~(95)Zr在茶叶土壤系统中的迁移与分布动态

采用模拟污染物的同位素示踪技术进行了95Zr在茶树 土壤系统中的迁移与分布动态研究 ,并应用库室模型和非线性回归方法确定了各分室的拟合方程。结果显示 :1 茶树从土壤中吸收的95Zr主要集中在茎秆中 ,且茎秆中的95Zr比活度随时间呈缓慢增加 ,并在一段时间后逐渐趋于动态平衡 ;其余各部位的比活度较低 ,大部分接近于本底水平 ,表明95Zr被茶树茎皮部吸收后不易在其体内迁移、输运 ;2 喷施进入土壤中的95Zr主要滞留在表层 ( 1～ 5cm)土壤中 ,占总量的 98 9% ,表明95Zr被表层土壤吸附 ,不易随渗流水向下迁移 ;3 对实验数据进行回归分析 ,得茶树和土壤中95Zr比活度的消长动态拟合方程分别为Ct(t) =9 2 3 60 ( 1 -e- 0 14 59t)和Cs(t) =486 84( 0 1 4 58-0 0 0 0 0 82e- 0 14 59t) ,经方差分析 ,表明回归方程较好地反应了95Zr在茶树 土壤系统中的消长动态。     

小麦—土壤系统中^95Zr的消长动态

采用模拟污染物的同位素示踪技术研究了^95Zr在小麦－土壤系统中的迁移、消长和分配动态，并建立了其行为规律的数学模型。结果表明：（1）^95Zr由表土进入系统后即在系统中发生迁移，小麦主要经根吸收^95Zr，然后向其它各部位转移和分配。小麦植株中^95Zr比活度起初随时间迅速增高，在达到某一最大值后开始下降。根中^95Zr比活度显著高于植株其它部位，小麦各部位中^95Zr比活度的大小顺序为：麦根＞麦秸＞麦壳＞麦粒。（2）土壤中^95Zr主要滞留于表层6cm内，其比活度与距土表深度呈单项指数负相关。（3）^95Zr在小麦－土壤系统中比活度的动态变化规律由多项指数描述。（4）小麦对土壤中的^95Zr具有一定的富集能力。     

放射性锆在小麦生态系统中的迁移和消长动态

采用同位素示踪技术,模拟降雨,研究了污染物95Zr在小麦-土壤系统中的迁移、消长和分配动态。结果显示:95Zr由小麦地上部进入系统后,随即在系统中发生迁移,茎叶、颖壳和根系中95Zr的比活度均较高,但麦粒中接近于本底水平。土壤中95Zr比活度随时间累积逐渐升高,主要滞留在表层(0~6cm),为总土壤含量的97%以上,表明95Zr被表层土壤吸附,不易随水流向下迁移。经分析表明非线性回归方程较好地反应了95Zr在小麦-土壤系统中的消长动态。     

放射性核素~(95)Zr在土壤中吸附的研究

应用同位素示踪技术研究了95Zr在小粉土、黄红壤、青紫泥和海泥中的吸附 ,并研究了不同比活度95Zr对土壤吸附比的影响 ,测定了吸附等温线。结果表明 ,95Zr进入淹水土壤后迅速被土壤吸附达到吸附平衡。不同土壤有不同的饱和吸附率 ,海泥 >青紫泥 >小粉土 >黄红壤     

水生植物对水体中低浓度95Zr的富集效应

采用模拟污染物的同位素示踪技术研究了 3种水生植物对水体中低浓度95Zr的富集效应。结果表明 :( 1 )水生植物 (金鱼藻、卡州萍和水葫芦 )对低浓度水体中的95Zr均具有较强的富集能力 ,富集系数CF值达 5 6 78～ 1 1 2 94,因此这 3种水生植物可作为检测水体95Zr污染的指示生物 ;( 2 )在 95Zr轻微污染的水体中放养水生植物后 ,水中的95Zr比活度随时间呈下降趋势 ,放养 3d就下降了 5 0 % ,因此 ,可用这 3种水生植物净化被95Zr轻微污染的水体 ,其中以水葫芦最为合适 ;( 3)放养水生植物前后 ,底泥中95Zr的比活度和总活度均非常接近 ,仅下降0 5 % ,表明底泥吸附的95Zr不易解吸而进入水体 ,底泥对95Zr具有强烈的吸附和固定作用。因此 ,通过放养水生植物净化底泥中的95Zr污染物效果不明显     

放射性核素^95Zr在土壤中吸附的研究

应用同位素示踪技术，研究了^99Zr在小粉土、黄红壤、青紫泥和海泥中的吸附。结果表明，^95Zr进入淹水土壤之后，将迅速地被土壤吸附而达到吸附平衡。不同土壤有不同的饱和吸附率，就它们吸附^95Zr能力来说，海泥＞青紫泥＞小粉土＞黄红壤。还测定了吸附等温线。     

~（95）Zr在土壤中的淋溶和迁移分布

采用模拟土柱法研究了95Zr在2种淹水土壤（小粉土、红黄壤）中的淋溶和垂直迁移。结果表明：（1）淋溶后收集到的全部淋溶液中95Zr的含量较少,小粉土淋溶液中95Zr为总活度的3.05%,黄红壤淋溶液中95Zr为总活度的3.00%;（2）滞留于土壤中的95Zr绝大部分分布在土壤表层0～1.0cm范围内,小粉土中有67.80%～80.18%的95Zr滞留于0～1.0cm土层范围内,黄红壤中有74.05%～86.95%的95Zr滞留于0～1.0cm土层范围内;（3）土壤中95Zr比活度与距土壤表层深度分布呈单项指数规律。     

铅-锌-镉复合污染物在土壤-芥菜/油菜系统中的迁移及交互作用

了解重金属复合污染物在土壤-植物系统中的迁移分配情况对污染土壤的安全利用、土壤环境质量标准的修订以及重金属污染土壤的植物修复具有重要意义。通过盆栽试验,以芥菜和油菜为例,研究了铅-锌-镉复合污染物在土壤-植物系统中的迁移分配情况。结果表明:与对照相比,复合污染条件下,芥菜和油菜体内重金属含量显著提高,且Cd含量的提高程度要远远高于Pb和Zn;芥菜和油菜对Cd的吸收达到了100 m g/kg以上,表现出超富集植物的吸收水平。重金属的富集系数大小依次为Cd>Zn>Pb,地下部富集系数要高于地上部,转运系数大小为Cd≈Zn>Pb。Pb、Zn、Cd的富集系数均随各自元素在土壤中含量增大而减小,而且表现为低含量时显著减小,高含量时缓慢减小;重金属在土壤-植物系统的迁移分配深受共存元素的影响,且在不同元素之间和不同浓度范围内表现出不同的特点。Pb、Zn、Cd在芥菜和油菜体中积累量,均与其各自在土壤中的含量成正相关;Zn和Cd对Pb的吸收积累以及Pb对Zn的吸收积累具有明显的抑制作用;Zn-Cd对Zn的吸收积累具有正的交互作用,而对Cd的吸收积累具有负的交互作用。     

~(60)Co在小麦-土壤系统中的消长动态

采用模拟污染物的核素示踪技术研究了60Co在小麦-土壤系统中的迁移、消长和分配动态,并建立了其行为规律的数学模型。结果表明:(1)60Co由表土进入系统后即在系统中发生迁移,小麦主要经根部吸收60Co,然后向其他各部位转移和分配。小麦植株中60Co比活度起初随时间迅速增高,达到某一最大值后开始下降。根中60Co比活度显著高于植株其他部位,小麦各部位中60Co比活度的大小顺序为:麦根>麦秸>麦壳>麦粒;(2)土壤中60Co主要滞留于表层6cm内,其比活度与距土表深度呈单项指数负相关;(3)60Co在小麦-土壤系统中比活度的动态变化规律由多项指数描述;(4)小麦对土壤中的60Co具有一定的富集能力。     

95Zr在水-土体系中的消长动态研究

采用同位素示踪技术进行了95Zr在六种水—土体系中的消长动态研究 ,并应用非线性回归方法确定了各体系的拟合方程。结果显示 :1 .水体中的95Zr比活度起初随时间呈快速下降 ,而后逐渐趋缓 ,不同水—土体统中的下降速率各不相同 ,表明底泥对95Zr有强烈的吸附作用 ,其吸附强弱顺序为 :泮畈红壤 >海盐红壤 >青紫泥 >小粉土 >海泥 >黄沙 ;2 .底泥中95Zr的比活度随时间呈同步增加 ,并在经历一段时间后达到一平衡值 ,不同底质土壤达到平衡的时间各不相同 ,其平衡时间的大小顺序为 :海盐红壤 (1 3.1 0d) <泮畈红壤 (1 5 .53d)<黄沙 (1 5 .64d) <青紫泥 (1 7.85d) <小粉土 (2 0 .65d) <海泥 (2 1 .46d) ;3 .对各体系的消长动态拟合方程进行方差分析 (测定系数r2 、置信区间 ) ,表明各回归方程较好地反应了95Zr在水体和底质土壤中的行为过程。     

Distribution and Migration of 95Zr in Marine Ecosystems

In order to get a better understanding of the environmental behavior of ⁹⁵Zr and to generate fundamental data for evaluation of its ecological risk, an experiment was conducted to study the distribution and the migration of ⁹⁵Zr in a simulated fish/seawater/sediment system over a period of 20 days. The concentration of ⁹⁵Zr in seawater decreased rapidly with time, and its half-life is only 0.2 day. Most of adsorbed ⁹⁵Zr was found in upper 2.5 cm in sediment, and more than 99.3% of applied ⁹⁵Zr was detected in upper 2.5 cm duringthe whole experimental period, which implied that the ⁹⁵Zr in seawater could be adsorbed strongly by sediment and it could not readily migrate downwards with percolating water. After taken in by fish, it was accumulated in viscera, gill, and fin. The concentration of ⁹⁵Zr was very low in meat, bone, liver and roe, which was only slightly greater than the detection limit. The dynamics of ⁹⁵Zr concentrations in fish, seawater and sediment can be described with exponential function.     

棉花调亏灌溉的生理响应及其优化农艺技术

在移动式防雨棚下，采用盆栽土培法和测坑微区试验相结合的方法，分析了调亏灌溉对棉花不同生育阶段蒸腾速率（Tr）、光合速率（Pn）、光合产物积累与分配、经济产量（Y）和水分利用效率（WUE）的影响，盆栽试验采用二因素（水分调亏阶段和调节亏水度）随机区组设计，测坑微区试验采用三因素（水分调亏度、施肥水平和植株密度）正交旋转组合设计。结果表明：适时适度的水分调亏使得Tr明显下降，而Pn下降不明显，复水后光合产物具有超补偿积累，且有利于向经济产品（籽棉）运转与分配。棉花调亏灌溉（RDI）的适宜指标是：苗期轻、中度调亏，0～40cm土层湿度下限为50％FC～60％FC（田间持水量）；蕾期轻度调亏，0～40cm土层湿度控制下限为60％FC；花铃期不宜调亏，0～40cm土层湿度应不低于75％FC；吐絮期可中度调亏，0～40cm土层湿度可控制在50％FC～55％FC。     

Zirconium-Modified Activated Sludge as a Low-Cost Adsorbent for Phosphate Removal in Aqueous Solution

A highly effective zirconium-modified activated sludge (Zr(IV)-AS) adsorbent was prepared from activated sludge and applied to remove phosphate from aqueous solutions by batch and column experiments. Characterized results revealed that zirconium was successfully loaded onto the activated sludge (AS), and the specific surface area and pore volume were substantially improved after zirconium loading on the AS. Zr(IV)-AS exhibited a high adsorption affinity for phosphate and the maximum adsorption amount was 27.55 mg P·g^?1 at 25 °C. Adsorption isotherms of phosphate could be described by the Langmuir model, and the adsorption kinetics were well described by the pseudo-second-order model. Phosphate adsorption on Zr(IV)-AS increased monotonically with decreasing solution pH. The presence of SO₄^2? in water resulted in slightly decreased phosphate adsorption on the adsorbent even at a high concentration (25 mmol/L), and a greater influence of HCO₃^? on adsorption could be ascribed to the increased solution pH with the addition of the HCO₃^?. Column adsorption experimental results showed that the adsorbent has excellent phosphate adsorption properties and that the effluent can meet the requirement of phosphorus in the national wastewater discharge standard of China. Phosphate-saturated Zr(IV)-AS can be effectively desorbed in 0.1 mol L^?1 NaOH solution, and the regenerated adsorbent still possessed the high capacity. The adsorption between the adsorbent and the phosphate is due to the electrostatic interaction and anionic exchange at the surface of the Zr(IV)-AS. Furthermore, this approach provides a possibility of treating wastewater with waste and has the potential for industrial applications for the removal of phosphate from wastewater.     

生态沟渠对中华鳖温室养殖排放水体的净化效果

研究采用生态沟渠技术体系——"水生植物(凤眼莲,Eichhornia crassipes)-微生物(枯草芽孢杆菌,Bacillus subtilis)-水生动物(螺蛳,Margarya)"共生系统联合净化处理中华鳖温室养殖排放水体,并连续数月采样分析处理污水中各项主要营养盐污染物指标的动态变化规律。结果表明:经过近5个月的生态沟渠技术体系处理,中华鳖温室养殖排放水体中总氮(TN)浓度减少75%,铵氮(NH4+-N)浓度减少91%,总磷(TP)浓度减少83%,化学需氧量(CODCr)减少62%,溶解氧(DO)增加近4倍,水体酸碱度(pH)维持在中性水平,处理污水由初始的黄色或棕色、浑浊逐渐转变为微黄色、微浑浊,且无异味。由此可知,利用生态沟渠技术体系——"水生植物-微生物-水生动物"共生系统联合修复中华鳖温室养殖排放水体效果显著,具有良好的推广和应用前景。     

Assessing selenium cycling and accumulation in aquatic ecosystems

We conducted a joint experimental research and modeling study to develop a methodology for assessing selenium (Se) toxicity in aquatic ecosystems. The first phase of the research focused on Se cycling and accumulation. In the laboratory, we measured the rates and mechanisms of accumulation, transformation, and food web transfer of the various chemical forms of Se that occur in freshwater ecosystems. Analytical developments helped define important Se forms. We investigated lower trophic levels (phytoplankton and bacteria) first before proceeding to experiments for each successive trophic component (invertebrates and fish). The lower trophic levels play critical roles in both the biogeochemical cycling and transfer of Se to upper trophic levels. The experimental research provided the scientific basis and rate parameters for a computer simulation model developed in conjunction with the experiments. The model includes components to predict the biogeochemical cycling of Se in the water column and sediments, as well as the accumulation and transformations that occur as Se moves through the food web. The modeled processes include biological uptake, transformation, excretion, and volatilization; oxidation and reduction reactions; adsorption; detrital cycling and decomposition processes; and various physical transport processes within the water body and between the water column and sediments. When applied to a Se-contaminated system (Hyco Reservoir), the model predicted Se dynamics and speciation consistent with existing measurements, and examined both the long-term fate of Se loadings and the major processes and fluxes driving its biogeochemical cycle.