农田杂草种子库动态及其生态学意义

研究土壤杂草种子的杂草种类组成、数量、分布及动态,对于研究杂草种群的消长规律、预测杂草群落的演替具有重要意义,可为持久稳定地控制农田杂草发生与危害提供科学依据。详细总结了农田杂草种子库方面的国内外研究进展,并对今后在农田杂草种子库的研究应当关注的问题进行了探讨。

Environmentally‐friendly carbon nanomaterials for photocatalytic hydrogen production

Currently,the energy crisis is the crucial problem faced by the world,and photocatalytic hydrogen(H_(2))production is recognized with a chance to be a standout amongst those guaranteeing results to this issue.For a long time,photocatalytic H_(2) production has mainly relied on the noble metal cata‐lysts.However,the limitations of noble metals themselves,such as scarcity and high cost,have se‐verely restricted their large‐scale application.Therefore,it is urgent to seek a cheaper,more effi‐cient,and stable catalyst for photocatalytic H_(2) production.Fortunately,the emergence of carbon nanostructured materials(CNMs)has brought dawn.Its excellent structure and semiconductor performance can effectively participate in photocatalytic H_(2) production.CNMs have developed rap‐idly since they appeared in the field of photocatalytic water splitting.Therefore,it is necessary to summarize the latest progress of CNMs promptly for further development.This review introduced the CNMs,including carbon dots,fullerenes,carbon nanotubes,graphene,and graphdiyne,which is a powerful assistant in photocatalytic H_(2) production.CNMs can provide abundant adsorption and active sites,charge separation and transport channels,photocatalysts,co‐catalysts and photosensi‐tizers.Then,this review has introduced the strategy for enhancing CNMs in photocatalytic H_(2) pro‐duction based on recent research.Finally,the challenge faced by CNMs in photocatalytic H_(2) produc‐tion has prospected.

Effect of bismuth tungstate with different hierarchical architectures on photocatalytic degradation of norfloxacin under visible light

The photocatalytic degradation of norfloxacin by bismuth tungstate(Bi2WO6)with different hierarchical architectures wasinvestigated under visible light irradiation.Bi2WO6was prepared by hydrothermal method with the reaction solution pH rangingfrom4to11.The relatively ultrathin Bi2WO6nanoflakes prepared at pH4showed excellent adsorption and photodegradationefficiency towards norfloxacin.The characterization results showed that Bi2WO6prepared at pH4had a larger specific area andfaster photo-generated carrier separation rate.The decay rate reached the maximum in weak alkaline reaction solution,which couldbe attributed to the presence of moderate OH-anions.The present study demonstrated that the smaller size of Bi2WO6could be anefficient photocatalyst on the degradation of norfloxacin in the aquatic environment.

Effects of Amino Acid Foliar Fertilizer on the Yield and Quality of Different Vegetables

In order to explore the effects of amino acid foliar fertilizer on the yield and quality of different vegetables, we tested the spraying of an amino acid foliar fertilizer(Wanfeng 2) onto the leaves of cucumbers, eggplants and water spinach through contrast experiment in a greenhouse. The results showed that the yield increments of amino acid foliar fertilizer treatments in cucumbers, eggplants and water spinach were 11.57%, 4.43% and 12.41% respectively, and the output-input ratios were 64.52 ∶ 1, 53.31 ∶ 1 and 55.14 ∶ 1 respectively. Amino acid foliar fertilizer can influence the quality of greenhouse vegetables. The total sugar content of the cucumbers, eggplants, and water spinach significantly increased by 12.00%, 22.30%and 12.10% respectively. The vitamin C content increased by 4.76%, 24.80%, and10.90% respectively compared with the control. In conclusion, the spraying of amino acid foliar fertilizer could improve the yield and the nutritive quality of vegetables such as cucumbers, eggplants and water spinach.

Preparation of Sludge-Based Biomass Carbon and Cu^2+ Adsorption in Water

In this study,biomass carbon was prepared by pyrolysis by using sewage sludge as raw material.The effects of activator concentration,impregnation ratio,impregnation time,carbonization temperature and carbonization time on the preparation of sludge-based biomass carbon were investigated.The adsorption isotherm and adsorption kinetics of sludge-based biomass carbon prepared under optimal conditions were analyzed.The results showed that the optimum preparation condition of sludge-based biomass carbon was as follows:the concentration of activator was 15%,the impregnation ratio was 1∶1,the impregnation time was 4 h,the carbonization temperature was 750℃,and the carbonization time was 40 min.The adsorption process accords with the quasi-second-order reaction kinetics model,and the isothermal adsorption curve follows the Freundlich isotherm model,which indicates that the adsorption of Cu^2+on sludge-based biomass carbon ismulti-layered.

Distribution characteristics and environmental risk assessment following metal(loid)s pollution incidents at Southwest China mining site

Limited information is available on long-term effects of metal(loid)s pollution incidents. Here, we analyze the distribution characteristics and quantification of elements in the Southwest China Keda mining site, which is one of the most populated sites and enables human health and ecological risk assessments of elemental pollution. The results on modified degree of contamination indicated that the soil and sediment were highly contaminated near Dahu Lake.The health risk of children was almost 2.5 times that of adults in surface water, and 7.1 times in soil, respectively.Moreover, Tl and As were the main health risk contributors in surface water and soil, respectively, and As posed the highest ecological risk both in soil and sediment. These results indicated the potential impact of toxic metal(loid)s on the health of residents and environment. Hence, more scientific attention and proper management need to be paid to this environmental challenge in the future.

Fixation of Multiple Metals in Contaminated Soil by Different Passivators

The effects of 4 passivators, zeolite, lime, red mud and peanut shell biochar, on the fixation of Cd, Pb, Cu and Zn in acidic multi-metal contaminated soils were studied by passivator culture experiment in order to screen out the passivator with better fixation effects. The results showed that the soil pH values of zeolite, lime, red mud and peanut shell biochar increased significantly by 0.511.02, 0.821.29, 0.720.89 and 0.300.35 respectively. The effects of 4 passivators on the fixation of Cd and Zn in soil are lime>red mud>zeolite>peanut shell biochar. The order of effects on the fixation of Pb is red mud>lime>zeolite>peanut shell biochar. The order of the fixation effects of Cu is red mud>lime>peanut shell carbon>zeolite. The contents of Cd, Pb, Cu and Zn in the extractable state of CaCl2 decreased with the increase in the dosage of 4 passivators. Lime and red mud showed good fixation effects on Cd, Pb, Cu and Zn. The contents of Cd, Pb, Cu and Zn in the extractable state of CaCl2 at the low dosage(2.5 g/kg) of lime and red mud decreased by 41%, 84%, 76% and 83% respectively. Soil pH value was negatively correlated with CaCl2-Cd, Pb, Cu and Zn(P<0.01). Lime and red mud had significant fixation effects on Cd, Pb, Cu and Zn in acidic multi-metal contaminated soils at low application dosages.

Adsorption-desorption Characteristics and Thermodynamics of Quinclorac on Minerals

Adsorption-desorption characteristics of quinclorac on montmorillonite, attapulgite and goethite were investigated by the batch equilibrium techniques. The sorption mechanisms of minerals were discussed based on sorption thermodynamics. The results showed that the adsorption of quinclorac on the 3 minerals was included in both rapid stage and slow equilibrium stage. The adsorption kinetics consisted with the pseudo-second-order equation, the particle diffusion equation, and elovich equations, and among them, fitting from the pseudo-second-order was the best. In addition, it could be seen from the nonzero constant C in the particle diffusion equation that the rate of particle diffusion was not a sole factor. The isotherm adsorption-desorption of quinclorac on the 3 clay minerals all fitted Linear and Freundlich equation very well. The adsorption capacities of minerals for quinclorac followed the order of goethite〉montmorillonite〉attapulgite, The desorption of quinclorac presented obvious hysteresis phenomenon on minerals. The study on thermodynamic behavior indicated that the sorption processes of quinclorec onto minerals were spontaneous, and the sorption spontaneity was strengthened with the temperature increasing.

Effects of Cadmium on the Energy Substances and Immune Detoxification Enzyme System of Infected Pirata subpiraticus

In order to investigate the effects of cadmium on the immune defense function of spiders infected with bacteria,Pirata subpiraticus was taken as research object,and the cadmium-treated group and the control group were all infected with bacteria(S.aureus and E.coli).After 6 and 24 h of infection,the energy substances contents and the activity of immune detoxification enzyme system in Pirata subpiraticus were determined.The results showed that after 6 and 24 h of infection with S.aureus and 6 h of infection with E.coli,the amount of soluble sugars and soluble proteins of Pirata subpiraticus in the cadmium-treated group increased significantly.Compared with the control,after 6 h of infection with S.aureus and 24 h of infection with E.coli,the activity of acetylcholinesterase(AChE)of Pirata subpiraticus in the cadmium-treated group decreased significantly.This indicated that cadmium inhibited the activity of AChE in infected Pirata subpiraticus.After 24 h of infection with S.aureus and 6 h of infection with E.coli,the activity of polyphenol oxidase(PPO)was signicantly higher than that of the control,indicating that cadmium induced the activity of PPO in infected Pirata subpiraticus.These results suggested that cadmium can affect the content of energy substance and immune detoxification enzyme activity in infected Pirata subpiraticus.

Study on Soil Properties of Eucalyptus Plantation inHainan

Taking Hainan Eucalyptus plantation as the research object with 4 other kinds of plantations or natural forest as reference plots, the effects of different forest land types on soil nutrient contents were analyzed, and the differences of soil properties were discussed. The results showed that: (1) Eucalyptus plantations were relatively helpful to reduce soil bulk density and enhance the stability of water-stable aggregates;(2) Eucalyptus plantations can improve the content of soil organic matter;(3) Soil pH showed an overall acidi fication trend under forest land conditions in Hainan;total nitrogen and alkali-hydrolyzed nitrogen content of Eucalyptus plantations showed a downward trend with the deepening of soil layer;total phosphorus and available phosphorus content showed a downward trend, while organic matter, total potassium and available K showed an upward trend. (4) The contents of total phosphorus and available phosphorus in the soil of Eucalyptus plantations of different ages did not change significantly, whereas the contents of other nutrients decreased gradually with the increase of soil depth.

Study on the Effects of Nitrogen and Phosphorus Absorptionby Ecological Ditches

By using the simulated ditch experiment,the differences of nitrogen and phosphorus absorption capacities of 9 aquatic plants were studied,and the better varieties of nitrogen and phosphorus absorption capacity were selected to construct the ecological ditch and oxidation pond to study the nitrogen and phosphorus absorption effect.The results showed that the nitrogen and phosphorus residues in the simulated ditch water were signi ficantly reduced after planting aquatic plants.The biomass of Canna glauca,Myriophyllum elatinoides,Sorbaria sorbifolia,Pontederia cordata and Zizania was high,and the uptakes of nitrogen and phosphorus were high.Among them,the effect of planting Canna glauca and Myriophyllum elatinoides was the best.The concentration of nitrogen and phosphorus in farmland drainage decreased signi ficantly after being absorbed by aquatic plants in ecological ditches;the concentration of total nitrogen,soluble nitrogen and total phosphorus in main ditches decreased by 39.6%,40.1% and 36.9% respectively on average;the concentration of total nitrogen,soluble nitrogen and total phosphorus in branch ditches decreased by 6.6%,10.3% and 13.6% on average.The concentration of total nitrogen and total phosphorus in the oxidation pond could be further reduced by 17.7%and 13.3%.Ecological ditches can effectively intercept nitrogen and phosphorus in water,and have good ecological benefits of purifying water to obtain improved water quality.