Cost-effectiveness of the Baltic Sea Action Plan

The governments around the Baltic Sea have agreed on a new set of targets for nutrient load reductions. The major motive for this is new and better knowledge about the link between nutrient loads and water transparency in different parts of the sea. The Baltic Sea Action Plan (BSAP) defines target for transparency in different marine basins, the load reductions necessary to meet transparency targets and a scheme for the distribution of the abatement burden between countries adjacent to the sea.     

Mise en évidence expérimentale des facteurs nutritifs limitants de la production du micro-nanoplancton et de l'ultraplancton dans une eau côtière de la Méditerranée orientale (Haïfa,Israël)

Enrichment experiments were carried out on seawater samples from the Israeli coast to characterise the nature of nutrient limitation. Phytoplankton chlorophyll, ATP, PC, PN, PP and bicarbonate and orthophosphate uptake rates indicate that phosphorus limitation is more extreme than that of nitrogen. A large increase in total nitrogen observed with P enrichment suggests that a substantial nitrogen fixation is mediated by picocyanobacteria in this kind of oligotrophic mediterranean waters.

     

Nitrate in groundwater and N circulation in eastern Botswana

Nitrate pollution due to deep leaching from pit latrines has caused water supply wells in eastern Botswana to exceed health limits concerning nitrate. It was deduced from the estimated intake of salt and protein by the population that, as an average, about 10 percent of the human nitrogen excretion is leached to the groundwater. This fraction was also found in southern India, where on-the-ground excretion is customary. The nitrogen circulation in general in the savanna ecosystem is not appreciably affected in spite of a large livestock density. Overall nitrate leaching is in the order of 1.5 kg N/ha/y, similar to that in another semiarid area in southern India. However, in India, there seems to be a more diffuse areal leaching from agriculture as well as from villages.Measures to minimize the nitrate leaching could be to plant deep-rooted trees adjacent to pit latrines or to use latrines that separate the urine from the faces for a more near-surface infiltration facilitating plant uptake. Measures to minimize leaching will also lessen the rick for bacterial pollution of the groundwater.     

Large-scale impacts of bottom trawling on shelf primary productivity

Disturbance of the seabed resulting from bottom trawling affects ecosystem processes, such as the rate and magnitude of nutrient regeneration. The potential responses of the plankton community arising from such effects can be modelled, provided that reliable data on the effects on nutrient fluxes are available. In a north Cretan outer continental shelf and upper slope fishing ground (Heraklion Bay, Crete, Eastern Mediterranean) we applied a new field instrument which can simulate the passage of trawl groundropes across the sea floor and made direct seasonal measurements of the rate of dissolved and particulate nutrient releases resulting from seabed disturbance. These observational data were then integrated in a 3D ecosystem model. Results revealed that bottom trawling may trigger off considerable productivity pulses, in addition to pulses from the natural seasonal cycle.     

三峡库区紫色土坡地养分状况及养分流失*

紫色土是三峡库区移民安置区的主要坡地土壤。本研究采用典型区域调查,代表性土壤剖面养分分析,结合实验小区人工降雨的方法,初步研究了发育于侏罗纪紫色砂泥岩母质上紫色土的养分状况、养分流失特点、过程及影响养分流失因素。     

湖泊氮素生物地球化学循环及微生物的作用

氮素是影响湖泊富营养化的关键元素之一,对湖泊中氮素生物地球化学循环整个过程进行全面的了解,有利于对湖泊富营养化进行控制和治理.本文综述了湖泊生态系统(特别是富营养化湖泊)中氮素的输入、输出及其在沉积物-水界面的迁移转化规律,着重分析和比较了藻型湖泊和草型湖泊的不同食物链中的氮素营养循环过程,重点讨论了微生物参与的硝化作用、反硝化作用、生物固氮和厌氧氨氧化等过程的最新研究进展,并对氮循环相关的研究方法和技术进行了小结.最后指出当前国内外研究中亟待解决的问题,并对湖泊氮循环今后的研究方向提出了建议.     

Water and nutrient fluxes in a cool temperate rainforest at the Cordillera de la Costa in southern Chile

Water and nutrient fluxes were studied during a 12-month period in an alerce (Fitzroya cupressoides) forest, located in a remote site at the Cordillera de la Costa (40°05′S) in southern Chile. Measurements of precipitation, throughfall, stemflow, effective precipitation, soil infiltration and stream flow were carried out in an experimental, small watershed. Simultaneously, monthly water samples were collected to determine the concentrations and transport of organic-N, NO₃-N, total-P, K⁺, Ca²⁺, Na⁺ and Mg²⁺ in all levels of forest. Concentration of organic-N, NO₃-N, total-P and K⁺ showed a clear pattern of enrichment in the throughfall, stemflow, effective precipitation and soil infiltration. For Ca²⁺ and Mg²⁺, enrichment was observed in the effective precipitation, soil infiltration and stream flow. Annual transport of K⁺, Na⁺, Ca²⁺ and Mg²⁺ showed that the amounts exported from the forest via stream flow (K⁺=0·95, Na⁺=32·44, Ca²⁺=8·76 and Mg²⁺=7·16 kg ha⁻¹ yr⁻¹) are less than the inputs via precipitation (K⁺=6·39, Na⁺=40·99, Ca²⁺=15·13 and Mg²⁺=7·61 kg ha⁻¹ yr⁻¹). The amounts of organic-N and NO₃-N exported via stream flow (organic-N=1·04 and No₃-N=3·06 kg ha⁻¹ yr⁻¹) were relatively small; however, they represented greater amounts than the inputs via precipitation (organic-N=0·74 and NO₃-N=0·97 kg ha⁻¹ yr⁻¹), because of the great contribution of this element in the superficial soil horizon, where the processes of decomposition of organic material, mineralization and immobilization of the nutrients occurs. © 1998 John Wiley & Sons, Ltd.     

Diffusive equilibrium in thin films provides evidence of suppression of hyporheic exchange and large‐scale nitrate transformation in a groundwater‐fed river

The hyporheic zone of riverbed sediments has the potential to attenuate nitrate from upwelling, polluted groundwater. However, the coarse‐scale (5–10 cm) measurement of nitrogen biogeochemistry in the hyporheic zone can often mask fine‐scale (<1 cm) biogeochemical patterns, especially in near‐surface sediments, leading to incomplete or inaccurate representation of the capacity of the hyporheic zone to transform upwelling NO₃^?. In this study, we utilised diffusive equilibrium in thin‐films samplers to capture high resolution (cm‐scale) vertical concentration profiles of NO₃^?, SO₄^2?, Fe and Mn in the upper 15 cm of armoured and permeable riverbed sediments. The goal was to test whether nitrate attenuation was occurring in a sub‐reach characterised by strong vertical (upwelling) water fluxes. The vertical concentration profiles obtained from diffusive equilibrium in thin‐films samplers indicate considerable cm‐scale variability in NO₃^? (4.4 ± 2.9 mg N/L), SO₄^2? (9.9 ± 3.1 mg/l) and dissolved Fe (1.6 ± 2.1 mg/l) and Mn (0.2 ± 0.2 mg/l). However, the overall trend suggests the absence of substantial net chemical transformations and surface‐subsurface water mixing in the shallow sediments of our sub‐reach under baseflow conditions. The significance of this is that upwelling NO₃^?‐rich groundwater does not appear to be attenuated in the riverbed sediments at <15 cm depth as might occur where hyporheic exchange flows deliver organic matter to the sediments for metabolic processes. It would appear that the chemical patterns observed in the shallow sediments of our sub‐reach are not controlled exclusively by redox processes and/or hyporheic exchange flows. Deeper‐seated groundwater fluxes and hydro‐stratigraphy may be additional important drivers of chemical patterns in the shallow sediments of our study sub‐reach. © 2015 The Authors. Hydrological Processes Published by John Wiley & Sons Ltd.     

湖泊沉积物-水界面营养元素的生物地球化学作用和环境效应 Ⅰ.界面氮循环及其环境效应

发生在沉积物-水界面的剧烈生物地球化学作用对沉积物和上覆水体具重要的环境效应，然而此方面研究很少。本文通过云贵高原四个湖泊湖水和孔隙水NH和NO剖面，沉积物柱芯不同结合态氮含量剖面分布，界面扩散通量，影响氮循环的因素及它们季节性变化规律等的对比研究，初步揭示了湖泊沉积物一水界面的氮循环及其环境效应。     

滇池微生物解磷与聚磷作用的实验研究及磷的现代沉积与微生物成矿作用

滇池是世界上磷质来源最丰富的湖泊，是研究磷的现代沉积和微生物对磷循环作用及微生物成矿的天然场所。研究发现，滇池微生物种群和数量繁多，但能对磷溶解、转化、迁移、聚集、沉积的微生物主要有解磷菌和聚磷菌两类。这两类微生物与滇池磷的含量之间有一系列规律的相关性：在底泥磷高含量区域，解磷菌的种群和数量与底泥磷含量成负相关关系，与水体磷含量成正相关关系，而聚磷菌的种群和数量与底泥磷含量成正相关关系，与水体磷含量成负相关关系；在底泥磷低含量区域，上述相关性则相反。滇池中这种活着的微生物在自然环境条件下对磷的溶解、转化、迁移、聚集和沉积的作用，对古磷块岩微生物成矿说提供了可靠的依据，而且对以磷为限制性因子的湖、海、江河环境污染的防治提供了理论资料。