不同类型河岸缓冲带水质净化效果研究

以广东省杨溪河灌草、竹林植被岸坡两种类型河岸带为研究对象,对河岸带2 m、4 m和6 m宽度情况下的TP、TN和COD等面源污染物质去除效果进行研究。研究结果表明,不同类型河岸缓冲带及宽度对污染物的截污能力有所不同,总体来看灌草缓冲带对污染物的去除率最高,为55%~87%,其次为竹林缓冲带为56%~80%。从缓冲带去除TN、TP和COD的角度出发,同时考虑土地占用问题,宽度为6 m的两种类型缓冲带是较佳的河岸缓冲带设置宽度。研究结果可为缓冲带的构建提供有益的参考。     

沈阳地区河岸植被缓冲带对氮、磷的削减效果研究

为充分了解河岸植被缓冲带对地表径流污染物的去除效果, 本研究选取辽宁省沈阳市两条典型河流——浑河与蒲河为对象, 研究其滨水不同河岸植被缓冲带对地表径流氮、磷污染物的削减效果。结果表明: 在6 种河岸植被带中, 人工林草地对氮的削减效果最好, 对总氮、硝态氮和铵态氮的平均削减率分别为47%、36%和31%; 人工林地对磷的削减效果较好, 平均削减率为74%; 而人工林地对氮以及人工草地对磷的削减效果较差。随长度增加, 河岸植被缓冲带对地表径流污染物的削减效果基本呈增强趋势。以上研究结果说明不同河岸植被缓冲带对地表径流中氮、磷的削减各有优点。在对遭受污染的河流进行生态修复时, 应考虑环境污染特点和地表特征, 以充分发挥河岸植被缓冲带对污染物的削减优势。     

河岸植被缓冲带生态水文功能研究进展

河岸植被缓冲带是河岸生态系统的重要组成部分,对河岸生态系统的生态及水文过程具有重要的影响。世界上许多国家已将河岸植被缓冲带列为河岸生态系统管理的一个重要内容,并在一些国家被作为控制农业流域非点源污染的最佳管理措施。河岸植被缓冲带的生态水文功能体现在控制河岸侵蚀、截留地表径流泥沙和养分、保护河溪水质、调节水温、为水陆动植物提供生境、维护河溪生物多样性和生态系统完整性以及提高河岸景观质量等多个方面。本文综述河岸植被缓冲带生态水文功能方面的研究进展,总结了一些研究中提出的不同河岸植被缓冲带功能发挥所需要的宽度,同时指出由于河岸生态系统保护的目标,侧重的功能,研究区域土壤、地形、植被、排水特征等因素各异,河岸植被缓冲带生态水文功能发挥所要求的实际宽度也有所不同。     

植被缓冲带在水源地面源污染治理中的作用

在山地丘陵区遭遇高强度降雨时,常常发生水土流失;水流携带泥沙下泄,过量施入农田的肥料、农药等化学物质随之进入河流、水库、湖泊等地表水和地下水水体,进而造成水体富营养化等面源污染,危害水源地安全。为梳理植被缓冲带能够控制水土流失、阻控污染物移动、解决水源地面源污染问题,明确该项技术措施减少和治理水源地面源污染的机制,为水源地面源污染防治和水环境改善提供参考。在概括介绍植被缓冲带的类型、功能的基础上,对该项技术措施减少和治理水源地面源污染的机制进行讨论。植被缓冲带治理水源地面源污染的机制主要有:①植物在生长过程中自身对氮磷等物质的吸收;②利用植被固结土壤,减少水土流失;③植被覆盖、拦蓄能够延长径流在地面的停留时间而增加水分入渗、减少氮磷等物质随地表径流流失;④植物根系参与土壤中多种物理、化学和生物过程,加速碳、氮、磷等物质的形态转化。针对水源地面源污染特点和植被缓冲带的建设技术及其应用要点,提出相关建议,并对今后该技术的发展进行了展望。     

集约轮流放牧对河岸侵蚀和鱼类的影响

河岸缓冲带能够改善因持续放牧而退化的河流。但由于种植缓冲带会增加农民的费用 ,因此 ,其推广应用受到限制。在美国将河岸的集约轮流放牧作为恢复河流生态系统的一种措施。 1996～ 1997年 ,在威斯康星出产鳟鱼的 2 3条河段 ,对集约化轮流放牧、持续放牧、种植绿草缓冲带和树木缓冲带 4种情况下的河岸侵蚀、鱼类生境质量、鳟鱼丰度以及以鱼为基础的生物群落完整性指数进行比较。统计结果表明 ,在集约化轮流放牧和建立绿草缓冲带两种情况下河岸侵蚀最小 ,河道的沉积物最少 ;持续放牧有显著的河岸侵蚀和较多的沉积物。河岸土地利用方式对河道的宽深比、河流的掩蔽、小潭的百分比、生活环境质量指数、鳟鱼的丰度以及生物群落完整性指数值没有较大影响。但整个流域的状况会影响这些参数。缓冲带和集约轮流放牧对威斯康星河流的恢复具有相同的效果     

滨岸缓冲带截留污染物机理和效果的研究进展

滨岸缓冲带是指与河流（包括湿地和湖泊）相邻的对污染物、沉积物和洪水具有一定缓冲功能的水陆生态系统交错带,是一种重要的控制面源污染和保护水体环境的方法。滨岸缓冲带的研究存在较多的方向和不同的立足点。为了更好地总结和梳理已有研究成果,该文通过大量的文献调研,构建了滨岸缓冲带的研究框架,从其作用机理、结构、功能与效果等方面对国内外的有关研究和实践进行了系统分析和总结,并提出了未来的研究展望。     

曹家路流域面源污染的特征及规律

通过连续的野外试验,对北京市重要水源地密云水库水源区曹家路流域的土壤理化特征、面源污染产汇污机制、污染物迁移转化特征等进行了初步分析和研究。研究内容包括:不同土壤类型的理化特征及养分含量随深度的变化规律;一场短时暴雨水文情形下,各面源污染特征指标的变化规律及产汇污机制;不同土地覆盖条件下,流域内各子河段面源污染的变化特征。最后,针对该研究区域面源污染特征,提出了污染物削减及控制的相关对策。     

秦淮河流域农业污染源调查及入河量计算

生活源和农业面源污染已成为一些河流水环境质量恶化的重要因素,本文在深入分析第一次全国污染源普查数据基础上,对南京市秦淮河流域生活源和农业面源对水环境污染情况进行了研究,对潜在的水质污染问题进行了研讨,并据此提出了该河流污染防治的对策和建议。     

不同入流条件下草本缓冲带对污染物削减作用

草本缓冲带能够有效拦截坡面径流中泥沙、总氮、总磷等污染物,是农业面源污染防控的主要措施之一。通过人工配水模拟地表径流,研究不同径流量对草本缓冲带截污能力的影响。结果表明:草本缓冲带对污染物都有一定的削减作用,草本缓冲带对泥沙削减效果最好,对总磷削减效果最差,白三叶对污染物的削减能力总体较黑麦草强。径流量对草本缓冲带总氮、总磷削减率影响较大,对泥沙削减率影响较小;当流量从0.08 L/s增加至0.24 L/s时,草本缓冲带对总氮、总磷削减率减少至9%和6%,而泥沙削减率为34%。随着放水冲刷时间增加,出流总氮、总磷、泥沙浓度不断降低并逐渐达到稳定,流量增大至0.24 L/s时,总氮、总磷浓度范围为11.5~24.7,1.6~2.3 mg/L,泥沙浓度在不同流量下无明显差异。草本缓冲带对总氮、总磷去除作用受流量影响较大,在大流量时缓冲带对总氮、总磷基本无去除作用,但缓冲带对泥沙去除作用受流量影响较小。     

河岸缓冲带植被布局对氮流失的影响

河岸缓冲带（Rriver Buffer Strips,RBSs）已被证明能有效拦截水流并去除氮,该研究旨在揭示缓冲带不同配置的脱氮效果的影响。实地布置河岸植被缓冲带,开展地下径流试验。缓冲带设置3种不同植物种类（水曲柳,五叶枫,杨树）,和不同宽度（5、10、20、30 m）,河岸坡度为3%,树木密度为540株/hm2。在此条件下,研究各类河岸植被缓冲带对地下径流铵态氮、硝态氮和总氮的截留效果。结果表明：20 m宽度河岸植被缓冲带能很好地截留各形态氮素。30 m宽度下,河岸植被缓冲带径流水中的铵态氮、硝态氮和总氮的截留率最高,分别为70.4%、67.7%和69.1%。在不同植物种类缓冲带比较中,杨树可显著降低径流铵态氮和总氮浓度,水曲柳可显著降低径流硝态氮浓度。在宽度与不同植物种类的交互关系中,20 m宽度杨树缓冲带对铵态氮和硝态氮的截留率最高,其各自的截留率为71.9%、64.2%,30 m宽度杨树缓冲带对总氮的截留率最高,为62.1%。研究结果可为东北地区中小型河流河岸缓冲设计最大化截留径流氮污染物提供参考。     

Effects of Restored Stream Buffers on Water Quality in Non-tidal Streams in the Choptank River Basin

Restoration of riparian buffers is an important component of nutrient reduction strategies in the Chesapeake Bay watershed. In 1998, Maryland adopted a Conservation Reserve Enhancement Program (CREP), which provides financial incentives to take agricultural land out of production to plant streamside vegetation. Between 1998 and 2005, 1–30% of streamside vegetation (average?=?11%), was restored to forest or managed grass in 15 agriculturally dominated sub-basins in the Choptank River basin, a tributary of Chesapeake Bay. Pre-existing forested buffers represented 10–48% of the streamside (average?=?33%), for a total of 12–61% buffered streamsides (average?=?44%). Using multi-year water quality data collected before and after CREP implementation (1986, 2003–2006), we were unable to detect significant effects of CREP on baseflow nutrient concentrations based on the area of restored buffer, the percentage of restored streamside, or the percentage of total riparian buffer in the sub-basins (p?>?0.05). Although CREP increased the average buffered streamside from 33% in the 1990s to 44% by 2005, N and P concentrations have not changed or have increased in some streams over the last 20 years. Reductions may not have occurred for the following reasons: (1) buffer age, width, and connectivity (gaps) between buffers are also important to nutrient reductions; (2) agricultural nutrient inputs may have increased during this period; and (3) riparian buffer restoration was not extensive enough by 2005 to have measurable affects on the stream water quality in these sub-basins. Significant effects of CREP may yet be resolved as the current CREP buffers mature; however, water quality data through 2006 in the Choptank basin do not yet show any significant effects.     

Bird community structure across riparian buffer strips of varying width in a coastal temperate forest

Buffer strips are strips of forest retained along streamsides after harvesting to mitigate negative impacts of forestry on aquatic and riparian fauna and water quality. The capacity of riparian buffer strips of old-growth forest to maintain species richness and abundance of natural bird communities was explored in coastal montane forest on Vancouver Island, Canada. Breeding bird communities in buffer strips of varying widths along rivers were compared with controls of equivalent area in uncut old-growth riparian forest to identify shifts in species richness, diversity, abundance and composition. We observed that effects on riparian bird communities were greatest in very narrow buffers with high amounts of edge habitat. Several forest-interior species were found almost exclusively in wider buffers and abundances dropped dramatically between wide (125 m) and medium (41 m) width buffers with replacement by open-edge species in narrow buffers. Species composition of communities in wide buffers were very similar to controls while narrow buffers shared less than half of their species with controls. Species richness and diversity increased in buffers over the three years while remaining constant in controls. Increases in species richness and abundance within buffers were positively correlated with similar increases in the adjacent clearcuts, suggesting that regeneration in clearcuts may facilitate recolonization of forest in remnant buffers. For the forest-interior species found primarily in wide buffers, buffers >100 m may need to be retained.     

土壤团聚体研究进展

土壤团聚体是土壤的重要组成部分,影响了土壤的各种物理化学性质,对土壤侵蚀有重要影响,其水稳性和数量是评价土壤可蚀性的重要评价指标。综述了土壤团聚体的形成、影响土壤团聚体水稳性的因素、以及土壤团聚体研究方法的研究的最新进展,针对其中存在问题,指出今后可能的发展方向。     

河岸带植被对非点源氮、磷以及悬浮颗粒物的截留效应

选取草地河岸带和人工林地河岸带,开展了人工模拟农田施肥和径流污染物截留效果的现场试验。分别采集地表径流和渗透水水样,测定分析了总磷(TP)、总氮(TN)、氨氮(NH4—N)以及固体颗粒物的浓度。结果表明,草地河岸带对地表径流TP的截留效果显著优于林地河岸带,草地和林地河岸带对氮元素的截留效果趋于一致;河岸带对地表径流和渗透水中TN,TP和NH4—N的截留率是相似的;草地河岸带对固体颗粒物的截留效果优于林地河岸带;河岸带越宽,其截污功能越强;人为干扰造成了人工林地河岸带截污能力的减弱。并提出了河岸带管理的相关建议。     

汾河河岸带土壤氮、磷的时空分布规律及其影响因素研究

为明晰汾河临汾段河岸带土壤氮、磷时空分布规律及其影响因素,采用现场检测、空间分析及数理统计方法,探讨了自然河岸带及强人工干扰河岸带土壤氮、磷的化学计量学特征、时空分布特征及其与土壤、水文特性的相关性。结果表明:(1)各水期强人工干扰河岸带土壤TN、TP储量及其变异系数均大于自然河岸带,自然河岸带土壤氮、磷元素的生态化学计量存在弱稳态性;(2)汾河临汾段河岸带土壤TN、TP含量随枯水期—平水期—丰水期表现为先减小后增大的趋势,横向来看河岸带近岸土壤TN、TP含量大于远岸部分,土层深度方向上TN、TP含量随土层深度增加而减小;(3)河流水质、土壤容重和土壤孔隙度是影响汾河河岸带土壤TN含量的相关因子,土壤容重、土壤孔隙度和N/P是影响河岸带土壤TP含量的相关因子。研究结果表明汾河河岸带土壤氮分布与河流水文特性有一定的响应关系,土壤磷分布与河流水文特性无明显的响应关系。     

三峡水库消落区生态环境保护与利用对策研究

三峡水库投入使用后，在库区两岸形成周期性变化的水陆交错地带即消落区。通过调查消落区的类型、分布、面积等基本情况，从消落区水、土相互作用角度，分析了消落区在水、土交互作用下对水、陆生态系统的影响，提出了利用生物缓冲带等技术来建立消落区生态保护的措施。     

Observing Changes in Riparian Buffer Strip Soil Properties Related to Land Use Activities in the River Njoro Watershed, Kenya

Riparian buffer strip guidelines are under scrutiny in the River Njoro Watershed in Kenya. This study investigated soil properties (bulk density, carbon, nitrogen, and phosphorus) in different land use types (small scale agriculture in recent settlements, mixed agriculture in established peri-urban settlements, large-scale commercial agriculture, and the gazetted forest reference condition) and their adjacent buffer strips. Bulk density, carbon, nitrogen, and phosphorus within 30-m riparian buffer strips adjacent to recent settlement land use areas were similar to those of the gazetted forest reference condition, but only bulk density of the buffer strips adjacent to peri-urban and commercial agriculture land use areas were similar to the gazetted forest reference condition. Phosphorus is a sensitive indicator of the impacts of human activity, as increased concentrations were observed with increasing scale of land use activity. For riparian buffers adjacent to recent settlements, soil phosphorus was significantly higher in buffers narrower than 30?m (5.01?mg?P?kg^?1) than gazetted forest (3.40?mg?P?kg^?1) but not significantly different for riparian buffers wider than 30?m (3.81?mg?P?kg^?1) compared to gazetted forest. Based on the research, it is recommended that policies governing riparian buffer strips become (1) stricter, with the current ??maximum?? of 30?m considered a minimum; and (2) adaptive, with 30?m used in small-scale agricultural areas, and wider riparian buffer strips used in medium- and large-scale agricultural areas.     

Prevalence of Concentrated Flow Paths in Agricultural Fields in Southern Illinois

Literature on prevalence of concentrated flow paths (CPFs) in agricultural fields are limited at field scale with only few studies that address occurrence of CFPs at large geographic extent. This study used high-resolution Light Detection and Ranging (LiDAR) data to identify CFPs in agricultural fields and calculate the percentage of the fields drained by CFPs at a county scale. In 389 agricultural fields across Jackson County, southern Illinois, this study also investigated the association between field characteristics and CFP formation using multiple regression and CART analysis. The mean number of CFPs in a field was 5 with a minimum of 0 and maximum of 17 CFPs. The majority of the CFPs fell under the large category for CFP length and drainage area that corresponds with high mean percent (81%) of field area drained by the CFPs. Further, 85% of the fields had more than 70% of their area drained by CFPs. The multiple regression and CART analysis showed slope as an important factor influencing CFP characteristics such as number of CFPs and CFP length. Both analyses also indicated physical soil properties such as bulk density, soil erodibility factor, saturated hydraulic conductivity, LS factor, organic matter, and percent sand were also predictors of the CFP characteristics. However, these factors explained only 2 to 12% of the variation observed. The significant presence of CFP’s has important implications for water quality since current conservation practices such as riparian buffers were not designed to address concentrated flow from agricultural fields.     

Soil carbon dioxide (CO2) fluxes in permanent upslope pasture and downslope riparian buffers with varying vegetation

Background

Riparian buffers are primarily implemented for their water quality functions in agroecosystems. Their location in the agricultural landscape allows them to intercept and process pollutants from immediately adjacent agricultural land. Vegetated riparian buffers recycle soil organic matter, which elevates soil carbon (C), which upon processing, processes and releases carbon dioxide (CO₂). The elevated soil C and seasonally anoxic environments associated with riparian buffers promote denitrification and fermentation, further increasing soil CO₂ production.

Aim

Against this context, a replicated plot-scale experiment was established at North Wyke, UK, to measure the extent of soil CO₂ emissions in permanent pasture served by grass, willow, and woodland riparian buffers, as well as a no-buffer control.

Methods

Soil CO₂ was measured using the static chamber technique in conjunction with soil and environmental variables between June 2018 and February 2019.

Results

Cumulative soil CO₂ fluxes were in the descending order: woodland riparian buffer; 11,927.8 ± 1987.9 kg CO₂ ha^–1 > no-buffer control; 11,101.3 ± 3700.4 kg CO₂ ha^–1 > grass riparian buffer; 10,826.4 ± 2551.8 kg CO₂ ha^–1 > upslope pasture; 10,554.6 ± 879.5 kg CO₂ ha^–1 > willow riparian buffer; 9294.9 ± 1549.2 5 kg CO₂ ha^–1. There was, however, no evidence of significant differences among all treatments of the current study.

Conclusions

Despite the lack of significant differences, the results from our short-term study show that the woodland riparian buffer had relatively larger soil CO₂ emissions than the remainder of the other riparian buffers and the upslope pasture it serves. Our short-term findings may be useful in developing soil CO₂ mitigation strategies through careful selection of riparian buffer vegetation and may be useful in calibrating mechanistic models for simulating such emissions from similar agro systems.