首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
In Brazil most of the urban sewage is dumped without treatment into rivers. Because of this, it is extremely important to evaluate the consequences of organic matter rich sewage on the structure and functioning of river ecosystems. In this study we investigated the effects of urban sewage on the dissolved oxygen (O2), dissolved inorganic (DIC) and organic carbon (DOC), and electrical conductivity (EC) in 10 small streams of the Piracicaba River basin, southeast region of Brazil. In the Piracicaba River basin, which is one of the most developed regions of the country, only 16% of the total sewage load generated is treated. These streams were classified into two groups, one with heavy influence of urban sewage and another with less influence. Both concentrations and seasonal variability were distinct between the two groups. The streams that received sewage effluent had a combination of low O2 with high DIC, DOC, and EC. In the polluted streams, concentrations of dissolved carbon forms and EC were higher and O2 concentration lower during the low water period. In the less polluted streams seasonal variations in concentrations were small. We also investigated the efficiency of a sewage treatment plant installed two years ago in the catchment of one of these streams. It was observed an increase in the O2 concentration after the beginning of the treatment, and a decrease of DIC and DOC concentrations especially during the low water period. However, no significant change was observed in the EC, suggesting that the concentrations of major ions is still unaltered, and that a secondary treatment is necessary in order to reduce ion load into the stream.  相似文献   

2.
The decomposition of alder ( Alnus glutinosa ) and poplar ( Populus tremula ) leaf litter placed in direct contact with non-polluted and metal-polluted soil was investigated over 25 months in a controlled model-ecosystem experiment using the litterbag method. In addition to mass loss, we monitored the total and soluble concentrations of carbon, Cu, Zn, Cd and Pb. Leaves from trees grown on polluted soil had larger initial Zn, Cd and dissolved organic carbon concentrations. Neither the origin of the leaves (from trees grown on non-polluted or polluted soil) nor the placement of the leaves in polluted or unpolluted soil affected the decomposition process. Total metal contents increased in leaves placed on polluted soil over time. The solubility of metals in the leaf litter decreased over time, indicating that leaves acted as a temporary pool for metals from the soil in direct contact with the leaves. The sorbed metals were strongly bound in the litter even after two years of decomposition. The strong binding and thus reduced bioavailability of the metals provides an explanation for why they had no observable effects on litter decomposition.  相似文献   

3.
Based on the fact that streamwater quality reflects landscape conditions, the objectives of this study were: to investigate nitrogen (N), carbon (C), and major ion concentrations in six streams crossing minimally disturbed Atlantic Forest areas, with similar geomorphological characteristics; to determine N and C fluxes in one of these pristine streams (Indaiá); and assess the impact of human activity on the biogeochemistry of two other streams in the same region, crossing urbanized areas. The distribution pattern of carbon and inorganic nitrogen dissolved forms, as well as the major ion and biogenic gas concentrations in the streamwater, was similar in pristine streams, indicating that the C and N dynamics were determined by influence of some factors, such as climate, atmospheric deposition, geology, soil type, and land covering, which were analogous in the forested watersheds. The urban streams were significantly different from the pristine streams, showing low dissolved oxygen concentrations, high respiration rates, and high concentrations of carbon dioxide, dissolved inorganic nitrogen, dissolved inorganic carbon, and major ion. These differences were attributed to anthropogenic impact on water quality, especially domestic sewage discharge. Additionally, in the Indaiá stream, it was possible to observe the importance of rainfall over temporal dynamics of dissolved carbon forms, and also, the obtained specific flux of dissolved inorganic nitrogen was relatively elevated (approximately 11 kg ha?1 year?1). These results reveal the influence of human activity over the biogeochemistry of coastal streams and also indicate the importance N export of Atlantic Forest to the ocean.  相似文献   

4.
The objective of this study was to determine the impact of earthworm bioturbation on the distribution and availability of zinc in the soil profile.Experiments were carried out with Allolobophora chlorotica and Aporrectodea caliginosa in 24 perspex columns (∅ 10 cm), filled with 20-23 cm non-polluted soil (OM 2%, clay 2.9%, pH 0.01 M CaCl2 6.4), that was covered by a 3-5 cm layer of aged zinc spiked soil (500 mg Zn/kg dry soil) and another 2 cm non-polluted soil on top. After 80 and 175 days, columns were sacrificed and each cm from the top down to a depth of 15 cm was sampled. Earthworm casts, placed on top of the soil, were collected. Each sample was analyzed for total and CaCl2-exchangeable zinc concentrations.Effects of earthworm bioturbation were most pronounced after 175 days. For A. chlorotica, total and CaCl2-exchangeable zinc concentrations in the polluted layers were lower with than without earthworms. Total zinc concentrations in the non-polluted layers were higher in columns with earthworms. Casts of A. chlorotica collected on the soil surface showed slightly higher total zinc concentrations than non-polluted soil. Casts were found throughout the whole column. For A. caliginosa there were no differences in total zinc concentration between columns with and without earthworms. CaCl2-exchangeable zinc concentrations in the polluted layers were lower for columns with earthworms. Casts were mainly placed on top of the soil and contained total zinc concentrations intermediate between those in non-polluted and polluted soil layers.This study shows that different endogeic earthworm species have different effects on zinc distribution and availability in soils. A. chlorotica transfers soil throughout the whole column, effectively mixing it, while A. caliginosa decreases metal availability and transfers polluted soil to the soil surface.  相似文献   

5.
Background, Aim and Scope   Humic acids (HAs) are the most important humified component of dissolved organic carbon (DOC) present in sewage water used for irrigation. It is well known that HAs affect the toxicity and availability of heavy metals (HMs) in soil-plant systems, and may increase the human exposure to HMs in contaminated soil through plant uptake. This study was conducted to assess the effects of HAs on HM availability, plant growth and HM uptake. Materials and Methods: With wheat (Triticum aestivum) as a test plant, a greenhouse pot experiment was conducted to investigate the effects of HAs in irrigation water on the phytoavailability of cadmium (Cd) and lead (Pb) in soil. Cd and Pb were added to the soil at concentrations of 1.5 and 150 mg/kg, respectively. Wheat seedlings grown in Cd and Pb-contaminated soil were watered with 4 levels of HA solution (0, 140, 280 and 560 mg/kg of HAs, respectively). Results: In control and Pb treatments, both plant biomass and plant HM concentrations increased with increasing concentrations of HAs in the solution. Plant biomass was markedly decreased when metal concentrations in plants increased, particularly in Cd and Cd/Pb treatments. In the soil, extractable metals, and water soluble organic carbon (WSOC) and its fractions significantly increased with increasing HA concentrations. Discussion: The results suggested that the application of HAs in barren soils may improve plant nutrition by mobilizing soil nutrients and providing plants with carbon sources. On the other hand, HAs present in sewage water may increase both the availability and transfer of HMs in the soil-plant continuum and subsequently increase human exposure to HMs in polluted soil. Conclusions. Conclusions: HA solution as irrigation water significantly increased HM availability to plants cultivated in the HM-amended soil and may increase the environmental risk of sewage irrigation. Recommendations and Perspectives: These results suggested that, when assessing the effect of sewage irrigation on soil quality, HAs contained in sewage water should be taken into consideration.  相似文献   

6.
This study investigated the impact of epigeic and (epi)anecic earthworms on the distribution and availability of zinc in the soil profile. Experiments were carried out with Lumbricus rubellus and Lumbricus terrestris in perspex columns (Ø 10 cm), filled with 20 to 23 cm non-polluted soil [organic matter 2%, clay 2.9%, pH 6.4 (0.01 M CaCl2)], that was covered by a 3- to 5-cm layer of aged zinc-spiked soil (500 mg Zn/kg dry soil) and another 2 cm non-polluted soil on top. After 80 days, columns were sacrificed and sampled in a depth profile. Earthworm casts, deposited on top of the soil, were collected. Each sample was analyzed for total and 0.01 M CaCl2-exchangeable zinc concentrations. L. rubellus did not go deeper than 3 cm into the soil and therefore no effect on zinc distribution in the soil could be detected. For L. terrestris, total zinc concentrations in the non-polluted layers were slightly but significantly higher in columns with earthworms, and so were the CaCl2-exchangeable zinc concentrations in the polluted layers of these columns. Casts of L. terrestris collected from the soil surface showed higher total zinc concentrations than those from non-polluted soil. Casts were mainly placed on top of the soil. This study showed that these epigeic and (epi)anecic species have only a slight effect on zinc availability, and that deep burrowing species, like L. terrestris, are able to transport polluted soil from deeper layers to the soil surface.  相似文献   

7.
This study focused on the potential of using soil enzyme activities and general microbiological rates (respiration, N-mineralisation, nitrification) to evaluate the quality of soils affected by a pyrite mud spill which contained high concentrations of heavy metals. The quality of soils after restoration was estimated by comparing enzyme activities and general microbiological rates in three different types of experimental field plots: (i) non-polluted, (ii) polluted but restored, and (iii) polluted but un-restored soils. Non-polluted soils showed the highest levels of enzyme activity. Significant differences were detected for acid phosphatase, β-glucosidase and urease activities between all types of plots. However, arylsulfatase and alkaline phosphatase activities showed no significant differences between the restored plots and polluted but un-restored plots. Geometric mean statistics were used as an index of soil quality in terms of overall: (i) bioavailable heavy metal concentrations, (ii) assayed enzyme activities, and (iii) general microbiological rates, in order to compare plots differing in the degree of pyritic mud pollution. The results indicate that it is important to consider these three criteria in to estimate the soil quality of heavy-metal contaminated soils. Typically, enzyme activities were negatively correlated with bioavailable Cd, Cu and Zn concentrations, but positively with soil pH values. In contrast, pH values were negatively correlated with bioavailable concentrations of Cd, Cu and Zn. It is unclear if the generalised lower enzyme activities found in restored soils, compared to non-polluted soils, is promoted by pH or bioavailable heavy metals concentrations, or a combination of both.  相似文献   

8.
Heavy metal polluted soils from a recent and a former sewage farm were studied in a 2.5 years‐column experiment under various irrigation regimes and/or liming treatment. The copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) concentrations in the soil and the leaching of these elements were studied. The amounts of the metals leached differed markedly between both soils, however, the effect of various irrigation treatments was less pronounced. The heavy metal content in the soil solid phase depended on the organic carbon content, however these dependencies differed for both soils as well as for particular metals. In lower soil horizons, the amount of heavy metals bound by unit mass of organic carbon was constant. It was assumed that the same amount of the heavy metals can be bound by the unit mass of the DOC. Under this assumption the amount of the DOC in the former sewage farm soil was in general too small to carry all heavy metals leached. Therefore leaching of their cationic forms has been postulated. The amount of the DOC in the present sewage farm soil could carry more heavy metals than these being leached. Therefore, an undersaturation of the DOC in heavy metals could occur in this soil.<?show $6#>  相似文献   

9.
Elevated phosphate concentrations at Safaga and Quseir, Red Sea, Egyptian coast, wererelated to some ecological and nutritional aspects of the macro-alga Cystoseira myrica during1985. The results obtained were compared with those recorded for a non-polluted control site atGhardaqa. Chemical analysis of surface seawater samples revealed that the concentrations of dissolvedphosphate at Safaga and Quseir were 3 and 20 times as much as that at Ghardaqa, respectively.The standing crop of C. myrica showed two peaks in spring and autumn. Maximum biomass yield(491 g m-2) and number of individuals (127 m-2) of C. myrica were recorded in the spring at theGhardaqa site. Quseir C. myrica samples contained significantly higher protein-N, total-N andtotal-P values but lower carbohydrate values than the Safaga and Ghardaqa samples (LSD at 1%level). Tissue N:P molar ratios for C. myrica, Laurencia papillosa and Ulva lactuca collected fromGhardaqa ranged from 68-98, compared to 30-59 for the same species collected at thephosphorus polluted sites at Safaga and Quseir. The carbon levels and the C:N ratios of C. myricaexhibited no significant variations in the three studied sites. However, the C:P ratios of Ghardaqaplants were significantly higher than those of Safaga and Quseir.  相似文献   

10.
Effect of 2,2′,5,5′-tetrachlorobiphenyl, benzo-a-pyren, cadmium and copper in an original sewage field soil and uptake of these substances by rye Rye was cultivated in pots on weakly polluted sewage field soil (R) and artificially polluted variants of this soil. The aim of the project was to study the combined effect of organic pollutants (PCB, PAH) and heavy metals (HM) to parameters of soil biology, biomass production and soil-plant transfer. R was contaminated with 2,2′,5,5′-tetrachlorobiphenyl (PCB 52), benzo-a-pyren (BaP), cadmium (Cd) or copper (Cu) as well as with combinations of these substances up to concentrations comparable with an extremely polluted sewage field soil. Rye showed significant yield reductions on all treatments enriched with copper ( > 60 ppm plant-available Cu in soil). In this context copper only produced the impairments of microbial activity in the soil and caused its phytotoxicity. The yield reductions were connected with higher copper contents and also higher cadmium contents of rye as a result of concentration effect. Added copper led to increasing mobility and availability for plants of Cd in the soil. Addition of copper in combination with organic pollutants to soil R increased also availability of Cd for plants.  相似文献   

11.
We investigated dissolved organic matter (DOM) from soil, sewage sludges, water from waste disposal sites, and composts as sorbents and potential carriers for hydrophobic polycyclic aromatic hydrocarbons (PAHs) in soil. Partition coefficients (expressed log KDOC) for two 5-ring compounds were 4·8–4·9 for DOM from soil, 4·5–47 from composts, and 4·3–4·4 from sewage sludges. The DOM from compost and sewage sludge can influence the transport of non-ionic organic contaminants because of the large concentrations of dissolved organic carbon (DOC) released from these materials. Leachates from waste disposal sites did not sorb PAHs. The DOM from compost contained a large percentage of organic molecules > 14 000 Da (32–46%), whereas DOM from waste disposal leachates contained only 7-lo%, and so bound less PAHs. The percentage of total hydrophobic components, as characterized by XAD-8 chromatography, was 50 ± 9% for most of the DOM solutions and did not express the differences in affinity of the organic sorbents to PAHs in the same way as the KDOC values. Isolated molecular-weight fractions of DOM from composts sorbed benzo(k)fluoranthene in each fraction. The log KDOC values were 4·1–4·3 for both fractions, < 1000 and 1000–14 000 Da, and 4·8–5·0 for the fraction > 14 000 Da. The interaction of PAHs with DOM < 1000 Da cannot be explained by partitioning within intramolecular nonpolar environments of dissolved macromolecules; rather it seems to be due to the amphoteric properties of DOM. This type of interaction of PAHs with small DOM molecules might affect the mobility of hydrophobic organic chemicals in soils.  相似文献   

12.
The Moroccan phosphate industry releases large amounts of heavy metals in the Atlantic Ocean in the surroundings of two places: Safi and Jorf Lasfar. The major waste, called phosphogypsum and composed of calcium sulphate and other additional salts, is introduced into sea water in particulate form. After dissolution of the particles, heavy metal concentrations can be influenced near the release point. Two multi-element analytical techniques were used to measure 47 element concentrations in various materials involved in the study of the phosphate pollution: Inductively Coupled Plasma Mass Spectrometry (ICPMS) and instrumental neutron activation analysis (INAA). At first, phosphate and phosphogypsum were characterized in order to recognize the overall features of the heavy metal pollution source. From the yearly amount of phosphogypsum produced by the Moroccan industry and the element concentrations in phosphogypsum, it has been possible to estimate a yearly flux of heavy metals introduced in the Atlantic Ocean. Algae were used as bio-accumulator materials of heavy metals in the marine environment, in the region of Jorf Lasfar, in order to significantly reveal the signal of the heavy metal pollution. Ulva lactuca Linnaeus was selected to assess heavy metal pollution around the waste release point. Accumulation factors were determined for 47 elements in U. lactuca, by comparing mean concentrations obtained in algae collected in non-polluted sites (background sites) and an average sea water concentration given in the literature. The ratio between the concentration in U. lactuca, collected in a polluted site to the background concentration in U. lactuca, was determined, giving an estimate of the pollution factor for the same elements by the phosphate industry. The decrease of the pollution due to the dilution in the sea water was observed as far as 6 km southward of the release point. A specific variation was observed for lead and its isotopic composition, denoting that the phosphate industry is not the only pollution source in this region. Natural processes were likely involved to induce the lead concentrations variations along the littoral.  相似文献   

13.
In this article we report the relationships between heavy metals(Pb, Cd, Zn, Cu) in soil and settleable particulate matter usingdata from 6 yr at six different sampling points withinCartagena, a Spanish Mediterranean city. The use of enrichmentfactors and factor analysis allowed us to predict the majorsources of these metals. Soils were classified as one of threetypes: soils from polluted zone L, soils from polluted zone Z,and non-polluted soils. Settleable particulate matter was alsoclassified in the following three groups: Industrial zone, Urbanzone, and Intermediate zone. Enrichment factors showed that soilsfrom polluted zone L are enriched in Pb and Cd when compared with soils from polluted zone Z, and soils from polluted zone Zare enriched in Zn and Cu when compared with soils from pollutedzone L. In this context, soils from polluted zones L and Z areidentified as specific sources of metals in the settleableparticulate matter samples. We also suggest the importance ofanthopogenic contribution of metals to soil-enrichment fromancient times up to the present. This process was most severeduring the XIX century, when our city suffered an importantindustrial development. The concentration of these heavy metalsare also affected by regional meteorological conditions, whichinclude scarce rainfalls and a significant wind dispersion ofsoil aerosols.  相似文献   

14.

Purpose

This study aims to study the effect of sewage sludge amendment on crop yield and on microbial biomass and community structure in Swedish agricultural soils.

Materials and methods

Topsoil samples (0–0.20 m depth) from four sites where sewage sludge had been repeatedly applied during 14–53 years were analysed for total C, total N, pH and phospholipid fatty acids (PLFAs). Heavy metals were analysed in both soil and plant samples, and crop yields were recorded.

Results and discussion

At all four sites, sewage sludge application increased crop yield and soil organic carbon. Sludge addition also resulted in elevated concentrations of some heavy metals (mainly Cu and Zn) in soils, but high concentrations of metals (Ni and Zn) in plant materials were almost exclusively found in the oldest experiment, started in 1956. PLFA analysis showed that the microbial community structure was strongly affected by changes in soil pH. At those sites where sewage sludge had caused low pH, Gram-positive bacteria were more abundant. However, differences in community structure were larger between sites than between the treatments.

Conclusions

At all four sites, long-term sewage sludge application increased the soil organic carbon and nitrogen content, microbial biomass and crop yield. Long-term sewage sludge application led to a decrease in soil pH. Concentrations of some metals had increased significantly with sewage sludge application at all sites, but the amounts of metals added to soil with sewage sludge were found not to be toxic for microbes at any site.  相似文献   

15.
Heavy metal contamination can inhibit soil functions but it is often difficult to determine the degree of pollution or when soil reclamation is complete. Enzyme assays offer potential as indicators of biological functioning of soils. However, antecedent water content of soil samples may affect the outcome of biological measurements. In Mediterranean regions, for much of the year ‘field moist’ surface soil can have water content similar to that of air-dry samples. The objectives of this study were to: (1) determine the sensitivity of a range of enzyme assays to detect the degree of pollution from a heavy metal mine spill; (2) evaluate rewetting field-dry soil as a pre-treatment for enzyme assays; and (3) test multivariate analysis for improving discrimination between polluted, reclaimed and non-polluted soils. The Aznalcóllar mining effluent spill provided a unique opportunity to address these objectives. This accident released toxic, heavy metal-contaminated (As, Bi, Cd, Cu, Pb, Tl, Zn…) and acid tailings into the Guadiamar watershed (SW Spain) in 1998, severely affecting the riparian zone along more than 4000 ha. Contaminated soils were collected from the highly polluted upper watershed and less polluted lower watershed along with reclaimed soil at both sites. Enzyme activities (phosphatases, arylsulfatase, β-glucosidase, urease and dehydrogenase) were assessed on both field-moist samples and soils rewetted to 80% of water-holding capacity and then incubated at 21 °C for 7 d prior to the assay. The reclaimed soils had higher activities than polluted soils but, typically, 1.5-3 times lower levels of activity than the non-polluted soil. Regardless of the moisture pre-treatment, all enzymes showed significant effects due to pollution, with urease and β-glucosidase showing the greatest discrimination between degrees of contamination. In general, rewetting field-dried soils increased activities on non-polluted and reclaimed soils which improved discrimination with polluted soils. Another method to increase the potential of soil enzyme activities to detect soil contamination could be to combine them in multivariate analysis, which provides a more holistic representation of the biochemical and microbial functionality of a soil.  相似文献   

16.
  相似文献   

17.
为了解滨城区新立河水质的污染状况,选取水库出水闸、西谢庄桥、黄河2路桥、黄河5路桥、黄河8路桥、黄河12路桥、黄河15路桥及北外环路桥8个河段处为取样点,利用蚕豆根尖细胞微核技术对各采样点进行了生物监测。调查了各河段样点的排污口数及水质表观特征,综合评价了新立河水质的污染情况。结果表明,在污染最严重的黄河5路桥至黄河15桥河段污染指数均3.50,该河段污染来源主要来自生活污水及工业废水,排污口数达调查河段的58.54%。排放污水为黑色,带有明显恶臭。利用蚕豆根尖细胞微核技术监测结果与现场调查的水质表观污染状况基本吻合。综合分析表明,新立河水质污染较严重,且有导致生物染色体分裂异常现象,需加大力度进行治理。  相似文献   

18.
Mycorrhizae are ubiquitous symbiosis which can mediate uptake of some plant nutrients. In polluted soils they could be of great importance in heavy metal availability and toxicity to plants. Mycorrhizae have also been reported to protect plants against toxic metals. We investigated the occurrence and infectivity of arbuscular mycorrhizal (AM) spores as affected by heavy metal levels and other soil properties in Norwegian soils collected from heavy metal polluted, high natural background and non-polluted areas. Spore numbers, mycorrhizal infectivity and spore germination of indigenous mycorrhizal fungi and of a reference strain (Glomus mosseae) in soils showed lower values in two soils with high metal concentrations and in one soil with a low pH. Mycorrhizal infectivity was negatively correlated with extractable metals. Spore number and mycorrhizal infectivity in a soil with naturally high heavy metal content were not different to in non-polluted soils, and indigenous AM fungi appeared more tolerant to metals than those in non-polluted soils. Mycorrhizal infectivity, expressed as MSI50 values, was significantly correlated (r′=0.89, P< 0.05) with the percentage of germinating G. mosseae spores in the soils. However, the number of spores per volume of soil was not significantly correlated with infectivity or spore germination of the reference strain. The spore germination method is discussed as a bioassay of heavy metal toxicity in soil.  相似文献   

19.
Carbon of humus acids （HSAC） and dissolved organic carbon （DOC） are the most active forms of soil organic carbon （SOC） and play an important role in global carbon recycling. We investigated the concentrations of HSAC, water-soluble organic carbon （WSOC）, hot water-extractable organic carbon （HWOC） and SOC in soils under different vegetation types of four copper mine tailings sites with differing vegetation succession time periods in Tongling, China. The concentrations of HSAC, WSOC, HWOC and SOC increased with vegetation succession. WSOC concentration increased with the accumulation of SOC in the tailings, and a linearly positive correlation existed between the concentrations of HSAC and SOC in the tailings. However, the percentages of HSAC and DOC in the SOC decreased during vegetation succession. The rate of SOC accumulation was higher when the succession time was longer than 20 years, whereas the speeds of soil organic matter （SOM） decomposition and humification were slow, and the concentrations of HSAC and DOC increased slowly in the tailings. The percentage of carbon of humic acid （HAC） in HSAC increased with vegetation succession, and the values of humification index （HI）, HAC/carbon of fulvic acid, also increased with the accumulation of HSAC and SOC in soils of the tailings sites. However, the HI value in the each of the tailings was less than 0.50. The humification rate of SOM was lower than the accumulation rate of SOM, and the level of soil fertility was still very low in the tailings even after 40 years of natural restoration.  相似文献   

20.
Effects of organic pollutants (PAH; PCB) and heavy metals in sewage fields on biomass production and heavy metal transfer of rye Rye was cultivated in pots on original sewage field soils and an artifically polluted soil. The weakly polluted sewage field soil (reference soil R) was contaminated with 2.2′,5.5′-tetrachlorbiphenyl, Benzo-a-pyren, cadmium or copper as well as with combinations of these organic pollutants and heavy metals. These treatments were compared with an extremely contaminated sewage field soil (GroBbeeren GB). Rye cultivated on the artifically polluted soil (R) showed typical symptoms of damage which were similar to effects on the extremely contaminated sewage field soil (GB). Damage from single substance copper was sometimes greater than those observed on soil GB. This may indicate interactions or synergistic effects.  相似文献   

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