沈阳市降雨径流污染物排放特征

城市降雨径流作为污染物迁移转化的主要驱动力,是城市非点源污染研究的热点和重点。本文以沈阳市典型区域为例,研究了坡顶屋面、平顶屋面和路面3种下垫面降雨径流的总悬浮颗粒物(TSS)、总氮(TN)、总磷(TP)、化学需氧量(COD)和主要重金属(Cd、Pb、Cr、Cu、Ni和Zn)共10种污染物的排放特征。结果表明:污染物的浓度峰值提前于径流峰值;路面径流的污染程度重于屋面径流,TN是屋面径流的主要污染物,TSS、TN、TP、Pb和Cr则是路面径流的主要污染物,TSS超过了国家污水二级排放标准,其余污染物均超过了国家V类地表水标准;径流中TSS与除TN以外的其他8种污染物有较强相关性,氮、磷营养元素与降雨量和雨强大小呈显著正相关,COD则易随着降雨时间的延长而逐渐释放到径流中;与其他国家和城市对比发现,沈阳屋面径流中TSS、TN、TP和COD较少,但却有一定的重金属污染;路面径流中TSS和TP浓度较高,但TN和COD浓度较低,且重金属中Pb、Cr、Cu和Zn的污染较严重。     

滤渠-塘组合系统对城市旅游区降雨径流污染的离线截控作用

提出了一种控制城市旅游区降雨径流污染的滤渠-塘离线组合处理系统,并研究了该系统对降雨径流污染的离线截控作用.结果表明:无论从单次降雨事件还是从年度上分析,该系统通过有效地分流初期污染降雨径流,均可降低降雨径流中污染物的浓度和体积平均粒径,并对降雨径流中污染物的负荷具有较高的持留效率,是一种高效的处理系统,比较适用于土地利用相对紧张的城镇区域.2005年该系统对降雨径流中总悬浮物(TSS)、化学需氧量(COD)、总氮(TN)和总磷(TP)负荷的年持留率分别达到86.4%、85.5%、83.9%和82.9%.以2005年6月26日的次降雨事件为例,该系统对降雨径流水量的削减率为67.9%,对污染物中各种形态氮的去除效率高于磷,对TSS、COD、TN和TP负荷的持留率分别为97.0%、89.2%、94.9%和96.2%.该系统还可以有效地拦截降雨径流中的大部分颗粒物.     

绿色屋面降雨径流水质及消减污染负荷研究

2011年5月至11月对12场降雨时段的屋面径流和干湿沉降进行采样监测,比较了屋面径流(绿色屋面和沥青屋面)、干湿总沉降和降雨中污染物的浓度和污染负荷,并运用多元统计方法分析了降雨特征对绿色屋面径流水质的影响。结果表明,从径流水质层面上分析,绿色屋面是总悬浮物(TSS)的汇,对p H值有较好的中和作用,对于总磷(TP)、溶解态铜(DCu)和溶解态锌(DZn)是非源非汇,是电导率(EC)、总氮(TN)、氨态氮(NH+4-N)、硝态氮(NO-3-N)、化学需氧量(COD)、5日生化需氧量(BOD5)和溶解态铅(DPb)的源;从污染负荷的角度分析,绿色屋面是NH+4-N、TSS和BOD5的汇,对于TN、DPb、DCu、DZn、TP和COD是非源非汇,是NO-3-N的源;与控制屋面相比,绿色屋面可以消减TSS、TP、BOD5、COD、NH+4-N、DZn和DPb的污染负荷,分别消减了90.53%、49.38%、41.31%、36.48%、35.45%、28.27%和14.20%;但是增加了NO-3-N和TN的污染负荷,分别增加了821.02%和275.48%;绿色屋面径流污染物的浓度与降雨量、降雨历时和降雨强度呈负相关关系,而与降雨间隔呈正相关关系。研究结果为绿色屋面的科学设计及正确评价绿色屋面对径流水质的影响提供依据。     

非完全淹水条件下稻田表面水体中三氮的动态变化特征研究

研究了稻田表面水体中三氮浓度的动态变化特征,结果表明,在独立排灌的稻田田面水中,每次施氮后,NH4^+和TN在1d后达到极大值,随时间推移,下降较快．NO3^-、NH4^+／TN、NO3^-／TN和(NH4^++NO3^-)／TN是先升后降,NH4^+和TN可作为农田水污染监测的主要氮素指标,NO3^-作为辅助监测指标,三氮浓度变化与施氮量呈明显正相关,施氮9d是防止三氮大量流失的关键时期．NH4^+和TN随时间动态变化的单因素模拟表达式为指数、对数、乘幂型或二次型;NO3^-的也是非直线型,却无合适的模拟模式,时间和施氮量两因素模拟表明,NH4^+和TN的模拟模式相同。     

杨麦间作系统枯落物持水能力对地表径流氮流失的影响

以太湖流域杨麦间作系统为研究对象, 对系统内不同枯落物蓄积量持水能力及对地表径流中不同形态氮流失效应进行定位观测, 结果表明: 随着枯落物蓄积量的增加, 蓄积量为0.4 t·hm–2最大持水量、最大拦截量和有效拦截能力＞0.2 t·hm–2＞0.1 t·hm–2, 最大持水量的变化范围为2.35-12.93 t·hm–2, 最大拦截量变化范围2.17-10.95 t·hm–2, 有效拦蓄能力在1.80-9.10 t·hm–2之间; 枯落物持水量与浸泡时间呈对数关系(R2＞0.90), 枯落物吸水速率与浸泡时间呈幂函数关系(R2＞0.99)。枯落物蓄积量越大, 对地表径流量及地表径流中不同形态氮流失的削减效果越显著。而2种间作密度下, A1处理对地表径流中TN、NO3–-N和NH4+-N的削减效果＞A2; 径流中以NO3–-N流失为主, TN、NO3–-N和NH4+-N流失量随枯落物蓄积量的增加呈下降的趋势, 蓄积量越大, 差异越显著。      

莴笋对不同形态氮素的反应

探讨了不同形态氮素对莴笋生长发育的影响及其营养特性。结果表明,莴笋幼苗根系对NH4^+ -N的亲和力稍大于NO3^- -N的亲和力;分别供给NO3^- -N+NO3^- -N及NH4^+ -N,莴笋的生物学产量和吸N量均依次递减（分别为100：56.9：12.4,100：48.9：8.6）,因此在水培条件下,NO3^- -N是最适合莴笋生长发育的氮源,NH4^+ -N与NO3^- -N各占50％时对莴笋的生长发育已有一定的抑制作用,仅以NH4^+ -N作氮源则莴笋很难生长;NH4^+ -N与NO3^- -N各占50％时,莴笋倾向于吸收较多的NH4^+ -N,而且在培养不同阶段NH4^+/NO3^-吸收比例均大于1,莴笋表现出喜铵性,但NH4^+ -N并非莴笋很适合的氮源;营养液中NO3^- -N不足,主要影响莴笋茎叶的生长,而NH4^+ -N所占比例达50％时,莴笋根系生长受到抑制,且有明显的受害症状;以NO3^- -N作氮源预培养两周,以含微量NO3^- -N的自来水为水源,再单独以NH4^+ -N为氮源,对莴笋生长有极大的促进作用,同时还大幅度降低了体内硝酸盐的含量。尿素作氮源莴笋未出现受害症状,但莴笋的生长发育状况明显劣于其它氮源。     

不同近地表土壤水文条件下雨滴打击对黑土坡面养分流失的影响

目前,土壤水分饱和和壤中流条件下,雨滴打击对养分流失的影响尚不清楚.通过3个近地表土壤水文条件(自由入渗、土壤水分饱和与壤中流)下,土槽上方架设与不架设尼龙纱网模拟降雨对比试验,研究雨滴打击对黑土坡面侵蚀过程及NO3-N、NH4-N与PO4-P随径流和侵蚀泥沙迁移的影响.结果表明,纱网覆盖消除雨滴打击后坡面侵蚀量和泥沙浓度分别减少59.4％-71.6％和57.3％ -73.0％,不同水文条件下减少量的排序为:自由入渗＞壤中流＞土壤水分饱和.消除雨滴打击后养分随径流流失的减少仅在自由入渗条件下体现较明显,该水文条件下NO3-N、NH4-N与PO4-P流失分别减少33.3％、23.1％和40.7％;3种水文条件下,消除雨滴打击均明显减少养分随泥沙的流失,其中自由人渗条件下减少效果最明显,该水文条件下,NO3-N和NH4-N流失分别减少20.9％ -54.9％和25.0％ -62.3％,而PO4-P流失减少在74.6％以上.雨滴打击增大了NO3-N的淋失,但对NH4-N与PO4-P的淋失几乎无影响.消除雨滴打击后,自由人渗条件下养分的等效径流迁移深度减少26.7％-42.6％,而土壤水分饱和与壤中流条件下基本无变化.以上研究结果为有效防治坡面土壤侵蚀和农业非点源污染提供科学理论依据,尤其是在壤中流出现的地方.     

红树植物人工湿地对生活污水的净化效果

研究了潜流型海桑（Sonneratia caseolaris）人工湿地、桐花树（Aegiceras corniculatum）人工湿地和木榄（Bruguiera gymnorrhiza）人工湿地对生活污水的净化效果。一年来,3种红树植物人工湿地对BOD5、CODCr、TP、TN、NH4^＋-N和NO2^--N的平均去除率分别达到83%、71%、41%、55%、50%和84%以上。人工湿地各处理周期之间,BOD5和CODCr去除率波动较小,而TP、TN、NH4^＋-N和NO2^--N去除率波动较大。3种红树植物人工湿地对各种污染物的净化效果存在一定的差异。海桑人工湿地和桐花树人工湿地对BOD5、CODCr、TP、TN和NH4^＋-N去除率明显高于木榄人工湿地,而海桑人工湿地和桐花树人工湿地相比较,除TP外,BOD5、CODCr、TN和NH4^＋-N去除率没有显著差异。人工湿地单一处理周期内,去除率随水力停留时间（HRT）的延长而增加。BOD5、CODCr、TN和NH4^＋-N在HRT为1d和2d的去除率分别为HRT为3d去除率的54%-65%和73%-84%,NO2^--N在HRT为1d和2d的去除率分别达到了HRT为3d的70%-81%和85%-94%,而TP在HRT为1d和2d的去除率分别只有HRT为3d的39%-50%和65%-74%。另外,红树植物人工湿地与风车草（Cyperus alternifoliu）人工湿地相比,前者的BOD5、CODCr、TP、TN和NH4^＋-N去除率明显小于后者（P〈0.05）。总体上看,3种红树植物人工湿地对生活污水的净化效果呈现海桑人工湿地≈桐花树人工湿地〉木榄人工湿地。     

草坪系统对城市降雨初期径流氮污染控制作用

为了控制城市旅游区降雨径流污染,在武汉动物园鹿苑区构建草坪系统,研究了草坪系统对城市降雨初期径流氮污染的控制与持留作用。结果表明：草坪系统使预处理后降雨径流中的总氮（TN）、溶解态总氮（DN）和铵态氮（NH₄⁺-N）浓度分别降低16.0％、13.9％和75.6％;草坪系统对氮素的持留率为NH₄⁺-N>90%、TN、DN>65％、硝态氮 (NO₃^--N)>5％;水力负荷显著影响TN出水浓度和处理效率,进水浓度相近、水力负荷从3.3 cm·d^-1升高到8.3 cm·d^-1,TN去除率由28.0%降低至19.8%;草坪宽度影响污染物出水浓度,NH₄⁺-N浓度随着草坪宽度增加而下降,而NO₃^--N浓度变化趋势与之相反,DN在流程10 m处出现最低值。草坪系统在净化降雨初期径流的同时利用了营养盐和水资源,降低了草坪维护的水肥投入。     

短期内^15N标记的铵盐和硝酸盐在青藏高原高寒草甸中的运移规律

运用^15N稳定性同位素示踪技术,对高寒草甸植物和土壤微生物固持沉降氮的能力及沉降氮在小嵩草（Kobresia pygaea)草甸中的运移规律进行了研究。施肥2周后,NO3^-－^15N和NH4^ －^15N的总恢复率分别为73．5％和78％。无论是NO3^-－^15N,还是NH4^ －^15N植物所固持的^15N总是比土壤有机质或者是土壤微生物固持的多。4周后,70．6％的NO3^-－^15N和57．4％的NH4^ －^15N被固持在土壤和植物中。其中,土壤微生物所固持。在施肥6周和8周后,NO3^-－^15N的总恢复率分别为58．4％和67％,而NH4^ －^15N的总恢复率分别为43．1％和49％。植物和土壤微生物所固持的NO3^-－^15N比NH4^ －^15N多。在整个实验期间,植物固持的NO3^-N较多,而且比土壤微生物固持了较多^15N。由于无机氮的含量一直很低,无机氮库所固持的^15N一般不超过1％。上述结果意味着短期内植物在高寒草甸中对沉降氮的去向起着决定作用。     

Nitrogen dynamics of storm runoff in the riparian zone of a forested watershed

The influence of storm runoff processes on stream nitrogen dynamics was investigated in a headwater riparian swamp on the Oak Ridges moraine in southern Ontario. Hydrologic data were combined with analysis of an isotopic tracer (¹⁸0) and nitrogen (NH ₄ ⁺ , NO ₃ ^– ) concentrations in saturation overland flow and stream discharge. Storm runoff was separated into its event and pre-event components using¹⁸O in order to examine the effect of water source on nitrogen chemistry. Laboratory experiments were also used to study nitrogen transformation associated with storm runoff-surface substrate interactions in the swamp. In most storms N0₃-N and NH₄-N concentrations in the initial 3–4 mm throughfall increment were 10–20x and 20–100x higher respectively than stream base flow concentrations. Maximum stream N0₃-N concentrations were < 2x to 6x higher than base flow concentrations and preceded or coincided with peak stream discharge. Storm-to-storm variations in stream N0₃-N behaviour also occurred during the hydrograph recession phase. NH₄-N concentrations attained an initial peak on the rising hydrograph limb, or at peak stream discharge. A second NH₄-N increase occurred during the late recession phase 3–5 h after maximum stream discharge. Inorganic-N concentrations in surface runoff were similar to peak streamflow.The close agreement between observed N0₃-N concentrations and values predicted from a chemical mixing model indicate that stream N0₃-N variations were controlled mainly by the mixture of throughfall and groundwater in surface stormflow from the swamp. Laboratory experiments also indicated that N0₃-N in surface runoff behaved conservatively when mixed with swamp substrates. With the exception of the late hydrograph recession phase, observed stream NH₄-N concentrations were much lower than concentrations predicted by the chemical mixing model. The rapid loss of NH₄-N from mixtures of surface stormflow and swamp substrates in laboratory experiments and the absence of uptake in sterilized substrates indicated that NH₄-N retention in surface storm runoff was due to biotic processes.     

Controlled release experiments to determine the effects of shade and plants on nutrient retention in a lowland stream

Understanding nutrient uptake and retention in streams remains an important challenge for lotic scientists. In this study a series of pulse and continuous releases of dissolved nutrients were made to shaded and unshaded (reference) reaches of a small lowland stream to determine whether suppression of macrophyte growth by riparian shade impaired nutrient retention. The nutrients were dissolved reactive phosphorus (DRP), total ammoniacal nitrogen (NH₄–N) and nitrate nitrogen (NO₃–N). Nutrient reductions ranged from 100% of DRP when stream water was anoxic, to 5–10% for NH₄–N and NO₃–N in the reference reach. Nutrient removals were affected by travel times in each reach. Percentage removals of NH₄–N (46 ± 10) and NO₃–N (52 ± 14) were higher in the shaded reach than in the swifter moving reference reach (15 ± 8 and 16 ± 10, respectively). DRP (%) removals were 75± 7 and 57 ± 12 for the shaded and reference reaches, respectively. The presence of emergent marginal macrophytes (Persicaria hydropiper) increased stream velocity in the reference reach by reducing the effective channel cross-section area. Shading reduced plant biomass, increased the channel cross-section and lowered velocity in the experimental reach, effecting dramatic reductions in nutrient concentrations over short distances. The opposite effect is more typical for larger, swifter streams having dense stands of submerged macrophytes, where lowering channel plant biomass will cause increased velocities and lower relative nutrient losses. Riparian shade does not necessarily impair nutrient uptake from small streams. Where invasive marginal species such as P. hydropiper dominate headwater streams shade may be beneficial to the protection of downstream waters from eutrophication. Where reduction of nutrient fluxes from small streams is a key objective for protection of downstream waters, active management of streams should seek to increase travel times, allowing greater potential for nutrient uptake. This will need to be weighed against the need for effective drainage in pastoral areas where reduced travel times are usually sought.     

三峡水库香溪河库湾春季水华期间悬浮物动态

在三峡水库香溪河库湾春季藻类水华期间开展了水体悬浮物动态研究.调查结果表明：总悬浮物浓度的中位数是6.80 mg·L^-1, 波动范围是0.66～134.92 mg·L^-1,从河口到库尾入库点呈现逐渐递增的趋势;无机悬浮物空间格局与总悬浮物基本相似,而有机悬浮物空间格局与总悬浮物差异较大,与叶绿素a较为相似.回归分析表明：库湾中部水域叶绿素a与总悬浮物、有机悬浮物均有显著的线性关系,分别解释了总悬浮物、有机悬浮物总变异的66.7%～96.7% 和 58.9%～85.5%;在库湾两端（河口与库尾）叶绿素a与悬浮物参数均没有显著的线性关系.在库湾中部水域,有机悬浮物比无机悬浮物更能解释总悬浮物的变异;在库湾两端,无机悬浮物比有机悬浮物更能解释总悬浮物的变异.这意味着库湾中间水域总悬浮物的动态主要受有机悬浮物内源性生产的影响,而河口或库尾总悬浮物的动态主要受外源性的无机悬浮颗粒物输入的影响.     

控释氮肥对洞庭湖区双季稻田表面水氮素动态及其径流损失的影响

用渗漏池模拟洞庭湖区2种主要稻田土壤(河沙泥和紫潮泥),研究了施用尿素(CF)和控释氮肥(CRNF)对双季稻田表面水pH、电导率(EC)、全氮（TN）、铵态氮（NH₄⁺-N）和硝态氮（NO₃^--N）浓度变化规律及TN径流损失的影响.结果表明,双季稻田施用尿素后,表面水TN、NH₄⁺-N浓度分别在第1、3天达到高峰,然后迅速下降;NO₃^--N浓度普遍很低;早稻表面水pH在施用尿素后15 d内(晚稻3 d)逐渐升高;EC与NH₄⁺动态变化一致.与尿素相比,施用CRNF能显著降低双季稻田表面水pH、EC、TN和NH₄⁺-N浓度,70% N控释氮肥的控制效果最显著;但后期NO₃^--N浓度略有升高.径流监测结果表明,洞庭湖区种植双季稻期间施用尿素的TN径流损失为7.70 kg·hm^-2,占施氮量的2.57%;施肥后20 d内发生的径流事件对双季稻田TN径流损失的贡献极为显著;与施用尿素相比,施用控释氮肥显著降低了施肥后10 d内发生的第1次径流液中的TN浓度,施用CRNF和70%N CRNF的氮素径流损失分别降低24.5%和27.2%.     

Linking fish trait responses to in‐stream habitat in reconstructed valley‐plugged stream reaches of the Coastal Plain,U.S.A.

Valley‐plug formation is a challenging consequence of stream channelization especially in physiographic regions with highly erodible soils. Upstream channel degradation and incision results in accelerated sediment delivery processes wherein downstream aggradation decreases stream power and creates sand‐clogged channels. Channel reconstruction is now meeting hydrogeomorphic goals related to valley‐plug remediation, yet there exists a need to understand how this practice also facilitates ecological restoration. We evaluated fish trait response to in‐stream habitat conditions in channelized, recently restored, and “least‐disturbed” reference reaches of Coastal Plain streams in West Tennessee. Restored reaches were ecologically similar to channelized reaches, having higher proportions of nest‐guarding omnivores that were correlated with higher percentages of pool habitats and lower wetted width:depth ratios compared to reference reaches. Reference reaches had higher proportions of fast‐water dwelling and specialized insectivores that were correlated with high abundance of large woody debris, high‐wetted width:depth ratios, and low percentages of pool habitats. We conclude that in‐stream habitats in reconstructed channels have yet to promote reach‐scale ecological restoration relative to fish assemblage organization because trait‐habitat associations were not similar to reference conditions. However, our results lend to the development of ecological restoration targets that can be incorporated in future channel reconstruction projects in valley‐plugged, channelized streams of the Coastal Plain.     

An off-line filtering ditch–pond system for diffuse pollution control at Wuhan City Zoo

An off-line filtering ditch–pond system was designed and constructed to control the small point and runoff pollution at the Wuhan City Zoo, Hubei Province, China. The quantity and quality of wastewater discharge and runoff from 16 rainfall events were measured to test the effectiveness of the off-line treatment train. The results showed that the water quality was improved and high retention rates for water and pollutants were also achieved by the off-line treatment train. In the outflows, the event mean concentrations (EMCs) of TSS, COD, TN, TDN, TP and TDP were reduced by 75%, 50%, 50%, 57%, 74% and 80% compared to the inflows. In 2005, the annual inflow volume in the catchment was 6783 m³ and the water retention rate was 80.1%. The retention rates in the annual loads of TSS, COD, TN and TP came to 86.4%, 85.5%, 83.9% and 82.9%, respectively. Therefore, the off-line filtering ditch–pond system was shown to be an effective and economical measure to control diffuse pollution. It would be worthwhile to extend the off-line treatment train to regions with limited land resources, especially in urban areas.     

Spatial variance of nutrient limitation of periphyton in montane, headwater streams (McLeod River, Alberta, Canada)

There have been few studies that have examined the spatial variance of nutrient limitation over the scale of an entire set of headwater streams. We used nutrient diffusing substrata experiments (control, nitrogen addition, phosphorus addition, and nitrogen+phosphorus addition) to examine how nutrient limitation varied throughout the five creeks that comprise the McLeod River headwaters (Alberta, Canada). We assessed the variance of chlorophyll a accrual at spatial scales within reach, within creek, among creeks and across linear distance within the entire watershed to assess the consistency and scale of nutrient limitation. We analyzed the importance of the spatial scale using several methods. We assessed the coefficient of variation at different scales, the spatial covariance of nitrogen and phosphorus deficiency indices using a spline correlogram, and the variance through traditional analyses of variance methods. Chlorophyll a accrual responded significantly to nutrients in all creeks, though the response varied in magnitude and in the limiting nutrient among reaches and among creeks. Variance in chlorophyll a accrual was due primarily to the factor of creek (R ²=0.40) and secondarily to reach (R ²=0.07). The CV was 31.4% among creeks, 18.4% among reaches, and 17.9% within reaches. The N deficiency index showed a positive correlation at sites located <4 km apart and a negative correlation at sites greater than 6.5 km apart. The P deficiency index showed no discernible spatial correlation. Our results suggest that nutrient limitation varies on small scales and is often driven by local processes.     

土地利用、溪流级别与溪流河水理化性质的关系

为研究土地利用对溪流水质的影响 ,对黑龙江省尚志市帽儿山境内阿什河流域的 1～ 5级溪流河水进行采样 ,同时记载森林覆盖度、邻近土地利用类型及地貌特征。对溪水样品的的 p H,浑浊度 ,NH 4- N、NO- 3- N和 PO3 3- P浓度进行分析测定。对不同溪流级别和土地利用类型的溪流河水进行分析。结果表明 :随着溪流级别的升高和土地利用类型由森林变为农田和村镇 ,溪流河水的 p H,浑浊度 ,NH 4- N、NO- 3- N和 PO3- 3- P浓度均显著升高。森林植被保存相对较好的 1、2级溪流水质最佳 ,但溪水中溶解无机磷和无机氮的浓度与美国温带地区相似的低级溪流相比 ,分别高 30倍和 1 0 0倍。河岸带破坏 ,土地利用的变化 ,放牧、樵采等频繁干扰造成的土壤侵蚀和养分流失输入是造成该流域溪流富营养化的主要原因     

Inter-annual,Annual, and Seasonal Variation of P and N Retention in a Perennial and an Intermittent Stream

Headwater streams represent the key sites of nutrient retention, but little is known about temporal variation in this important process. We used monthly measurements over 2 years to examine variation in retention of soluble reactive phosphorus (SRP) and ammonium (NH₄⁺) in two Mediterranean headwater streams with contrasting hydrological regimes (that is, perennial versus intermittent). Differences in retention between streams were more evident for NH₄⁺, likely due to strong differences in the potential for nitrogen limitation. In both streams, nutrient-retention efficiency was negatively influenced by abrupt discharge changes, whereas gradual seasonal changes in SRP demand were partially controlled by riparian vegetation dynamics through changes in organic matter and light availability. Nutrient concentrations were below saturation in the two streams; however, SRP demand increased relative to NH₄⁺ demand in the intermittent stream as the potential for phosphorus limitation increased (that is, higher dissolved inorganic nitrogen:SRP ratio). Unexpectedly, variability in nutrient retention was not greater in the intermittent stream, suggesting high resilience of biological communities responsible for nutrient uptake. Within-stream variability of all retention metrics, however, increased with increasing time scale. A review of studies addressing temporal variation of nutrient retention at different time scales supports this finding, indicating increasing variability of nutrient retention with concomitant increases in the variability of environmental factors from the diurnal to the inter-annual scale. Overall, this study emphasizes the significance of local climate conditions in regulating nutrient retention and points to potential effects of changes in land use and climate regimes on the functioning of stream ecosystems.