Water quality along a river continuum subject to point and diffuse sources     

Colin Neal  Helen P. Jarvie  Alison Love  Margaret Neal  Heather Wickham  Sarah Harman 《Journal of Hydrology》2008,350(3-4):154-165

The water quality along the River Kennet, in the Thames basin of southern England, was examined in terms of the influence of point- and diffuse-nutrient inputs. The river is supplied mainly from a Cretaceous Chalk aquifer and hence the waters are of a calcium bicarbonate type. The nitrate largely comes from agricultural sources, with concentrations decreasing downstream due to plant uptake and probable denitrification. In contrast, soluble reactive phosphorus (SRP) is largely associated with sewage inputs and concentrations increase downstream in line with effluents from major towns such as Newbury and Reading. Adjacent to the river in the lower half of the catchment is the Kennet and Avon Canal and the two are in places hydrologically connected. The canal inputs may influence calcium carbonate (calcite) precipitation and increase suspended sediment and particulate phosphorus concentrations in the river. Monitoring upstream and downstream of Marlborough sewage treatment works (STW) showed that SRP concentrations in the effluent were highly variable due to variable efficiency of P stripping and still sufficiently concentrated to dominate downstream river SRP with potential impacts on stream ecology. Biological recovery in this river following P stripping at STWs is complex and controlling those spikes in SRP that are above a threshold of 100 μg l⁻¹ may be a critical requirement. More stringent effluent targets than are currently recommended may be needed (less than 800 μg RP l⁻¹) to achieve good ecological status in this river depending on SRP concentrations upstream.  相似文献   

矿渣镁水泥初探          下载免费PDF全文

何荣昌  孙庆国 《盐湖研究》1999,7(3):45-51

研究了添加矿渣对传统镁水泥进行改性,同时探讨了磷酸盐对镁水泥耐水性能改善的效果,提高了镁水泥的经济价值和实用性。  相似文献   

磷矿的分布、特征与开发现状          下载免费PDF全文

吴发富  王建雄  刘江涛  曾国平  向鹏  胡鹏  向文帅 《中国地质》2021,48(1):82-101

世界磷矿储量近695亿t(2019年),但分布不均,磷矿储量最为丰富的北非地区集中了全球80％以上的磷矿资源.该区域的摩洛哥和西撒哈拉是世界磷矿资源最为丰富的国家,2019年其磷矿储量达500亿t,占世界的近72％.目前世界上主要利用的磷矿类型为沉积型磷块岩矿,其最主要的成矿时代为震旦—寒武纪和中生代—新生代,前者以中...  相似文献   

Nutrient distributions in baroclinic eddies of the oligotrophic North Atlantic and inferred impacts on biology   总被引：1，自引：0，他引：1  

Qian P. Li  Dennis A. Hansell 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1291

High-sensitivity (nanomolar) techniques for nitrate and phosphate were applied to study nutrient patterns in the euphotic zone of mesoscale eddies in the Sargasso Sea during the EDDIES project. Surface concentrations of nitrate plus nitrite (DNN) and phosphate (DIP) were found in the range of 1–20 nM with substantial spatial variability in the eddies, with resulting mean N:P molar ratios of 2.1. Chlorophyll biomass was well correlated with DNN but not DIP in the upper euphotic zone, suggesting N-limitation of marine phytoplankton at this time of year. Within the upper 140 m, the water column experienced a transition from a P-enriched (relative to Redfield ratio) shallow layer to a N-enriched deep layer, which may suggest downward transport and subsequent remineralization of high N/P biogenic products presumably originating from N₂ fixation. Chlorophyll biomass in the deep chlorophyll maximum of eddies was found to be tightly related to eddy–induced variability in major nutrients (N, P, Si) and nutrient stoichiometry, suggesting that the impact of eddies on biology is through control of nutrient availability. Because the eddies were likely to be in various phases of development (different degrees of both biological and physical maturity), full interpretation of eddy data and dynamics will require better coverage of a full eddy life cycle.  相似文献   

磷酸盐氧同位素组成的测定方法及分馏机理研究进展   总被引：4，自引：0，他引：4  

陈志刚  黄奕普  刘广山  蔡毅华  卢阳阳  刘润 《地球科学进展》2010,25(10):1040-1050

磷酸盐氧同位素组成在古气候和磷的生物地球化学循环研究中都具有十分重要的意义.测定方法和同位素的分馏机理是该类研究的基础.国际上已开展了一系列磷酸盐氧同位素的测定方法和分馏机理研究.在测定方法上,由初期的间接法,经高温还原/裂解法到氟化法,再演化到改进后的高温还原法(包括TC/EA-IRMS法),甚至激光原位技术,样品由实验室纯化学试剂扩展到各种复杂地质样品,在测量精确度、测量速度、样品用量、安全性和技术要求方面都有巨大改进.在分馏机理上,①尽管Longinelli等建立的关系式已获得了天然样品的验证,并认为是平衡分馏,但实验室模拟结果与其还存在较大差异(即没有达到平衡分馏).②在地表温度和pH条件下,无机过程均不会造成水体中溶解态磷酸盐和水之间的氧同位素交换.在高温(>70℃)及不同pH条件下,即使没有生物作用也会造成溶解磷酸盐和水分子之间进行氧的同位素交换,但不同实验室之间结果不一致.③在生物作用存在下,溶解无机磷酸盐和水之间在地表环境会发生强烈氧同位素交换,但除了PPase外,其余均没有达到平衡值.④磷灰石的氧同位素组成要比形成它的溶解态磷酸盐的值高1‰～1.4‰,因此在把Longinelli等关系式用于溶解态磷酸盐和水体系时,需要考虑该因素.同位素平衡分馏和条件有关,认为无机条件下的高温(>70℃)实验结果不一致,以及有生物参与的培养实验结果偏离平衡值,都是实验条件不同所致,包括pH、磷酸盐浓度、生物种类、生物量等.  相似文献   

Petrography, chemistry and genesis of phosphorite concretions in the Eocene Umm Rijam Chert limestone Formation, Ma'an area, south Jordan   总被引：1，自引：0，他引：1  

Khalid Tarawneh  Khaled Moumani 《Journal of Asian Earth Sciences》2006,26(6):627-635

Phosphorite concretions are recorded for the first time within the lower part of the Umm Rijam Chert Limestone Formation (Eocene) in the Ma'an area, southern Jordan. The phosphorite concretions are typically hosted and encountered as individual layer in moderately lithified sediments of marl, chalk and chalky marl. The phosphorite concretions are present in thin layer (10–30 cm thick). They are localized on a hardground surface that formed as a result of cementation of soft ground by bioclastic materials. Light grey and brownish to black colors are encountered with isometric, ellipsoid, elongated, subangular to subrounded phosphorite concretions (up to 6 cm in length). Most of the phosphorite concretions preserve bioturbation structures; they also include fecal pellets of various sizes. The main biogenic components are fragments of macrofossils (bivalves) and microfossils (planktonic foraminifera) in different proportions. Petrographic examinations reveal that the phosphorite concretions are composed of cryptocrystalline apatite that characteristically appears in cross-polarized light almost as isotropic phosphate and minor anisotropic phosphate. Apatite and calcite are the main mineral constituents of the phosphorite concretions identified by XRD. The apatite is identified as francolite (carbonate-flour-apatite). Chemical analyses of the phosphorite concretions using X-ray florescence indicate that the P₂O₅ content ranges from 18.8 to 31.19%, whereas SEM–EDS analyses indicate that the phosphorus proportion is around 14% by volume. It could be argued that the phosphorite concretions were transported after being reworked, or were derived from carbonate and chalk pebbles that were later phosphatized and subjected to erosion, forming residual lag deposit along the hardground surface.  相似文献   

Sedimentary Phosphate Fractions Related to Calcite Precipitation in an Eutrophic Hardwater Lake (Lake Alserio, Northern Italy)     

I. de Vicente  K. Cattaneo  L. Cruz-Pizarro  A. Brauer  P. Guilizzoni 《Journal of Paleolimnology》2006,35(1):55-64

P-fractional composition has been studied in a 64-cm long sediment core collected in an eutrophic hardwater lake (Lake Alserio, northern Italy) in an attempt to identify the main mechanisms (chemical or biologic) controlling CaCO₃ precipitation in the water column. The results of the sedimentary phosphate fractionation showed that the most important P fraction was an organic fraction extracted with hot NaOH: org-P_alkali (26% of P_sed). A digestion of the supernatant of the P-fraction bound to CaCO₃ allowed the detection of a large pool of org-P (19% of P_sed). Although the nature of this fraction is unclear, we suggest that it may be involved in the biologically mediated precipitation of CaCO₃. The high CaCO₃ concentration in the entire vertical sediment profile, as well as the presence of inorg- and org-P bound to Ca in both laminated and non-laminated zones, suggest that the CaCO₃ precipitation is not a recent process but is a process that has been occurring in the lake for some time. Accordingly, the change from a homogeneous sediment to a laminated sequence might be caused by the eutrophication process of Lake Alserio occurring since the 1960s, which has allowed the preservation of the varved sediment as a consequence of the drastic reduction in bioturbation.  相似文献   

The nature of surface complexation: a continuum approach     

M. A. Butkus  Domenico Grasso 《Environmental Geology》2001,40(4-5):446-453

Received: 3 March 2000 · Accepted: 9 May 2000  相似文献   

滇东磷块岩及工业磷矿床成因     

陶永和  梁永忠 《云南地质》2002,21(3):267-283

滇东地区存在两套含磷岩系，十个磷块岩层位，可归纳为三类成因、四个工业磷矿层，进一步划分为四个沉积阶段、四个工业磷矿床成矿区。其中，研究较深的中谊村段磷矿，是由成矿地质背景和环境因素控制的八种主要成矿作用和四个成矿富集阶段多重反复叠加形成的生物沉积磷块岩矿床。  相似文献   

Sorption von Schwermetallen durch Eisenphosphat-Kolloide in essigsauren Bodenextrakten     

S. Wmmel  W. Calmano 《洁净——土壤、空气、水》1995,23(2):76-79

Sorption of Heavy Metals from Acetic Acid Extracts by Ferric Phosphate Colloids A conceivable procedure to remedy heavy metal contaminated soil materials is given with extraction of organic acids, i. e. by the use of a biological degradable extraction agent. The following concentration step of heavy metal extracts should be carried out to a great extent without a change of the low pH values. A conventional precipitation of the heavy metals by rising the pH should be avoided in order to introduce no large amounts of salts into the wastewaters of the process and furthermore, to reduce the amount of sludge to be deposited. The process scheme developed with the objective of heavy metals recycling consists of the following steps: the extraction of the heavy metal contaminated soils with weak organic acids like acetic acid or citric acid, the electrolysis of the extract, and a concentration step in order to treat metal concentrations not fully removed by electrolysis. This third step, e.g. could contain sorption on iron phosphate colloids and precipitation within the acidic environment. It has been examined whether a removal of the heavy metals Pb, Cd, Cu, Sb, Cr, Ni and Zn from acetic aqueous solutions of pH between 2 and 3 can be carried out.  相似文献