Large-scale shrimp farming in coastal wetlands of Venezuela,South America: Causes and consequences of land-use conflicts

In Venezuela, large-scale shrimp farming began in the 1980s. By 1987, the Ministry of Environment and Natural Resources (MARNR) had received 14 proposals for approval. A developer illegally started the construction of ponds at the Píritu Lagoon in the State of Anzoátegui before the authorization process was completed. This action triggered a land-use conflict. This study identifies the causes for public protest and determines the consequences of this conflict for land-use management. The results show that public protest was based on the impacts of the partial construction of ponds. These impacts were related to direct removal of wetlands, interruption of natural patterns of surface flows, and alteration of feeding grounds of some bird species with migratory status. Consequences were identified in relation to the role that nongovernmental organizations (NGOs) play in land-use conflicts and the actions that MARNR could take in the future to prevent and solve similar situations.     

A proposed methodology for measuring incremental environmental benefits from using constructed wetlands to control agricultural non-point-source pollution

A binary response estimation procedure using contingent valuation data is proposed for estimating the incremental environmental benefits associated with the use of constructed wetlands to control agricultural waste-water runoff. The model uses two binary responses per individual while circumventing the non-independence problems associated with follow-up valuation questions. Case study results suggest that the methodology provides a potentially effective means for measuring the non-market benefits of constructed wetlands in addition to water-quality maintenance.1998 Academic Press     

QUANTIFICATION OF THE WATER BUDGET AND NUTRIENT LOADING IN A SMALL PEATLAND1

ABSTRACT: Few water budgets exist for specific types of wetlands such as peatlands, even though such information provides the basis from which to investigate linkages between wetlands and upland ecosystems. In this study, we first determined the water budget and then estimated nutrient loading from an upland farm field into a 1.5 ha, kettle-block peatland. The wetland contains highly anisotropic peat and has no distinct, active layer of groundwater flow. We estimated the depth of the active layer using Fick's law of diffusion and quantified groundwater flow using a chemical mass balance model. Evapotranspiration was determined using MORECS, a semi-physical model based on the Penman-Monteith approach. Precipitation and surface outflow were measured using physical means. Groundwater provided the major inflow, 84 percent (44,418 m³) in 1993 and 88 percent (68,311 m³) in 1994. Surface outflow represented 54 percent (28,763 m³) of total outflows in 1993 and 48 percent (37,078 m³) in 1994. A comparison of several published water budgets for wetlands and lakes showed that error estimates for hydrologic components in this study are well within the range of error estimates calculated in other studies. Groundwater inflow estimates and nutrient concentrations of three springs were used to estimate agricultural nutrient loading to the site. During the study period, nutrient loading into the peatland via groundwater discharge averaged 24.74 kg K ha^-1, 1.83 kg total inorganic P ha^d, and 21.81 kg NO₃-N ha^-1.     

围垦对海滨地区景观演变及其质心移动的影响——以盐城保护区部分区域为例

将盐城国家级自然保护区(新洋港-四卯酉河段)划分为未围区和围垦区,根据1984-2013 年6 个时相的景观资料,运用RS、GIS 技术和景观生态学方法,分析围垦活动影响下海滨湿地景观格局演变差异。结果如下:①未围区始终保持以自然景观为主,2013 年面积比例占84.6%;1984-2013 年,芦苇和互花米草湿地面积分别增长了4 770.6 和4 202.8 hm²,而碱蓬湿地面积减少了2 656.7 hm²。围垦区大致以2000 年为界,景观结构由自然景观占主导转为人工景观为主;除互花米草外自然植被面积呈下降趋势,而人工景观中水产养殖塘面积不断上升,2013 年比例达60.5%。②未围区景观破碎度自1995 年以后变幅较小,且保持在较低水平,维持在0.27~0.28,斑块形状趋于复杂、自然,景观多样性呈上升趋势,1984-2013 年上升了0.19。围垦区破碎化程度上升明显,1984-2013 年上升了0.27,整体景观趋于简单规则,景观多样性呈下降趋势,1984-2013 年下降了0.26。③未围区景观演变驱动力以自然因素为主,景观类型质心移动具有距离较为连续、方向相对单一的特征。而围垦区由于人类活动介入,围垦区景观类型质心移动更多地表现出无序多变、错综复杂的特征。     

中国滨海湿地CH4通量研究进展

滨海湿地严格的厌氧环境造成与其面积不成比例的碳储量,同时有利于CH₄的产生。探讨滨海湿地温室气体通量,尤其是CH₄通量,对确定滨海湿地究竟是温室气体的“源”还是“汇”,评估滨海湿地对全球变化的影响具有重要的作用。论文通过对中国滨海湿地CH₄通量的排放机制、时空变化以及影响因素进行阐述总结得出：闽江河口CH₄通量明显大于长江口和黄河口,主要原因在于温度和生物量的差异;江苏滨海湿地CH₄通量的研究相对薄弱,南方红树林湿地CH₄通量的空间差异较大。潮汐对滨海湿地CH₄通量的影响呈“M”型：涨潮开始时,CH₄通量逐渐增加,随着水位的加深,逐渐减少;当落潮到最适宜产生CH₄的水位深度时,大量原先产生的CH₄开始排放出来,待水位继续下降,产生的CH₄极容易被氧化,开始减少。目前缺乏研究滨海湿地CH₄通量的标准方法,而且针对潮汐变化,微生物以及酶活性对CH₄排放的影响研究比较薄弱,在此基础上,提出了利用箱法进行CH₄通量的研究需因地制宜,依据研究目的以及植被、土壤、水文的差异选择不同的样点布设原则和采样方法。     

石灰石沟-堆肥湿地系统处理酸性矿山废水的研究

为探讨石灰石沟-潜流堆肥湿地系统处理酸性矿山废水(AMD)的效果及影响因素,进行了6个月模拟试验,测定出水水质和植物生长等相关的影响因素.结果表明,石灰石沟可有效提高AMD的pH值,降低其酸度与重金属含量,但随着石灰石沟中氢氧化物的积累,后期处理性能下降;堆肥湿地可显著降低AMD的酸度与重金属,出水酸度随时间持续降低,出水的Cd、Pb在检测限以下,Zn、Cu平均浓度分别为1.8mg/L, 2.6μg/L,均达到农业灌溉水标准,而无前置堆肥的普通湿地后期Cd、Zn、Cu偏高;东南景天在湿地系统也能正常富积Cd/Zn;狭叶香蒲使堆肥湿地的产碱过程受到抑制,出水酸度升高,但其对堆肥湿地的重金属去除没有产生显著影响.     

海菜花-螺蛳经济湿地对农田低污染水的净化

为研究海菜花水培经济湿地对农田低污染水的净化效能及投放螺蛳对水体净化的影响,在进水ρ(TN)、ρ(NO₃--N)、ρ(TP)分别为(5.08±0.14)、(4.71±0.15)、(0.10±0.03)mg/L条件下,构建了无螺组(海菜花湿地)、有螺组(海菜花-螺蛳经济湿地)和空白组(无海菜花和螺蛳湿地)3种湿地,对比不同HRT(水力停留时间)对水质处理效果的影响,并考察了其经济效益. 结果表明:①HRT为7 d时,无螺组对TN、NO₃--N和TP的去除率分别为55.6%±5.8%、62.6%±5.8%和76.3%±4.8%,有螺组分别为50.8%±5.5%、61.2%±6.3%和75.5%±3.9%;HRT为42 d时的污染物去除率与HRT为28 d时相当,并且有螺组和无螺组也相当,对TN、NO₃--N和TP的去除率分别在76.8%、92.4%和84.8%以上. ②HRT为7和42 d时,投放螺蛳对N、P的去除均表现为抑制作用;HRT为7 d时有螺组浊度显著降低(P<0.05). ③HRT为7 d时,有螺组和无螺组对TN、TP的处理量均在800和228 kg/(hm2·a)以上,显著高于HRT为42 d〔141、46 kg/(hm2·a)〕时. ④HRT为7 d的有螺组经济效益最高,为20.3×104元/(hm2·a),其中海菜花收益为15.4×104元/(hm2·a),投加螺蛳增加经济效益为4.9×104元/(hm2·a). 综合考虑对农田低污染水的净化效能和经济效益,优选HRT为7 d的海菜花-螺蛳经济湿地处理农田低污染水.      

人工湿地中的SND机理以及DO、pH对其的影响

人工湿地中的水生植物向系统中输送大量的DO,并为系统中的微生物提供栖息地,使得系统中连续同时发生硝化和反硝化（SND）反应。DO的高低直接影响到人工湿地系统SND的效果,根据SND的发生机理,可采用复合植物床（系统前端栽种泌氧能力强、后端泌氧能力稍弱的水生植物）和间歇运行的的方式来改善整个系统的脱氮能力。pH过高或过低都会抑制人工湿地系统的SND作用,最适宜值为7．0,据此可以选择适当pH的湿地填料来提高系统的SND作用。     

潜流人工湿地经济植物根际微环境相关指标的研究

通过对潜流人工湿地中经济植物根际土壤微环境一些相关指标的测定,探究了这些指标在湿地中水平方向和垂直方向的变化趋势与湿地NH4＋－N ,TN去除率之间的关系。研究结果表明,硝化作用强度、土壤脲酶活性在水平方向和垂直方向呈逐渐降低的趋势;反硝化作用强度呈中间高,两端低的趋势,垂直方向则沿程降低。湿地土壤硝化作用强度、反硝化作用强度、脲酶活性与湿地氮素去除能力相关性明显,且与栽种植物种类有关。     

垂直流人工湿地MgFe-LDHs覆膜改性基质净化效果研究

选取生物陶粒、无烟煤、沸石3种垂直流人工湿地常用基质,采用金属摩尔比(M2+ : M3+)为2:1的MgCl2溶液和FeCl3溶液在碱性条件下共沉淀即时生成MgFe-LDHs,并将其覆膜于所选3种垂直流人工湿地基质表面;构建模拟基质试验柱,对改性前后的6种基质进行垂直流人工湿地模拟柱净化受污染湖水的小试试验,并进行对比分析.结果表明:该种针对垂直流人工湿地典型基质的MgFe-LDHs覆膜改性方式可行;改性后的3种基质对CODCr、氨氮、总磷的净化效果均有不同程度的提高;其中,无烟煤基质的覆膜改性性能最优,改性后的无烟煤基质对CODCr、氨氮、总磷的平均去除率分别超过了80%、60%和90%.