土壤中拟除虫菊酯微生物降解研究

微生物降解是拟除虫菊酯类农药从土壤中消去的主要途径。本文介绍了拟除虫菊酯降解菌的分离鉴定、降解基因的克隆以及微生物降解机理研究的近期成果,综合介绍了拟除虫菊酯异构体选择降解的特征、原因以及可能产生的环境效应,重点分析了农药疏水性、土壤吸附、重金属、土壤养分及长期施肥、共存农药对土壤中拟除虫菊酯微生物降解的影响,最后对土壤微生物修复前景进行了展望。     

浓硫酸纯化-气相色谱法测定土壤中拟除虫菊酯农药残留

建立了土壤中拟除虫菊酯类农药新的前处理方法。样品以乙腈提取,浓硫酸-乙醇进行纯化,毛细管柱气相色谱法测定土壤中的拟除虫菊酯农药。结果表明:4种菊酯在3种土壤样品中的添加回收率在84.14%～105.51%之间,变异系数为1.24%～5.82%。该方法具有省时、省溶剂、操作简单、纯化效果好、实用性强的特点。     

拟除虫菊酯类农药微生物降解研究进展

拟除虫菊酯类农药是杀虫剂中的第三大类,这类农药残留已成为目前农产品中的主要农药残留类型之一。而微生物在降解农药残留中具有重要的作用,微生物降解技术已成为去除农药残留的绿色生产技术。拟除虫菊酯类农药的微生物降解国内外已有的研究主要集中在降解现象,菌株的分离、鉴定及生理生化特性,酶学,不同光学异构体的降解、降解途径等方面,本文对此进行了较详细的回顾,并对将来的研究方向进行了展望。     

稀土元素在水体中的环境化学行为及其生物效应

综述了稀土元素在水体中的来源、分布、迁移、转化等环境化学行为生物效应及其研究概况。     

拟除虫菊酯类农药残留降解菌的筛选及其生理特性研究

从活性污泥的富集培养物中分离得到可降解几种拟除虫菊酯农药的菌株qw5,初步鉴定qw5为地衣芽孢杆菌 (Bacilliuslicheniformis)。菌株qw5在通气、pH7～ 8、温度 3 0℃左右的环境条件下生长较好。培养 5天 ,菌株qw5对氰戊菊酯、氯氰菊酯、溴氰菊酯的降解率分别为 5 3 .8%、41 .2 %和 61 .7%。经质谱分析 ,菌株qw5降解氰戊菊酯产生中间代谢产物 3 -苯氧基苯甲醛。qw5对小白鼠无致病力 ,对几种常用的抗生素敏感。盆钵和小区试验表明 ,菌株qw5对青菜中残留的拟除虫菊酯有明显去除效果。     

土壤中拟除虫菊酯类残留农药的气相色谱测定方法研究

建立了土壤中氯氰菊酯、氰戊菊酯和溴氰菊酯的提取、净化以及毛细管气相色谱的测定方法。运用石油醚-丙酮（P／P，2：1）混合溶剂提取，用氟罗里硅土进行层析净化，60ml石油醚／乙酸乙酯（V／V，9：1）进行洗脱，电子捕获-气相色谱测定，单点外标法定量。实验表明：土样中添加0．08mgkg^-1的氯氰菊酯、氰戊菊酯和溴氰菊酯3种农药混标时，方法回收率为89．67％～90．62％，添加0．40mgkg^-1时．方法回收率为91、07％～93．02％；操作中相对标准偏差（RSD）为2．02％～3．70％，最小检出量可达1．00pg。在检测色谱精密度实验中，5次测定3种农药混标，相对标准偏差（RSD）为1．37％～2．88％。实验表明，该法具有灵敏度高、操作简便、净化效果好、重现性好等特点。     

厌氧复合菌群JZ-1降解拟除虫菊酯的特性和组成多样性研究

从农药厂废水中分离到能够降解多种拟除虫菊酯的复合菌群JZ-1,对该菌群降解特性研究结果表明,最佳降解条件为pH7、温度30℃;在最佳条件下培养15d,对100mg·L-1甲氰菊酯、氟氯氰菊酯、氯氰菊酯的降解率分别为53.27%、33.36%、41.39%。对该菌群的16S rDNA进行扩增和RFLP及测序分析结果表明,该菌群含有丰富的细菌资源,该菌群的优势种群包括红假单胞菌属（Rhodopseudomonas）和紫单孢菌科细菌（Porphyromonadaceae bacterium）。该研究为拟除虫菊酯的降解菌资源的挖掘和利用提供了理论参考。     

土壤中多种拟除虫菊酯类农药残留的提取与检测方法

研究建立了土壤中甲氰菊酯、三氟氯氰菊酯、顺式氯菊酯、反式氯菊酯、氯氰菊酯、氟氰戊菊酯、氰戊菊酯和溴氰菊酯8种拟除虫菊酯类农药残留的超声提取-硅胶柱净化-气相色谱(GC)检测方法。以石油醚/丙酮(v/v,2:1)溶液为有机提取剂,超声提取土壤样品,旋转蒸发仪浓缩,经自制硅胶柱以10 ml石油醚/乙酸乙酯(v/v,9:1)溶液进行分离净化并浓缩后用正己烷定容,样品采用气相色谱法FID检测器检测。研究结果表明,该方法对土壤样品中8种拟除虫菊酯的加标回收率较高,平均值在84.9%~101.3%之间。通过实验优化了8种拟除虫菊酯类化合物的分离和测定条件。该提取和检测方法具有简便、快捷、成本低、净化效果和重现性好等特点,适合于土壤中痕量拟除虫菊酯类农药残留的测定。     

The impact of environmental changes on the sediment loads of Norwegian rivers

The impact of unusual events on the sediment dynamics in rivers is discussed in this paper. The increase in the number of extreme precipitation events and other unusual weather events in Norway strongly suggests that weather conditions are changing. It is difficult to monitor sediment transport during large magnitude floods. It is however well known that they may deliver substantial amounts of sediment. The suspended sediment load in the upper Atna river during the springflood in 1995 was 44 times the mean load measured during the preceding years. The recurrence interval of this flood was estimated to be 100–200 years. The conditions during the occurrence of a particular flood event may also be of considerable importance and measurements during rainfall on frozen ground have indicated unusually high runoff and erosion rates.The seasonal distribution of runoff in several parts of Norway has changed in recent years and higher winter temperatures have produced an increase in the frequency of flood events. A very long lasting flood caused by a prolonged period of rain occurred in the Vikka stream during September to December 2000. The availability of sediment increased with the increasing soil moisture content in the area. As the ground became saturated, more active slope processes caused erosion rates to increase markedly. The combined effects of climate change and human impact on sediment transport in rivers appear to enhance downstream sediment delivery. Flood protection works along river channels prevent sediment from being deposited on the floodplain. River channels that have been lowered in order to reduce groundwater levels in agricultural floodplain areas will experience the same effect. During the last decade extensive ecological changes have taken place in the coastal areas of southern Norway as 90% of the sugar kelp forest has been lost. This change has been attributed to an apparent increase in sediment delivery to the sea along with a rise in sea temperatures.     

Decoupling effects of driving factors on sediment yield in the Chinese Loess Plateau

Investigations of runoff and sediment yield changes and their relationships with potential driving factors provide good insights for understanding the mechanisms of hydrological processes. This study attempted to present a comprehensive investigation on the spatiotemporal variations of sediment yield in the Loess Plateau using continuous observed data at 46 hydrological stations during 1961–2016, and its responses to changes of precipitation, land use/cover and vegetation cover were analyzed by using the Partial Least Squares-Structural Equation Model (PLS-SEM). The results indicated that sediment yield reduced pronouncedly during 1961–2016 in the Loess Plateau, and 77.9% of this variation was explained by the combined effects of precipitation, land-use change, vegetation dynamics and runoff reduction. Indirect effects of precipitation, land-use change, and vegetation cover on sediment yield were 0.242, ?0.528 and ?0.630 (P < 0.05), respectively, and direct effect of runoff on sediment yield was 0.833 (P < 0.05). According to the Pearson Correlation Coefficient, the strongest positive correlation existed between annual sediment yield and runoff (r = 0.88, P < 0.05), followed by vegetation cover (r = ?0.47, P < 0.05) and land-use change (i.e. forest land and grassland) suggesting their significant trapping effects on soil erosion. However, lower correlations were examined between sediment yield and precipitation indices (?0.14<r < 0.34), and a relatively higher relationship was examined between sediment yield and heavy rainfall (P₂₅) (r = 0.34). Overall, changes in runoff and land-use/vegetation cover well explained variations in sediment yield in the Loess Plateau. The findings are expected to provide scientific and technical support for future soil and water conservation planning in the Loess Plateau, and are valuable for sustainable water resources and sediment load management in the Yellow River Basin.     

Modelling the effects of land-use change on runoff and sediment yield for a meso-scale catchment in the Southern Pyrenees

The Southern Pre-Pyrenees experienced a substantial land-use change over the second half of the 20th century owing to the reduction of agricultural activities towards the formation of a more natural forest landscape. The land-use change over the last 50 years with subsequent effects on water and sediment export was modelled with the process-based, spatially semi-distributed WASA-SED model for the meso-scale Canalda catchment in Catalonia, Spain. It was forwarded that the model yielded plausible results for runoff and sediment yield dynamics without the need of calibration, although the model failed to reproduce the shape of the hydrograph and the total discharge of several individual rainstorm events, hence the simulation capabilities are not yet considered sufficient for decision-making purposes for land management. As there are only a very limited amount of measured data available on sediment budgets with altered land-use and climate change settings, the WASA-SED model was used to obtain qualitative estimates on the effects of past and future change scenarios to derive a baseline for hypothesis building and future discussion on the evolution of sediment budgets in such a dryland setting. Simulating the effects of the past land-use change, the model scenarios resulted in a decrease of up to 75% of the annual sediment yield, whereas modelled runoff remained almost constant over the last 50 years. The relative importance of environmental change was evaluated by comparing the impact on sediment export of land-use change, that are driven by socio-economic factors, with climate change projections for changes in the rainfall regime. The modelling results suggest that a 20% decrease in annual rainfall results in a decrease in runoff and sediment yield, thus an ecosystem stabilisation in regard to sediment export, which can only be achieved by a substantial land-use change equivalent to a complete afforestation. At the same time, a 20% increase in rainfall causes a large export of water and sediment resources out of the catchment, equivalent to an intensive agricultural use of 100% of the catchment area. For wet years, the effects of agricultural intensification are more pronounced, so that in this case the intensive land-use change has a significantly larger impact on sediment generation than climate change. The WASA-SED model proved capable in quantifying the impacts of actual and potential environmental change, but the reliability of the simulation results is still circumscribed by considerable parameterisation and model uncertainties.     

Investigating the effects of afforestation on soil erosion and sediment mobilisation in two small catchments in Southern Italy

Annual soil losses in southern Italy can exceed 100–150 t ha^− 1 year^− 1. Where erosion on agricultural land is particularly severe, land use change and afforestation are frequently seen as the most appropriate means of reducing erosion risk. However, the overall effectiveness of afforestation in reducing soil erosion remains uncertain, due to the poor development of the forest cover in some areas, leading to significant areas with sparse tree cover, and the erosional impact of forest harvesting, which commonly involves clearcutting. The study reported here addresses this uncertainty and focuses on two small catchments (W2 and W3) located in Calabria, southern Italy, for which measurements of suspended sediment yield are available. Both the catchments originally supported a rangeland vegetation cover and they were planted with eucalyptus trees in 1968. Currently, only catchment W3 supports a continuous forest cover. In catchment W2 the forest cover is discontinuous and there is a significant area of the catchment (ca. 20%) where the tree cover is sparse and the vegetation cover is dominated by natural grasses. Two additional erosion plots were established within catchment W2 in 1991, in order to explore the effect of the density of the tree cover on soil erosion. Information on the sediment yields from the two catchments and the plots for 10 storm events that occurred during the period December 2005–December 2006 and associated information on the ¹³⁷Cs and excess ²¹⁰Pb of the sediment, have been used to investigate the effectiveness of afforestation in reducing sediment mobilisation and net soil loss from the catchments involved. The results demonstrate that the areas of greatest soil loss are associated with the slopes where the tree cover is discontinuous, and that forest harvesting by clearcutting causes significant short-term increases in sediment mobilisation and sediment yield. These findings, which are consistent with previous work undertaken within the same area, emphasize the importance of vegetation cover density in influencing rates of soil loss in the study catchments. The study also provided a useful demonstration of the potential for using measurements of the ¹³⁷Cs and ²¹⁰Pb_ex content of sediment, in combination with more traditional sediment monitoring, to investigate sediment sources and to compare the sediment dynamics of catchments subjected to different land management practices.     

Enantioselective degradation and chiral stability of pyrethroids in soil and sediment

Synthetic pyrethroids contain two or three chiral centers, making them a family of chiral pesticides with a large number of stereoisomers. Recent studies showed significant differences in aquatic toxicity between enantiomers from the same diastereomers of pyrethroids. To better understand the ecotoxicological effect and fate of pyrethroid insecticides, chirality in biodegradation must also be considered. In this study, we examined enantiomer compositions of selected pyrethroids in field sediment samples taken from various locations in southern California. Enantioselective degradation was frequently observed for cis-bifenthrin, permethrin, and cyfluthrin under field conditions. We further conducted long incubation experiments under laboratory-controlled conditions using single enantiomers of cis-bifenthrin, cis-permethrin, and cypermethrin. The half-lives for individual enantiomers were calculated to be 277-770 days for cis-bifenthrin enantiomers, 99-141 days for cis-permethrin enantiomers, and 52-135 days for cypermethrin enantiomers, respectively. The direction and degree of enantioselectivity in degradation were found to closely depend on the specific compound as well as experimental conditions. Because no significant difference in degradation was observed after samples were sterilized, the observed enantioselectivity may be attributed to preferential biological transformations.     

Vegetation barrier and tillage effects on runoff and sediment in an alley crop system on a Luvisol in Burkina Faso

The effects of vegetation barriers and tillage on runoff and soil loss were evaluated in an alley crop system at a research station in central Burkina Faso. On a 2% slope of a sandy loam various local species (grasses, woody species and a succulent) were planted as conservation barriers in order to examine their influence on sediment transport. After each erosive storm, runoff and sediment yield was determined. The dense effective barriers (Andropogon gayanus and dense natural vegetation) slow down flow velocity, build up backwater and promote sedimentation uphill. The through flow in the less effective barriers with woody species and succulents (Ziziphus mauritania and Agave sisalana) was slightly hampered and flow velocity was not reduced enough, resulting in a higher soil transport. Under degraded conditions soil loss diminished 50% with less effective and 70–90% with effective barriers. During the initial cropping phase (light tillage; sowing) erosion was reduced 40–60% with effective barriers and showed an increase of 45% with less effective barriers. In the full tillage (weeding) period erosion decreased by 80–90% for effective and 70% for less effective barriers, aided by the development of the barrier and the crop on the alley. Barriers of natural vegetation and A. gayanus are preferred for diminishing soil loss.

Sediment yield could best be predicted by the erosivity index (AI_m), second best by runoff amount (mm), closely followed by maximum peak intensity. All these parameters are related to the volume of overland flow needed to transport soil particles. Correlation of soil loss with small rain showers was poor and correlation with big showers was good. Sediment transport with no barrier had the highest correlation, closely followed by less effective barriers. Due to the heterogeneity in development of the effective barrier, correlations were much lower. The bulk of soil loss was only dependent on a few extreme events during the observation period.     

Slope and rainfall effects on the volume of sediment yield by gully erosion in the Souar lithologic formation (Tunisia)

The Souar lithologic formation in semi-arid Tunisia is undergoing severe gully erosion which is threatening soil and water resources. Soil conservation strategies have focused more on terracing than on gully control techniques, since the contribution of gully sediment yield in the overall soil loss from watersheds is unknown. The paper reports investigations into the sediment yield provided by head-cut as well as sidewall–floor erosion of first order gullies on gentle and steep slope catchments underlined by the Souar lithologic formation. We measured mean field sediment volumes evacuated by different headward reaches of 10 and 9 gullies located on gentle and steep slope catchments, respectively. Two equations between the length of the gully head cutting and the corresponding volume of evacuated sediment were established. The treatment with a Geographic Information System (Arc View) of air photographs of six flights from 1952 to 2000 allowed the calculation of the volume of sediment provided both by head cutting and gully sidewalls–floor erosion through the following up of gully extension in eight catchments during the five periods separating the dates of these flights. Total gully erosion was on average 1.66 m³ ha^− 1 year^− 1 for the gentle slopes and 5.603 m³ ha^− 1 year^− 1 for the steep slopes. Sidewalls–floor contribution in total erosion was on average 81.5% for the gentle slopes and 77.8% for the steep slopes. We found out that the mean annual rainfall resulting from 40 mm daily rainfall threshold explained better the variation of annual head cutting sediment yield for these five periods than any other annual rainfall resulting from lower daily rainfall thresholds. Two equations between these two variables were established both for gentle and steep slope catchments.     

Prolegomena to sediment and flow connectivity in the landscape: A GIS and field numerical assessment

This paper presents two new definitions of sediment and water flux connectivity (from source through slopes to channels/sinks) with examples of applications to sediment fluxes. The two indices of connectivity are operatively defined, one (IC) that can be calculated in a GIS environment and represents a connectivity assessment based on landscape's information, and another that can be evaluated in the field (FIC) through direct assessment. While IC represent a potential connectivity characteristic of the local landscape, since nothing is used to represent the characteristics of causative events, FIC depend on the intensities of the events that have occurred locally and that have left visible signs in the fields, slopes, etc.IC and FIC are based on recognized major components of hydrological connectivity, such as land use and topographic characteristics. The definitions are based on the fact that the material present at a certain location A reaches another location B with a probability that depends on two components: the amount of material present in A and the route from A to B. The distance to B is weighted by the local gradient and the type of land use that the flow encounters on its route to B, while the amount of material present in A depends on the catchment surface, slope gradient and type of land use of said catchment.Although IC and FIC are independent from each other, and are calculated using different equations and different inputs, they complement each other. In fact, their combined use improves IC's accuracy. Hence, connectivity classes can afterward be rated using IC alone.This procedure has been applied in a medium-size watershed in Tuscany (Italy) with the aim of evaluating connectivity, identifying connected sediment sources and verifying the effects of mitigation measures.The proposed indices can be used for monitoring changes in connectivity in areas with high geomorphological or human induced evolution rates.     

螯合剂对沉积物中铬的去向的影响

A laboratory investigation on reaction between chelating agents and chromium was conducted to evaluate the effect of chelating agents on the adsorption and desorption of chromium in sediment. The amount of adsorbed chromium(Ⅵ) in sediment decreased slightly by 5%-10% because of addition of chelating agents. Chelating agents inhibited the removal of Cr(Ⅲ) by sediment from solutions and the inhibiting effect was in the order: citric acid > tartaric acid > EDTA, salicylic acid. No effect of chelating agents on desorption of chromium in sediment was observed.