关中地区元代干旱灾害与气候变化

通过对元代关中地区历史资料的搜集、整理和分析,对该时期关中地区的干旱灾害等级、干旱灾害事件在时间上的变化及其成因进行了研究。结果表明:关中地区从元代早期(公元1266年)至元代晚期(公元1359年)的94年中,共发生干旱灾害33次,平均每2.85年发生一次;元代关中地区的干旱灾害主要以轻度旱灾为主,占旱灾总数的42.4%,其次是中度旱灾,占旱灾总数的24.2%,特大旱灾的发生频率也较高,占旱灾总数的21.2%,大旱灾发生频率最低,占旱灾总数的12.1%。关中地区干旱灾害在元代早、中、晚期分布不均匀,从早期到中期再到晚期,干旱灾害呈现出由少变多又变少的趋势;降水量的年内分布不均匀是该区在元代发生轻度和中度干旱灾害的主要原因,而气候的异常明显变干是该区在元代中期干旱灾害加剧和大旱灾频繁发生的主要原因。该地区自身的地理位置,所处的气候背景以及人类活动导致植被破坏也加剧了干旱灾害的发生。元代关中地区发生了1次干旱气候事件,时间在1326—1332年。初步确定元代关中大旱灾发生年份主要灾区的年均降水量为400 mm左右,特大旱灾发生年份主要灾区的年均降水量为350 mm左右。     

西安地区约8500aBP来气候变化与风尘堆积

根据野外调查、土层厚度测定、室内粒度分析、CaCO3含量分析和微结构鉴定资料,研究了西安地区约8500aBP来气候变化与风尘堆积的变化。结果表明,西安地区全新世以来的气候与末次间冰期第1阶段气候相比具有频繁变化和变异特点;3100aBP以来风尘堆积与沙尘暴活动比75~10kaBP之间的末次冰期还要强,风尘堆积与沙尘暴活动强的原因主要是气候的变干。全新世黄土发育条件分析表明,黄土高原的黄土可以发育在冰期,也可以发育在与现代气候相近的间冰期,可以发育在冬季风占优势的气候条件下,也可以发育在冬、夏季风活动强度相近的条件下。全新世气候的不稳定性为预测未来长期气候变化带来了不确定性,深入研究全新世气候变异特点对预测未来长期气候变化具有非常重要的意义。     

黄土高原西部上新统风成红粘土的微形态特征及其古环境意义

黄土高原中新统-上新统风成红粘土沉积序列是记录东亚季风演化和亚洲内陆干旱化历史的重要载体。红粘土沉积前可能存在相当程度的风化过程,准确区分物源区原生信号和沉积后次生成壤信号是红粘土古气候重建的基础。偏光显微镜下土壤微形态可直观反映沉积结构和成壤程度。本研究以黄土高原西部董湾剖面厚约73.7 m的中新统-上新统（7.1~3.52 Ma）红粘土及其中的钙积层为对象,在野外考察的基础上,对该剖面上部12 m厚度的红粘土进行详细的土壤微形态分析和扫描电镜观察,并与上覆第四纪黄土沉积对比。结果显示,大部分红粘土及碳酸钙淀积层中,光性定向粘土不显著,粘化程度低,次生碳酸盐及晶体沿根孔和裂隙分布,古土壤总体为中等或弱发育程度。部分红粘土层中存在粘粒胶膜或铁锰结核,指示土壤发育相对较强。碳酸钙的淋溶淀积形式和红粘土序列中普遍存在的铁锰胶膜,与红粘土的透水性差、裂隙发育、地形和地下水位波动等因素有关,与古气候之间的关系存在一定的不确定性。红粘土序列中水的参与度高于第四纪黄土,流水侵蚀和地下水位波动影响区域之间地层对比和红粘土理化性质,亟需综合多种研究手段更准确认识红粘土的古气候和古环境意义。

     

Assessing the influence and distribution of shrimp pond effluent in a tidal mangrove creek in north-east Australia

Effluent from a land based shrimp farm was detected in a receiving creek as changes in physical, chemical and biological parameters. The extent and severity of these changes depended on farm operations. This assessment was conducted at three different stages of shrimp-pond maturity, including (1) when the ponds were empty, (2) full and (3) being harvested. Methods for assessing farm effluent in receiving waters included physical/chemical analyses of the water column, phytoplankton bioassays and nitrogen isotope signatures of marine flora. Comparisons were made with an adjacent creek that served as the farms intake creek and did not directly receive effluent. Physical/chemical parameters identified distinct changes in the receiving creek with respect to farm operations. Elevated water column NH(4)(+) (18.5+/-8.0 microM) and chlorophyll a concentrations (5.5+/-1.9 microg/l) were measured when the farm was in operation, in contrast to when the farm was inactive (1.3+/-0.3 microM and 1.2+/-0.6 microg/l, respectively). At all times, physical/chemical parameters at the mouth of the effluent creek, were equivalent to control values, indicating effluent was contained within the effluent-receiving creek. However, elevated delta(15)N signatures of mangroves (up to approximately 8 per thousand) and macroalgae (up to approximately 5 per thousand ) indicated a broader influence of shrimp farm effluent, extending to the lower regions of the farms intake creek. Bioassays at upstream sites close to the location of farm effluent discharge indicated that phytoplankton at these sites did not respond to further nutrient additions, however downstream sites showed large growth responses. This suggested that further nutrient loading from the shrimp farm, resulting in greater nutrient dispersal, will increase the extent of phytoplankton blooms downstream from the site of effluent discharge. When shrimp ponds were empty water quality in the effluent and intake creeks was comparable. This indicated that observed elevated nutrient and phytoplankton concentrations were directly attributable to farm operations.     

How multiagency partnerships can successfully address large-scale pollution problems: a Hawaii case study

Oceanic circulation patterns deposit significant amounts of marine pollution, including derelict fishing gear from North Pacific Ocean fisheries, in the Hawaiian Archipelago [Mar. Pollut. Bull. 42(12) (2001) 1301]. Management responsibility for these islands and their associated natural resources is shared by several government authorities. Non-governmental organizations (NGOs) and private industry also have interests in the archipelago. Since the marine debris problem in this region is too large for any single agency to manage, a multiagency marine debris working group (group) was established in 1998 to improve marine debris mitigation in Hawaii. To date, 16 federal, state, and local agencies, working with industry and NGOs, have removed 195 tons of derelict fishing gear from the Northwestern Hawaiian Islands. This review details the evolution of the partnership, notes its challenges and rewards, and advocates its continued use as an effective resource management tool.     

ENSO事件与山西气候的关系

通过搜集和整理1955-2008年大同、河曲、原平、太原、阳泉、介休、离石、长治、临汾、运城等地的气象资料,分析了山西的降水量、气温与ENSO事件的关系,研究了ENSO事件对山西气候的影响。结果表明,1955-2008年ENSO事件呈现出起伏波动的特点,1980年以后波动趋势更为剧烈;大致可分为两个阶段:1955-1980年为第1阶段,ENSO冷事件的频次略高于暖事件,但强度更大;1981-2008年为第2阶段,ENSO暖事件的频次和强度均高于冷事件。ENSO事件对山西降水量的影响表现十分明显,ENSO暖事件当年降水量明显偏低,次年降水量明显增加或达到最高趋势明显。ENSO冷事件年全省降水量均明显增加。ENSO事件对山西气温的影响也十分显著,ENSO暖事件年大多表现为气温偏高或升温,ENSO冷事件年一般表现为气温偏低或降温。     

Movement of water infiltrated from a recharge basin to wells

Local surface water and stormflow were infiltrated intermittently from a 40-ha basin between September 2003 and September 2007 to determine the feasibility of recharging alluvial aquifers pumped for public supply, near Stockton, California. Infiltration of water produced a pressure response that propagated through unconsolidated alluvial-fan deposits to 125 m below land surface (bls) in 5 d and through deeper, more consolidated alluvial deposits to 194 m bls in 25 d, resulting in increased water levels in nearby monitoring wells. The top of the saturated zone near the basin fluctuates seasonally from depths of about 15 to 20 m. Since the start of recharge, water infiltrated from the basin has reached depths as great as 165 m bls. On the basis of sulfur hexafluoride tracer test data, basin water moved downward through the saturated alluvial deposits until reaching more permeable zones about 110 m bls. Once reaching these permeable zones, water moved rapidly to nearby pumping wells at rates as high as 13 m/d. Flow to wells through highly permeable material was confirmed on the basis of flowmeter logging, and simulated numerically using a two-dimensional radial groundwater flow model. Arsenic concentrations increased slightly as a result of recharge from 2 to 6 μg/L immediately below the basin. Although few water-quality issues were identified during sample collection, high groundwater velocities and short travel times to nearby wells may have implications for groundwater management at this and at other sites in heterogeneous alluvial aquifers.