粤东柘林湾柱状沉积物中氮、磷的垂直分布

对柘林湾代表性水区柱状样沉积物中不同形态氮、磷的含量进行了分析,研究了其垂直分布规律及其历史演变趋势。研究结果显示,除湾西北三百门(S2站)和湾中央大规模网箱渔排养殖区中心(S6站)外,其余各测站柱状沉积物中的有机氮(TOM)、凯氏氮(TKN)及各形态磷含量基本呈现"沉降-降解-堆积"三阶段的分布特征,反映了成岩作用的结果。S2、S6测站柱状沉积物中的多项氮磷指标,在表层10 cm以深不降反升与这两测站的高污染压力和弱水体交换能力导致的污染物快速堆积有关。底栖动物对沉积物垂直方向的扰动可能是各氮磷指标在沉降和降解阶段产生波动变化的重要原因之一,但生物扰动对NH4 的垂直变化影响最大。自生磷(Au-P)与有机磷(OP)在表层以下随深度呈一定的镜像关系,与Au-P和OP在成岩过程中的相互转化有关。Au-P随深度的变化幅度比OP的大,表明磷在Au-P和OP之间的转移并不是磷再分配的唯一途径,其它形态的磷也可能参与磷的再分配,而两者在表层不呈镜像关系主要与微生物对两者的降解有关。     

A Meta-analysis of the Effects of Organic and Inorganic Fertilizers on the Soil Microbial Community

In order to investigate the general tendency of soil microbial community responses to fertilizers, a meta-analysis approach was used to synthesise observations on the effects of inorganic and organic fertilizer addition (N: nitrogen; P: phosphorus; NP: nitrogen and phosphorus; PK: phosphorus and potassium; NPK: nitrogen, phosphorus and potassium; OF: organic fertilizer; OF+NPK: organic fertilizer plus NPK) on soil microbial communities. Among the various studies, PK, NPK, OF and OF+NPK addition increased total phospholipid fatty acid (PLFA) by 52.0%, 19.5%, 334.3% and 58.3%, respectively; while NP, OF and OF+NPK addition increased fungi by 5.6%, 21.0% and 8.2%, respectively. NP, NPK and OF addition increased bacteria by 6.4%, 9.8% and 13.3%, respectively; while NP and NPK addition increased actinomycetes by 7.0% and 14.8%, respectively. Addition of ammonium nitrate rather than urea decreased gram-negative bacteria (G ^-). N addition increased total PLFA、bacteria and actinomycetes in croplands, but decreased fungi and bacteria in forests, and the F/B ratio in grasslands. NPK addition increased total PLFA in forests but not in croplands. The N addition rate was positively correlated with the effects of N addition on gram-positive bacteria (G ⁺) and G ^-. Therefore, different fertilizers appear to have different effects on the soil microbial community. Organic fertilizers can have a greater positive effect on the soil microbial community than inorganic fertilizers. The effects of fertilizers on the soil microbial community varied with ecosystem types. The effect of N addition on the soil microbial community was related to both the forms of nitrogen that were added and the nitrogen addition rate.     

Carbon and nitrogen primary productivity in three North Carolina estuaries

Uptake of inorganic carbon and ammonium by the plankton community of three North Carolina estuaries was measured using ¹⁴C and ¹⁵N isotope methods. At 0% light, C appeared to be lost via respiration, and at increasing light levels uptake of inorganic carbon increased linearly, saturated (mean I_k = 358±30 μEin m⁻² s⁻¹), and frequently showed inhibition at the highest light intensities. At 0% light NH₄⁺ uptake was significantly greater than zero and was frequently equivalent to uptake in the light (light independent); at increasing light levels NH₄⁺ uptake saturated (mean I_k = 172±44 μEin m⁻² s⁻¹) and frequently indicated strong inhibition. Light-saturated uptake rates of inorganic carbon and NH₄⁺ were a function of chlorophyll a (r² = 0·7−0·9); average assimilation numbers were 625 nmol CO₂ (μg chl. a)⁻¹ h⁻¹ and 12·9 nmol NH₄⁺ (μg chl. a)⁻¹ h⁻¹ and were positively correlated with temperature (r² = 0·3−0·7). The ratio of dark to light-saturated NH₄⁺ uptake tended to be near 1·0 for large algal populations at low NH₄⁺ concentrations, indicating near light independence of uptake; whereas the ratio was lower for the opposite conditions. These data are interpreted as indicative of nitrogen stress, and it is suggested that uptake of NH₄⁺ deep in the euphotic zone and at night are mechanisms for balancing the C:N of cellular pools. A 24-h study using summed short-term incubations confirmed this; the cumulative C:N of CO₂ and NH₄⁺ uptake during the daylight period was 10–20, whereas over the 24-h period the ratio was 6 due to dark NH₄⁺ uptake. Annual carbon and nitrogen primary productivity were respectively estimated as 24 and 4·0 mol m⁻² year⁻¹ for the South River estuary, 42 and 7·3 mol m⁻² year⁻¹ for the Neuse River estuary, and 9·6 and 1·6 mol m⁻² year⁻¹ for the Newport River estuary.     

Water quality in New Zealand rivers: current state and trends

River water quality, particularly in lowland catchments, is a matter of concern to the New Zealand public. We assessed river water quality and biological state and trends using data from more than 900 monitoring sites. Parallel state and trend analyses were carried out using all sites and a subset of lowland river sites. Median water-quality state in urban and pastoral land-cover classes was poorer than in exotic forest and natural land-cover classes, and lowland sites in the urban and pastoral classes had the poorest water quality. Nutrient and Escherichia coli concentrations increased and visual clarity and Macroinvertebrate Community Index scores decreased as proportions of catchments in high-intensity agricultural and urban land cover increased. Ten-year trends (2004–2013) indicated recent improvements in ammoniacal nitrogen, dissolved reactive phosphorus and total phosphorus in the pastoral and urban classes, possibly reflecting improved land management. In contrast, trends in nitrate-nitrogen in the exotic forest and cool-dry/pastoral classes indicated worsening conditions.     

Sedimentary records of eutrophication in the Changjiang Estuary upwelling area over last 100 a

The upwelling area in the Changjiang Estuary was selected to collect the core, where the red tide occurred frequently and hypoxic existed. The total organic carbon （TOC）, total nitrogen （TN）, biogenic silica （BSi） and stable organic carbon isotopic ratios（δ13 Corg） were determined on the 210pb-dated sediment core. The concentrations of TOC, TN, BSi as well as their sedimentation fluxes have in- creased to some extent since the 1970s. TOC and TN fluxes increased about 45%, 36% respectively. The average δ13 Coorg value in the core was -23.67 ×10^-3 which remained nearly constant before the 20 century. The δ13 Corg values increased after the 1900s, two marked increases were observed from the 1950s and the 1970s. A simple δ13 Cors model was used to estimate the contribution of terrigenous and marine organic matter inputs for the sediment, which indicated the increase in accumulation since the 1970s has been almost exclusively marine. The increasing of marine organic matter accumulation （TOC, TN and BSi） was corresponding with the increasing of fertilizer consumption and the NO3-N budgets from the Changjiang River. The riverine runoff of fertilizers and nutrients stimulated the algae blooming. Enhanced primary production resulted in an enrichment of organic matter in the sediment. These data support the hypothesis that anthropogenic nutrient loading has been a significant factor on the eutrophication in the Changjiang Estuary.     

The distribution of dimethylcarbazoles in oils from the Pearl River Mouth Basin, South China Sea

C2-carbazole isomers have been investigated in crude oils from the Hui-Liu Structure Ridge (HLSR) in the Pearl River Mouth Basin (PRMB), South China Sea. The NH shielded isomer, as well as the NH partially shielded isomers, was detected in high abundance and the NH exposed isomers in lower abundance. A small-enrichment trend of 1,8-dimethylcarbazole (DMC) was observed in crude oils along the western part of HLSR (WPHLSR), which may indicate little effect of migration on the C2-carbazole distributions. Two strikingly different distribution patterns of NH partially shielded isomers were observed in the reservoirs along the WPHLSR: one with a preference of 1,3- and 1,6-DMCs and the other with a preference of 1,4- and 1,5-DMCs. All of the oils occurring in the Upper reservoirs have a preference of 1,3- and 1,6-DMCs, whereas those trapped in the Lower reservoirs show a preference of 1,4- and 1,5-DMCs, which may indicate there are two petroleum migration systems in the WPHLSR.     

Determination of Carbon,Hydrogen, Nitrogen and Sulfur in Geological Materials Using Elemental Analysers

This article describes a series of methods developed for the determination of total carbon (C_Total), organic carbon (C_org), hydrogen, nitrogen and sulfur. The following elemental analysers were used: LECO model RC‐412 for the determination of organic carbon, total carbon and hydrogen; LECO model CS‐200 for the determination of total carbon and sulfur; LECO model TN‐400 for the determination of nitrogen; and LECO model TruSpec CHNS for the determination of organic carbon, total carbon, hydrogen, nitrogen and sulfur. Uncertainty and limits of detection and quantification were calculated for each method, as well as the running costs to define the most effective instrument for each material and each analyte. Accuracy was checked by the application of the Sutarno–Steger test. Finally, a compilation of the results obtained in the determination of C_Total, C_org, H, N and S in forty‐nine reference materials is presented.     

长春市土壤重金属污染特征及其潜在生态风险评价

以长春市区土壤为对象,研究土壤中重金属污染的特征,并采用Hakanson提出的潜在生态危害指数法对土壤中重金属的潜在生态危害进行了评价。结果表明,长春市区土壤重金属污染较重,尤其是铅和镍。污染源的空间差异性引起不同功能区土壤中重金属元素的含量不同。长春市土壤达到轻微生态危害,且铅、铜和锌对土壤生态危害达到轻微生态危害;不同功能区达到生态危害程度的顺序依次是公园>郊区耕地>工业区>住宅区>开发区。     

太湖梅梁湾沉积物中氮铁硫转化细菌的毫米级垂向分布及对氮磷迁移转化的潜在影响

本研究在太湖梅梁湾采集沉积柱,采用一种自制的毫米级柱状沉积物自动垂向分层切割装置对表层50 mm沉积物进行垂向切割(间隔2 mm),结合高通量测序技术分析沉积物中细菌群落的毫米级垂向分布;同时采用毫米级高分辨透析技术和薄膜扩散梯度技术(DGT)分析溶解态和DGT可获取态铵态氮(NH₄⁺-N)、硝态氮(NO₃^--N)、Fe、P的垂向分布特征。结果显示,沉积物中细菌群落与溶解态和DGT可获取态氮铁磷浓度在垂向上呈现显著的异质性。细菌硝酸盐还原主要发生在-16～0 mm沉积物深度,这可能导致了溶解态和DGT可获取态NO₃^--N含量在该沉积物深度的明显减少。细菌铁还原主要分布在-32～-18 mm沉积物深度,细菌硫酸盐还原主要分布在-50～-34 mm的沉积物深度;细菌硫酸盐还原是导致沉积物溶解态和DGT可获取态铁磷浓度从-32 mm随沉积物的深度增加而显著增加的主要原因。本研究加深了对富营养化湖泊沉积物中细菌影响氮磷在垂向上迁移转化的认识。     

Lagged response of phytoplanktonic photosynthetic competence to variation of nitrogen concentration in Jiaozhou Bay, China

Fluorescence-based maximal photochemical efficiency, Fv/Fm, is widely used as an indicator to photosynthetic competence in marine systems. It has been considered a useful parameter diagnosing the nutrient stress on phytoplankton photosynthesis, but many studies argue its usefulness. In the present study, we try to find a temporal relationship between Fv/Fm and nitrogen concentration, and provide a possible explanation on the controversy. We continuously measured Fv/Fm and nitrogen concentration once every 10 days from September 2003 to March 2004 at two stations in Jiaozhou Bay, northern China. It was found that Fv/ffm did not significantly correlate to synchronous nitrogen concentration, but the variation （i.e. the change between two adjacent cruises） of nitrogen concentration of the previous cruise and the variation ofFv/Fm of the current cruise were strongly correlated. This result indicates that a time lag exists between the variation of nutrient status and the subsequent Fv/Fm response. Length of the time lag seems just matched the interval of our measurements （10 days）. In the field, direct dependence of Fv/Fm on nitrogen concentration may not be found because of the lagged response of Fv/Fm to nitrogen concentration variations or physiological acclimation. Our results provide a possible way to explain the previously reported conflicting results on the relationship between Fv/Fm and nutrient status. To give a more-accurate estimate about the length of the time lag, an investigation that includes more frequent measurements is needed.