铜锈环棱螺生物扰动对"蓝藻水华"水体底泥及其间隙水中碳、氮、磷含量的影响

实验室内建立小型模拟生态系统,根据铜锈环棱螺(Bellamya aeruginosa)的密度设置了3个处理组和1个对照组.结果显示:铜锈环棱螺对底泥0～0.5 cm及0.5～2 cm有机质影响较明显,显著降低了底泥中的C:P.处理组3和处理组2间隙水NH4+-N含量分别在底泥0～0.5cm及0.5～2 cm深度和对照组之间存在显著差异(p＜0.05).间隙水中NO2--N+NO3--N的变化较复杂,处理组NO2--N+NO3--N含量在0～0.5 cm,0.5～2cm及2～4cm与对照组相比差异显著(p＜0.05).间隙水中DIP含量随底泥深度先增后减,在2～4 cm处含量达最大,DIP含量在0.5～2 cm深度处理组与对照组之间有显著差异(p＜0.05).铜锈环棱螺生物干扰增加了底泥表层有机质的含量,同时降低了其稳定性.     

室内模拟试验铜锈环棱螺及其体表周丛生物对水中氮形态及含量的影响

铜锈环棱螺及附着于其体表的周丛生物在水体氮循环过程中均扮演着重要角色。此次试验以铜锈环棱螺及其体表周丛生物为研究对象, 通过室内模拟试验探讨铜锈环棱螺及周丛生物对水中氮形态和含量的影响。试验分无螺对照组CK、处理1(具有周丛生物的螺壳)、处理2(去除周丛生物的活体螺)和处理3(具有周丛生物的活体螺)。结果表明, 试验结束时, 处理2和处理3水中总氮(TN)含量分别为CK的25倍和44倍, 活体螺显著增加了水中总氮含量(P<0.05)。与处理2相比, 具有周丛生物的处理1和处理3氨氮(NH3-N)和亚硝氮(NO2–-N)转化效率更快; 与CK相比, 处理组水中硝氮(NO3–-N)占比显著增加(P<0.05), 且具有周丛生物的处理1和处理3比无周丛生物的处理2更早到达硝氮占比峰值; 螺体表面周丛生物中较高的氨氧化和亚硝氮氧化功能基因(AOB-amoA、AOA- amoA和nxrA)丰度促进了水中NH3-N和NO2–-N向NO3–-N的转化。     

九龙江河口区养虾塘沉积物-水界面营养盐交换通量特征

通过对九龙江河口区陆基养虾塘水样和沉积物样品采集分析及结合室内模拟实验,探讨了虾塘在不同养殖阶段沉积物-水界面营养盐通量时间变化特征及其主要影响因素。虾塘沉积物向上覆水体释放NO_x~--N(NO_2~--N和NO_3~--N)、NH_4~+-N和PO_4~(3-)-P能力均呈现随养殖时间推移而降低的特征。沉积物在养殖中期和后期分别呈现对上覆水体NO_x~--N和PO_4~(3-)-P的吸收现象,但总体表现为释放(平均通量分别为(1.87±1.15)、(1.58±0.52)mg m~(-2)h~(-1)和(1.22±0.62)mg m~(-2)h~(-1))。沉积物-水界面溶解无机氮交换以NH_4~+-N为主(沉积物平均释放通量为(46.18±13.82)mg m~(-2)h~(-1))。沉积物间隙水与上覆水间的营养盐浓度差(梯度)及温度对上述交换通量的时间动态特征具有重要调控作用。研究结果表明养殖初期或中期沉积物较高的无机氮(尤其是NO_2~--N和NH_4~+-N)释放是养殖塘水质恶化的一个极具潜力的污染内源,可能会对虾的健康生长产生负面效应,控制沉积物无机氮释放是养虾塘养殖初期和中期重要的日常管理活动之一。     

铜锈环棱螺对水华中常见藻类的抑制效应

藻类水华频发已成为全球性的水环境问题,近年来,生物控藻法因具有环境友好的特点而备受关注。本研究以我国富营养化湖泊中常见大型底栖动物铜锈环棱螺为操纵生物,通过室内培养试验,研究了其对水华水体中常见蓝藻铜绿微囊藻、绿藻普通小球藻和斜生栅藻生长及光合活性的影响,以期阐明螺-藻间相互作用关系,探究铜锈环棱螺作为生物操纵物种的可行性。结果表明: 铜锈环棱螺能在短时间内大量摄食藻细胞,其对铜绿微囊藻产毒株和不产毒株以及斜生栅藻的去除率均在12 h内达到最大值,分别为73.7%、73.2%和51.1%;其对普通小球藻的摄食强于其他藻类,至试验结束时去除率达到99.2%。产毒铜绿微囊藻产生的微囊藻毒素会在铜锈环棱螺体内累积并促发其肝脏病理学变化,进而阻碍铜锈环棱螺的摄食。试验后期各处理组藻细胞光合活性均显著低于对照组,表明铜锈环棱螺的摄食作用对藻细胞造成了损伤,抑制了其大量增殖。此外,当不产毒铜绿微囊藻与斜生栅藻混合时,铜锈环棱螺的选择摄食性导致微囊藻的优势地位被斜生栅藻所取代。因此,铜锈环棱螺可以通过摄食作用抑制藻类的光合活性并降低其生物量,从而在一定程度上抑制或减缓水华的形成。     

池塘内循环流水养殖模式对养殖塘上覆水-沉积物-间隙水磷时空分布特征及释放通量的影响

为了揭示池塘内循环流水养殖模式(Inner-circulation Pond Aquaculture, IPA)上覆水-沉积物-间隙水不同磷形态时空分布特征, 探讨沉积物-水界面磷的释放通量及其主要影响因素, 在IPA一条水槽前后端设置6个采样点, 共设置4条, 同时对常规传统池塘(Usual Pond Aquaculture, UPA)设置5个采样点, 采用SMT(磷形态标准测试程序)法测量沉积物中磷的形态组成, 对上覆水-沉积物-间隙水磷时空分布特征进行了分析, 统计了磷释放通量及主要影响环境因子的关系。结果表明: (1)从整体上, IPA上覆水及间隙水中不同形态磷含量低于UPA, 且IPA水体磷空间分布差异较大, 水槽后端沉积物向上覆水释放, 水槽前端则表现为上覆水向沉积物汇集; (2)在养殖中后期, 空间上, IPA水槽后端沉积物不同磷形态随着距离增加逐渐降低, 且均低于UPA; 时间上, 2种模式TP、IP、OP和Fe/Al-P随着养殖的进行而显著增加, Ca-P呈先降低后增加的趋势; (3)UPA基本表现为沉积物对磷的吸收, 而IPA磷释放通量时空差异较大, 养殖初期, 水槽前端表现对磷的吸收, 水槽后端10 m内则少量释放; 至养殖中后期, 槽后端10 m内表现对磷的大量释放; 而后端20和30 m在养殖初期磷通量较小, 至养殖中期均转变为对磷的吸收, 至养殖末期则转变为对磷的释放; (4)2种模式磷通量和环境因子的关系基本一致, TP、IP释放通量和pH呈显著正相关, 各形态磷释放通量和沉积物Eh呈显著负相关, 其中温度的升高对各沉积物不同形态磷的释放有显著的促进作用。综上所述, IPA沉积物磷组分时空差异较大, 主要集中分布在水槽后端10 m内, 且在养殖中后期向上覆水大量集中释放。研究旨在为IPA改进固体颗粒物拦截方法、提高残饵和粪便的收集效率及养殖水环境调控提供理论依据。     

锌胁迫对铜锈环棱螺致死率、富集性、CAT和SOD活性的影响

以浙江省温州市瓯海茶山某河内的铜锈环棱螺Bellamya aeruginosa为受试生物,研究了不同浓度Zn2+胁迫下,铜锈环棱螺的致死效应、铜锈环棱螺对锌的富集性以及锌对铜锈环棱螺体内的过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性的影响.结果表明Zn2+对铜锈环棱螺具有较大的毒害影响.当Zn2+浓度达到3.0 mg/L时,就会引起个别铜锈环棱螺死亡,死亡率为2.66％.随着Zn2+浓度的增大(0.3 mg/L到2.4 mg/L)和处理时间的增加(2d到8d),除个别组外,铜锈环棱螺对锌的累积量均随之上升,具有一定的时间效应和剂量效应.铜锈环棱螺在锌胁迫下,肝胰腺的CAT和SOD活性受到较大的影响.当Zn2+浓度较低时,CAT和SOD活性均有较大的升高,但当Zn2+浓度较高时,CAT和SOD活性则受到一定的抑制.     

太湖春季沉积物间隙水中磷的分布特征及界面释放的影响

通过对太湖春季不同湖区水体和沉积物间隙水中磷的分布特征研究,探讨了间隙水中磷的释放对上覆水环境的影响。结果表明,颗粒态磷(PP)和溶解态有机磷(DOP)是太湖水体中主要的磷形态,占总磷的58%～95%。不同湖区沉积物间隙水磷的剖面变化可能与生态特征及水动力引起的沉积物-水界面的扰动强度密切相关。湖心和西部沿岸沉积物扰动强烈,致使间隙水中磷含量向上逐渐降底,而梅梁湾和贡湖间隙水磷的垂向变化不大。东太湖和竺山湖沉积物界面间隙水中磷含量偏高,可能是由于表层沉积物的有氧环境使Fe2+被氧化固定下来,并促进了总磷(TP)和溶解态活性磷(DRP)的扩散释放。总体而言,间隙水中各形态磷具有向上覆水体释放的趋势,其中DRP的扩散潜力最大,竺山湖沉积物-水界面DRP扩散通量高达11.42mg.m-2.d-1,表明春季浮游植物的复苏生长对DRP的迫切需求。     

铜锈环棱螺(Bellamya aeruginosa)对藻华水体中浮游动物群落的影响

本文通过围隔试验研究了淡水腹足纲动物铜锈环棱螺(Bellamya aeruginosa)对藻华水体中浮游动物群落的影响。实验根据铜锈环棱螺生物量设置了高、中和低3个密度组和一个不投放螺的对照组。分别于试验开始后0、3、7、11、15、23、31、46和61 d采集样品并计数浮游动物的种类和数量。结果表明:试验期间共鉴定出浮游动物33属52种,其中原生动物15种、轮虫28种、枝角类6种、桡足类3种;桡足类无节幼体、晶囊轮虫(Asplanchra)、多肢轮虫(Polyarthra)和臂尾轮虫(Brachionus)为浮游动物优势类群;主响应曲线分析显示,所有处理组中的浮游动物群落均与对照组存在显著差异;铜锈环棱螺的存在显著减少了有壳肉足虫、砂壳纤毛虫和轮虫种群数量,其中丰度降低最多的为螺形龟甲轮虫(Keratella cochlearis)、曲腿龟甲轮虫(Keratella valga)和砂壳虫(Difflugia sp.),在高密度组中的数量分别由试验开始时的481、545.3和359.7 ind·L~(-1)下降至试验结束时的0.1、0.1和9.2 ind·L~(-1);铜锈环棱螺的存在还导致高密度组中剑水蚤(Cyclops sp.)的数量由试验开始时的46.4 ind·L~(-1)增加至试验结束时的420.1 ind·L~(-1)。这些结果说明,铜锈环棱螺的存在显著影响了藻华水体中浮游动物的群落动态,而这些影响更多的是来自于铜锈环棱螺的间接影响而不是直接滤食。     

铜锈环棱螺对沉积物中重金属的生物积累及其与重金属赋存形态的关系

以铜锈环棱螺（Bellamya aeruginosa）为测试生物,采用28 d沉积物生物积累试验研究铜锈环棱螺对污染河流沉积物中重金属的生物积累,并探讨其与重金属赋存形态的关系.结果表明：铜锈环棱螺肝胰脏对Cd、Pb、Cu、Cr、Zn和Mn均具有较强的积累作用.不同重金属的积累量存在较大差别,Zn的积累量最多,占重金属总积累量的84.32%±4.36%,其次为Cu,占7.67%±2.84%;Pb、Cr和Mn的比例相对较少,分别为3.62%±1.84%、2.22%±1.03%和1.33%±0.15%;Cd所占比例最少,为0.83%±0.53%.肝胰脏中重金属元素之间的相关性均不显著.肝胰脏金属污染指数与沉积物污染综合指数具有显著的正相关关系,铜锈环棱螺可以作为沉积物重金属污染的监测生物.不同沉积物Cd、Cr、Zn和Mn的生物-沉积物积累因子（BSAF）具有较大的差异,Cu和Pb的BSAF比较稳定.Cd的生物积累与沉积物中Cd的可交换的与酸可溶态及可氧化态显著相关;Pb的生物积累与Pb的可还原态显著相关;Cu的生物积累与Cu的可氧化态显著相关;Mn的生物积累与Mn的可交换的与酸可溶态和可还原态显著相关;Cr和Mn的生物积累与其不同形态和总量均不相关.BSAF不宜作为衡量铜锈环棱螺对沉积物中重金属生物积累能力的指标.     

铜锈环棱螺对藻华水体理化指标的影响

采用池塘围隔对比试验的方法,研究了不同密度(392 ind·m^-2、196 ind·m^-2、98 ind·m^-2、0 ind·m^-2)铜锈环棱螺(Bellamyaaeruginosa)对藻华水体主要理化因子的影响.实验从2009年9月14日开始,持续60d.结果显示:环棱螺可以明显提高藻华水体的透明度(SD),实验中、后期,三个处理组围隔水体的SD均能保持在60cm以上,而对照组SD改变不明显,波动于29～40.3cm之间;多数时间内处理组水体的溶解氧(DO)含量都显著低于对照组,说明环棱螺的存在可直接或间接降低水体DO浓度.试验表明,单一投放螺类可有效降低藻华水体的叶绿素a(Chl-a)含量,但难以削减营养盐浓度.实验条件下,围隔水体总氮和正磷酸盐浓度的下降趋势均与螺的密度呈现负相关性(R=-0.9851,p<0.05;R=-0.9678,p<0.05);对SD、DO、pH、Chl-a、NH₄⁺-N、NO₃^--N、PO₄^3--P等7个主要理化指标数据进行了Duncan多重比较分析以及聚类分析,结果显示对照组和处理组在p<0.05水平上均存在显著差异,说明环棱螺的投放能在一定程度上调控水体质量.     

Oxygen concentration profiles and exchange in sediment cores with circulated overlying water

SUMMARY. 1. The overlying water of intact sediment cores was constantly stirred with an impeller at a rate sufficient to mix turbulently the water column and maintain the diffusive boundary layer at a determined thickness. The system allowed standardization of water circulation in laboratory sediment core experiments.
2. Both oxygen concentration and oxygen penetration depth in the sediments decreased, the former by 70% and the latter from 4.2 mm to 2.0 mm, when the overlying water was not stirred for 24 h, as measured with oxygen microelectrodes in a lake sediment core.
3. Oxygen profiles measured in sediment cores in the laboratory were similar to those measured in situ when the overlying water was stirred with an impeller at such a rate that a similar thickness of the diffusive boundary layer at the sediment-water interface developed in the laboratory as that in situ.
4. Sediment oxygen consumption was calculated from: (1) measured oxygen profiles in the diffusive boundary layer and the molecular diffusion coefficient for oxygen in water; (2) the measured oxygen decrease in the top of the sediments and the estimated diffusion coefficient in the sediment; and (3) by oxygen differences in the overlying water after incubation of sediment cores.     

Removal of hydrogen sulfide using crushed oyster shell from pore water to remediate organically enriched coastal marine sediments

Hydrogen sulfide is highly toxic and fatal to benthic organisms as well as causing depletion of dissolved oxygen and generating blue tide in eutrophic coastal seas. The purposes of this study are to reveal adsorption characteristics of hydrogen sulfide onto crushed oyster shell, and to evaluate removal efficiency of hydrogen sulfide from pore water in organically enriched sediments using container experiment in order to develop a coastal sediment amendment. The crushed oyster shell was mainly composed of CaCO₃ with calcite and CaO crystal phase. The batch experiment showed removal kinetics of hydrogen sulfide can be expressed as the first order equation and Langmuir plot fitted well in describing the adsorption behavior with the adsorption maximum at 12 mg-S g⁻¹. The container experiments suggested the oyster shell adsorbs hydrogen sulfide in pore water effectively and reduces oxygen consumption in the overlying water. Furthermore, oxidation–reduction potential of the sediment was higher with addition of crushed oyster shell than the control without oyster shell. Thus, it is concluded that crushed oyster shell can be an effective amendment to remediate organically enriched sediments in eutrophic coastal seas.     

The effect of nitrate in stream water on the relationship between gentrification and nitrification in a stream-sediment microcosm

SUMMARY 1. Microcosm experiments were carried out to simulate, in the laboratory, the conditions occurring at the water-sediment interface of a stream draining agricultural land. Constant boundary conditions were attained by passing synthetic 'stream water', saturated with dissolved oxygen and containing 1 mmol NO₃?N dm^?3 (or 1 mmol Cl? dm^?3, control), once only over the sediment surface. 2. Measurements were made of inorganic-N (nitrate, nitrite, ammonium), redox potential, potential denitrification and nitrification activities, and readily mineralizable carbon sediment profiles at three incubation times up to 24 days. The peaks in denitrification and nitrification activity moved down the profile with time in the nitrate-treated sediment, but stayed relatively stationary in the control treatment. Although the zone of nitrification was restricted to the top 2–3 mm of sediment in the control treatment, high fluxes of both dissolved oxygen and NH₄?N maintained a high nitrifier activity within this zone for the duration of the experiment. 3. Increases in denitrifier activity immediately below the nitrifier activity peak indicated that a coupled nitrification-denitrification sequence was operating in both the control and nitrate-treated sediment. The greater depth of nitrification when nitrate was present in the ‘stream water’ was attributed to a feedback mechanism in which enhanced denitrification in the sediment reduced the local demand for oxygen and permitted dissolved oxygen to diffuse further into the sediment. The progressively greater depth to which oxygen penetrated caused the contiguous peaks of potential nitrifier and denitrifier enzyme activity to migrate farther from the interface. However, diffusion rates of the reactants limited the depth to which these coupled reactions could extend. 4. The possible effect of this feedback mechanism on the nitrate status of natural sediment-stream water systems is briefly discussed.     

Effects of environmental salinity and 17alpha-methyltestosterone on growth and oxygen consumption in the tilapia, Oreochromis mossambicus

Effects of environmental salinity and 17α-methyltestosterone (MT) on growth and oxygen consumption were examined in the tilapia, Oreochromis mossambicus. Yolk-sac fry were collected from brood stock in fresh water (FW). After yolk-sac absorption, they were assigned randomly to one of four groups: FW, MT treatment in FW, seawater (SW) and MT treatment in SW. All treatment groups were fed to satiation three times daily. The fish reared in SW (both control and MT-treated groups) grew significantly larger than either group in FW from day 43 throughout the experiment (195 days). The fish fed with MT added to their feed grew significantly larger than their respective controls from day 85 in FW and in SW until the end of the experiment. The routine metabolic rate (RMR) was determined monthly from month 2 (day 62) to month 5 (day 155). A significant negative correlation was seen between RMR and body mass in all treatment groups. Among fish of the same age, the SW-reared tilapia had significantly lower RMRs than the FW-reared fish. The MT-treated fish in SW showed significantly lower RMRs than the SW control group at months 3–5, whereas MT treatment in FW significantly increased the RMR at month 3. Comparison of regression lines between RMR and body mass indicates that MT treatment in FW caused a significant increase in oxygen consumption at a given mass of the fish, whereas MT treatment was without effect on RMR in SW-reared fish. These results clearly indicate that SW-rearing and MT treatment accelerate growth of tilapia, and that RMR decreases as fish size increased. It is also likely that the increased RMR and growth in MT-treated tilapia in FW may be due to the metabolic actions of MT, although the reason for the absence of MT treatment in SW is unclear.     

The potential effect of sustained hypoxia on nitrogen cycling in sediment from the southern North Sea: a mesocosm experiment

The potential effect of sustained hypoxia (up to 70 days) on the production of N₂ gas through denitrification and anammox, as well as sediment–water exchange of nitrite, nitrate and ammonia, oxygen consumption and penetration, were measured in mesocosms using sediment collected from the southern North Sea (north of Dogger Bank). As expected, both the penetration of oxygen into, and consumption of oxygen by, the sediment decreased by 42 and 46 %, respectively, once hypoxia was established. Importantly, the oxygen regime did not change significantly (P > 0.05) during the experiment, suggesting that organic carbon was not depleted. During the first 10 days, the exchange of NO₃ ^?, NO₂ ^? and NH₄ ⁺ between the sediment and water was erratic but once a steady state was established the sediment acted as either a sink for fixed nitrogen under hypoxia or as a source in the controls. Over the course of the mesocosm experiment the rate of both anammox and denitrification increased, with anammox increasing disproportionately under hypoxia relative to the controls, whereas the rate of increase in denitrification was the same for both. Under sustained hypoxia the production of N₂ gas increased by 72 % relative to the controls, with this increase in N₂ production remaining constant regardless of the duration of hypoxia. Longer periods of stratification and oxygen depletion are predicted to occur more regularly in the bottom waters of shallow coastal seas as one manifestation of climate change. Under sustained hypoxia the potential for nitrogen removal by the production of N₂ gas in this region of the southern North Sea was estimated to increase from 2.1 kt N 150 days^?1 to 3.6 kt 150 days^?1, while the efflux of dissolved inorganic nitrogen ceased altogether; both of which could down regulate the productivity of this region as a whole.     

引黄灌区土壤有机碳密度剖面特征及固碳速率

为揭示灌溉耕作对土壤有机碳密度剖面(0—100 cm)分布产生的影响,通过在宁夏引黄灌区进行实地调查与采样,以无灌溉耕作的自然土壤作为对照,研究不同灌溉耕作时间序列下灌区土壤有机碳密度的剖面分布特征,并估算其平均固碳速率。结果表明:灌区土壤有机碳含量具有随土层深度增加而下降的剖面分布特征,灌溉耕作对增加表层土壤有机碳含量作用最明显;灌区土壤剖面碳密度与灌溉耕作时间和土壤类型均显著相关(P0.01),相关系数分别为0.63和0.74,且因灌溉耕作时间和土壤类型的不同,土壤有机碳密度差异性显著(P0.05);灌溉耕作影响的土层深度及剖面土壤有机碳密度的增加量因灌溉耕作时间长短的不同而异;引黄灌区5类土壤的平均固碳速率为0.53 MgC·hm-2·a-1。引黄灌溉耕作在增加农田土壤固碳中发挥着重要作用。     

Distribution of Pseudomonas aeruginosa in a riverine ecosystem

The distribution of Pseudomonas aeruginosa in navigation pool 8 of the upper Mississippi River was investigated by acetamide broth enrichment of water, sediment, and swab (solid-water interface) samples. Among the 152 P. aeruginosa isolates, serological type 1 was most prevalent (34.2%), and a small number (13.2%) showed carbenicillin resistance. Pigmentation was variable, with only 44.7% elaborating typical blue-green pigment. P. aeruginosa was most commonly isolated from sediment, with solid-water interfaces (aufwuchs samples) also exhibiting high frequencies of isolation. Current velocity, oxygen and nutrient availability, surface tension, desiccation, and negative phototropism were important factors in the riverine distribution of this epibacterium.     

Distribution of Pseudomonas aeruginosa in a riverine ecosystem.

The distribution of Pseudomonas aeruginosa in navigation pool 8 of the upper Mississippi River was investigated by acetamide broth enrichment of water, sediment, and swab (solid-water interface) samples. Among the 152 P. aeruginosa isolates, serological type 1 was most prevalent (34.2%), and a small number (13.2%) showed carbenicillin resistance. Pigmentation was variable, with only 44.7% elaborating typical blue-green pigment. P. aeruginosa was most commonly isolated from sediment, with solid-water interfaces (aufwuchs samples) also exhibiting high frequencies of isolation. Current velocity, oxygen and nutrient availability, surface tension, desiccation, and negative phototropism were important factors in the riverine distribution of this epibacterium.     

温度对外源性^32P在水、铜绿微囊藻和底泥中迁移的影响

采用同位素示踪法,在实验室模拟研究不同温度下外源性无机磷酸盐在水、铜绿微囊藻(Micro-fystis aeruginoas)和底泥中的迁移过程,外源性³²P加入水中后,首先是一种与温度无关的快速物理化学分配,大量溶解性磷酸盐迅速进入底泥和微囊藻中,随后水中³²P的迁移主要受微囊藻生长状况的影响,温度升高有利于微囊藻的生长,并提高了微囊藻吸磷的速度,微囊藻中最大外源性磷浓度只与水环境中的初始磷浓度有关,25℃时铜绿微囊藻的生长曲线有7d的对数期,没有明显的稳定期就转入衰亡期,在25℃时,当微囊藻超积累P到一定程度后,其对数生长同细胞内含P量无关,随着时间的推移,外源性³²P不断向底泥中迁移,实验末期所有的³²P都转移到底泥中,提高温度使水中溶解性外源性磷的下降速率加快,7d后水中溶解的外源性磷浓度低于0．00716mg·L^-1。     

坝地剖面泥沙有机碳分解特征及其影响因素

黄土高原地区已建成的5.6万余座淤地坝累计拦截有机碳0.95 Pg,是陆地生态系统重要的碳汇,但是目前对其分解机制仍知之甚少,难以量化其在陆地碳循环中的作用。本研究通过模拟原始沉积条件下的泥沙环境(缺氧条件)进行矿化培养,并比较假定泥沙暴露在有氧情况下的有机碳分解速率,探究有机碳分解速率的影响因素。结果表明: 坝地泥沙在原始沉积条件和暴露在有氧条件下有机碳分解速率均值分别为(6.47±4.06)和(56.66±17.78) mg C·kg^-1·d^-1,坝地泥沙在埋藏条件下有机碳分解速率仅为被暴露在有氧条件下的11.4%,表明埋藏显著降低了有机碳分解速率。在缺氧条件下泥沙化学性质比有机碳分解相关微生物对泥沙有机碳分解速率的影响更大;在有氧条件下则表现为有机碳分解相关微生物对泥沙有机碳分解速率的影响更显著;泥沙物理性质对缺氧和有氧条件下泥沙有机碳分解速率的影响均较小。自然情况下,淤地坝表现为碳汇,但当发生溃坝时,原本在沉积缺氧条件下储存的泥沙有机碳会迅速暴露在空气中,有机碳分解速率显著提高,表现为碳源。