Diffusive movement of simazine and lindane in river-bed sediments

River-bed sediments are active zones for pesticide deposition and subsequent movement by diffusion, mass transport and sorption to solids. The aim of this work was to investigate the importance of diffusion as a means of pesticide movement. In laboratory experiments, simazine and lindane were introduced to well-mixed aqueous solutions overlying two different river sediments. Sediment cores were sectioned horizontally and analyzed for pesticide content by supercritical fluid extraction. Experiments were used to determine sorption isotherms of the compounds to suspended sediments at 10°C. Vertical profiles of the pesticides in the sediments showed that the compounds reached a maximum depth of 89 mm over a period of 37 days. A mathematical model was developed to describe pesticide transport by diffusion within the sediment porewaters and sediment sorbed phases, taking into account sorption of the compounds to sediment particles. Effective diffusion coefficients ((0.5–1.6)×10^-10 m² s^-1) were obtained for simazine and lindane in the characterized sediments. These were used to calculate values for diffusion in the dissolved phase (0.38×10^-10 and 6·16×10^-10 m² s^-1 for simazine and lindane respectively) and diffusion in the sorbed phase (0.39×10^-10 m² s^-1 for simazine and negligible for lindane). Sorption onto the sediment significantly influenced the rate of penetration of the compounds into the sediment; thus although lindane had a larger effective diffusion coefficient than simazine, its larger sorption affinity and negligible diffusion in the sorbed phase led to less penetration into the sediment. © 1998 Society of Chemical Industry     

Occurrence and mobility of the insecticide permethrin in rivers in the Southern Humber catchment,UK

The synthetic pyrethroid insecticides cis‐ and trans‐permethrin are widely used, particularly in sheep‐dips and for mothproofing within the textile industry. This study aims to establish the concentrations and mobility of permethrin within rivers in the Humber catchment, which contain some of the highest densities of wool‐scouring activity in the world. Our approach was to utilise three different surveys: (a) weekly and storm‐responsive sampling of ‘whole waters’ in the rivers Aire, Ouse, Don, Trent and Calder; (b) intensive sampling of ‘whole waters’ and suspended sediments in the rivers Aire (0.5 h) and Calder (1 h); (c) a bed‐sediment survey of the River Calder. Sediments were extracted by supercritical fluid extraction and all samples were analysed by gas chromatography with mass spectrometry. Results demonstrated the presence of permethrin in ‘whole waters’ and sediments, particularly in the rivers Aire and Calder, and at concentrations in the bed‐sediment likely to cause ecotoxicological effects to benthic macro‐invertebrates. Mass‐balance calculations indicated some loss of permethrin from the water column during transport, with the greatest losses at low river‐discharge. Isomer ratios (trans:cis) give retention times of permethrin in different components of the system as ‘whole water’ < suspended sediments < bed‐sediments, with estimates of 4–26 days for suspended sediments and a maximum of 103–125 days for surface bed‐sediments. © 2000 Society of Chemical Industry     

Current- and past-use pesticide prevalence in drainage ditches in the Lower Mississippi Alluvial Valley

BACKGROUND: Pesticide application is common in agriculture and often results in applied pesticides entering adjacent aquatic systems. This study seasonally analyzed a suite of 17 current‐ and past‐use pesticides in both drainage waters and sediments to evaluate the prevalence of pesticides in drainage ditches across the Lower Mississippi Alluvial Valley (LMAV). RESULTS: There were significantly higher concentrations (P < 0.05) of current‐use than past‐use pesticides; however, there were consistently high numbers of detections of past‐use pesticides in sediments. Sediment pesticide concentrations were an order of magnitude higher (150–1035 µg kg^?1) than water samples (6–20.9 µg L^?1). Overall, 87% of all samples analyzed for current‐ and past‐use pesticides were non‐detects. p,p′‐DDT was detected in 47.5% of all drainage waters and sediments sampled. There were significant correlations (0.372 ≥ r²≤0.935) between detected current‐use water and sediment concentrations, but no significant correlations between past‐use water and sediment concentrations. CONCLUSION: Overall, there was a high percentage (87%) of sediment and water samples that did not contain detectable concentrations above the lower limit of analytical detection for each respective pesticide. This lack of pesticide prevalence highlights the improved conditions in aquatic systems adjacent to agriculture and a potential decrease in toxicity associated with pesticides in agricultural landscapes in the LMAV. Copyright © 2011 Society of Chemical Industry     

Organochlorine pesticides and polycyclic aromatic hydrocarbons in water and sediment of the Bosten Lake,Northwest China

We evaluated organic pollution in Bosten Lake, Xinjiang, China, by measuring the concentrations and distributions of organochlorine pesticides(OCPs) and polycyclic aromatic hydrocarbons(PAHs). Water and sediment samples were collected from 19 sites(B1–B19) in the lake for analysis. Our analytical results show that the concentrations of total OCPs in water ranges from 30.3 to 91.6 ng/L and the concentrations of PAHs ranges from undetectable(ND) to 368.7 ng/L. The concentrations of total OCPs in surface(i.e., lake bottom) sediment ranges from 6.9 to 16.7 ng/g and the concentrations of PAHs ranges from 25.2 to 491.0 ng/g. Hexachlorocyclohexanes(HCHs) and dichlorodiphenyltrichloroethanes(DDTs) account for large proportions of the OCPs. Low α- to γ-HCH ratios in both water and sediment samples indicate possible contributions from both industrial products and lindane. DDTs in water are probably from historical input, whereas DDTs in sediments are from both historical and recent inputs. Moreover, DDT products in both water and sediments were from multiple sources in the northwestern part of the lake(B11, B12, B13, and B14). Fugacity ratios for DDT isomers(p,p′-DDE and p,p′-DDT) at these sites were generally higher than equilibrium values. These results suggest that the input from the Kaidu River and diffusion of DDTs from the sediment to the water are responsible for DDT pollution in the water. Lower-molecular-weight PAHs, which originate primarily from wood and coal combustion and petroleum sources, represent the major fraction of the PAHs in both water and sediment samples. Our findings indicate that OCPs and PAHs in Bosten Lake can be attributed primarily to human activities. A risk assessment of OCPs and PAHs in water and sediment from Bosten Lake, however, suggests that concentrations are not yet high enough to cause adverse biological effects on the aquatic ecosystem.     

Diazinon reduction and partitioning between water,sediment and vegetation in stormwater runoff mitigation through rice fields

BACKGROUND: Contamination of surface waters by pesticides is a concern in the United States and around the world. Innovative mitigation strategies are needed to remediate this potential environmental contaminant. One potential solution is to divert pesticide‐laden drainage or surface water through agricultural rice fields. With a hydroperiod, hydrosoil and hydrophyte (rice), these systems serve essentially as a type of constructed wetland. In both summer and fall experiments, diazinon‐amended water was diverted through two rice ponds at the University of Mississippi Field Station. Likewise, a non‐vegetated control pond was amended with diazinon‐laden water. Water, sediment and plant samples were taken spatially and temporally to determine the distribution of diazinon within systems. RESULTS: Outflow diazinon concentrations decreased significantly (P < 0.05) from inflow in both vegetated ponds for both preharvest and post‐harvest experiments. Although sorption to rice plants was minimal in the overall mass distribution of diazinon (1–3%), temporal data indicated that diazinon concentrations reached the outflow sediment of the non‐vegetated control twice as fast as in either vegetated (rice) system. In both vegetated systems, sediment diazinon concentrations decreased (77 and 100%) from inflow to outflow, while a decrease of <2% was noted in the non‐vegetated control. CONCLUSIONS: Diversion of pesticide‐contaminated water through rice fields demonstrated potential as a low‐cost, environmentally efficient mitigation practice. Studies on these systems are continuing to evaluate the optimal chemical retention time for rice field mitigation, as well as diazinon transfer to rice grain seeds that may be used as a food source. Published in 2009 by John Wiley & Sons, Ltd.     

The influence of lipophilicity and formulation on the distribution of pesticides in laboratory-scale sediment/water systems

Pesticide reaching surface waters will be sorbed by sediment. This sorption process and the influence of pesticide formulation have been examined at 10 degrees C in small-scale systems having 2-cm depth of sediment and 8-cm overlying water stirred gently. Eight pesticides (triasulfuron, isoproturon, chlorotoluron, phenmedipham, difenoconazole, chlorpyrifos, pendimethalin and permethrin), spanning a range of physicochemical properties, were applied individually to the water. Sorption equilibrium was reached at between 15 and 30 days, the proportion of pesticide then in the sediment ranging from 20% for the acidic and therefore polar triasulfuron to 97% for the lipophilic permethrin; this behaviour was not influenced by formulation. Sorption coefficients measured in batch tests over 2 h gave good estimates of the equilibrium distribution. Some degradation was observed for all compounds over 90 days; for some compounds and formulations, enhanced degradation occurred after 20 to 60 days. It is concluded that lipophilicity is the chief determinant of pesticide distribution in sediment/water systems.     

Numerical simulations of flow and sediment transport within the Ning-Meng reach of the Yellow River,northern China

Effective management of a river reach requires a sound understanding of flow and sediment transport generated by varying natural and artificial runoff conditions. Flow and sediment transport within the Ning-Meng reach of the Yellow River(NMRYR), northern China are controlled by a complex set of factors/processes, mainly including four sets of factors:(1) aeolian sediments from deserts bordering the main stream;(2) inflow of water and sediment from numerous tributaries;(3) impoundment of water by reservoir/hydro-junction; and(4) complex diversion and return of irrigation water. In this study, the 1-D flow sediment transport model developed by the Yellow River Institute of Hydraulic Research was used to simulate the flow and sediment transport within the NMRYR from 2001 to 2012. All four sets of factors that primarily control the flow and sediment transport mentioned above were considered in this model. Compared to the measured data collected from the hydrological stations along the NMRYR, the simulated flow and sediment transport values were generally acceptable, with relative mean deviation between measured and simulated values of 15%. However, simulated sediment concentration and siltation values within two sub-reaches(i.e., Qingtongxia Reservoir to Bayan Gol Hydrological Station and Bayan Gol Hydrological Station to Toudaoguai Hydrological Station) for some periods exhibited relatively large errors(the relative mean deviations between measured and simulated values of 18% and 25%, respectively). These errors are presumably related to the inability to accurately determine the quantity of aeolian sediment influx to the river reach and the inflow of water from the ten ephemeral tributaries. This study may provide some valuable insights into the numerical simulations of flow and sediment transport in large watersheds and also provide a useful model for the effective management of the NMRYR.     

内蒙古呼伦湖沉积物营养元素分布及环境污染评价

对呼伦湖各采样点表层沉积物营养元素(TN、TP和TOC)的分布特征及相互关系进行了分析,并对表层沉积物进行了营养元素的环境评价和重金属的地积累指数评价。结果表明:新开河、乌尔逊河及克鲁伦河入湖点(A10、F9、I2)营养元素的含量均低于其它采样点,且TOC与TN和TP的环境行为近似,说明TN和TP的沉积与生物有机质的沉积相伴随;呼伦湖沉积物碳氮比的均值约为10.2,说明内、外源有机质基本达到平衡状态。通过对沉积物的环境污染评价发现,呼伦湖沉积物有机污染较轻,仍处于较清洁状态,但有机氮的污染程度较为严重;地积累指数评价显示,主要污染元素为Cd和As,Hg、Cu和Zn属于无污染状态。     

塔里木河河床渗透系数及其渗漏水量分析

为明晰塔里木河的水文过程,实现水资源的优化配置,采用颗粒分析法,分析塔里木河上中游河床沉积物渗透系数的时空变化特点,并借助达西定律确定了不同来水情景下4个河段的渗漏水量。结果表明:1塔里木河河床沉积物土壤颗粒的粒径0.000 5~0.5 mm,砂类土的比重为83%,因此,Sauerbrei公式用于该河流河道渗透系数的计算。2河床沉积物渗透系数与水温的变化具有一致性,段2、段4、段1和段3的年均渗透系数分别为115.3m·d~(-1)、74.5 m·d~(-1)、71.4 m·d~(-1)、45.2 m·d~(-1),呈逐渐减小趋势。3在12.5%、50%和87.5%的3个来水频率下,河段耗水量、渗漏水量及单位河长渗漏水量均呈现递减趋势;上中游总渗漏水量分别为10.85×108m3、9.94×108m3、9.13×108m3,水量渗漏集中在5—10月。4在同一来水频率下,河段渗漏水量依次为:段1段4段2段3,而单位河长渗漏水量为:段1段4段3段2。验证结果表明,渗漏水量计算结果与定量分离结果误差仅为2%,故渗漏水量及渗透系数计算结果合理。该研究可为实现塔里木河生态引水工程的合理布局和生态保护提供科学依据和技术支撑。     

Kepone distribution in the water column of the James River estuary--1976-78

Concentration of Kepone residues in water collected from the James River estuary in 1976-78 ranged from 0 to 1.20 ppb. The majority of water samples collected showed no detectable residues. Kepone concentrations at the surface and bottom of the water column were similar. Water column residues varied according to seasonal and spatial differences. Levels peaked during the summer months and averaged higher in the middle reach of the estuary. Residues in the water were 1-5 orders of magnitude lower than reported residues in James River bed sediments. There was a significant correlation between water column and underlying bed sediment residues.     

雨强和植被覆盖度对典型坡面产流产沙的影响

应用先进的UGT水蚀测量仪,研究黄土高原祖厉河流域雨强和植被覆盖度对典型坡面产流产沙的影响。结果表明:黄土高原半干旱区间隔为15min的产流量、径流含沙量和产沙量与15min雨强具有相同的增减趋势,呈三次曲线关系y=b0+b1x+b2x2+b3x3。7种雨强条件下,人类扰动撂荒地的产流量、径流含沙量和产沙量均明显大于植被自然恢复的撂荒地,覆盖度20%的撂荒地是覆盖度35%撂荒地的平均径流系数的2.35倍,径流含沙量的4.48倍,产沙量的14.06倍。相对于受到扰动的撂荒地,植被自然恢复的撂荒地水土保持效益显著。     

策勒绿洲-沙漠过渡带不同植被沙丘表面风沙沉积物粒度特征分析研究

通过对策勒绿洲-沙漠过渡带不同植被类型下沙丘表层风沙沉积物粒度分布特征进行研究,探讨不同荒漠植被类型下风沙沉积物的沉积规律。结果表明:胡杨、骆驼刺、柽柳、花花柴灌丛沙堆表层沉积物粒级组成均以极细砂(57.20%-60.37%)为主,其次为极粗粉砂(18.47%-21.34%)和细砂(16.56%-19.03%),骆驼刺灌丛沙堆表面整体风沙沉积物平均粒径最细(84.06μm),胡杨沙堆表面整体沙物质平均粒径最粗(88.88μm)。四种植被沙堆表面沙物质的分选性总体上在中等-较好水平,分选系数介于1.44-2.02之间,胡杨沙堆表层沙物质的偏度值在顶部附近属于极负偏,骆驼刺、柽柳、花花柴灌丛沙堆表面沙物质均为负偏。峰度值介于0.95-1.51之间,胡杨沙堆顶部附近及骆驼刺沙堆表层沙物质主要属于窄峰态,柽柳、花花柴沙堆表面沙物质属于中等峰态。沙物质平均粒径与偏度值呈极显著正相关性(p<0.01),沙物质的分选系数与峰度值呈极显著正相关性,沉积物粒度特征空间差异主要受物源、植被高度、冠型、疏透度等因素影响。     

浑善达克沙地东部地区天然水体的水化学组成及其控制因素

浑善达克沙地东部地区位于内蒙古高原,其天然水体为淡水。利用原始型Durov三线图对其天然水体进行水化学分类,结果表明,地表水水化学类型属于碳酸氢盐组,而地下水属于碳酸氢盐组、混合组和硫酸盐组多种类型。天然水体样品在Gibbs图中的分布表明,岩性控制是形成该地区天然水体水化学组成的主要因素,这种情况不同于我国西部和中部沙漠由于蒸发强烈而受控于蒸发-结晶作用的天然水体。天然水体的离子比例关系表明,地下水中蒸发盐岩和硅酸盐岩的风化程度较高,而碳酸盐岩风化程度低,这可能是由于地下水的水-岩作用时间长、二氧化碳供给不充分引起的;相反,由于水-岩作用时间短、二氧化碳供给充分,地表水中蒸发盐岩和硅酸盐岩的风化程度较低,而碳酸盐岩风化程度高。     

Variation in chlorotoluron photodegradation rates as a result of seasonal changes in the composition of natural waters

BACKGROUND: It is important to understand the degradation of organic molecules in surface waters to ensure that risk assessments, intended to prevent adverse effects on human health and the environment, are robust. One important degradation mechanism in surface waters is photodegradation. This process is generally studied in laboratory test systems, and the significance of the results is then extrapolated to the field. The aim of this work was to assess how fluctuations in the composition of surface water influence the photodegradation rate of chlorotoluron. RESULTS: Photodegradation DT₅₀ values in the lake (mean = 26.0 days) and pond (mean = 26.0 days) were significantly slower than in the river (mean = 6.8 days) and stream (mean = 7.3 days) samples. The DT₅₀ values in the pond and lake samples were similar to the direct photolysis value (mean = 28.6 days). Photodegradation was significantly faster in the stream and river samples, suggesting that indirect photolysis was significant in those waters. Principal component analysis indicated a strong inverse correlation between nitrate concentration and degradation rate. CONCLUSIONS: Nitrate concentration had a strong influence on the rate of photodegradation, with increasing nitrate concentrations sharply reducing the DT₅₀. However, this effect was restricted to a narrow concentration range and levelled off quite quickly, such that further increases in the nitrate concentration had no significant effect on the rate of degradation. Extrapolating photodegradation rates of chlorotoluron from the laboratory to the field should be relatively straightforward, provided the nitrate concentrations in the waters are known. Copyright © 2012 Society of Chemical Industry     

Residues of dalapon and TCA in sediments and irrigation water

When dalapon and TCA are used for the management of aquatic weeds in irrigation distribution systems, they are often applied to established stands of Typha spp. and Phragmites australis in autumn or early winter, after draining water from the system. It has been assumed that the herbicides would dissipate from the sediments within 6 weeks, so that water supplies could be safely restored. In field experiments the decay of dalapon and TCA in sediments followed the classical pattern for a microbially mediated process, with a slow lag-phase, followed by a rapid phase of decline, but not to completion. Particularly for TCA, there was a final slow phase in which residues were sufficient to contaminate eluting water at concentrations much greater than the legally prescribed tolerance, even when the interval between herbicide treatment and water re-supply was more than 6 weeks. Although the overall pattern of dissipation in the sediment was similar for the two herbicides, concentrations of TCA were higher than those of dalapon in the elution water, probably reflecting differences in herbicide mobility and elution efficiency. Dye tracers were used in three field experiments to investigate the efficiency of herbicide elution and carryover of contaminated water when canals were filled to capacity, drained and refilled. Together with the rate of dissipation from sediments, canal topography and draining efficiency determined the safety of the elution process in removing surplus residues before re-supply of water for irrigation. In large-scale management operations, where the dissipation interval was only 17-19 days, the TCA was eluted from the sediment into flowing water in proportion to the square root of time, giving average concentrations over 3 days of discharge of more than 0.4gm^?3. Ideally, the interval between spraying and water re-supply should be extended beyond 6 weeks. Alternatively, herbicide use should be restricted, or provision made for elution of surplus residues and disposal of contaminated water to waste, or onto tolerant crops or fallow land.     

Is tile drainage water representative of root zone leaching of pesticides?

Given the methods presently available, determination of flux-averaged concentrations of pesticides in structured soils is always a compromise. Most of the available methods entail major uncertainties and limitations. Tile drainage monitoring has several advantages, but the extent to which it is representative of overall leaching has been questioned because it comprises a mixture of water of different origins. This literature review evaluates whether drainage water pesticide concentrations are representative of root zone leaching of pesticides. As there are no reports quantifying the extent to which the flux-averaged concentration of pesticides in drainage water differs from that found between the drains, evidence-based conclusions cannot be drawn. Nevertheless, the existing literature does suggest that the concentration in drainage water does not always correspond to the concentration at drain depth between the drains; depending on the conditions pertaining, the concentrations may be higher or lower. As to whether the flux-averaged concentration of pesticides in drainage water is representative of the interdrain concentration at drain depth it is concluded that (1) the representativeness of drainage water concentrations can be questioned on very well-drained soils and on poorly drained soils with little capacity for lateral transport beneath the plough layer, (2) the conditions provided by relatively porous soils and moderate climatic conditions are conducive to the drainage water concentration being representative and (3) drainage water will be more representative in the case of weakly sorbed pesticides than for strongly sorbed pesticides. Used critically, it is thus believed that drainage water concentrations can serve to characterize the flux-averaged concentration of pesticides at drain depth. However, the use of drainage water for determining average concentrations necessitates thorough investigation and interpretation of precipitation, percolation, drain outflow and concentration dynamics.     

Exposure risk assessment and evaluation of the best management practice for controlling pesticide runoff from paddy fields. Part 1: Paddy watershed monitoring

Rice pesticide concentrations in surface water along with hydrological balance and water management conditions were investigated in a paddy watershed of about 100 ha at the Sakura river basin in Tsukuba, Japan, for 3 years from April 2002. Monitoring on different hydrological scales ranging from a paddy plot up to a watershed determined the importance of water management associated with rainfall events and the cyclic irrigation for reducing pesticide discharge into aquatic environments. Surface drainage significantly increased as a response to rainfall events greater than about 1.5 cm day(-1). A total of 16 herbicides were detected in the stream water and their peak concentrations mostly occurred from early to mid-May following the pesticide application period. Two water management factors influencing the pesticide runoff from paddy fields were defined: excess water storage capacity (EWSC) and water holding period (WHP). Uncertainty analyses of pesticide discharge from a paddy plot for dymron (daimuron) and imazosulfuron (IMS) were performed using Monte Carlo simulation (MCS) with prescribed probability of rainfall and water management practice from observations over a period of 3 years. Application of an intermittent irrigation scheme with shallow water depth practice and high drainage gate to maintain the EWSC > 2 cm and increasing WHP from the current Japanese Agricultural Chemicals Regulation law of 3-4 days to at least 10 days were recommended for reducing the pesticide runoff from paddy fields in a monsoon region such as in Japan. The combination of good water management in field plots and small-scale water cycling is the best management practice for controlling pesticide discharge from paddy watersheds.     

SWAT—A Semi-empirical Model to Predict Concentrations of Pesticides Entering Surface Waters from Agricultural Land

A semi-empirical model called SWAT has been developed to predict concentrations of agriculturally applied pesticides moving to surface waters, an aspect which is not well described by current models for pesticide fate. The model is based upon a direct hydrological link established between soil type and the amount of water moving rapidly to streams in response to rainfall. Attenuation factors describe the decrease in concentrations of pesticide between field application and loss in water moving from the site into surface waters. Evaluation of model predictions against available field data from three sites and four soil types in England shows that SWAT is capable of predicting the transient peak concentrations of a wide range of pesticides during rapid water movement to streams in response to rainfall. Predicted concentrations were too great when rainfall initiated water movement to streams very soon after pesticide application, particularly for the more mobile pesticides, and some predictions for pesticides sorbed very strongly to soil were relatively poor. Almost all of the predicted concentrations were within one order of magnitude of measured values.     

Low detection of glyphosate in rivers following application in forestry

BACKGROUND

Glyphosate is the most commonly used herbicide in the world, and is used in agriculture, forestry, and urban settings. In regions with high glyphosate use, such as agricultural, glyphosate and its' major derivative aminomethylphosphonic acid (AMPA) are frequently detected in surface waters. In Canadian forestry glyphosate-based herbicides are used to control vegetation that competes with conifer trees and are applied one to two times during a rotation, leading to infrequent application to the same area. Forestry occurs over a large spatial extent, and the cumulative application in space can lead to a large percentage of the land base receiving an application through time. To assess the frequency and concentration of glyphosate and AMPA in surface waters of a region where forestry is the dominant use sector, we conducted three monitoring programs targeting: (i) immediately after application, (ii) after rainfall, and (iii) cumulative application over a large spatial extent.

RESULTS

Across all monitoring programs we collected 296 water samples between August and October from eight river systems over two years and detected glyphosate in one sample at 17 ppb.

CONCLUSION

Glyphosate is not likely present in surface waters during baseflow conditions as a result of applications in forestry. Lack of detection is likely because soil capacity to bind glyphosate remains high due to infrequent applications to the same area, and factors that limit sediment transport to surface waters such as buffers. Additional sampling is needed during other stream conditions, ideally spring freshet, to determine peak concentrations. © 2023 National Research Council Canada. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. Reproduced with the permission of the Minister of Innovation, Science, and Economic Development.     

博斯腾湖人工湿地中微生物群落空间分布特征

博斯腾湖人工湿地是典型的多级表面流污水人工湿地处理系统。本研究采集博斯腾湖人工湿地各级子系统进水和出水口的水样及沉积物,通过高通量测序技术,分析了多级湿地系统中水和沉积物中的微生物群落空间分布特征。结果表明:总体上人工湿地沉积物中的微生物多样性和丰度高于水体。在多级湿地系统中微生物群落丰度及多样性自入口起始,先增加后由潜流湿地排入博斯腾湖后减小。水中核心门类为变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、放线菌门(Actinobacteria)及浮霉菌门(Planctomycetes)。其中变形菌门整体呈上升趋势,从初始进水口的59.11%上升至最终出水口的84.80%,而厚壁菌门类整体呈下降趋势,从24.05%降至6.83%。但厚壁菌门类细菌仍是优势菌种,这表明该门类细菌在废水处理系统中是优势菌种。沉积物中变形菌门类和厚壁菌门类细菌依然占主导地位,厚壁菌门类细菌丰度也是先增加后减少,而变形菌门类细菌整体上随处理深度呈下降趋势;拟杆菌门(Bacteroidetes)和绿弯菌门(Chloroflexi),两者在整个处理过程中呈现出完全相反的趋势。尽管水和沉积物中优势门类细菌均为变形菌门,并且最主要的功能类群均为氨基酸运输和代谢,但微生物群落整体结构及功能仍显著不同。