RIVERINE INORGANIC CARBON DYNAMICS： OVERVIEW AND PERSPECTIVE

1INTRODUCTION River systems are the major linkage between the land and the ocean, not only transporting carbon from terres- trial environment to the ocean, but also exchanging CO2 with the atmosphere, actively involved in the global car- bon biogeochemical cycle (RICHEY et al., 2002; COLE and CARACO, 2001). The inorganic carbon, mainly o- riginating from soil CO2, carbonate minerals and atmo- sphericCO2,constitutedthegreatpart(about 60%) ofthe riverine carbon exported to the ocean…     

Species and distribution of inorganic selenium in the Bohai Sea

1 INTRODUCTION Selenium is a ubiquitous trace element that ex- ists in multiple chemical forms in seawater in dif- ferent oxidation states and organic metalloid com- pounds. Selenium is essential for the growth of various photosynthetic species in natural…     

Nitrogen uptake in light versus darkness of the seagrass Zostera noltei: integration with carbon metabolism

We conducted a study that shows that light and dark conditions do not affect the uptake rates of ammonium and nitrate by the seagrass Zostera noltei. This is an important advantage over some seaweed species in which these rates are severely reduced at night. In the light, the ammonium uptake rates were initially higher (15 and 20 μmol·g^?1·h^?1) and stabilized at a rate of 5 μmol·g^?1·h^?1 after 1 h, whereas in the dark the rates remained constant at a rate of 10 μmol·g^?1·h^?1 over the first 180 min of incubation. The rates of nitrate uptake in the light were high within the first 120 min of incubation (7.2–11.1 μmol·g^?1·h^?1) and decreased afterwards to lower values (0.8–3.9 μmol·g^?1·h^?1), whereas in the dark the rates fluctuated around 0.0–11.1 μmol·g^?1·h^?1 throughout the whole incubation time (7 h). The soluble sugar content of Z. noltei leaves increased significantly with both ammonium and nitrate incubations in the light, indicating the metabolic outcome of photosynthesis. In the dark, there was no significant variation in either the soluble sugar or in the starch content of leaves, rhizomes or roots in either the ammonium or nitrate incubations. However, the total starch content of plants decreased at night whereas the total soluble sugars increased, suggesting a process of starch catabolism to generate energy with the consequent production of smaller monosaccharide products. The starch content of rhizomes decreased significantly during the light incubations with nitrate but not with ammonium. These results suggest that carbohydrate mobilization is necessary for Z. noltei to account for extra energetic costs needed for the uptake and assimilation of nitrate. Furthermore, our results suggest that nitrate uptake, at least during the day, requires the mobilization of starch whereas the uptake of ammonium does not.     

Carbon and nitrogen pools in Padanian soils (Italy): Origin and dynamics of soil organic matter

Carbon and nitrogen elemental (C-N, wt%) and isotopic (δ¹³C-δ¹⁵N, ‰) investigation has been carried out on alluvial and deltaic soils from the Padanian plain (northern Italy), an area interested by intensive agricultural activities, to refine previous inferences on depositional facies, pedogenetic processes and anthropogenic influences. Soil analysis, carried out by EA-IRMS, have been focused on inorganic and organic fractions properly speciated by a thermally-based method, whereas further insights on the organic matter constituents have been obtained by sequential fractionation. The bulk EA-IRMS analyses reveal a remarkable compositional heterogeneity of the investigated soils (TC 0.89 to 11.93?wt%, TN 0.01 to 0.78?wt%, δ¹³C_TC -1.2 to -28.2‰, δ¹⁵N -1.2 to 10.0‰) that has to be explained as an integration between inorganic and organic pools. The latter have been subdivided in Non-Extractable Organic Matter (NEOM, δ¹³C -16.3 to -28.6‰) and in extractable fractions as Fulvic (FA, δ¹³C -24.7 to -27.5‰, δ¹⁵N 0.6 to 5.7‰) and Humic (HA, δ¹³C -24.6 to -27.0‰, δ¹⁵N 1.0 to 9.7‰) Acids, which have been used to infer soil dynamics and Soil Organic Matter (SOM) stability processes. Results indicate that SOM at depth of 100?cm was generally affected by microbial reworking, with the exception of clayey and peaty deposits in which biological activity seems inhibited. Peaty and clayey soils display an organic fraction loss of ca. 20% toward the surface, suggesting deterioration possibly induced by intensive agricultural activities. These latter may be the cause of the ubiquitous losses of organic fraction throughout the investigated area over the last seventy years, evaluated by the comparison with historical data on corresponding topsoils. The obtained insights are very important because these soils are carbon (and nitrogen) sinks that are vulnerable and can be degraded, loosing agricultural productivity and potentially contributing to greenhouse gases fluxes.     

鄂尔多斯盆地地下水无机指标数据集(2014-2015年度)

本数据集包含了2014年、2015年两年内在鄂尔多斯盆地采集的742个地下水样品的位置信息、取样层位信息及35项无机地球化学成分测试结果信息。采样过程规范,结果均由合格实验室测试完成,数据质量可靠。可以真实反映该时段鄂尔多斯盆地地下水质量状况,为研究鄂尔多斯盆地地下水循环演化提供地球化学指标参考。     

Simulating estuarine nitrous oxide production by means of a dynamic model

We describe a dynamic model developed from a commercially available modeling package (ECoS-III) to simulate estuarine dissolved inorganic nitrogen (DIN) dynamics, and consequent N(2)O production and atmospheric flux on the timescale of tidal cycles. Simulated model state variables were NH(4)(+), NO(3)(-) and N(2)O concentrations, and salinity. Model outputs were evaluated through comparison with summer field data for the Tyne estuary, UK. The model adequately reproduced the observed axial profiles of NH(4)(+), NO(3)(-) and N(2)O concentrations. Nitrification was shown to be the dominant N(2)O source and estimates of the ratios nitrification to DIN load and N(2)O emission to DIN load are considerably lower than the corresponding values adopted in global scale models of estuarine N(2)O emissions based on DIN transformations. Hence our results are consistent with the requirement imposed by atmospheric N(2)O growth rate constraints that the amount of atmospheric N(2)O arising from agriculturally related sources, including estuarine transformations of N, be revised downward.     

高岭石/醋酸钾插层复合物的制备及其影响因素

利用浸泡法制备了高岭石/醋酸钾插层复合物,进行X射线衍射分析,探讨了影响插层的因素。结果表明,醋酸钾对高岭石的插层作用与高岭石的结晶度、插层剂浓度、pH值密切相关。高岭石结晶度越高,越有利于插层作用的进行;高浓度的插层剂(≥30%)可以在较短的时间(12 h)内完成插层作用,而低浓度的插层溶液则需要非常长的时间(≥144 h)才能完成,且获得的插层率较低;pH=10的弱碱性条件最有利于插层的进行;温度对高岭石的插层作用影响不大,在室温就可获得较好的插层效果。     

地下水中无机多元素测定监控样的制备与应用

根据中国地质调查局正在组织开展全国性1:50000～1:250000地下水污染调查评价工作中对重点区要求必测的无机元素项目要求,用天然基体的地下水制备地下水无机多元素测定监控样。采集的地下水经初步分析后,进行有关组分的添加处理,制备需要研制的实验室监控样品。通过均匀性和稳定性检验,判定监控样的均匀性良好,在监测期间内性质稳定。探讨了该监控样在地下水无机元素测定质量监控工作中可以用于校准仪器、评价测量方法的准确度和用作分析质量保证。     

黄海南部的溶解无机氮

根据 1998年 5月的调查资料 ,分析并讨论了春季黄海南部海区溶解无机氮的分布特征。结果表明 :( 1)因受长江冲淡水及沿岸流的影响 ,NH+4 - N、NO-2 - N浓度的平面分布基本呈周边高、中央低 ,NO-3 - N的浓度则基本呈长江口外海域高、中北部深水区低的分布规律。 ( 2 )调查海域深水区的溶解无机氮存在明显的层化现象 ,且底层等值线上凸密集。 10 m以浅水体 ,NO-3 - N的浓度分布均匀 ,10 m以深水体 ,NO-3 - N的浓度急剧增加 ,且呈现出随深度增加而增加的趋势 ,NH+4 - N、NO-2 - N浓度的垂直分布比较均匀。 ( 3)黄海南部表层叶绿素 a的浓度呈现周边高、中央低的分布特征。     

三亚湾海水温度季节变化及溶解无机氮的垂直分布特征

根据2000年4月－2001年3月在三亚湾的定点现场观测资料分析结果表明：6－8月份受外来冷水上升流的入侵和影响，使该湾水域在该季节形成明显的温跃层，底部和中部有明显的低温层。在上升流入侵期间，该湾水域平均温跃层强度为0．138－0．283℃.m^-1，最大温跃层强度为419－0．440℃.m^-1，底部最低水温在22℃左右。9月－翌年3月温跃层消失，海水混合流动充分，温度垂直分布均匀。3月份水温开始升高，至5月水温总体升至最高，并由于高气温及强太阳的辐射作用，5月份形成温跃层。溶解无机氮（DIN）的分布特征表明，硝酸盐、亚硝酸盐在冷水上升流入侵季节，其含量明显提高，比平时分别提高：10．20％（表层）、37．20％（中层）、83．81％（底层）和60．04％（表层）、82．96％（中层）、119．41％（底层）。氨态氮不直接受上升流影响，但季节变化特征明显。