Simulating the influence of various nutrient sources on hypoxia off the Changjiang River Estuary

Hypoxia is increasingly reported off the Changjiang River Estuary with the confluence of multiple high volume nutrient sources. The Regional Ocean Modeling System coupled with a biological model was used to analyze the effect of different nutrient sources on the development of hypoxia off the Changjiang River Estuary. By comparing to observed data, our model suitably captured the regional dynamics of chlorophyll a, dissolved oxygen, and nutrient concentration. A series of sensitivity experiments were conducted to investigate the hypoxia response to the various nutrient sources, such as loading from the Changjiang River, Kuroshio and Taiwan Warm Current. Our model results indicated that nutrients from different sources significantly influenced the hypoxia off the Changjiang River Estuary, and it was mostly affected by nutrients sourced from the Kuroshio. The nutrients input from the Changjiang River had larger impacts on the hypoxia in the north of 30°N than that in the south of 30°N. The nutrients sourced from the Taiwan Strait had a least influence on the hypoxia off the Changjiang River Estuary.     

海南新村潟湖潮汐、潮流特征及其对营养盐的影响

基于海南新村潟湖2020年12月水文和水质多要素实测数据,研究了该海域的潮汐、潮流变化特征,并探讨了潮位变化对潟湖营养盐的影响。结果表明,新村潟湖的潮汐为不规则全日潮,潟湖口门处的潮流为往复流,涨潮历时15 h,落潮历时10 h。大、小潮期间3个观测站点溶解性无机氮(DIN)浓度变化范围为0.91~20.87 μmol/L,磷酸盐(PO3-4)浓度变化范围为0.11~5.92 μmol/L,硅酸盐(SiO2-3)浓度变化范围为2.36~134.75 μmol/L。大、小潮期间,潟湖内3个观测站点DIN、PO3-4、SiO2-3浓度随着涨、落潮过程发生变化。潟湖口门处流速对观测站点潮位变化有着重要的影响,潮通量基本决定了潮位的变化。潟湖口门处和渔排密集区域的营养盐浓度与潮位呈现显著的负相关关系,潮流流速对口门处和渔排密集区域的营养盐变化有着重要影响。该研究结果将为新村潟湖的污染治理及生态修复提供科学依据。     

The Influence of Plantation on Soil Carbon and Nutrients: Focusing on Tibetan Artificial Forests

As terrestrial ecosystem carbon (C) sinks, plantation ecosystems play essential roles in species diversity protection, resource supply and climate change. Artificial afforestation is of great important in improving the ecological condition, economic development and production in Tibet. Forests can improve soil property changes, yet the understanding of how plantations influence soil C and nutrient conditions in Tibet is still insufficient. This review combines with previous studies to explore the characteristics of soil nutrients, involving nitrogen (N) and phosphorus (P) on Tibetan poplar plantations. Generally, plantations have better abilities in improving the soil C and N cycles, and enhancing the soil stability. In this review, we further analyze the factors, including the modality of land-use, afforested period, tree species, climate factors and soil properties, which may affect the soil C and nutrients. (1) The patterns of land-use affect the accumulation of soil organic matter, thus influence the accumulation of soil C and nutrients; (2) Soil C and N increase with the years of artificial forests, while soil P is on the contrary; (3) The effects of different tree species on soil C and nutrients vary widely; (4) In terms of climate, the C sink of Tibetan plantation soil is most likely to be affected by precipitation, while the nutrient is more likely to be influenced by temperature; (5) Among soil properties, the most related factor to C is soil texture. Furthermore, our review pointed out that future research on soil ecological functions should be focused on soil microbes on Tibet plantation. At the end, we concluded three major challenges for the future research. Therefore, this review contributes to a better understand the effects of plantation on soil C and nutrients on the Tibetan Plateau.     

Elevation,slope aspect and integrated nutrient management effects on crop productivity and soil quality in North-west Himalayas,India

On farm bio-resource recycling has been given greater emphasis with the introduction of conservation agriculture specifically withclimate change scenarios in the mid-hills of the north-west Himalaya region（NWHR）. Under this changing scenario, elevation, slope aspect and integrated nutrient management（INM） may affect significantly soil quality and crop productivity. A study was conducted during 2009-2010 to 2010-2011 at the Ashti watershed of NWHR in a rainfed condition to examine the influence of elevation, slope aspect and integrated nutrient management（INM） on soil resource and crop productivity. Two years of farm demonstration trials indicated that crop productivity and soil quality is significantly affected by elevation, slope aspect and INM. Results showed that wheat equivalent yield（WEY） of improved technology increased crop productivity by -20%-37% compared to the conventional system. Intercropping of maize with cowpea and soybean enhanced yield by another 8%-17%. North aspect and higher elevation increased crop productivity by 15%-25% compared to south aspect and low elevation（except paddy）. Intercropping of maize with cowpea and soybean enhanced yield by another 8%-15%. Irrespective of slope, elevation and cropping system, the WEY increased by -30% in this region due to INMtechnology. The influence of elevation, slope aspect and INM significantly affected soil resources（SQI） and soil carbon change（SCC）. SCC is significantly correlated with SQI for conventional（R2 = 0.65＊）, INM technology（R2 = 0.81＊） and for both technologies（R2 = 0.73＊）. It is recommended that at higher elevation.（except for paddy soils） with a north facing slope, INM is recommended for higher crop productivity; conservation of soil resources is recommended for the mid hills of NWHR; and single values of SCC are appropriate as a SQI for this region.     

Uptake and recovery of soil nitrogen by bryophytes and vascular plants in an alpine meadow

Due to their particular physiology and life history traits, bryophytes are critical in regulating biogeochemical cycles and functions in alpine ecosystem. Hence, it is crucial to investigate their nutrient utilization strategies in comparison with vascular plants and understand their responses to the variation of growing season caused by climate change. Firstly, this study testified whether or not bryophytes can absorb nitrogen(N) directly from soil through spiking three chemical forms of 15N stable isotope tracer. Secondly, with stronger ability of carbohydrates assimilation and photosynthesis, it is supposed that N utilization efficiency of vascular plants is significantly higher than that of bryophytes. However, the recovery of soil N by bryophytes can still compete with vascular plants due to their greater phytomass. Thirdly, resource acquisition may be varied from the change of growing season, during which N pulse can be manipulated with 15N tracer addition at different time. Both of bryophytes and vascular plants contain more N in a longer growing season, and prefer inorganic over organic N. Bryophytes assimilate more NH4+ than NO3– and amino acid, which can be indicated from the greater shoot excess 15N of bryophytes. However, vascular plants prefer to absorb NO3– for their developed root systems and vascular tissue. Concerning the uptake of three forms N by bryophytes, there is significant difference between two manipulated lengths of growing season. Furthermore, the capacity of bryophytes to tolerate N-pollution may be lower than currently appreciated, which indicates the effect of climate change on asynchronous variation of soil N pools with plant requirements.     

胶州湾冬季浮游植物光合作用特征原位研究

目前关于中国近海浮游植物光合作用特征的研究较少,尤其是海洋浮游藻类冬季光合生理生态方面的研究少见报道。本实验利用浮游植物荧光仪Phyto-PAM测量了胶州湾浮游植物最大光化学量子产量、快速光曲线、光化学淬灭以及非光化学淬灭,通过显微镜镜检获得浮游植物群落结构组成与丰度结果,结合相应的环境因子,对胶州湾冬季浮游植物进行了原位光合作用特征研究。结果表明:调查期间胶州湾浮游植物具有较高的光合活性与潜力,最大光化学量子产量保持在0.69左右,光能利用效率大部分处于0.2—0.3之间,快速光曲线十分典型,当光强超过1000μmol/(s·m2)后依然能保持较好的光合活性,光化学淬灭值较高;当光强超过1500μmol/(s·m2)后,相对电子传递速率开始下降,实际光量子收益达到最低,非光化学淬灭升高,此时海洋浮游植物将光合机构吸收的过量光能以热能的形式耗散掉,有效地保护了胶州湾浮游植物的光合器官不因高光强的照射而受到损伤。冬季大部分时期胶州湾浮游植物丰度极低,但是湾内浮游植物具有较强的光合活性,加上相对稳定的水文、生物等环境以及较丰富的营养盐和相对有利的营养盐结构,是推动冬季浮游植物高峰期出现的关键生理生态因素。     

九龙江-河口表层水体营养盐含量的时空变化及潜在富营养化评价

分别于2012年9月、2013年1、6月,对九龙江两大支流北溪、西溪及河口区开展了3个航次的营养盐监测.研究结果表明,河口区表层水体溶解无机氮（DIN）、总磷（TP）和活性磷酸盐（PO4-P）质量浓度范围分别为0.13-17.35、0.14-1.00和0.00-0.38 mg/dm3,受上游输入和海水稀释作用,营养盐浓度由淡水端至海水端逐渐降低.北溪表层水体的DIN、TP和活性磷酸盐质量浓度范围分别为1.99-24.92、0.12-1.47和0.04-0.68 mg/dm3,受龙岩地区工农业生产及城市进程影响,由上游至下游逐渐降低.西溪表层水体的DIN、TP和活性磷酸盐质量浓度范围分别为2.74-20.61、0.14-0.92和0.02-0.37 mg/dm3,受上游农业生产和下游漳州地区人类活动影响,上下游的DIN质量浓度较高.此外,九龙江沿岸的人类活动可能影响了该地区水体中的溶解无机氮形态组成：北溪和西溪上游的NH4-N和NO3-N占比分别较高.水期分析表明,2013年1月的DIN浓度显著高于其他水期,而不同区域TP和活性磷酸盐的水期波动不尽相同.营养盐结构分析表明,九龙江总体处于磷限制状态,但在河口及北溪部分站位,CDIN/CPO4-P比值已达到适合浮游生物生长繁殖的水平.潜在富营养化程度评价表明,九龙江河口多数站位均处于N或P限制的富营养化级别,但由于N、P营养盐的绝对浓度较高,具有水华暴发的潜在风险.     

温度对沸石吸钾量检测的影响研究

沸石具有选择性吸附钾离子的特性,吸钾量是沸石应用中一项重要的物化性能,温度是影响吸钾量测量结果准确度的重要因素。在现有的吸钾量测试方法中,由于对测试温度的规定较为模糊,基本不作设定或只注明室温,而室温随季节变化较大,测试方法的准确度和精密度无法得到保证。为完善吸钾量的测试方法,本文研究了实际温度对沸石吸钾量的影响。结果表明,在试验的温度范围内(11.5~80℃),沸石样品的吸钾量与温度呈稳定且相对固定的负相关,由此提出了吸钾量计算公式:E20=Et+k(t-t20)。根据该定量关系,本文提出吸钾量测试方法中需要明确规定吸钾量的测试温度为20℃;如果是在非20℃的实际温度下测量得到的吸钾量,可根据温度校正系数(k)转换到20℃条件下的吸钾量。这种吸钾量测试方法可在实际室温下进行,操作简单,无需使用控温装置;又能消除因时间和地域差异导致的室温波动的影响,使吸钾量测试结果具有更好的精密度和准确度。     

The challenge of dating early pleistocene fossil teeth by the combined uranium series–electron spin resonance method: the Venta Micena palaeontological site (Orce,Spain)

The palaeontological site of Venta Micena (Orce, Andalusia, Spain) lies in the eastern sector of the Guadix–Baza basin, one of the best documented areas in Europe for Plio‐Pleistocene biostratigraphy. The combination of biochronological and palaeomagnetic results, combined with the radiometric data obtained for Atapuerca Sima del Elefante, indicated that the Venta Micena stratum was formed between the Jaramillo and Olduvai palaeomagnetic events, most likely between 1.22 and 1.77 Ma. Five fossil teeth from two outcrops (sites A and B) were selected to assess the potential of combined uranium series–electron spin resonance (US‐ESR) dating of Early Pleistocene sites. Although the US‐ESR results of the first outcrop showed a large scatter between the three teeth, the mean age of 1.37 ± 0.24 Ma can be considered a reasonable age estimate for Venta Micena. The mean ESR age of 0.62 ± 0.03 Ma obtained for site B seems to be a severe underestimation when compared with the independent age control. This underestimation is attributed to a relative recent U‐mobilization event that led to some U‐leaching. The results show that any ESR age calculations of old samples are extremely sensitive to variations in the measured ²³⁰Th/²³⁴U ratios in dental tissues. Although the results demonstrate that ESR can in principle be applied to Early Pleistocene sites, they also reveal the complexity of dating such old teeth. It is necessary to continue research in several directions, such as study of the behaviour of ESR signals in old teeth and understanding recent U‐mobilization processes, to improve the reliability of the combined US‐ESR dating method applied to Early Pleistocene times, a period for which the number of available numerical dating techniques is very limited. Copyright © 2011 John Wiley & Sons, Ltd.