Exploratory study of suspended sediment concentrations downstream of harvested peat bogs

Peat bog harvesting is an important industry in many countries, including Canada. To harvest peat, bogs are drained and drainage water is evacuated towards neighboring rivers, estuaries or coastal waters. High suspended sediment concentrations (SSC) were found in the drainage water at one particular site during the 2001–2002 spring seasons in New Brunswick (Canada). The main objective of this study was to verify this observation at other sites, compare SSC levels leaving harvested peat bogs with those leaving an unharvested bog, and to determine if high SSC events happen only in Spring or all year round. Suspended sediment concentrations were monitored downstream of three harvested peat bogs and an unharvested reference bog located in New Brunswick during the ice free seasons of 2003–2004. On average, SSC at the harvested sites exceeded 25 mg/l, which is the recommended daily maximum concentration, 72% of the time, while the same concentration was exceeded 30% of the time at the unharvested sites. SSC were found to be significantly higher at harvested sites than at the reference sites for all seasons. The highest SSC medians were recorded in the Fall but SSC was elevated in all seasons. High SSC levels in receiving waters may be caused by field ditching activities and insufficient sediment controls. Findings suggest the NB Peat Harvesting 25 mg/l SSC guideline should be reviewed.     

长江流域养殖池塘氮磷污染负荷估算

长江流域平原区水网密布、渔业发达,养殖池塘造成的氮磷污染问题突出,是河湖富营养化的重要污染源之一;从大空间尺度,精细化估算养殖池塘的氮磷污染负荷,对水污染的精准防控具有重要意义.以长江流域为研究区,依托Google Earth Engine遥感大数据平台,构建了基于机器学习算法的养殖池塘识别模型,精细化识别了长江流域养殖池塘的分布与类型;梳理养殖坑塘的氮磷污染研究案例,针对长江流域养殖坑塘的特征,构建氮磷污染负荷的估算方法,评估氮磷污染负荷的时空分布.研究结果表明：2021年,长江流域养殖池塘总面积为14567km²,包括鱼塘5820 km²、虾蟹塘8747 km²、氮磷排放量分别为95059、16224 t;中部地区的氮磷污染负荷最大,东部地区次之,西部地区最小.本研究是遥感大数据在大尺度污染负荷定量分析的尝试应用,方法适用于其它类型污染负荷的估算.     

Suitability of Golf Course Ponds for Amphibian Metamorphosis When Bullfrogs Are Removed

Abstract:  Managing areas designed for human recreation so that they are compatible with natural amphibian populations can reduce the negative impacts of habitat destruction. We examined the potential for amphibians to complete larval development in golf course ponds in the presence or absence of overwintered bullfrog tadpoles ( Rana catesbeiana ), which are frequently found in permanent, human-made ponds. We reared larval American toads ( Bufo americanus ), southern leopard frogs ( R. sphenocephala ), and spotted salamanders ( Ambystoma maculatum ) with 0 or 5 overwintered bullfrog tadpoles in field enclosures located in ponds on golf courses or in experimental wetlands at a reference site. Survival to metamorphosis of American toads, southern leopard frogs, and spotted salamanders was greater in ponds on golf courses than at reference sites. We attributed this increased survival to low abundance of insect predators in golf course ponds. The presence of overwintered bullfrogs, however, reduced the survival of American toads, southern leopard frogs, and spotted salamanders reared in golf course ponds, indicating that the suitability of the aquatic habitats for these species partly depended on the biotic community present. Our results suggest that ponds in human recreational areas should be managed by maintaining intermediate hydroperiods, which will reduce the presence of bullfrog tadpoles and predators, such as fish, and which may allow native amphibian assemblages to flourish.     

养殖塘CH4通量时空变化特征及其影响因素

本研究基于多通道密闭式动态箱法对亚热带典型养殖塘CH₄通量的时空变化特征及其影响因素进行了分析.结果表明：亚热带养殖塘CH₄主要排放方式是冒泡,CH₄扩散及冒泡通量均呈现明显的季节变化特征.春、夏、秋、冬4个季节CH₄扩散通量分别为：0.113,0.830,0.002,0.005μmol/（m²·s）,冒泡通量分别为0.923,1.789,0.006,0.007μmol/（m²·s）,冒泡通量占总通量的比例分别为89.04%、68.29%、78.95%和60.52%.在冬、春季养殖塘没有人工管理措施的情况下,CH₄通量随着离岸距离的增加而增大,冬、春季养殖塘中间区域CH₄总通量分别是岸边浅水区的34.70和2.98倍.夏季养殖活跃期CH₄通量在空间上呈现出：人工投食区（7.371μmol/（m²·s））>自然生长区（2.151μmol/（m²·s））>人工增氧区（0.888μmol/（m²·s））>岸边浅水区（0.206μmol/（m²·s））的特征.在0.5h尺度上,春季CH₄扩散通量与水温呈显著正相关关系,与风速呈负相关关系,秋季CH₄扩散通量与水温、风速呈正相关关系,冒泡通量和水温呈正相关关系.在日尺度上,水温是CH₄扩散通量和冒泡通量的主控因子,两者均随着水温升高呈指数增加,并且冒泡通量的水温敏感性Q₁₀（12.72）大于扩散通量（7.78）.     

The effect of turbulence on the rate of evaporation of LNG on water

The present study provides new measurements of the rate of evaporation of cryogenic liquids, liquefied natural gas (LNG) and liquid nitrogen (LN₂), floating on a water surface with different levels of turbulence intensity. The turbulent water surface is generated with an upward-pointing submerged jet with controlled jet velocity, an approach which has often been used in studies of free-surface turbulence. Direct measurements of the rate of evaporation were carried out for different pool thicknesses and turbulence intensities of the water surface. These tests reveal a strong dependence of the evaporation rate on the turbulence intensity, as well as a dependence on the thickness of the cryogenic liquid layer above the water surface. Models of LNG spills on water currently use a single rate of evaporation; these findings show that this approach is inadequate. Future models should incorporate the water turbulence intensity, and possibly the LNG spill thickness for improved accuracy.     

Investigation of oil vapor emission and its evaluation methods

In oil operations such as storage, loading, and unloading, there are many chances for oil vapor to be emitted from tanks, tankers or truck tanks into the air. Oil vapor emission (OVE), having serious harmful effects on people and the environment, is always an important research topic for scientists, engineers or managers engaged in the fields of oil production and transportation, fire prevention, and environmental protection. As the second greatest oil consuming country in the world, China has particular interests in investigating ways to better methods to realize and then control the OVE. In this paper, three evaluation methods for the OVE are introduced and summed up. In particular, a set of self-founded OVE’s appraisement methods, which work by theoretical deduced equations integrated with both a software PELES-2.0 and a simple correction method, was systematically investigated. This appraisement system can conveniently and accurately be applied to evaluate the OVE, and further it can also provide base references and/or guides for the law makers, enterprise managers and equipment developers in controlling OVEs.     

尾矿库溃坝淹没范围的定量计算方法研究

为降低人造高势能饱和体-尾矿库在金属非金属矿山安全生产中的危险,提高尾矿库工程溃决的预报预测水平,以溃坝洪水与泥浆的动力学过程作为研究重点,以溃坝洪水运动为主线,综合运用水文学、水动力学等运动理论和有限差分数值计算方法,建立描述尾矿库溃决泥浆运动的数值模型,研究得到尾矿库溃坝淹没范围的定量评估方法。最后进行实际工程预测,计算表明该模型和计算方法可为尾矿库溃坝风险等级的划分提供依据。     

Mangrove mapping in Ecuador: The impact of shrimp pond construction

A cooperative mangrove mapping project between the Ecuadorian Center for Remote Sensing (CLIRSEN) and the University of Delaware was begun in August 1982. The objectives of the project were to create historical maps of mangrove ecosystem extent and change, while transferring aerial photographic interpretation techniques to Ecuadorian personnel. The result of this cooperation was a series of three 125,000 scale maps of historical mangrove extent and change from 1966 to 1982 in the southern Gulf of Guayaquil. This multitemporal study showed a 16% decrease in mangrove extent and a 27% increase in shrimp pond development. If these rates of change prevail into the future, mangroves in Ecuador will reach parity with shrimp ponds in 1984 and completely disappear by mid-1990. Recognizing the significance of this loss to shellfish and fish production along the coast, Ecuadorian scientists at CLIRSEN have subsequently initiated a nationwide mangrove mapping program to create a historical base for future mangrove management strategies.     

寒冷地区小城镇污水处理厂调节池性能的研究

小城镇污水处理厂进水的水质水量变化较大,针对哈尔滨市松北集乐污水处理厂中调节池的作用进行了研究,以期为污水厂的优化运行提供技术支持以及为调节池的设计提供理论依据。在调节池前后以及后续单元的出水处取样,每隔2个小时取一个样,总共取24个小时,然后进行COD、氨氮、总氮、总磷的测定。在冬季调节池对于水质的调节有明显的作用,但是污水厂出水的总氮、总磷浓度达不到一级A的标准。建议可以将一部分剩余污泥回流到调节池以强化脱氮除磷效果。     

Changes in the cell size of the diatom Cylindrotheca closterium in a hyperhaline pond

Cell length of the diatom Cylindrotheca closterium (Ehr.) Reimann & Lewin was investigated on a fortnightly basis from January to April 2000 in a hyperhaline pond (Sardinia, Mediterranean Sea) and relationships, with changes in temperature, salinity, and nitrite concentrations were assessed using single and multiple regression analyses. Results of our study indicate that C. closterium cell size was inversely related to temperature changes, but that salinity and nitrite concentrations may have a major idiosyncratic effect on cell size variability.