Nutrient retention in tile-fed and non-tile reconstructed oxbows in north central Iowa

Nutrient export from the agricultural Midwest threatens the Gulf of Mexico and new conservation practices are needed to reduce the loss of nutrient from subsurface tile drainage systems. Oxbows are natural waterbodies formed when a river cuts off a meander loop and water quality benefits of reconstructed oxbows are being increasingly recognized. In this study, we monitored four reconstructed oxbow sites (two tile-fed, two non-tile) over a 2-year period in north-central Iowa and assessed their capacity for NO₃-N and dissolved reactive phosphorus (DRP) reductions. Water flow and quality monitoring of tiles, shallow groundwater, oxbow and receiving streams documented that the oxbows were dominated by tile drainage inputs. NO₃-N concentrations were highest in the drainage tiles flowing into the tile-fed oxbows (mean 8–10 mg/L) and much lower in floodplain groundwater (<1–2 mg/L). Annual NO₃-N loads into the tile-fed oxbows were substantially larger than input loads into the non-tiled oxbows. For the two tile-fed oxbows, the 2-year NO₃-N retention efficiencies were very similar (0.76–0.77) and on a monthly basis, greater retention efficiencies were measured in summer and fall. DRP concentrations and loads into the tile-fed oxbows were too low to allow for meaningful estimates of retention. Reconstructing oxbows to receive tile drainage water should be considered a sustainable conservation practice for tile drainage treatment in agricultural areas.     

On Differentiation of Water Bodies with Respect to 90Sr Accumulation by Fish

Russian Journal of Ecology -     

气相色谱——火焰光度法测定废水中黄磷的方法研究

研究了以苯为萃取剂，用气相色谱－－火焰光度法测定废水中的微量黄磷。结果色谱分离良好，萃取率大于９４％，水样易于保存，溶剂和杂质不干扰测定，水样加标回收率大于８８．４８％，精密度重复测定的变异系数不大于３．２％，定性检出限为２μｇ／Ｌ，定性检出限为６μｇ／Ｌ。     

Phosphorus export by runoff from agricultural field plots with different crop cover in Lake Taihu watershed

ＩｎｔｒｏｄｕｃｔｉｏｎＷａｔｅｒｅｕｔｒｏｐｈｉｃａｔｉｏｎｉｓｏｎｅｏｆｔｈｅｇｌｏｂａｌｅｎｖｉｒｏｎｍｅｎｔａｌｐｒｏｂｌｅｍｓ ,ａｎｄａｇｒｉｃｕｌｔｕｒａｌｎｏｎｐｏｉｎｔｓｏｕｒｃｅｐｏｌｌｕｔｉｏｎｈａｓｂｅｅｎｇｉｖｅｎｉｎｃｒｅａｓｅｄａｔｔｅｎｔｉｏｎ (Ｓｈａｒｐｌｅｙ ,1994 ;Ｈａｒｒｉｓ ,1995;Ｔｉｅｓｓｅｎ ,1995;Ｔｏｎｄｅｒｓｋｉ,1996;Ｄａｎｉｅｌ,1998) .Ｌａｋｅｅｕｔｒｏｐｈｉｃａｔｉｏｎｈａｓｂｅｅｎｉｄｅｎｔｉｆｉｅｄａｓａｃｒｉｔｉｃａｌｐｒｏｂｌｅｍｏｆｓｕｒ…     

~（110m）Ag在鲤鱼体内的转移、积累与分布

为了探讨水中１１０ｍＡｇ在鲤鱼体内的行为，将鲤鱼喂养在１１０ｍＡｇ比活度为３．７×１０２Ｂｑ／Ｌ、３．７×１０３Ｂｑ／Ｌ、３．７×１０４Ｂｑ／Ｌ水中，于喂养后隔一定时间取样解剖，测各组织器官的放射性，结果表明，鲤鱼通过鳃和消化管将１１０ｍＡｇ很快吸收到体内，并随血液运输到全身各处，主要分布在软组织中。在相同喂养时间内，鱼体各组织器官１１０ｍＡｇ积累量随水中１１０ｍＡｇ比活度增加而增加。鳃、消化管、心脏、肌肉、骨骼等组织器官中１１０ｍＡｇ积累量随喂养时间呈单峰曲线变化；肝胰脏中１１０ｍＡｇ积累量随喂养时间则直线上升。它们对１１０ｍＡｇ的积累能力依次为：肝胰脏＞鳃＞消化管＞心脏＞肌肉＞骨骼。     

星云湖、杞麓湖磷污染来源比较

通过对星云湖、杞麓湖水体磷含量变化情况、流域产业结构和磷入湖途径的比较分析，认为近年来星云湖水体磷含量水平的大幅提高，使星云湖水质由Ⅲ类在大约5a的时间里下降为Ⅴ类、劣Ⅴ类，与星云湖流域及周边磷化工产业的快速发展息息相关。而杞麓湖由于流域内无磷矿资源也没有大的磷化工产业，其磷含量水平得于稳定。     

Critical phosphorus concentrations in winter wheat genotypes with various phosphorus efficiencies

１ＩｎｔｒｏｄｕｃｔｉｏｎＡｓａｎｕｎｒｅｎｅｗａｂｌｅｍｉｎｅｒａｌｒｅｓｏｕｒｃｅ，ｐｈｏｓｐｈｏｒｕｓｉｓｏｎｅｏｆｔｈｅｉｍｐｏｒｔａｎｔｅｓｅｎｔｉａｌｅｌｅｍｅｎｔｓｆｏｒｌｉｖｉｎｇｂｅｉｎｇｓ．Ｐｈｏｓｐｈｏｒｕｓｈａｓｍａｄｅａｇｒ...     

含泥沙水样总磷测定方法的研究

对含泥沙水样消解后不用滤膜过滤而改为直接定容于 5 0mL比色管中 ,经钼酸盐、抗坏血酸试剂显色后离心 ,取清液测定。经对比实验表明 ,该法灵敏度、精确度、准确度均满足环境监测技术规范要求 ,有效消除了泥沙对TP测定的影响     

连续流间歇曝气工艺的氮磷脱除功能研究

连续流间歇曝气工艺是在对传统活性污泥法的改造中发展起来的一种工艺。本文针对该工艺的氮磷脱除功能进行了小试研究 ,由试验结果可看出 ,连续流间歇曝气工艺简便易行 ,去除有机物及氨氮的效果稳定 ,在碳源满足脱氮除磷要求的条件下 ,可达到良好的氮磷脱除效果