elevated (80 nmol mol−1) atmospheric O3 on Ginkgo biloba (4-years-old) in urban area. The air with ambient O3 (AA, ≈ 45 nmol mol−1) was used as control. The leaf mass and size, leaf area index, net photosynthetic rate (PN), apparent quantum yield, transpiration rate, and stomatal conductance were decreased by elevated O3 (EO) exposure. Visible foliar injury, which is light-brown flecks, was observed in the EO OTCs after 90 d of exposure. Carboxylation efficiency (ΦCO2) and photorespiration and dark respiration rates were enhanced by EO exposure in the first half of the season, but all of them turned to be lower than those of the AA control at the end of experiment. Stomata limitation of photosynthesis was significantly higher than control in the whole season (p<0.05). Chlorophyll (Chl) content was lower in EO variant than in the control and the difference became more and more apparent through the season. Hence the decrease in PN of G. biloba exposed to EO was the result of both stomatal and non-stomatal limitations. In the early season, the inhibition of photosynthesis was mainly caused by the stomatal limitation, and the earliest response was photoprotective down-regulation of photosynthesis but not photodamage. However, at the end of the season, the non-stomatal limiting factors such as decrease in Chl content, decrease in ΦCO2, and anti-oxidative enzyme activity became more important.

Effects of Elevated O3 and/or Elevated CO2 on Lipid Peroxidation and Antioxidant Systems in Ginkgo biloba Leaves

Four-year-old seedlings of Ginkgo biloba were exposed to elevated O3, elevated CO2 and elevated O3 plus elevated CO2 in open-top chambers (OTCs) to study the responses of antioxidant system in Ginkgo biloba leaves. No significant changes in reactive oxygen production and scavenging systems were detected in seedlings exposed to high CO2. Significant increase in H2O2 and MDA content were induced by elevated O3. The ascorbate content and antioxidative enzymes activity were increased significantly by exposure to high O3 as well. But the promoted ability in scavenging did not prevent the increase in H2O2 content and cell membrane lipid peroxidation. The increase was mitigated by high CO2 in the combined exposure, but the effect was hardly significant.

Spatial variations and ecological risk assessment of heavy metals in surface sediments on the upper reaches of Hun River, Northeast China

The distribution, accumulation, and ecological risk of heavy metals (Cu, Cd, Pb, Zn, Ni, Cr, and As) in the surface sediment were investigated in the upper reaches of Hunhe River, Northeast China. Sediment samples from 51 points throughout the upper reaches of Hunhe River were collected and measured for heavy metal concentrations, TN content, and TP content. Results showed that heavy metal concentrations at the vicinity of mines and towns were higher than those at other locations. According to sediment quality guidelines (SQGs), Cd and Zn were enriched in the sediments. The correlation analysis and principal component analysis (PCA) were conducted to assess the heavy metal sources. Close correlations between metal distribution and TP indicated that the sediments may be affected by application of phosphate fertilizer. Elements, Cu, Cd, Pb, Zn, and As, were grouped together, reflecting they were released from the same sources. PCA suggested that their primary sources were anthropogenic, namely mining and extensive use of fertilizers. Therefore, heavy metal pollution due to mining and agricultural intensification in the upper Hunhe River basin should be taken into account during the formation of regional management strategies for the water environment.

Haze removal based on advanced haze-optimized transformation AHOT for multispectral imagery

Ever-present spatially varying haze contamination in satellite scenes limits applications using visible and near-infrared bands of low-temporal-resolution multispectral satellite images. A relative atmospheric correction technique, the virtual cloud point (VCP) method, which is based on advanced haze-optimized transformation (AHOT), is developed for haze removal. It is an improved algorithm of the previous dark-object subtraction (DOS) based on haze-optimized transformation (HOT). In AHOT, extra steps are added to HOT to remove confusion caused by some land-cover types. The VCP method uses the upper bound of the histogram, as well as the lower bound, so that it enlarges the digital number (DN) variance reduced by haze, which is not considered in DOS. To evaluate this algorithm, hazy subsets of one Landsat Thematic Mapper (TM) and one QuickBird image are employed. Through before-and-after comparison using true-colour images and the normalized difference vegetation index (NDVI), it proves that the VCP method based on AHOT is apparently better than DOS based on HOT, when haze is distributed over urban areas where vegetation is sparse.

Responses of soil microbial communities to experimental warming in alpine grasslands on the qinghai-tibet plateau.

Global surface temperature is predicted to increase by at least 1.5°C by the end of this century. However, the response of soil microbial communities to global warming is still poorly understood, especially in high-elevation grasslands. We therefore conducted an experiment on three types of alpine grasslands on the Qinghai-Tibet Plateau to study the effect of experimental warming on abundance and composition of soil microbial communities at 0–10 and 10–20 cm depths. Plots were passively warmed for 3 years using open-top chambers and compared to adjacent control plots at ambient temperature. Soil microbial communities were assessed using phospholipid fatty acid (PLFA) analysis. We found that 3 years of experimental warming consistently and significantly increased microbial biomass at the 0–10 cm soil depth of alpine swamp meadow (ASM) and alpine steppe (AS) grasslands, and at both the 0–10 and 10–20 cm soil depths of alpine meadow (AM) grasslands, due primarily to the changes in soil temperature, moisture, and plant coverage. Soil microbial community composition was also significantly affected by warming at the 0–10 cm soil depth of ASM and AM and at the 10–20 cm soil depth of AM. Warming significantly decreased the ratio of fungi to bacteria and thus induced a community shift towards bacteria at the 0–10 cm soil depth of ASM and AM. While the ratio of arbuscular mycorrhizal fungi to saprotrophic fungi (AMF/SF) was significantly decreased by warming at the 0–10 cm soil depth of ASM, it was increased at the 0–10 cm soil depth of AM. These results indicate that warming had a strong influence on soil microbial communities in the studied high-elevation grasslands and that the effect was dependent on grassland type.

Factors associated with farmland area changes in arid regions: a case study of the Shiyang River basin, northwestern China

Expansion of farmland is recognized as one of the most important human alterations to the environment around the globe. Using field investigations and socioeconomic data in combination with thematic mapper images taken in 1986 and 2000, we analyze farmland area changes and factors correlated with those changes in Liangzhou and Minqin oases, located near the middle and lower reaches of the Shiyang River basin in Gansu province, northwestern China. Between 1986 and 2000, farmland area increased in both oases, but the increase was greater at Minqin oasis. Population growth was positively correlated with farmland area expansion in both locations, as were improved agricultural techniques and economic development. In Liangzhou oasis, farmland expansion was closely linked to the amount of surface water present, while in Minqin oasis, farmed area growth was affected by environmental and weather conditions. These results suggest that economic development at Liangzhou oasis may be leading to environmental degradation downstream, at Minqin oasis.

Coordinated Regulation of Arbuscular Mycorrhizal Fungi and Soybean MAPK Pathway Genes Improved Mycorrhizal Soybean Drought Tolerance

Mitogen-activated protein kinase (MAPK) cascades play important roles in the stress response in both plants and microorganisms. The mycorrhizal symbiosis established between arbuscular mycorrhizal fungi (AMF) and plants can enhance plant drought tolerance, which might be closely related to the fungal MAPK response and the molecular dialogue between fungal and soybean MAPK cascades. To verify the above hypothesis, germinal Glomus intraradices (syn. Rhizophagus irregularis) spores and potted experiments were conducted. The results showed that AMF GiMAPKs with high homology with MAPKs from Saccharomyces cerevisiae had different gene expression patterns under different conditions (nitrogen starvation, abscisic acid treatment, and drought). Drought stress upregulated the levels of fungi and soybean MAPK transcripts in mycorrhizal soybean roots, indicating the possibility of a molecular dialogue between the two symbiotic sides of symbiosis and suggesting that they might cooperate to regulate the mycorrhizal soybean drought-stress response. Meanwhile, the changes in hydrogen peroxide, soluble sugar, and proline levels in mycorrhizal soybean as well as in the accelerated exchange of carbon and nitrogen in the symbionts were contributable to drought adaptation of the host plants. Thus, it can be preliminarily inferred that the interactions of MAPK signals on both sides, symbiotic fungus and plant, might regulate the response of symbiosis and, thus, improve the resistance of mycorrhizal soybean to drought stress.

Solar activity, global surface air temperature anomaly and pacific decadal oscillation recorded in urban tree rings

A tree ring width chronology developed from 58 samples taken from Chinese pine trees (Pinus tabulaeformis Carr.) growing in Shenyang city was studied to analyze the effects of solar activity, Global Surface Air Temperature Anomalies (GSATA) and the Pacific Decadal Oscillation (PDO) on annual radial growth. An excellent response of tree rings to solar activity and global environmental change was revealed, indicating that these urban Chinese pine trees are a suitable proxy for Sun-Earth system research despite their location in Shenyang, an industrial city. The information derived from annual growth rings of urban Chinese pine trees coincides with records from undisturbed trees in a natural location, and demonstrates significant synchronous response to solar activity in the periodic bands of 5–8, 10–12 and 20–30 years. The wave signal of tree growth was also affected and amplified by the combined effect of the PDO from 1900 to 2004 and GSATA from 1880 to 2004 with a short lag time, revealing 5–8, 11–13, and 20–23 year oscillatory modes. At 20–30 year timescale, Chinese pines validated the strong GSATA influence signal at 20.8 years, and may be the primary cause of the 20 and 23 year periodic waves of tree rings. Shenyang urban tree ring growth also showed high frequency variation (2—4 y) that may be due to low periodicity of solar activity, GSATA, PDO and local climate variations, especially in the 2–4 years band width.RésuméUne chronologie de largeur de cernes a été développée à partir de 58 échantillons prélevés sur des pins chinois (Pinus tabulaeformis Carr.) poussant dans la ville de Shenyang, afin d’analyser les effets de l’activité solaire, de l’anomalie globale de surface de la température de l’air (GSATA) et de l’Oscillation Pacifique décadaire (OPD) sur la croissance radiale. Cette étude a révélé une forte corrélation entre croissance des cernes et activité solaire d’une part, et changement global de l’environnement d’autre part, indiquant que ces pins urbains permettent des études sur les relations Soleil — Terre, malgré leur localisation dans une ville industrielle comme Shenyang. L’information dérivée de la croissance annuelle des cernes coïncide avec des enregistrements sur des arbres non perturbés dans un environnement naturel. De plus elle révèle une réponse significative synchrone avec l’activité solaire avec des périodes de 5–8, 10–12, et 20–30 ans. Le signal de vague de croissance des arbres a été aussi affecté, amplifié par l’effet combiné d’OPD de 1900 à 2004 et de l’anomalie globale de 1880 à 2004 avec un temps de latence réduit, et des modes d’oscillations de 5–8, 11–13 et 20–23 ans. À une échelle de temps de 20–30 ans, les pins chinois ont validé la forte influence du signal de l’anomalie globale à 20,8 années. L’anomalie globale peut être la cause primaire des 20 et 23 années de vagues périodiques des cernes des arbres. La croissance des cernes des arbres urbains de Shenyang a aussi montré une variation importante de fréquence de 2–4 ans qui est peut-être due une faible périodicité de l’activité solaire, de GSATA, de PDO et à des variations climatiques locales, en particulier dans une période de temps de 2–3 ans.