The Role of Macrophytes in the Retention of Phosphorus in the River Thame,England

The effects of the growth of the dominant species of macrophytes on phosphorus transport in the River Thame, a nutrient enriched lowland clay catchment in southern England, were assessed using a mass-balance approach. Macrophyte abundance was estimated between late March and early June at three sites along the river. the plant biomass of phosphorus and the total phosphorus content of sediments in the main part of the river channel and sediments associated with the plant roots were measured on each occasion. Total phosphorus concentrations in the river water were measured at weekly intervals at a gauging station at the lower end of the study reach.

The results showed that the phosphorus content of plants at the site most impacted by sewage derived phosphorus was < 1% of the flux of total phosphorus estimated for the water column in April and May. Phosphorus contained in the total standing crop of macrophytes at the least impacted site was estimated as approximately 3% of the mean daily flux of total phosphorus in the water. Although no trends were found in the total phosphorus contents of the roots, shoots or sediments through the season, differences in the phosphorus content of the sediments were found between sites with different phosphorus loading. Higher porewater and Equilibrium Phosphate Concentrations (EPC_oS) were recorded at the site most impacted by sewage effluent when compared to an upstream sampling site.     

Chemical speciation and potential ecological risk assessment of heavy metals in volcanic rocks of Southern Qinghai,China

ABSTRACT

Seven volcanic rocks samples were collected from Southern Qinghai to analyze chemical speciation and migration behavior of heavy metals by sequential chemical extraction procedure and column leaching test. The geo-accumulation index, ecological risk index and the risk assessment code were applied to assess the heavy metal pollution and potential environmental effects in this area. Results revealed that the total concentrations of heavy metals did not exceed the background values in soil of this area. Most of the samples produced acid rock drainage. The order of heavy metal migration and transformation sequence in the volcanic rocks of Zhiduo region was Cd?>?Pb?>?As?=?Cu?=?Zn?=?Mn based on the geo-accumulation index and Cd caused heavy pollution, which was also confirmed by the leaching test. Moderate potential ecological risk posed by heavy metals occurred in the study area based on the potential ecological risk index. Cd contributed to most of ecological risk while the remaining heavy metals (except As) exerted medium to high risks to the environment according to the risk assessment code evaluation results. In summary, volcanic rocks possessed potential risks to the surroundings due to potential release of heavy metals. Cd that caused the pollution should be paid special attention.     

不同减量施肥条件下稻田田面水氮素动态变化及径流损失研究

采用过量施用化肥获得高产已成为近年来太湖地区的普遍现象,而由此引发的农业面源污染对水体生态环境恶化的贡献值也越来越大。通过对苕溪流域地区的田间试验,研究了8种不同减量施肥处理条件下,稻田田面水中氮素的动态变化特征和径流损失量,研究结果表明,（1）各处理铵氮浓度在施肥后迅速上升,1～3d达到最大值,而总氮在施肥后第1天便达到峰值,之后随时间变化逐渐下降,铵氮、总氮浓度在一周之后均降至较低水平。（2）田面水中铵氮／总氮比在施肥后3～7d达到峰值,之后逐渐下降。（3）田间任何1次的径流排水均会造成田面水氮素的流失,径流排水发生的时间与施肥时间间隔越小氮素的流失负荷就越大。（4）各减量化施肥处理年度累计流失负荷较常规施肥处理下降6％～53％,当季稻田氮素流失率在1．4％～2．6％之间。为减少农田氮肥使用量,降低氮素流失量,减缓农业面源污染提供理论依据。     

巢湖典型低山丘陵区不同土地利用类型壤中流养分流失特征

以巢湖典型低丘山区坡地的6种主要土地利用类型（弃耕地、尾矿裸地、灌木林地、荒草地、马尾松林地和人工恢复林地）为研究对象,通过定位观测与收集坡面壤中流,探讨该地区壤中流养分流失动态变化特征。结果表明,巢湖低丘山区典型土地利用类型壤中流发生概率为灌木林地和荒草地较高,尾矿裸地最低（仅在0～20cm土层产生）;表层壤中流氮含量为尾矿裸地最高,人工恢复林地最低,壤中流磷含量为弃耕地最高,尾矿裸地最低;壤中流氮素流失以溶解态NO3-N为主,并随雨季的到来而呈下降趋势,随土层加深呈先下降后升高趋势;磷主要以有机溶解态形式流失,随土层加深而呈下降趋势。相关分析表明,地表总盖度、地表植被均匀度、土壤养分含量与壤中流氮、磷含量间存在显著相关性,而降雨特征（降雨量、降雨强度）与壤中流氮、磷含量问相关性不显著。由于人为开采严重,在分析该地区壤中流氮素含量时,应注意干湿沉降的影响。     

武汉市郊区蔬菜地土壤磷素释放的主要影响因素研究

以武汉市城乡结合部蔬菜地土壤为研究对象,通过室内模拟实验,分析施磷水平、土壤含水率、淹水深度、淹水时间等对土壤磷素释放的影响。研究结果表明:①高水平施磷易导致磷素在土壤中的积累,当积累量超过土壤吸磷极限时,在雨水、浇灌水等的作用下磷素易进入水体;②土壤含水率对Olsen-P影响不显著;③淹水深度对土壤释磷量有着很大影响,在淹水初期,随着淹水深度提高,土壤释磷量增加;④在3 cm和6 cm淹水深度下,在0~3 d时间里,样品土壤释磷量占到整个淹水期总释磷量的80%~95%以上,随后急剧减小日趋缓和,直至达到一个相对稳定水平。     

住宅用通风换热器的研究

提出了一种自行加工设计的用于空调余热回收的通风换热器,并对该换热器的性能进行了实验研究.结果表明,该换热器具有换热效果好,阻力小的特点,说明其在实际应用中是可行的,也是有效的,是值得推广的空调节能技术.     

水质约束条件下确定土壤允许流失量的方法

已有土壤允许流失量（T值）定义多以防止土壤肥力减退、土地生产力下降为目标,考虑的主要因素为成土速度、土层厚度和土壤肥力减退,确定T值的依据是土壤侵蚀速率不大于成土速率,保证土壤资源得到不断更新。然而土壤侵蚀并不完全是人为因素造成的,更是一种客观自然过程,土壤侵蚀除导致土壤养分流失,土壤生产力下降,还可能对侵蚀发生地以外的地区产生一系列环境问题。为保证人类社会可持续发展,制定控制土壤侵蚀目标时,只局限于提高土壤生产力已与时代发展不合拍了,应将视野扩展到保护和改善人类生产、生活和生存环境,引入生态环境影响符合可持续发展的时代要求。因此,在前人研究基础上结合保护水体环境质量要求建立了一种新的确定T值方法,该法体现了多目标特点,可实现既保护土壤资源又维护水环境质量的目标。以随泥沙入湖的TN、TP对湖水养分影响为例,探讨了水质约束条件下确定T值的一般方法。     

损失瓦斯量与煤的破坏类型关系研究

损失瓦斯量是准确获取煤层瓦斯含量的基础数据。通过实验室测定和不同损失量计算模型的对比分析,表明采用 传统的t法和幂函数法获取损失瓦斯量时,Ⅱ类、Ⅲ类和Ⅳ类煤符合性较好,误差小于20%,I类煤和Ⅴ类煤的损失瓦斯 量误差为25%~31%;煤中孔隙结构的差异是误差产生的原因,I类煤中原生孔隙占多数,Ⅴ类煤的孔隙受构造影响最大, 其它类型煤的孔隙结构介于I类煤和Ⅴ类煤之间;对于I类煤和Ⅴ类煤,采用表征原生孔隙和构造孔隙双孔隙特征的模型 获得的损失瓦斯量误差低于10%。研究结论对煤层瓦斯含量测定具有重要意义。     

江西省赣州市稀土矿开采导致的水土保持价值损失评估

稀土矿的无序开采既造成了稀土资源的浪费,也导致了水土流失和环境污染等一系列环境问题。论文基于通用土壤流失方程（USLE）,利用江西省赣州市的稀土矿调查点数据、遥感数据、气象数据和基础地理数据分别测算了基准参考区（未受稀土开采干扰的植被覆盖较好的区域）与稀土矿开采所导致的植被破坏区内的土壤侵蚀量,通过对二者的横向对比估算由稀土开采所导致的土壤侵蚀量,并进一步对稀土开采所导致的水土保持实物量及价值量损失进行了核算。结果表明：1）赣州市稀土开采所导致的土壤侵蚀极为严重,相较于基准参考区较低的土壤侵蚀模数 [平均为2 345.9 t/(km²·a)],矿区及其周边的平均土壤侵蚀模数达到了8 487.5 t/(km²·a),土壤侵蚀严重区甚至高达70 000 t/(km²·a)以上,总体上,赣州市2013年稀土矿开采所导致的土壤侵蚀量为646 917 t;2）赣州市稀土开采所导致的水土保持实物量及价值量损失巨大,2013年,赣州市稀土开采所导致的水土保持价值损失量为461 921.3万元,占到了其当年总产值的12.35%。论文构建的水土保持价值损失评估方法可为其他类似矿区的评估提供解决思路,研究结果可为稀土矿区生态评估、稀土资源定价以及矿区的生态环境管理提供依据。     

Work division of floral scent compounds in mediating pollinator behaviours

Floral scents are known as an olfactory signal for attracting pollinators, but why the flowers pollinated by highly specialised pollinators emit scents consisting of mixtures of many compounds and dominated by one or a few compounds is still poorly understood. We supposed that each (especially characteristic) chemical in floral scents may play a specific role in mediating pollinator behaviours and tested this supposition in a fig-fig wasp mutualism. Ficus curtipes is obligately pollinated by an undescribed Eupristina species. In the scent of F. curtipes receptive figs, over 50 compounds have been identified, and the scent is dominated by two compounds, 6-methyl-5-hepten-2-ol (OL) and 6-methyl-5-hepten-2-one (NE). We therefore tested the roles of the two major chemicals in mediating the pollinator behaviours. Our results show that OL and NE, respectively, act as a long-distance attractant and a fig-entry behaviour stimulant to the obligate pollinator wasp. Namely, OL attracts the wasps to the figs and NE guides the wasps into the figs. This finding on the work division of floral scent compounds partially explains the maintenance mechanism of the fig-fig wasp mutualism and the significance of the chemical diversity of floral scent in plant–pollinator interactions, especially in specialised pollination systems.