痕量甲烷碳同位素真空制样系统的研制与贵州省一些水稻田甲烷碳同位素组成的初步测定

甲烷碳同位素（δ~(13)C）在辩识甲源汇和提示甲烷的产出机理、传输途径方面有重要作用国内因痕量甲烷的同位素制样问题未能开展有关的研究工作。我们研制了一套痕量甲烷碳同位素的真空制样系统，并对贵州省内一些水稻田的甲烷δ~(13)C值作了初步测定。痕量甲烷碳同位素真空制样系统充分考虑到气样中CO_2、H_2O、CO和非甲烷烃等杂质气体对甲烷同位素制样的干扰，在吸收和借鉴前人工作基础上研制出来，在设计上具有以下特点：（1）制样过程中杂质气体的清除采用多环“冷阱串”，保证冷冻过程的可靠性和稳定性。（2）甲烷的高温转化使用了新型HA-02贵金属催化剂，实验检测表明：在较低的温度下（400 ℃ - 500 ℃）HA-02催化剂能确保甲烷的充分氧化分解。（3）CO_2气样设计有样品管和熔封管两种接收方式，便于收集和贮存。（4）真空制样系统可以制备气样中CO_2、CO的同位素样本，与质谱仪配合可以同步监测CO_2、CO的碳氧同位素组成。同位素条件检测实验证明了痕量甲烷碳同位素真空制样的可行性。用自行研制的真空系统对贵州省内一些水稻田甲烷的δ~(13)C值初步测定表明：稻田甲烷以富集轻同位素为特征，δ~(13)C变化在-54.05 ～ -64.47‰，平均为-60.67 ± 3.56‰，比较接近肯尼亚水稻田的研究结果，同时甲烷δ~(13)C值在一天中从上竿到晚上有逐步富集~(13)C的趋势。

Carbon and nitrogen emissions from stored manure and cropped fields in irrigated mountain oases of Oman

Little is known about gaseous carbon (C) and nitrogen (N) emissions from traditional terrace agriculture in irrigated high mountain agroecosystems of the subtropics. In an effort towards filling this knowledge gap measurements of carbon dioxide (CO_2), methane (CH_4), ammonia (NH_3) and dinitrous oxide (N_2O) were taken with a mobile photoacoustic infrared multi-gas monitor on manure-filled PE-fibre storage bags and on flood-irrigated untilled and tilled fields in three mountain oases of the northen Omani Al Jabal al Akhdar mountains. During typical 9-11 day irrigation cycles of March, August and September 2006 soil volumetric moisture contents of fields dominated by fodder wheat, barley, oats and pomegranate ranged from 46-23%. While manure incorporation after application effectively reduced gaseous N losses, prolonged storage of manure in heaps or in PE-fibre bags caused large losses of C and N. Given the large irrigation-related turnover of organic C, sustainable agricultural productivity of oasis agriculture in Oman seems to require the integration of livestock which allows for several applications of manure per year at individual rates of 20 t dry matter ha^−1.

Seawater carbonate chemistry and community calcification during Shiraha coral reef (Ishigaki Island, Japan) studies, 1995

Only about half of all the CO_2 that has been produced by the burning of fossil fuels now remains in the atmosphere. The CO_2 "missing" from the atmosphere is the subject of an important debate. It was thought that the great majority of the missing CO_2 has invaded the ocean, for this system naturally acts as a giant chemical regulator of the atmosphere. Although it is clear that ocean processes have a major role in the regulation of the carbon dioxide content of the atmosphere through air-sea exchange processes, recent studies of the oceanic carbon cycle and air-sea interaction indicate that oceanic carbon is in a quasi-steady state via the system of biological and physical processes in the ocean interior. It is difficult to determine whether the ocean has the capacity to take up the increasing air-born CO_2 released by human activities over the past five or six decades. To understand this enigma, we need a better understanding of the natural variability of the oceanic carbon cycle.

Lack of bipolar see-saw in response to Southern Ocean wind reduction

A cessation of the Atlantic meridional overturning circulation (AMOC) significantly reduces northward oceanic heat transport. In response to anomalous freshwater flux, this leads to the classic 'bipolar see-saw' pattern of northern cooling and southern warming in surface air and ocean temperatures. By contrast, as shown here in a coupled climate model, both northern and southern cooling are observed for an AMOC reduction in response to reduced wind stress in the Southern Ocean (SO). For very weak SO wind stress, not only the overturning circulation collapses, but sea ice export from the SO is strongly reduced. Consequently, sea ice extent and albedo increase in this region. The resulting cooling overcompensates the warming by the reduced northward heat transport. The effect depends continuously on changes in wind stress and is reversed for increased winds. It may have consequences for abrupt climate change, the last deglaciation and climate sensitivity to increasing atmospheric CO_2 concentration.

In-situ seawater pH and temperature during and fitness traits of a calcifying polychaete after a reciprocal transplant experiment in June-July near Ischia, italy

Ocean acidification (OA) is likely to exert selective pressure on natural populations. Our ability to predict which marine species will adapt to OA, and what underlies this adaptive potential, are of high conservation and resource management priority. Using a naturally low pH vent site in the Mediterranean Sea (Castello Aragonese, Ischia) mirroring projected future OA conditions, we carried out a reciprocal transplant experiment to investigate the relative importance of phenotypic plasticity and local adaptation in two populations of the sessile, calcifying polychaete /Simplaria /sp. (Annelida, Serpulidae, Spirorbinae): one residing in low pH and the other from a nearby ambient (i.e. high) pH site. We measured a suite of fitness related traits (i.e. survival, reproductive output, maturation, population growth) and tube growth rates in laboratory-bred F2 generation individuals from both populations reciprocally transplanted back into both ambient and low pH /in situ/ habitats. Both populations showed lower expression in all traits, but increased tube growth rates, when exposed to low pH compared to high pH conditions, regardless of their site of origin suggesting that local adaptation to low pH conditions has not occurred. We also found comparable levels of plasticity in the two populations investigated, suggesting no influence of long-term exposure to low pH on the ability of populations to adjust their phenotype. Despite high variation in trait values among sites and the relatively extreme conditions at sites close to the vents (pH < 7.36), response trends were consistent across traits. Hence, our data suggest that, for /Simplaria /and possibly other calcifiers, neither local adaptations nor sufficient phenotypic plasticity levels appear to suffice in order to compensate for the negative impacts of OA on long-term survival. Our work also underlines the utility of field experiments in natural environments subjected to high level of /p/CO_2 for elucidating the potential for adaptation to future scenarios of OA.