首页 | 本学科首页   官方微博 | 高级检索  
检索     
共有20条相似文献,以下是第1-20项 搜索用时 93 毫秒

1.  Variation of soil fertility and carbon sequestration by planting Hevea brasiliensis in Hainan Island, China  被引次数:2
   CHENG Chun-man  WANG Ru-song  JIANG Ju-sheng《环境科学学报(英文版)》,2007年第19卷第3期
   The development of rubber industry depends on the sustainable management of rubber plantation. To evaluate the environmental effects of planting Hevea brasiliensis on a subsystem of tropical forest ecosystem, the variation of soil fertility and carbon sequestration under rubber plantation within 30-year life period were investigated in Hainan Island. Results showed that (1) with the increase of stand age of rubber plantation, soil fertility decreased all along. From 1954 to 1995, soil organic matter, total N, available K and available P decreased by 48.2%, 54.1%, 56.7% and 64.1%, respectively. (2) If the complete return of litters was considered without additional fertilizer application to the soil of the rubber plantations, the consumption periods for P, N, K, Mg were only 825 years, 329 years, 94 years and 65 years, respectively~ To improve soil fertility is essential for rubber plantation development. (3) The C sequestration of rubber trees per hectare accounts for 272.08 t within 30-year life period and 57.91% of them was fixed in litters. In comparison with C sequestration by rain forest (234.305 t/hm^2) and by secondary rain forest (150.203 t/hm^2), rubber forest has more potentials for C fixation. On the base of above results, the following measures would benefit the maintenance of soil fertility and the development of rubber industry, including applying fertilizer to maintain the balance of soil nutrients, intercropping leguminous plant to improve soil fertility, reducing the collection of litters, optimizing soil properties to improve element P availability such as applying CaCO3. The information gathered from the study can be used as baseline data for the sustainable management of rubber plantation elsewhere.    

2.  Toxicological effects involved in risk assessment of rare earth lanthanum on roots of Vicia faba L. seedlings  
   Chengrun Wang  Mei He  Wen Shi  Jessie Wong  Tao Cheng  Xiaorong Wang  Lingling Hu  Fenfen Chen《环境科学学报(英文版)》,2011年第23卷第10期
   Combined chemical analyses and biological measurements were utilized to investigate potential toxicological effects and possible mechanisms involved in risk assessment of rare earth elements (REEs) on Vicia faba L. seedlings, which were hydroponically cultivated and exposed to various concentrations of lanthanum (La) for 15 days. The results showed that La contents in both the solution and roots increased with the increase of extraneous La, contributing to hormetic dose responses of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), ascorbate peroxidase (APX) and endoprotease (EP) isozymes activities, and HSP 70 production enhanced at low doses but suppressed at higher doses of La. These physiological responses constituted antioxidant and detoxification systems against La-induced oxidative stress. The elevated La levels also contributed to oxidatively modified proteins, which were most responsible for subsequent cell death and growth retardation of the roots. By combination of hormetic and traditional threshold dose levels, the threshold dose range was deduced to be 108-195 μg La/g dry weight in the roots, corresponding to 0.90-3.12 mg/L of soluble La in the culture solution. It suggests that persistent applications of REEs may lead to potential ecological risk in the environment.    

3.  Imazaquin degradation and metabolism in a sandy loam soil amended with farm litters  
   WANG Hui-li  LI Yan-yan  WEI Guo-hui  WANG Xue-dong《环境科学学报(英文版)》,2007年第19卷第9期
   Irnazaquin applied in legume crops has a long residual time in soil, which often impacts safety of the susceptible crops. To increase safety of imazaquin application, two composted litters, bovine manure (BM) and chicken manure (CM), were used to determine their effects on imazaquin environmental behavior by incorporating each kind of manure into the tested sandy loam soil at 10% (w/w). The degradation of imazaquin in BM- and CM-amended soil was about 2.4 and 1.5 times, respectively, faster than that in unamended soil. The half-lives of imazaquin in BM-amended soil varied between 6.7 and 15.4 d over the temperature range of 20 to 40℃, and the degradation rate constant (k) increased by a factor of about 1.5 for every 10℃ change. Higher mix ratio did not significantly increase the degradation, and the optimal active degradation of imazaquin was observed approximately at the mix ratio of 10:1 of soil to BM. The different moisture levels had negligible effect on imazaquin degradation. In both unamended and BM-amended treatments, two metabolites were observed at 5, 10 and 30 d after treatment. One metabolite at retention time (RT) of 8.4 rain was identified as 2-(4- hydroxyl-5-oxo-2-imidazolin-2-yl) quinoline acid, originating from the loss of isopropyl group and hydroxylation at the 4-position of imidazolinone ring. The other at RT of 12.9 rain was identified as quinoline-2,3-dicarboxylic anhydride, resulting from detachment of imidazolinone ring and the forming of dicarboxylic anhydride. This finding suggested that the addition of farm litters into soil might be a good management option since it can not only increase soil fertility but also contribute to increase safety of imazaquin application to the following susceptible crops.    

4.  Phosphatase activity and culture conditions of the yeast Candida mycoderma sp. and analysis of organic phosphorus hydrolysis ability  
   Mang Yan  Liufang Yu  Liang Zhang  Yuexia Guo  Kewei Dai  Yuru Chen《环境科学学报(英文版)》,2014年第26卷第11期
   Orthophosphate is an essential but limiting macronutrient for plant growth. About 67% cropland in China lacks sufficient phosphorus, especially that with red soil. Extensive soil phosphorus reserves exist in the form of organic phosphorus, which is unavailable for root uptake unless hydrolyzed by secretory acid phosphatases. Thus, many microorganisms with the ability to produce phosphatase have been exploited. In this work, the activity of an extracellular acid phosphatase and yeast biomass from Candida mycoderma was measured under different culture conditions, such as pH, temperature, and carbon source. A maximal phosphatase activity of 8.47 × 10^5±0.11× 10^5 U/g was achieved by C. Mycoderma in 36 hr under the optimal conditions. The extracellular acid phosphatase has high activity over a wide pH tolerance range from 2.5 to S.0 (optimum pH 3.5). The effects of different phosphorus compounds on the acid phosphatase production were also studied. The presence of phytin, lecithin or calcium phosphate reduced the phosphatase activity and biomass yield significantly. In addition, the pH of the culture medium was reduced significantly by lecithin. The efficiency of the strain in releasing orthophosphate from organic phosphorus was studied in red soil (used in planting trees) and rice soil (originating as red soil). The available phosphorus content was increased by 230% after inoculating 20 days in rice soil and decreased by 50% after inoculating 10 days in red soil. This work indicates that the yeast strain C. mycoderma has potential application for enhancing phosphorus utilization in plants that grow in rice soil.    

5.  Complex behaviour of trivalent rare earth elements by humic acids  
   Geng An chao  Zhang Shen  Harald Hфiland《环境科学学报(英文版)》,1998年第10卷第3期
   The complexation behaviours of trivalent rare earth elements (La, Ce, Ho and Yb) by two types of humic acids were investigated under a specified set of conditions. Humic acids show quite different complexation capacities an conditional formation constants with the REEs. Apparently there are two types of binding sites in the functional groups of humic acid, in which the first binding sites have stronger ability than the second. Cerium shows the largest complexation capacities and highest formation constants among the four REEs with two humic acids, this anomaly may be relative to the distribution pattern of the REEs in seawater. The experimental results were comparable to the values of other metals reported and provided the basic data for environmental geochemistry of rare earth elements.    

6.  Modeling of acute cadmium toxicity in solution to barley root elongation using biotic ligand model theory  
   Xuedong Wang  Mingyan Wu  Jingxing Ma  Xiaolin Chen  Luo Hua《环境科学学报(英文版)》,2016年第42卷第4期
   Protons(H+)as well as different major and trace elements may inhibit cadmium(Cd)uptake in aquatic organisms and thus alleviate Cd toxicity.However,little is known about such interactions in soil organisms.In this study,the independent effects of the cations calcium(Ca2+),magnesium(Mg2+),potassium(K+),H+and zinc(Zn2+)on Cd toxicity were investigated with 5-day long barley root elongation tests in nutrient solutions.The tested concentrations of selected cations and trace metal ions were based on the ranges that occur naturally in soil pore water.The toxicity of Cd decreased with increasing activity of Ca2+,Mg2+,H+and Zn2+,but not K+.Accordingly,conditional binding constants were obtained for the binding of Cd2+,Ca2+,Mg2+,H+,and Zn2+ with the binding ligand:log KCdBL5.19,logKCaBL2.87,logKMgBL2.98,logKHBL5.13 and logKZnBL5.42,respectively.Furthermore,it was calculated that on average 29% of the biotic ligand sites needed to be occupied by Cd to induce a 50% decrease in root elongation.Using the estimated constants,a biotic ligand model was successfully developed to predict the Cd toxicity to barley root elongation as a function of solution characteristics.The feasibility and accuracy of its application for predicting Cd toxicity in soils were discussed.    

7.  Effects of field application of phosphate fertilizers on the availability anduptake of lead, zinc and cadmium by cabbage (Brassica chinensis L.)in a mining tailing contaminated soil  被引次数:1
   WANG Biling  XIE Zhengmiao  CHEN Jianjun  JIANG Juntao  SU Qiufeng《环境科学学报(英文版)》,2008年第20卷第9期
   A field trial was conducted to evaluate the reduction of bioavailability of heavy metals including lead (Pb), zinc (Zn) and cadmium (Cd) in a soil contaminated by mining tailings in Shaoxing, Zhejiang, China. Three commercial phosphate (P) fertilizers including phosphate rock (PR), calcium magnesium phosphate (CMP), and single superphosphate (SSP) were applied to the plot at three P application rates, 50, 300, and 500 g/m2 with 9 treatments and control (CK). Plants, water soluble and exchangeable (WE) extra...    

8.  Temporal-spatial distribution and variability of cadmium contamination in soils in Shenyang Zhangshi irrigation area, China  
   SUN Li-n  ZHANG Yao-hu  SUN Tie-heng  GONG Zong-qiang  LIN Xin  LI Hai-bo《Journal of environmental sciences (China)》,2006年第18卷第6期
   Heavy metal contamination in soils has been of wide concern in China in the last several decades. The heavy metal contamination was caused by sewage irrigation, mining and inappropriate utilization of various agrochemicals and pesticides and so on. The Shenyang Zhangshi irrigation area (SZIA) in China is a representative area of heavy metal contamination of soils resulting from sewage irrigation for about 30 years duration. This study investigated the spatial distribution and temporal variation of soil cadmium contamination in the SZIA. The soil samples were collected from the SZIA in 1990 and 2004; Cd of soils was analyzed and then the spatial distribution and temporal variation of Cd in soils was modelled using kriging methods. The kriging map showed that long-term sewage irrigation had caused serious Cd contamination in topsoil and subsoil. In 2004, the Cd mean concentrations were 1.698 and 0.741 mg/kg, and the maxima 10.150 and 7.567 mg/kg in topsoils (0-20 cm) and subsoils (20-40 cm) respectively. These values are markedly more than the Cd levels in the second grade soil standard in China. In 1990, the Cd means were 1.023 and 0.331 mg/kg, and the maxima 9.400 and 3.156 mg/kg, in topsoils and subsoils respectively. The soil area in 1990 with Cd more than 1.5 mg/kg was 2701 and 206.4 hnl2 in topsoils and subsoils respectively; and in 2004, it was 7592 and 1583 hm^2, respectively. Compared with that in 1990, the mean and maximum concentration of Cd, as well as the soil area with Cd more than 1.5 mg/kg had all increased in 2004, both in topsoils and subsoils.    

9.  Fractionation and solubility of cadmium in paddy soils amended with porous hydrated calcium silicate  被引次数:4
   ZHAO Xiu-Lan  Saigusa Masaihiko《环境科学学报(英文版)》,2007年第19卷第3期
   Previous studies have shown that porous hydrated calcium silicate (PS) is very effective in decreasing cadmium (Cd) content in brown rice. However, it is unclear whether the PS influences cadmium transformation in soil. The present study examined the effect of PS on pH, cadmium transformation and cadmium solubility in Andosol and Alluvial soil, and also compared its effects with CaCO3, acidic porous hydrated calcium silicate (APS) and silica gel. Soil cadmium was operationally fractionationed into exchangeable (Exch), bound to carbonates (Carb), bound to iron and manganese oxides (FeMnOx), bound to organic matters (OM) and residual (Res) fraction. Application of PS and CaCO3 at hig rates enhanced soil pH, while APS and silica gel did not obviously change soil pH. PS and CaCO3 also increased the FeMnOx-Cd in Andosol and Carb-Cd in Alluvial soil, thus reducing the Exch-Cd in the tested soils. However, PS was less effective than CaCO3 at the same application rate. Cadmium fractions in the two soils were not changed by the treatments of APS and silica gel. There were no obvious differences in the solubility of cadmium in soils treated with PS, APS, silica gel and CaCO3 except Andosol treated 2.0% CaCO3 at the same pH of soil-CaC12 suspensions. These findings suggested that the decrease of cadmium availability in soil was mainly attributed to the increase of soil pH caused by PS.    

10.  Startup and operation of anaerobic EGSB reactor treatingpalm oil mill effluent  被引次数:2
   ZHANG Yejian  YAN Li  CHI Lin  LONG Xiuhu  MEI Zhijian  ZHANG Zhenjia《环境科学学报(英文版)》,2008年第20卷第6期
   A bench-scale expanded granular sludge bed (EGSB) reactor was applied to the treatment of palm oil mill ettluent (POME).The reactor had been operated continuously at 35℃ for 514 d,with organic loading rate (OLR) increased from 1.45 to 17.5 kg COD/(m3·d).The results showed that the EGSB reactor had good performance in terms of COD removal on the one hand,high COD removal of 91% Was obtained at two days’ of hydraulic retention time (HRT),and the highest OLR of 17.5 kg COD/(m3·d).On the other hand,only 46% COD in raw POME Was transformed into biogas in which the methane content was about 70% (v/v).A 30-d intermittent experiment indicated that the maximum transformation potential of organic matter in raw POME into methane Was 56%.Volatile fatty acid (VFA) accumulation was observed in the later operation stage,and this Was settled by supplementing trace metal elements.On the whole,the system exhibited good stability in terms of acidity and alkalinity.Finally, the operational problems inherent in the laboratory scale experiment and the corresponding countermeasures were also discussed.    

11.  Emission control for precursors causing acid rain(V): Improvement of acid soil with the bio-briquette combustion ash  
   DONG Xu-hui  SAKAMOTO Kazuhiko  WANG Wei  GAO Shi-dong  ISOBE Yugo《Journal of environmental sciences (China)》,2004年第16卷第5期
   The bio-briquette technique which mixes coal, biomass and sulfur fixation agent and bio-briquettes under 3-5 t/cm^2 line pressure has aroused people‘s attention in view of controlling the air pollution and the acid rain. In this paper, the physicochemical properties of bio-briquette and its ash were investigated. And the acid soil was improved by the bio-briquette combustion ash, which contained nutritive substances such as P, N, K and had the acid-neutralizing capacity(ANC). The pH, EC, effective nutrient elements(Ca, Mg, K, P and N), heavy metal elements(AI, Cu, Cd, Cr, Zn and Mn) and acid-neutralizing capacity change of ash-added soils within the range of 0-10%, were also studied. Specially, when 5% bio-briquette combustion ash was added to the tested soil, the content of the effective elements such as Ca, Mg and K rose by 100 times, ? times and twice, respectively. The total nitrogen also increased by about twice. The results showed the oxyanions such as that of AI, Cu, Cd, Cr, Zn and Mn were not potentially dangerous, because they were about the same as the averages of them in Chinese soil. It is shown that the ANC became stronger, though the ANC hardly increases in the ash-added soil. On the basis of the evaluation indices, it is concluded that the best mixture ratio is to add 2.5%--8% of the bio-briquette combustion ash to the tested soil.    

12.  Effects of soil water and nitrogen availability on photosynthesis and water use efficiency of Robinia pseudoacacia seedlings  
   Xiping Liu  Yangyang Fan  Junxia Long  Ruifeng Wei  Roger Kjelgren  Chunmei Gong  Jun Zhao《环境科学学报(英文版)》,2013年第25卷第3期
   The efficient use of water and nitrogen (N) to promote growth and increase yield of fruit trees and crops is well studied.However,little is known about their effects on woody plants growing in arid and semiarid areas with limited water and N availability.To examine the effects of water and N supply on early growth and water use efficiency (WUE) of trees on dry soils,one-year-old seedlings of Robinia pseudoacacia were exposed to three soil water contents (non-limiting,medium drought,and severe drought) as well as to low and high N levels,for four months.Photosynthetic parameters,leaf instantaneous WUE (WUEi) and whole tree WUE (WUEb) were determined.Results showed that,independent of N levels,increasing soil water content enhanced the tree transpiration rate (Tr),stomatal conductance (Gs),intercellular CO2 concentration (Ci),maximum net assimilation rate (Amax),apparent quantum yield (AQY),the range of photosynthetically active radiation (PAR) due to both reduced light compensation point and enhanced light saturation point,and dark respiration rate (Rd),resulting in a higher net photosynthetic rate (Pn) and a significantly increased whole tree biomass.Consequently,WUEi and WUEb were reduced at low N,whereas WUE i was enhanced at high N levels.Irrespective of soil water availability,N supply enhanced Pn in association with an increase of Gs and Ci and a decrease of the stomatal limitation value (Ls),while Tr remained unchanged.Biomass and WUEi increased under non-limiting water conditions and medium drought,as well as WUEb under all water conditions;but under severe drought,WUEi and biomass were not affected by N application.In conclusion,increasing soil water availability improves photosynthetic capacity and biomass accumulation under low and high N levels,but its effects on WUE vary with soil N levels.N supply increased Pn and WUE,but under severe drought,N supply did not enhance WUEi and biomass.    

13.  Impact of industrial effluent on growth and yield of rice (Oryza sativa L.) in silty clay loam soil  
   Mohammad Anwar Hossain  Golum Kibria Muhammad Mustafizur Rahman  Mohammad Mizanur Rahman  Abul Hossain Moll  Mohammad Mostafizur Rahman  Mohammad Khabir Uddin《环境科学学报(英文版)》,2015年第27卷第4期
   Degradation of soil and water from discharge of untreated industrial effluent is alarming in Bangladesh. Therefore, buildup of heavy metals in soil from contaminated effluent, their entry into the food chain and effects on rice yield were quantified in a pot experiment. The treatments were comprised of 0, 25%, 50%, 75% and 100% industrial effluents applied as irrigation water. Effluents, initial soil, different parts of rice plants and post-harvest pot soil were analyzed for various elements, including heavy metals. Application of elevated levels of effluent contributed to increased heavy metals in pot soils and rice roots due to translocation effects, which were transferred to rice straw and grain. The results indicated that heavy metal toxicity may develop in soil because of contaminated effluent application. Heavy metals are not biodegradable, rather they accumulate in soils, and transfer of these metals from effluent to soil and plant cells was found to reduce the growth and development of rice plants and thereby contributed to lower yield. Moreover, a higher concentration of effluent caused heavy metal toxicity as well as reduction of growth and yield of rice, and in the long run a more aggravated situation may threaten human lives, which emphasizes the obligatory adoption of effluent treatment before its release to the environment, and regular monitoring by government agencies needs to be ensured.    

14.  Seasonal exports of phosphorus from intensively fertilised nested grassland catchments  
   Ciaran Lewis  Rashad Rafique  Nelius Foley  Paul Leahy  Gerard Morgan  John Albertson  Sandeep Kumar  Gerard Kiely《环境科学学报(英文版)》,2013年第25卷第9期
   We carried out a one year (2002) study of phosphorus (P) loss from soil to water in three nested grassland catchments with known P input in chemical fertilizer and animal liquid slurry applications. Chemical fertilizer was applied to the grasslands between March and September and animal slurry was applied over the twelve months. The annual chemical P fertilizer applications for the 17 and 211 ha catchments were 16.4 and 23.7 kg P/ha respectively and the annual slurry applications were 10.7 and 14.0 kg P/ha, respectively. The annual total phosphorus (TP) export in stream-flow was 2.61, 2.48 and 1.61 kg P/ha for the 17, 211 and 1524 ha catchments, respectively, compared with a maximum permissible (by regulation) annual export of ca. 0.35 kg P/ha. The export rate (ratio of P export to P in land applications) was 9.6% and 6.6% from the 17 and 211 ha catchments, respectively. On average, 70% of stream flow and 85% of the P export occurred during the five wet months (October to February) indicating that when precipitation is much greater than evaporation, the hydrological conditions are most favourable for P export. However the soil quality and land use history may vary the results. Particulate P made up 22%, 43% and 37% of the TP export at the 17, 211 and 1524 ha catchment areas, respectively. As the chemical fertilizer was spread during the grass growth months (March to September), it has less immediate impact on stream water quality than the slurry applications. We also show that as the catchment scale increases, the P concentrations and P export decrease, confirming dilution due to increasing rural catchment size. In the longer term, the excess P from fertilizer maintains high soil P levels, an antecedent condition favourable to P loss from soil to water. This study confirms the significant negative water quality impact of excess P applications, particularly liquid animal slurry applications in wet winter months. The findings suggest that restricted P application in wet months can largely reduce the P losses from soil to water.    

15.  Organic carbon stock in topsoil of Jiangsu Province, China, and the recent trend of carbon sequestration  被引次数:11
   PAN Gen-xing  LI Lian-qing  ZHANG Qi  WANG Xu-kui  SUN Xing-bin  XU Xiao-bo  JIANG Ding-an《Journal of environmental sciences (China)》,2005年第17卷第1期
   Data collection of soil organic carbon(SOC) of 154 soil series of Jiangsu, China from the second provincial soil survey and of recent changes in SOC from a number of field pilot experiments across the province were collected. Statistical analysis of SOC contents and soil properties related to organic carbon storage were performed. The provincial total topsoil SOC stock was estimated to be O. 1 Pg with an extended pool of 0.4 Pg taking soil depth of 1 m, being relatively small compared to its total land area of lOl?00 km^2. One quarter of this topsoil stock was found in the soils of the Taihu Lake region that occupied 1/6 of the provincial arable area. Paddy soils accounted for over 50% of this stock in terms of SOC distribution among the soil types in the province. Experimental data from experimental farms widely distributed in the province showed that SOC storage increased consistently over the last 20 years despite a previously reported decreasing tendency during the period between 1950--1970. The evidence indicated that agricultural management practices such as irrigation, straw return and rotation of upland crops with rice or wheat crops contributed significantly to the increase in SOC storage. The annual carbon sequestration rate in the soils was in the range of 0.3-3.5 tC/(hm^2. a), depending on cropping systems and other agricultural practices. Thus, the agricultural production in the province, despite the high input, could serve as one of the practical methods to mitigate the increasing air CO2.    

16.  Heavy metal (Pb,Zn) uptake and chemical changes in rhizosphere soils of four wetland plants with different radial oxygen loss  被引次数:2
   Junxing Yang  Zuoluo M  Zhihong Ye  Xueyan Guo  Rongliang Qiu《环境科学学报(英文版)》,2010年第22卷第5期
   Lead and Zn uptake and chemical changes in rhizosphere soils of four emergent-rooted wetland plants; Aneilema bracteatum,Cyperus alternifolius, Ludwigia hyssopifolia and Veronica serpyllifolia were investigated by two experiments: (1) rhizobag filled with“clean” or metal-contaminated soil for analysis of Pb and Zn in plants and rhizosphere soils; and (2) applied deoxygenated solution foranalyzing their rates of radial oxygen loss (ROL). The results showed that the wetland plants with di erent ROL rates had significante ects on the mobility and chemical forms of Pb and Zn in rhizosphere under flooded conditions. These e ects were varied withdi erent metal elements and metal concentrations in the soils. Lead mobility in rhizosphere of the four plants both in the “clean”and contaminated soils was decreased, while Zn mobility was increased in the rhizosphere of the “clean” soil, but decreased in thecontaminated soil. Among the four plants, V. serpyllifolia, with the highest ROL, formed the highest degree of Fe plaque on the rootsurface, immobilized more Zn in Fe plaque, and has the highest e ects on the changes of Zn form (EXC-Zn) in rhizosphere under both“clean” and contaminated soil conditions. These results suggested that ROL of wetland plants could play an important role in Fe plaqueformation and mobility and chemical changes of metals in rhizosphere soil under flood conditions.    

17.  The effect of low-molecular-weight organic-acids(LMWOAs)on treatment of chromium-contaminated soils by compost-phytoremediation: Kinetics of the chromium release and fractionation  
   Huixia Chen  Junfeng Dou  Hongbin Xu《环境科学学报(英文版)》,2018年第8期
   A soil–plant biological system was developed from chromium(Cr) polluted soil treated by the compost-phytoremediation method. The transformation and migration of the Cr in this system is comprehensively studied in this research. The results illustrated that the co-composting treatment can reduce the Cr availability from 39%(F1 was about 31% of total, F2 was about 8% of total) to less than 2% by stabilizing the Cr. However, herbaceous plants can accumulate the concentrations of Cr from 113.8 to 265.2 mg/kg in the two crops,even though the concentration of soluble Cr in the substrate soil was below 0.1 mg/L.Cr can be assimilated and easily transferred in the tissues of plants because the lowmolecular-weight organic-acids(LMWOAs) derived from the plant root increase the bioavailability of Cr. The amount of extracted Cr dramatically increased when the organic acids were substituted in this order: citric acid malic acid tartaric acid oxalic acid acetic acid. On average the maximum(147.4 mg/kg) and the minimum(78.75 mg/kg) Cr were extracted by 20 mmol/L citric acid and acetic acid, respectively. The desorption of Cr in different acid solutions can be predicted by the pseudo second-order kinetics. The exchangeable Cr, carbonate-bound Cr, and residual Cr decreased, while Fe–Mn oxide bound Cr and organic bound Cr increased in the soil solid phase. According to the experimental results, the organic acids will promote the desorption and chelation processes of Cr, leading to the remobilization of Cr in the soil.    

18.  Adsorption and desorption of Cu(Ⅱ) and Pb(Ⅱ) in paddy soils cultivated for various years in the subtropical China  被引次数:5
   Liang M  Renkou Xu  Jun Jiang《环境科学学报(英文版)》,2010年第22卷第5期
   The adsorption and desorption of Cu(Ⅱ) and Pb(Ⅱ) on upland red soil, and paddy soils which were originated from the upland soil and cultivated for 8, 15, 35 and 85 years, were investigated using the batch method. The study showed that the organic matter content and cation exchange capacity (CEC) of the soils are important factors controlling the adsorption and desorption of Cu(Ⅱ) and Pb(Ⅱ).The 15-Year paddy soil had the highest adsorption capacity for Pb(Ⅱ), followed by the 35-Year paddy soil. Both the 35-Year paddy soil and 15-Year paddy soil adsorbed more Cu(Ⅱ) than the upland soil and other paddy soils. The 15-Year paddy softs exhibited the highest desorption percentage for both Cu(Ⅱ) and Pb(Ⅱ). These results are consistent with the trend for the CEC of the soils tested. The high soil CEC contributes not only to the adsorption of Cu(Ⅱ) and Pb(Ⅱ) but also to the electrostatic adsorption of the two heavy metals by the soils. Lower desorption percentages for Cu(Ⅱ) (36.7% to 42.2%) and Ph(Ⅱ) (50.4% to 57.9%) were observed for the 85-Year paddy soil. The highest content of organic matter in the soil was responsible for the low desorption percentages for the two metals because the formation of the complexes between the organic matter and the metals could increase the stability of the heavy metals in the soils.    

19.  Effects of climate change on water resources in Tarim River Basin, Northwest China  被引次数:7
   CHEN Ya-ning  LI Wei-hong  XU Chang-chun  HAO Xin-ming《环境科学学报(英文版)》,2007年第19卷第4期
   Based on hydrology, temperature, and precipitation data from the past 50 years, the effects of climate change on water resources in Tarim River Basin in Northwest China were investigated. The long-term trends of the hydrological time series were detected using both parametric and nonparametric techniques. The results showed that the increasing tendency of the temperature has a 5% level of significance, and the temperature increased by nearly 1℃ over the past 50 years. The precipitation showed a significant increase in the 1980s and 1990s, and the average annual precipitation exhibited an increasing trend with a magnitude of 6.8 mm per decade. A step change occurred in both the temperature and precipitation time series around 1986. The streamflow from the headwater of the Tarim River exhibited a significant increase during the last 20 years. The increase in temperature, precipitation, and streamflow may be attributed to global climate change.    

20.  Simulating study on the effect of acid precipitation on forest soil weathering  
   Liu Quanyou  Li Changsheng《Journal of environmental sciences (China)》,1991年第3卷第3期
   The effect of acid rain on the forest soils in China was discussed on the basis of simulating studies. The soils were collected from five typical areas, including Chongqing in Sichuan Province and Guiyang in Guizhou Province, where there has been heavier acid rain in southwest China, and Huitong in Hunan Province, Zhouzhi in Shaanxi Province, and Xinglong in Hebei Province, all of which were selected as control. Field investigation and sampling were made in the typical forests in all the above five areas. The relationship between pH values in precipitation and rates of soil weathering, the difference between the rates of soil weathering in different areas, and the cause of such a difference, have been worked out. The prediction was also conducted on the supply dynamics of nutrient and toxic elements in various forest ecosystems which were affected by acid deposition in order to understand the long-term effects of acid precipitation on the forest ecosystems studied.    

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号