Local extinction of a foundation species in a hypoxic estuary: integrating individuals to ecosystem

We integrated across individual, population, community, and ecosystem levels to understand the impact of environmental stress by tracking the foundation species Mytilus edulis in the hypoxic estuary Narragansett Bay, Rhode Island, USA. Our initial surveys revealed that the mussels occurred in nine extensive (2-28 ha) dense (814-9943 individuals/m2) subtidal reefs that attracted a diverse suite of predators (sea stars, crabs, gastropods). Hypoxia occurred in the summer of 2001, and a mussel transplant experiment revealed overall reduced growth rates of individuals, and higher mortality rates among larger mussels. At the population level, large decreases in densities and cover of mussels were correlated with dissolved oxygen concentrations, leading to extinction at one site and reductions of over an order of magnitude at others. Within one year, seven of the eight remaining populations were edged to extinction, and the previously extinct population was recolonized. At the community level, a predator exclusion experiment indicated that predation was an unimportant source of mussel mortality during the hypoxic period, in part due to the emigration of sea stars, as predicted by the Consumer Stress Model. However, mussels were too intolerant to hypoxia to have a net benefit from the predation refuge. The seasonal (summer) occurrence of hypoxia allowed sea stars to return following a lag, as predicted by a stress return time model, and the resumption of predation contributed to the subsequent extinction of mussel populations. At the ecosystem level, the initial filtration rate of the mussel reefs was estimated at 134.6 x 10(6) m3/d, equivalent to filtering the volume of the bay 1.3 times during the 26-d average residence time. That function was reduced by >75% following hypoxia. The effect of hypoxia on each level of organization had consequences at others. For example, size-specific mortality and decreased growth of individuals, and reduced filtration capacity of reefs, indicated a loss of the ability of mussels to entrain planktonic productivity and potential to control future eutrophication and hypoxia. Our study quantified patterns of loss and identified pathways within an integrative framework of feedbacks, summarized in a conceptual model that is applicable to similar foundation species subjected to environmental stress.     

影响雨生红球藻797株生长和虾青素积累的某些因素

研究了雨生红球藻 (Haematococcuspluvialis) 797株的N源需求和营养盐吸收 ,并利用高光强和乙酸钠处理该藻 ,研究虾青素累积情况以及超氧化物歧化酶 (SOD)活性、营养盐、细胞状态的变化 .NH+ 4 N培养的生长速率明显高于NO-3 N培养 ,平均生长速率分别为 0 .2 79d-1和 0 .190d-1.NH+ 4 N培养所消耗的N、P营养盐比NO-3 N培养的消耗少 .两种N源下强光照处理 1d和 7d均导致雨生红球藻细胞数减少而静细胞比例增加 .在虾青素合成阶段 ,藻液N含量急剧下降而P含量基本保持稳定 ,说明虾青素合成对N的需要量大而对P的需要小 .在NO-3 N培养下 ,乙酸钠的加入则对虾青素的生产无显著影响 .在NH+ 4 N培养下SOD活性下降而虾青素含量升高 ;在NO-3 N培养下SOD活性与虾青素含量同时升高 .图 2表 4参 15     

Environmental impact of nitrogen fertilization in tea eco-system

To quantify the nitrogen losses through runoff and leaching under a tea plantation in hilly soil, a field experiment was conducted from October 2001 to October 2002 at United Planters Association of Southern India (UPASI), Coonoorin Nilgiri district. Runoff water was collected in the collection tub on most rainy days but the leachate was collected in the soil water sampler when the rainfall exceeded 150 mm. Higher nitrogen fertilization levels significantly influenced the NO3-N concentration in both the runoff and leachate and it was likely to cause adverse environmental impact at the delivery end. The NH4-N and NO3-N concentrations in runoff decreased with the days after fertilizer application. NH4-N concentration reduced from 10.27 mg/l on the 9th day to 1.72 mg/l on the 34th day after fertilizer application. NO3-N concentration reduced from 23.5 mg/l on the 9th day to 4.32 mg/l on the 34th day after fertilizer application. Nitrogen loss varied depending on the quantity of rainfall and runoff. The NO3-N concentration in the leachate increased with increase in depth (18.06 mg/l at 22.5 cm depth to 20.98 mg/l at 45 cm depth) whereas NH4-N concentration decreased with increase in depth (6.32 mg/l at 22.5 cm depth to 5.79 mg/l at 45 cm depth.     

Use of epilithic diatoms to evaluate water quality in the Karasu River of Turkey

Epilithic diatom assemblages were used to evaluate water quality in the Karasu River basin (Turkey), which was polluted by industrial, agricultural and urban wastes. A total of 73 diatom taxa belonging to 22 genera were found from all seven sampling stations located in the River basin. The most pollution tolerant species Gomphonema parvulum, Nitzchia palea, Navicula cryptocephala were found in high densities at the polluted stations. Organic load (COD), biological oxygen demand in 5 days (BOD5) and concentrations of nutrients NO3(-)-N, NO2(-)-N, NH4(+)-N and PO4(3-)-P) were correlated negatively with dissolved oxygen. Except for generic index of diatoms (GI), all diatom indices were correlated significantly with COD, BOD5 dissolved oxygen and concentrations of nutrients. Saprobity index (SI), trophic diatom index (TDI) and the percentage pollution tolerant valves values suggested that the stations III, IV located in the River basin were eutrophicated and organically polluted.     

Early responses of soil ammonium and nitrate nitrogen to forest gap harvesting of a Pinus massoniana plantation in the upper reaches of Yangtze River北大核心CSCD

To understand the short-term effects of forest gap by human harvesting on soil available nutrient in Pinus massoniana plantations, the variations of soil ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3-N) concentrations in the gap center and gap edge during growing season were observed in seven gaps of different size (Gl: 100 m2; G2:225 m2; G3:400 m2; G4:625 m2; G5:900 m2; G6:1225 m2; G7:1600 m2) and pure understory of a 39-year-old masson pine plantation in a hilly area of the upper reaches of Yangtze River. The results showed that in the early stage of gap formation, the gap size had significant effect on NH4+-N, the season changes on NP3--N, and the interaction effect of gap size and seasonal variation on NH4+-N and NO3--N. The difference of NH4+-N and NO3--N between the gap center and gap edge was not significant. (I) The NH4+-N content was 4.30-11.99 mg kg-1, and NO3--N content was 2.57-10.81 mg kg-1. There was no obvious difference in NH4+-N and N03--N among gaps of different size in early or late growing seasons, when both increased first and decreased afterwards in the middle of growing season. The gaps of 100∼400 m2 area had a higher content of available nitrogen. (2) The seasonal dynamic differed between NH4+-N and NO3--N, with the former lower in middle growing season whereas the latter higher in the middle growing season but lower in the end of growing season. The soil NH4+-N was higher than NO3- -N in the early and late periods, but lower in the middle period. (3) The soil NH4+-N and NO3--N in parts of gaps were lower than understory in the early and late growing season. (4) Correlation analyses showed that NH4+-N had significant positive correlation with microbial biomass nitrogen (MBN), and NO3--N with soil temperature, MBN and organic matter. But the impact of soil water content on available nitrogen was not significant. These results suggested that soil temperature and microbial activity variation caused by gap harvesting are the main factors affecting soil available nitrogen content of Pinus massoniana plantations.     

沿淮麦区大气无机态氮质量浓度的观测研究

2010年6月6日至6月16日,运用采样器TH-110B和TH-150C收集了地处沿淮麦区3个观测点的气体（NH3和NO2）和气溶胶样品,初步探讨了小麦收获期大气气态氮和颗粒态氮质量浓度的特征。结果表明：气态氮质量浓度以NO2最高,其时均质量浓度和日均质量浓度分别为0.57～0.64 mg.m-3和0.29～0.63 mg·m-3,且均超标（0.24和0.12 mg·m-3）;颗粒态氮质量浓度以NH4＋-N最高（4.12～78.28μg·m-3）,占总氮的47.00%～71.19%。此外,农业活动如收割,可增加大气气溶胶及无机态氮的质量浓度。     

三种载体上生物膜硝化作用动力学初步研究

通过测定水中COD、：NH4^ —N、NO2^-—N及NO3^-—N的浓度变化，研究了淹没式废水处理装置中沸石、活性炭和沙粒3种载体上硝化作用生物膜的动力学过程和反硝化作用。结果表明，3种载体上生物膜降解有机物(以COD表示)的过程可用一级动力学方程描述，反应速率常数分别为：沙粒0．0848h^-1、活性炭0．1187h^-1、沸石0．1334h^-1。3种载体上生物膜去除氨态氮的过程则可用零级动力学方程描述，反应速率常数分别为：沙粒-0．7743h^-1、活性炭-0．9886h^-1、沸石-1．0714h^-1．附着于沙上的生物膜去除亚硝酸盐氮的过程也可用零级动力学方程描述，反应速率常数为-0．6057h^-1，水中硝酸盐氮浓度较高时，载体沸石和活性炭上可能附着生长反硝化菌。图5表2参15。     

天然沸石对农田退水中氨氮的去除

利用静态吸附实验研究了沸石颗粒大小、氨氮初始浓度、接触时间及Na+离子浓度等因素对天然白银沸石去除模拟黄灌区农田退水中氨氮(NH4+-N)效果的影响,同时研究了吸附等温线特征,并考察了其吸附机理.研究结果表明,沸石颗粒大小、接触时间及NH4+和Na+初始浓度对NH4+-N交换容量都会产生一定影响;根据复相关系数(R2),NH4+-N的吸附等温线更符合三参数等温线模型;而对于两参数等温线模型,Langmuir模型比Freundlich模型能更好地描述NH4+-N在天然沸石上的离子交换过程;NH4+-N吸附实验数据与Elovich模型拟合最好(R2≥0.9766).研究结果表明了天然白银沸石是一种适合NH4+-N去除的离子交换剂,可用于黄灌区农田退水中NH4+-N的去除.     

菰和菖蒲在污水中的生长特性及其净化效果比较

通过漂浮栽植菰(Zizania latifolia)和菖蒲(Acoruscalamus),研究了它们在低、中、高3种浓度污水中的生长特性及其对这3种浓度污水的净化效果.结果表明,菰和菖蒲均在中浓度污水中生长最好.菰在中浓度污水中的生物量显著高于低浓度和高浓度中;菖蒲在中浓度污水中的生物量略高于低浓度和高浓度中,但差异不显著.菰对中浓度污水中TN、NH3-N、TP和CODCr的去除率分别为97.4%、95.3%、98.5%和71.4%,对高浓度污水中TN、NH3-N、TP和CODCr的去除率分别为96.4%、97.7%、88.2%和76.1%,净化效果均显著高于低浓度中.菰可作为中、高浓度污水的净化植物.菖蒲净化中浓度污水的效果最好,对TN、NH3-N、TP和CODCr的去除率分别为97.5%、94.1%、98.5%和72.7%;对高浓度污水中的NH3-N和CODCr去除效果也较好,去除率分别为97.8%和86.7%,但对TN和TP的去除率分别为89.5%和70.9%,显著低于对低浓度和中浓度污水中TN和TP的去除率.图1表4参13     

螯台球菌TAD1在高温曝气生物滤池中的异养硝化-反硝化性能

初步实验证实螯台球菌(Chelatococcus daeguensis)TAD1在高温下具有异养硝化-反硝化的能力,为验证其可应用性,采用曝气生物滤池工艺,研究了TAD1在温度为50℃的异养硝化-反硝化性能.结果表明,TAD1在曝气生物滤池中可同时进行好氧反硝化和异养硝化.当分别以硝氮、氨氮及硝氮和氨氮为氮源时,12 h的氮去除率均达到100%,氮的去除能力分别为12.67 mg.L-.1h-1、3.62 mg.L-.1h-1及16.53 mg.L-.1h-1.虽然在脱氮过程中,亚硝盐在6 h迅速积累到76 mg.L-1(硝氮为氮源)和52.6 mg.L-1(硝氮和氨氮为氮源),但在随后的几个小时内又快速降低至0(检测限之外).因而,TAD1具有应用于高温生物脱氮工艺的能力和优势.     

Analysis of AchE and LDH in mollusc, Lamellidens marginalis after exposure to chlorpyrifos

The enzymes Acetylcholinesterase (AchE) and Lactatedehydrogenase (LDH) are used as biological markers in the present study. Enzymes are highly sensitive and used to evaluate the biological effects of organophosphate pesticide chlorpyrifos in freshwater mussel Lamellidens marginalis. The test organisms were exposed to sub-lethal concentration (5 ppm) of chlorpyrifos for 30 days and allowed to recover for seven days. A distinct reduction of the enzyme AchE (34 +/- 3.3 U l(-1)) was found in the treated hepatopancreas. A significant increase in LDH activity in gill, hepatopancreas and muscle was observed. There was a significant recovery in AchE and LDH in the different tissues, after seven days recovery period.. Hence, the changes in the enzymes are found as the best biomarkering tool to evaluate the effect of organophosphate pesticide chlorpyrifos on the aquatic biota.     

太湖流域典型地区农村生活污水中污染物在表层土壤中的削减特征与测算

原位采集太湖流域典型平原河网地区农户化粪池排污口附近的表层土壤及化粪池出水,人工模拟研究区域典型降雨（夏季30 mm·次-1,冬季5mm·次-1）、气温（夏季27℃,冬季5℃）条件以及排污负荷[TN：（2.35±0.06） g·m^-2 ·d^-1,NH4＋-N：（2.08±0.04）g·m^-2· d^-1,TP：（0.21±0.01）g·m^-2·d^-1,COD：（11.14±0.59）g·m^-2·d^-1],并进行室内模拟土柱试验,测算不同季节（夏季和冬季）、不同天气过程（雨前、雨天和雨后）排污口表层土壤对农村生活污水各类污染物的削减率并探讨其削减规律.结果表明：在季节差异上,雨前、雨天和雨后TN削减率均表现为夏季＜冬季（P＜0.05或P＜0.001）,NH4＋-N削减率则均表现为夏季＞冬季（P＜0.01）;雨前和雨后TP削减率表现为夏季＞冬季（P＜0.001）,COD削减率无显著季节性差异;雨天TP和COD削减率则均表现为夏季＜冬季（P＜0.01或P＜0.001）.在天气过程差异上,夏季土壤TN削减率表现为雨后＞雨前＞雨天（P＜0.01）,夏季TP和COD削减率表现为雨前≈雨后＞雨天（P＞0.05,P＜0.01）,而夏季NH4＋-N,冬季TN、NH4＋-N、TP和COD削减率在不同天气过程之间无显著差异（P＞0.05）.据此划分,夏季雨前、雨天和雨后及冬季TN削减率分别为38.5％、-25.0％、46.0％和50.4％,夏季和冬季NH4＋-N削减率分别为91.5％和85.5％,夏季雨天、夏季其余时间及冬季TP削减率分别为63.3％、93.1％和82.7％,夏季雨天及其余时间COD削减率分别为8.2％和66.2％.     

生物法-人工湿地组合工艺对小城镇混合污水氮素去除效果研究

在华南热带亚热带地区,利用生物法-人工湿地组合工艺（A/BCO-CW）处理小城镇片区混合污水。全年运行结果表明,A/BCO-人工湿地组合系统对TN和NH4-N具有好的处理效果,年均去除率分别为57.57%、87.73%,平均去除负荷量达到3.85和3.26g·m-2·d-1。A/BCO预处理系统在停留时间为3～6h条件下,对NH4-N去除效率达57.38%,好氧段充分曝气,有利于硝化过程的进行,有效地解决人工湿地因溶解氧不足造成的硝化过程受限制情况,减少了后续湿地所需面积的25%。在0.30～0.59m·d-1水力负荷率下,垂直流-表面流-水平潜流人工湿地组合系统对TN和NH4-N平均去除负荷达到了2.56、0.90g·m-2·d-1;TN、NH4-N去除速率常数为39.8和41.62m·yr-1,这些数值均处于文献中k值范围的高量程内。在进水NH4-N变动范围为6.27～18.8mg·L-1时,出水水质均能稳定达到GB3838—2002《地表水环境质量标准》的IV类水1.5mg·L-1的标准。通过探讨A/BCO-CW组合工艺用于混合污水处理效率,实现了A/BCO和CW二者间在处理氮素过程中的优势互补。     

利用根箱法解析水稻根际土壤中氮的行为

为研究水田土壤中氮的行为,施给15NH4 或15NO3-标记的硝胺(NH415NO3或15NH4NO3)的沙壤土(Shirasu soil)添充在根箱里,对Japonica水稻(品种Hinohikari)进行温室栽培6周.收割后,水稻植株分地上部和根部,对各自的全氮,15N atom％进行测定.根箱各区域的土壤按着鲜土形态进行采取后,对此全氮,NO3-N,水溶性NH4-N,KCl抽出NH4-N和其各自的15N atom％进行测定.研究结果表明,土壤全氮含量与栽培前相比,在非根际明显降低,但在根际比非根际要高,保持了与栽培前相同的水平.土壤NO3-N浓度从非根际到根际递增,但与其栽培前相比显著地降低,在整个根箱里,施给NO3-N的79％为因脱氮而损失.土壤中NO3-N的大部分来自于土壤氮化合物,来自施肥的比例却较低,尤其是在根际.反而,施给NO3-N的残存率约仅为16％左右,但其中有机态氮所占的比率在非根际里55％～86％,在根际却达到了93％.土壤水溶性NH4-N和KCl抽出NH4-N浓度靠近根际逐渐降低,而且在非根际两者匀由1∶10的比例存在,但在根际里水溶性NH4-N没被检索到.在非根际里,土壤KCl抽出NH4-N的35％～66％为来自施肥,但其比例在根际里却降到15％左右.在土壤中残存的来自施给NH4-N的氮化合物之中,有机态氮所占的比例在非根际里约为11％～65％,但在根际却达到了92％.以上结果表明,在水稻根际,氮的无机化和有机化的活性比非根际显著.     

利用根箱法解析甜椒根际土壤中氮的行为(英文)

为研究甜椒根际土壤中氮的行为,与既报同样的方法进行研究,即,利用15NH4+,15NO3-双标记的硝胺(NH,4>15NO3,15NH4NO3),在温室里对甜椒进行6周的根箱栽培.收割后,对土壤全氮,NO3-N,水溶性NH4-N,KCl抽出NH4-N和其各自的15N atom%进行测定.结果表明,土壤全氮从非根际到根际逐渐增加,与栽培前相比,土壤全氮在非根际中减少,却在根际中增大.土壤NO3-N浓度朝根际增加到离根际2 mm处,然后激减到根际.NO3-N的来自施给NO3-N的比例靠近根际逐渐升高,在根际达到了69%,反而,来自施给NH4-N的比例靠近根际逐渐降低,在根际将至7%左右.水溶性NH4-N和KCl抽出NH4-N浓度靠近根际逐渐降低,而且,从非根际到根际,二者匀保持3∶10的比例.KCl抽出NH4-N的来自施给NO3-N的比例靠近根际逐渐升高,但在根际仍低于3%,反而,其来自施给NH4-N的比例在非根际约为47%～55%,在根际降到41%.在整个根箱里,施用NO3-N的有機率达到62%,但其值在根际比非根圈要低.相反,施用NH4-N的有機率仅11%左右,但其值在根际比非根际要高.以上结果表明,在甜椒根际土壤中氮的无机化-有机化活性与水稻相比显著低.     

南四湖沉积物营养盐释放特性

通过营养盐静态释放模拟试验,研究了南四湖沉积物NH4＋-N、TP和有机质（OM）的释放能力;针对微山湖区（WS）沉积物氮含量较高、释放较强的特点,为明晰WS湖区的氮释放潜力,考察了该湖区16个点位沉积物对NH4＋-N的等温吸附特性.静态释放试验表明,沉积物TP和OM释放能力较弱,对南四湖上覆水水质影响不明显;而WS湖区的NH4＋-N释放能力较强.WS湖区沉积物的NH4＋-N等温吸附试验表明,湖心区沉积物NH4＋-N释放能力最强,吸附/解吸平衡浓度（CEAC）高于1 mg.L-1的区域面积约占微山湖的1/5,该区域沉积物NH4＋-N释放将会对南水北调东线调水水质产生不利影响.     

三江平原农田源头排水沟渠截留排水中氮素动态

通过小尺度野外原位试验,研究排水沟渠水体、底泥和植物中氮含量的变化规律.结果表明,随水体停留时间增加,沟渠对水体氮素的净化能力增强,认为停留8d左右较适宜.沟渠对NH4-N的截留率大于TN和NO3--N.渠水停留11d时,4条试验沟渠[氮浓度高、磷浓度低(NHPL),氮浓度高、磷浓度高(NHPH),氮浓度低、磷浓度低(NLPL),氮浓度低、磷浓度高(NLPH)]对NH4+-N的截留率均达100％,对NO3--N的截留率分别为84.63％、84.35％、75.67％和76.14％,对TN的截留率分别为88.02％、89.89％、90.88％和88.53％.试验结束时沟渠表层(0～15 cm)底泥氮含量降低,植物氮累积量远大于进水TN总量,说明植物生长同时吸收了水体、土壤和底泥中的氮,建议在秋季适时收割植物,以避免植物分解导致二次污染.     

厌氧消化过程中Fe,Co,Ni对NH4^＋—N的拮抗作用

论文以血清瓶为间歇反应器，以醋酸钙为基质，研究了厌氧消化过程中甲烷菌所需要的微量金属营养元素Ｆｅ、Ｃｏ、ＮＩ（１．０ｍｇ／（Ｌ．ｄ），０．１ｍｇ／（Ｌ．ｄ），０．２ｍｇ／（Ｌ．ｄ）对毒性物质ＮＨ４＾＋－Ｎ的拮抗作用，研究结果表明，Ｆｅ、Ｃｏ、Ｎｉ对毒性物质ＮＨ４＾＋－Ｎ有明显的拮抗作用，而且ＮＨ４＾＋－Ｎ浓度越高，Ｆｅ、Ｃｏ、Ｎｉ对其毒性的拮抗作用越明显。     

施用尿素和硫酸铵对红壤硝化和酸化作用的影响

通过室内恒温培养试验,研究施用CO(NH2)2和(NH4)2SO4对初始pH值分别为5.14、4.77和4.34的红壤酸化速率和硝化速率的影响。结果表明,施用CO(NH2)2显著增加了3种红壤的硝化速率,从而显著加速土壤酸化。培养结束时,3种红壤pH值较培养过程中最高值分别下降2.14、1.23和0.56。施用(NH4)2SO4抑制了初始pH<5.0的2种红壤的硝化作用,从而显著降低这2种红壤的硝化速率和酸化速率,但显著增加了初始pH>5.0红壤的硝化速率,对其酸化速率则未见显著影响。3种红壤的酸化速率与硝化速率间存在显著线性相关关系。硝化作用是导致农田红壤pH值下降的主要原因之一,但不同氮肥对红壤硝化速率和酸化速率的影响不同。     

新疆盐渍化土壤氮肥氨挥发损失特征初步研究

在室温下应用“静态吸收法”,研究不同盐渍化程度的盐化土壤和碱化土壤上氮肥氨挥发损失特征。结果表明:(1)除碱土外碱化土壤上氮肥氨挥发量随时间延长呈现下降趋势,在盐化土壤上氨挥发量随时间呈现先上升后下降趋势。(2)供试9个典型盐渍化土壤样品上氮肥氨挥发量(Y)与时间(t)关系均符合Y=at2 bt c动力学方程,相关性呈极显著水平。(3)氨挥发总量(Y)、氨挥发速率(Yi)与土壤含盐量(x)呈极显著正相关;氨挥发持续时间随着盐渍化程度的增加而延长。(4)氨挥发总量、挥发速率与盐渍土pH相关性未达到显著水平;盐渍土上pH值对氨挥发的影响需要进一步研究。以上结果表明,盐渍化耕作土壤上氮肥氨挥发的控制要依据盐渍化类型的不同而制定相应的措施。