Nutrients regeneration pathway, release potential, transformation pattern and algal utilization strategies jointly drove cyanobacterial growth and their succession

In order to better understand the contribution of nutrients regeneration pathway, release potential and transformation pattern to cyanobacterial growth and succession, 7 sampling sites in Lake Chaohu with different bloom degree were studied every two months from February to November 2018. The carbon, nitrogen (N) and phosphorus (P) forms or fractions in surface, interstitial water and sediments as well as extracellular enzymatic activities, P sorption, specific microbial abundance and community composition in sediments were analyzed. P regeneration pathway was dominated by iron-bound P desorption and phosphorus-solubilizing bacteria solubilization in severe-bloom and slight-bloom area respectively, which both resulted in high soluble reactive phosphorus (SRP) accumulation in interstitial water. However, in severe-bloom area, higher P release potential caused the strong P release and algal growth, compared to slight-bloom area. In spring, P limitation and N selective assimilation of Dolichospermum facilitated nitrate accumulation in surface water, which provided enough N source for the initiation of Microcystis bloom. In summer, the accumulated organic N in Dolichospermum cells during its bloom was re-mineralized as ammonium to replenish N source for the sustainable development of Microcystis bloom. Furthermore, SRP continuous release led to the replacement of Dolichospermum by Microcystis with the advantage of P quick utilization, transport and storage. Taken together, the succession from Dolichospermum to Microcystis was due to both the different forms of N and P in water column mediated by different regeneration and transformation pathways as well as release potential, and algal N and P utilization strategies.     

Selection of water source for water transfer based on algal growth potential to prevent algal blooms

Water transfer is becoming a popular method for solving the problems of water quality deterioration and water level drawdown in lakes. However, the principle of choosing water sources for water transfer projects has mainly been based on the effects on water quality, which neglects the influence in the variation of phytoplankton community and the risk of algal blooms. In this study, algal growth potential (AGP) test was applied to predict changes in the phytoplankton community caused by water transfer projects. The feasibility of proposed water transfer sources (Baqing River and Jinsha River) was assessed through the changes in both water quality and phytoplankton community in Chenghai Lake, Southwest China. The results showed that the concentration of total nitrogen (TN) and total phosphorus (TP) in Chenghai Lake could be decreased to 0.52 mg/L and 0.02 mg/L respectively with the simulated water transfer source of Jinsha River. The algal cell density could be reduced by 60%, and the phytoplankton community would become relatively stable with the Jinsha River water transfer project, and the dominant species of Anabaena cylindrica evolved into Anabaenopsis arnoldii due to the species competition. However, the risk of algal blooms would be increased after the Baqing River water transfer project even with the improved water quality. Algae gained faster proliferation with the same dominant species in water transfer source. Therefore, water transfer projects should be assessed from not only the variation of water quality but also the risk of algal blooms.     

盐结皮对艾比湖湿地土壤特性的影响及其自然要素分析

为探讨艾比湖湿地内土壤盐结皮(SSC)与土壤特性的相互作用关系,以及影响SSC厚度的自然要素。采用野外调查与室内试验相结合的方法,在湿地内选取30个具有代表性的样点,并在其周围选取无SSC的样点(30个)作对比,对研究区内有SSC和无SSC覆盖的土壤特性(有机质、容重、质量含水量、总盐、全氮、全磷和p H)进行对比分析,并结合气候要素(风速、气温、湿度和降水量)探讨其对SSC厚度的影响。结果表明:(1) SSC覆盖的土壤总盐平均含量为27.7 g/kg,质量含水量为16.8 g/kg,显著高于无SSC覆盖的土壤总盐(17.8 g/kg)和质量含水量(10.7 g/kg),有SSC覆盖的土壤有机质、全磷和全氮含量分别为6.9、0.88和0.63 g/kg,低于无SSC覆盖的土壤有机质(8.8 g/kg)、全磷(1.05 g/kg)和全氮(0.87 g/kg),有SSC覆盖的土壤碱性更强、容重更大;(2) SSC覆盖下的土壤总盐、容重和p H随深度增加而下降,质量含水量、全磷和全氮随深度增加而增加。SSC厚度与土壤总盐(0.676**)、质量含水量(0.513**)和容重(0.484*)成正相关,与有机质(-0.426*)、p H(-0.402*)、全磷(-0.233)和全氮(-0.303)呈负相关,随深度增加相关性逐渐减弱;(3)主成份分析表明SSC厚度3 cm时,土壤总盐、质量含水量和风速对其影响最大,权重分别为0.42、0.25和0.17。总之,SSC可以提高土壤保水性,增加土壤容重,但不利于养分的积累,会使土壤碱化、盐化更强烈。SSC的厚度受土壤总盐、质量含水量和风速的影响较大。     

扑草净水环境质量基准及风险评估

选择田间使用量大的扑草净为研究对象,分析了扑草净在南四湖流域地表水中的空间分布,推导了扑草净的水质基准,通过定性与定量风险评估方法评估了扑草净的生态风险.结果表明,南四湖流域28个地表水采样点中扑草净浓度为0~667.7ng/L,平均值为69.2ng/L.搜集筛选了15种水生生物慢性毒性数据,利用物种敏感度分布法,推导出扑草净的水质基准为82.4ng/L.使用商值法评估南四湖流域生态风险,结果表明,扑草净生态风险最高区域位于NS09,主要来源是地表径流与雨水冲刷.采用联合概率曲线法进一步分析生态风险,发现南四湖水体中扑草净对1%~5%的水生生物产生危害的概率为11.2%~6.4%.总体来看,南四湖流域扑草净的生态环境风险处于较低水平.     

湖底陷阱捕获内污染技术在浅水湖泊的应用

基于研发的湖底陷阱捕获内污染技术,在巢湖进行应用研究.结果表明,湖底陷阱可有效收集叶绿素a、有机质、总氮和总磷等湖底沉积物中内源污染物.不同位置和季节湖底陷阱收集的沉积物厚度差异显著,西巢湖收集的污染物含量最多,湖心区域收集污染物量最少;夏秋季节淤积较快,冬春季节淤积略慢.单位面积（1m²）湖底陷阱年收集叶绿素a、有机质、总氮和总磷可分别达2.37~15.28g、8.96~21.82kg、0.78~1.88kg和0.30~0.93kg.综合考虑湖流场、风浪场、湖底污染物分布及厚度,巢湖湖体内沿湖流汇集区可布置6条11~33km的湖底陷阱,并在7个主要入河口布置湖底陷阱,同时可利用现有航道,进一步加深后形成湖底陷阱,可为巢湖内源控制提供新的治理手段和管理方法.     

三峡库区汉丰湖水体氮磷及化学计量比季节变化特征

在分析2017年3月至2018年2月汉丰湖水体氮磷营养盐质量浓度季节性变化的基础上,利用氮磷化学计量摩尔比评估水体氮磷养分限制状态.结果表明：湖体TN、DN和NO₃^--N平均质量浓度分别为1.60、1.25和0.91 mg·L^-1,三者季节变化过程相似,均呈现出冬季最高、夏季最低的特点.NO₃^--N对水体TN贡献较大,NH₄⁺-N和NO₂^--N质量浓度维持在较低水平且变化平稳.TP、DP和PO₄^3--P平均质量浓度分别为0.13、0.09和0.06 mg·L^-1,TP和DP质量浓度变化相似,呈春夏季升高,秋冬季先降低再升高的趋势,而PO₄^3--P质量浓度则波动降低.TN/TP范围在11.07~56.02之间,均值为29.23,TN/TP呈季节性波动变化,最高值出现在冬季,最低值出现在夏季.汉丰湖水体多数时间适宜藻类生长繁殖,少数时间处于N限制状态,极少数时间处于P限制状态.降雨径流、肥料使用、污水排放和水生生物活动等因素皆会影响TN/TP的季节变化,同时根据汉丰湖水质特征提出保护建议.     

兴凯湖有色可溶性有机物来源与组成特征—中国境内特大型界湖

运用光谱吸收与三维荧光－平行因子分析法(EEMs-PARAFAC)分析了兴凯湖有色可溶性有机物(CDOM)吸收光谱、荧光光谱特征以及荧光组分与主要水质参数的相关性,以探究兴凯湖CDOM来源组成特征.结果表明:平行因子分析法解析CDOM三维荧光图谱,得到陆源类腐殖质C1、微生物作用类腐殖质C2、类酪氨酸C3和类色氨酸C4.兴凯湖中陆源类腐殖质C1能较好反演DOC、TN浓度变化,且在富营养化更强的小兴凯湖中反演效果更好.吸收系数a₂₅₄、荧光峰积分比值I_C:I_T、光谱斜率S_275-295、DOC与C1-C2、C4在兴凯湖中线性拟合程度均较好,与C1的相关性最好,这意味着陆源类腐殖质是兴凯湖CDOM库的主要贡献者,入湖河流输入是兴凯湖CDOM的重要来源之一.小兴凯湖DOC、a₂₅₄均极显著高于大兴凯湖,说明小兴凯湖的CDOM丰度要高于大兴凯湖.小兴凯湖CDOM的I_C:I_T、C1-C2和C4的值均极显著大于大兴凯湖(P<0.001),小兴凯湖S_275-295与光谱斜率比值S_R均极显著小于大兴凯湖,小兴凯湖PC1得分均值显著高于大兴凯湖品,意味着相较于大兴凯湖而言,小兴凯湖CDOM陆源输入信号更强烈,腐殖质化程度更高,亦即河流输入、农业面源污染导致小兴凯湖CDOM腐殖质化程度升高,且这一部分CDOM分子量较大,应加强兴凯湖流域中生态渔业、生态农业、生态旅游、农田退水等河流污染源排放的控制管理.     

利用CDOM吸收系数估算博斯腾湖水体表层DOC浓度

基于2021年夏秋两季西部干旱区博斯腾湖表层50个采样点位实测数据,通过对DOC特征的统计学分析、内外源因素影响的时空差异以及电导率相关性验证,将博斯腾湖划分为河口和非河口区域.然后以CDOM特征波长吸收系数a₂₅₀和a₃₆₅为自变量,以DOC浓度（c_DOC）为因变量,分别构建了基于CDOM的河口和非河口水域DOC浓度估算模型.结果表明：河流与湖泊进行水体交换的同时,会将大量陆源DOC输送到博斯腾湖中,使得河口区域DOC浓度明显高于非河口区域（t-tests,P<0.01）,河口区域的DOC浓度（c_DOC）约是非河口区域的2.2~2.3倍,且在河口区域c_DOC与电导率呈现显著相关关系（夏季：R²=0.81,P<0.01;秋季：R²=0.84,P<0.01）.本文构建拟合模型（c_DOC=α+β·α₂₅₀+γ·α₃₆₅）,并通过交叉验证的方法来检验模型精度.将夏季和秋季同区域数据统一建模,河口和非河口区域CDOM与DOC均存在较好的相关关系,且模型精度较高（河口区域：R²=0.60,RMSE=8.56%;非河口区域：R²=0.66,RMSE=8.77%）.本文所建立的模型可以在不增加环境因子变量的前提下提高精度,有利于实现卫星遥感反演.同时,本研究揭示了河流输入对博斯腾湖DOC分布和估算的时空影响,提出可利用CDOM估算DOC浓度,但需根据水文特征和c_DOC等因素区分河口和非河口区域.本研究对实现新疆水资源合理开发、有效保护以及综合治理提供科学依据,对我国西部干旱区湖泊DOC遥感动态监测具有重要意义.     

洞庭湖南缘农田土壤重金属特征及源解析

基于网格布点法于2020年4～8月在洞庭湖南缘农田中采集了1 589件表层土壤样品,采用ICP-MS、 ICP-OES、 HG-AFS和ISE方法测定土壤中As、 Cd、 Pb、 Cu、 Zn、 Ni、 Cr、 Hg元素含量及pH,重点研究了区内土壤重金属含量、潜在生态风险、空间分布特征及其来源解析.结果表明,土壤重金属ω(Zn)、ω(Cr)、ω(Pb)、ω(Cu)、ω(Ni)、ω(As)、ω(Cd)和ω(Hg)平均值依次为：118.18、 82.21、 52.1、 33.76、 32.81、 18.25、 0.42和0.13 mg·kg^-1.各重金属均处于中、高度变异,土壤以弱酸性为主,pH介于3.96～7.90之间,Hg和Cd存在较高的生态风险.各重金属元素空间分布规律均呈西南高东北低的趋势.采用PMF和PCA方法对8种重金属元素进行来源解析及贡献率计算,PMF结果表明,研究区土壤重金属来源贡献率依次为：农业活动源(36.98%)、自然源(32.94%)、水土交换源(17.05%)和大气干湿沉降源(13.03%),而PCA结果表明研究区土壤重金属主要来源于农业...     

他念他翁山中段仁措湖地区花岗岩风化晕生长侵蚀模型研究及原地生成宇宙成因核素测年思考

通过建立他念他翁山流域仁措湖地区的花岗岩风化晕生长模型与侵蚀模型,并利用此模型定量了仁措湖地区花岗岩暴露年代。研究结果显示：该地区花岗岩风化晕平均生长速率为4.88 mm? (10 ka) ^?1;平均侵蚀速率为2.15 mm?ka^?1。通过此模型对仁措湖地区的年代进行计算,得出该地区花岗岩风化时间约为(236±88)— (19834±1560) a。结合原地生成宇宙成因核素（terrestrial in situ cosmogenic nuclide,TCN）测年原理,推算出青藏高原花岗岩冰川沉积物至少侵蚀速率分别为：青藏高原东北部为(2.61±0.05) mm?ka^?1、青藏高原东南部为(3.43±0.70) mm?ka^?1、青藏高原中部为(3.42±0.34) mm?ka^?1、喜马拉雅中部为(3.71±0.72) mm?ka^?1、高原西部为(3.14±0.52) mm?ka^?1、喜马拉雅山脉西部为(3.36±0.67) mm?ka^?1、帕米尔高原东部为(3.45±0.59) mm?ka^?1、帕米尔高原西部为(3.11±0.41) mm?ka^?1、天山为(3.63±0.53) mm?ka^?1,恢复后整个青藏高原的TCN测年精度提高了10%左右。