闽江下游水环境问题浅析

分析闽江下游的水环境问题是:南、北港分流比变化造成北港冲刷,南港淤积,并带来严重后果;河道采砂过量使河床下切严重,破坏水工建筑物;水质存在一些问题,影响生活及工业用水;湿地遭到破坏,导致温地动植物数量与种类大量减少.针对这些问题,提出解决闽江下游水环境问题需要设计南、北港水量科学合理分配方案;设计合理的河道采沙方案;加强污水管理体制;对闽江河口湿地分区保护和管理;加强河道的监测工作;加强公众环境保护教育.要使专家研究、政府管理和提高公众环保意识相结合.     

河口湿地近地面大气 CO2浓度日变化和季节变化

2011年12月~2012年11月对闽江河口湿地近地面大气CO2浓度(摩尔分数)进行观测,研究CO2浓度的日变化和季节变化特征,结果表明,闽江河口湿地近地面大气CO2浓度的日变化和季节变化都呈典型的"单峰型",表现为"昼低夜高"和"夏低冬高"的规律,日变幅在16.96~38.30μmol·mol-1之间.春、夏、秋、冬这4个季节近地面大气CO2平均浓度分别为(353.74±18.35)、(327.28±8.58)、(354.78±14.76)和(392.82±9.71)μmol·mol-1,而年平均浓度为(357.16±26.89)μmol·mol-1.闽江河口湿地近地面大气CO2浓度的日变化与温度、风速、光合有效辐射、总辐射等主要气象因子呈负相关关系(P<0.05),而1月近地面大气CO2浓度日变化与潮汐水位呈负相关,7月与潮汐水位呈正相关.     

湿地植物对外源氮、磷输入的响应研究

通过人工控制试验,研究了氮、磷输入对沼泽湿地植物地上生物量,相对密度以及植物对氮、磷吸收量的影响.结果表明:营养物质氮、磷的长时间累积,导致湿地植物地上生物量和相对密度均呈逐渐下降的年际变化趋势,地上生物量和相对密度之间表现为微弱的单峰变化关系.在氮输入下,随着氮施用量的升高,氮的吸收率从62.3%下降到5.5%;在磷输入下,随着磷施用量的升高,磷的吸收率从3.1%下降到0.8%.氮、磷的施用量愈高,植物对氮、磷的吸收率愈小.氮、磷输入有可能改变湿地生态系统的物种组成和结构及湿地生态系统的稳定和保护,应当考虑湿地中营养物质的长期作用.      

模拟SO42-沉降对闽江河口潮汐淡水湿地温室气体排放通量的影响

为了探究SO₄2-沉降对潮汐淡水湿地温室气体排放通量的影响,在闽江河口短叶茳芏（Cyperus malaccensis）潮汐淡水湿地模拟SO₄2-沉降,采用静态箱法测定样地环境因子与3种温室气体（CH₄、CO₂、N₂O）通量随SO₄2-添加量和不同月份的变化,采用多元逐步回归分析影响温室气体通量的关键因子.结果表明:①各环境因子和3种温室气体通量均具有显著的月际变化. ②添加SO₄2-显著增加了短叶茳芏种群密度和间隙水ρ（SO₄2-）、ρ（NH₄+-N）,但对其他环境因子无显著影响. ③添加SO₄2-显著抑制了CH₄排放,当SO₄2-添加量（以SO₄2--S计,下同）为40和120 kg/（hm2·a）时,CH₄通量分别减少了33.8%、69.9%;CO₂和N₂O通量随SO₄2-添加量的变化不显著,但分别趋于减小和增加,其中,SO₄2-添加量为40和120 kg/（hm2·a）时,CO₂通量分别减少了5.2%、11.8%,N₂O通量则分别增加了98.0%、103.0%. ④相关分析和多元逐步回归分析结果显示,沉积物温度及间隙水ρ（SO₄2-）、ρ（NH₄+-N）、ρ（NO_x--N）（NO_x--N主要包括NO₃--N和NO₂--N）是影响样地3种湿地温室气体排放通量的关键因子. ⑤当SO₄2-添加量为40和120 kg/（hm2·a）时,3种温室气体排放产生的综合温室效应呈减小趋势,分别降低了5.5%和13.5%.研究推断,SO₄2-沉降速率的升高有助于缓解潮汐淡水湿地对全球气候变暖的贡献.      

Sediment manganese and biogenic silica as geochemical indicators in estuarine salt marshes of coastal Georgia, USA

Salt-marsh estuarine sediments are not homogeneous. It is obvious that a steady state cannot be assumed if the depositional environments under which salt marshes accumulate change from subtidal through non-vegetated intertidal to vegetated intertidal state during their formation. In addition to these, the supply of sedimentary material depends on the tidal prism which changes as salt marshes are formed. Based on the study of cores collected in the estuarine region of Georgia, USA, it was found that the Mn/Al ratios in sediments of marsh cores change from subtidal through non-vegetated intertidal to vegetated intertidal. The relative variation of biogenic silica preserved in sediments of marsh core reflects the relative supply rate of organic carbon (phytoplankton) produced in the water column to the sediment surface at the time of deposition. In this paper it is proposed that sediment manganese and biogenic silica may be applied as geochemical indicators of changing depositional environments and organic carbon originating from phytoplankton in the estuarine salt marsh sediments.     

近25a来江苏中部沿海盐沼分布时空演变及围垦影响分析

江苏沿海海涂广阔,其上分布着种类众多的盐沼植被。近些年来,大范围的围垦活动导致盐沼分布发生了巨大变化,充分把握围垦活动下盐沼分布与扩张规律,可为滩涂资源开发和环境保护提供决策支持。基于此,研究结合了NDVI和局部OTSU方法通过遥感影像提取了近25 a间7个时期的江苏中部沿海的盐沼并数字化出各时期新增垦区,利用GIS技术分析了盐沼分布的时空演变并讨论了盐沼对滩涂围垦的响应。结果表明:1盐沼面积历经先增后减的过程,26 a间约减少10%,在2000年后堤外盐沼宽度与覆盖度不断降低,盐沼分布由弶港北岸多、弶港南岸少的格局逐渐转变为新洋至斗龙港口岸段多、其余海岸少的格局;2滩涂围垦造成的盐沼消亡面积达569.47 km2,占盐沼消亡总量的85.4%,对弶港以北盐沼影响极大;3潮间带的围垦活动能够改变原潮滩的沉积环境,对盐沼扩张起到了一定的推动作用,这意味着盐沼有望在围垦后得以逐步恢复,但若围垦太快,堤外余留盐沼过少,盐沼恢复将难以为继。     

Response of gaseous carbon emissions to low-level salinity increase in tidal marsh ecosystem of the Min River estuary, southeastern China

Although estuarine tidal marshes are important contributors to the emission of greenhouse gases into the atmosphere, the relationship between carbon dioxide(CO_2), methane(CH_4)emission, and environmental factors, with respect to estuarine marshes, has not been clarified thoroughly. This study investigated the crucial factors controlling the emission of CO_2 and CH_4from a freshwater marsh and a brackish marsh located in a subtropical estuary in southeastern China, as well as their magnitude. The duration of the study period was November 2013 to October 2014. Relevant to both the field and incubation experiments, the CO_2 and CH_4emissions from the two marshes showed pronounced seasonal variations. The CO_2 and CH_4emissions from both marshes demonstrated significant positive correlations with the air/soil temperature(p 0.01), but negative correlations with the soil electrical conductivity and the pore water/tide water Cl-and SO_4~(2-)(p 0.01). The results indicate no significant difference in the CO_2 emissions between the freshwater and brackish marshes in the subtropical estuary, whereas there was a difference in the CH_4 emissions between the two sites(p 0.01). Although future sea-level rise and saltwater intrusion could reduce the CH_4 emissions from the estuarine freshwater marshes, these factors had little effect on the CO_2 emissions with respect to an increase in salinity of less than 5‰. The findings of this study could have important implications for estimating the global warming contributions of estuarine marshes along differing salinity gradients.     

Consumer Control of Salt Marshes Driven by Human Disturbance

Abstract:  Salt marsh ecosystems are widely considered to be controlled exclusively by bottom–up forces, but there is mounting evidence that human disturbances are triggering consumer control in western Atlantic salt marshes, often with catastrophic consequences. In other marine ecosystems, human disturbances routinely dampen (e.g., coral reefs, sea grass beds) and strengthen (e.g., kelps) consumer control, but current marsh theory predicts little potential interaction between humans and marsh consumers. Thus, human modification of top–down control in salt marshes was not anticipated and was even discounted in current marsh theory, despite loud warnings about the potential for cascading human impacts from work in other marine ecosystems. In spite of recent experiments that have challenged established marsh dogma and demonstrated consumer-driven die-off of salt marsh ecosystems, government agencies and nongovernmental organizations continue to manage marsh die-offs under the old theoretical framework and only consider bottom–up forces as causal agents. This intellectual dependency of many coastal ecologists and managers on system-specific theory (i.e., marsh bottom–up theory) has the potential to have grave repercussions for coastal ecosystem management and conservation in the face of increasing human threats. We stress that marine vascular plant communities (salt marshes, sea grass beds, mangroves) are likely more vulnerable to runaway grazing and consumer-driven collapse than is currently recognized by theory, particularly in low-diversity ecosystems like Atlantic salt marshes.     

Bacterial Degradation of Vegetable Oils

Following initial experiments presented elsewhere (2IOPS), the bacterial degradation of two vegetable oils was investigated in some detail. the number of aerobic and anaerobic heterotrophic bacteria, oil degrading and sulphate reducing bacteria were quantified during simulated spills on a salt marsh. the sediment fatty acid composition was also studied using GC-MS analysis. Degradation of linseed and sunflower oils was concomitant with an increase in the numbers of aerobic and anaerobic bacteria. Fatty acids analysis revealed preferential degradation of the principal components of the oils (18:3ω3 for linseed oil and 18:2ω6 for sunflower oil). the presence of several isomers of the usual polyunsaturated fatty acids was also detected. the identification of some of these new fatty acids has been carried out. Possible pathways of degradation of these vegetable oils are suggested.     

Tidal salt marsh sediment in California, USA. Part 2: occurrence and anthropogenic input of trace metals

Surface sediment samples (0–5 cm) from 5 tidal salt marshes along the coast in California, USA were analyzed to investigate the occurrence and anthropogenic input of trace metals. Among study areas, Stege Marsh located in the central San Francisco Bay was the most contaminated marsh. Concentrations of metals in Stege Marsh sediments were higher than San Francisco Bay ambient levels. Zinc (55.3–744 μg g⁻¹) was the most abundant trace metal and was followed by lead (26.6–273 μg g⁻¹). Aluminum normalized enrichment factors revealed that lead was the most anthropogenically impacted metal in all marshes. Enrichment factors of lead in Stege Marsh ranged from 8 to 49 (median = 16). Sediments from reference marshes also had high enrichment factors (2–8) for lead, indicating that lead contamination is ubiquitous, possibly due to continuous input from atmospherically transported lead that was previously used as a gasoline additive. Copper, silver, and zinc in Stege Marsh were also enriched by anthropogenic input. Though nickel concentrations in Stege Marsh and reference marshes exceeded sediment quality guidelines, enrichment factors indicated nickel from anthropogenic input was negligible. Presence of nickel-rich source rock such as serpentinite in the San Francisco Bay watershed can explain high levels of nickel in this area. Coefficients of variation were significantly different between anthropogenically impacted and non-impacted metals and might be used as a less conservative indicator for anthropogenic input of metals when enrichment factors are not available.