北方半干旱黄土丘陵区的农村能源建设

“七·五”期间，宁夏西吉县是半干旱黄土丘陵区域农村能源综合建设试点县．多年的综合建设有效地缓解了农村能源紧缺，促进了农村经济的发展．本文通过综合建设的后效应跟踪调查结果表明，在市场经济条件下，农村经济的发展已走向了不同层次，认为今后农村能源建设的基本路子应分三步走，逐步使农村能源真正成为产业，其生产、供应、服务均实现现代化．     

PHOSPHORUS ASSIMILATION IN A STREAM SYSTEM OF THE LAKE OKEECHOBEE BASIN1

ABSTRACT: The ability to predict how streams and wetlands retain phosphorus (P) is critical to the management of watersheds that contribute nutrients to adjacent aquatic systems such as lakes. Field and laboratory experiments were conducted to determine the P assimilatory capacity of a stream (Otter Creek) in the Taylor Creek/Nubbin Slough Basin located north of Lake Okeechobee, Florida. Dominant soils in this basin are sandy Spodosols; landuse is primarily dairy farms and beef cattle pastures. Estimates of P assimilation show that sediments assimilate approximately 5 percent of the P load. Phosphorus assimilation rates in the stream were estimated using first-order relationships based on the total P concentration of the water column as a function of distance from the primary source. This method assumes minimal lateral inputs. Stream lengths required for one turnover in P assimilation were estimated to be in the range of 3–16 km. Laboratory studies using intact sediment cores indicated a P assimilation rate of 0.025 m day^?1, and equilibrium P concentration of 0.16 ± 0.03 mg L^?1 in the water column. Dissolved P concentration gradients in the sediments showed upward flux of P at water column P concentration of <0.16 mg L^?1. Approximately 56–77 percent of the P assimilated in the above-ground vegetation during active growth was released or translocated within six months of senesence, suggesting short-term storage in above-ground vegetation. Bottom sediments and recalcitrant detrital plant tissue provide for long-term P assimilation in the creek. Although stream sediments have the potential to adsorb P, high flow rate and low contact period between water and sediment limits this process.     

QUALITY OF WATER AND BOTTOM SEDIMENTS IN THE TRINITY RIVER1

ABSTRACT: Data were developed to determine the quality of water and bottom sediments in the Trinity River, and the mobility of various contaminants when bottom sediments were mixed with the river water under simulated dredging conditions. Thirteen sampling sites were selected. A number of chemical tests including heavy metals and pesticides were conducted on river water, elutriates, and bottom sediments. Statis bioassays using Daphnia magna were conducted on river water and elutriates. Results indicated that the river in the upper reach is grossly polluted due to discharge of waste water effluents from several large treatment plants. High concentrations of nitrogen, phosphorus, organic carbon, COD, heavy metals, and pesticides were found in water and bottom sediments. The concentrations of most of these pollutants exceeded the EPA recommended limits. Elutriation gave no consistent results, perhaps because of release or uptake of contaminants from the sediments. High mortality of D. magna were also recorded in the upper reach of the river. The quality of water and bottom sediments gradually improved in lower reaches.     

Spatial variation of organochlorine pesticides and dissolved organic matter in urban closed lakes

Abstract

Closed lakes located in urban parks act as sinks of organochlorine pesticides (OCPs), which have been used, for decades, as insecticides, herbicides and fungicides. The closed lakes from Bucharest, Romania, are periodically managed to prevent eutrophication and accumulation of pollutants. However, it is not known if these practices reduce or enhance the legacy pollution with OCPs. The aim of this study was to explore the spatial variation of OCPs in closed lakes. The total concentration of OCPs in water and sediments ranged between 0.0176 and 37.1?µg/L, and between 122 to 1,890?ng/g, respectively. The concentrations of OCPs were compared with the consensus-based sediment quality guidelines (SQGs) in order to evaluate the ecological risks of sediments. The highest potential adverse effects were associated with γ-HCH exposure. Periodical draining and dredging of lakes lead to the resuspension of contaminants, increasing pesticide bioavailability and accumulation in sediments. In addition, we observed that fluorescent dissolved organic matter (DOM) might influence the OCPs cycle. The quantity and character of fluorescent DOM can provide further insight into OCPs degradation. Also, this study may help urban planners to determine the state of urban waters and to find the best solution for water management.     

Land-based sources of marine pollution: organochlorine pesticides in stream systems

BACKGROUND: Organochlorine pesticides (OCPs) have been dispersed ubiquitously in the environment. Bottom sediments act as sinks for these compounds and their concentrations often reflect the degree of anthropogenic pollution. This study was designed to evaluate the occurrence and distribution of OCPs in superficial streambed sediments and their relation to land use in two creeks that contribute to the coastal pollution of the southeastern region of Argentina. METHODS: Sampling sites were selected by a combination of land use and stream type. Las Brusquitas creek, which passes through vast agricultural areas, and La Tapera creek which originates in a natural wetland and passes through horticultural farming and urban areas. OCPs quantification was carried out by GC-ECD. RESULTS AND DISCUSSION: Results showed similar total OCP concentrations in sediments from both creeks in the range of 6-25 ng/g dry wt. However, when OCPs were expressed in ng/g total organic carbon (TOC), La Tapera creek presented 4-fold higher total levels as a consequence of a higher OCP input during the recent past in that watershed. La Tapera outfall showed 4-fold higher levels than that seen in Las Brusquitas, although both values were below the sediment quality criteria demanded to protect wildlife. Sigmaendosulfans, sigmaDDTs and sigmachlordanes were the main OCP group in all samples, with Endosulfan sulfate being the most frequent and abundant compound. The predominance of metabolites with respect to parent compounds suggests a contamination mainly by runoff from aged and weathered agricultural soils. CONCLUSIONS: Despite OCPs being banned, they still exist in creek sediments from the studied region, representing continuous contributions of land-based source contaminants to the marine environment. OUTLOOK: Future research on OCP levels in suspended sediments is recommended in order to determine the total OCP concentrations in the selected stream systems.     

黄土丘陵区降雨、径流、土壤水分的时空分布与利用对策

基于黄土丘陵区的延安燕沟多年监测资料，通过对燕沟流域的降雨、径流、及其不同土地利用方式下土壤水分等时空分布特征分析，明确了黄土丘陵区降雨的时间、空间分布具有显著差异性。降雨量在6～9月相对集中，年际、月际变异大；同时次降雨量、月降雨量均存在显著空间异质性，如降雨量沿燕沟沟道变化及坡向分异。径流特征是降雨及其下垫面特征的综合反映，3月左右由于气温上升，河道解冻，径流量出现小高峰，雨季后2个月出现最大高峰水量。对径流的利用则由于供水／需水时间错位，利用主要集中在枯水季节（4-6月），土壤水资源由于地形、降雨、植被覆盖等的差异性，特别是植被差异性利用，则存在时空异质性。土壤水分在雨季后1-2月在0～150cm形成高值期，150cm以下的土壤恢复缓慢。植被差异利用形成了土壤水分剖面不同：梯田〉草地〉拧条林〉拧条＋五角枫林〉沙棘林〉刺槐林。根据对水资源系统分析，提出了流域水资源开发利用的对策：农作物适雨种植制度；植被空间合理布局；降雨、土壤水、径流三水联合御旱，提高水资源利用效率。     

Heavy metals in surface water and stream sediments in Jamaica

The levels of heavy metals in water and stream sediments in Jamaica are presented and compared to levels in soils and environmental standards. Heavy metals (cadmium, chromium, copper, mercury, nickel, lead and zinc) appear to be less of a problem to Jamaica's freshwater environment than might be expected given the concentrations in soils. This can be explained by taking into account the dynamics of the Jamaican water environment and the relative absence of anthropogenic sources. The dynamics of the freshwater system on the other hand, could pass any environmental threat to the coastal environment. Because the stream sediments are relatively coarse and contain little organic material the bio-availability of micropollutants such as heavy metals from the sediments can be expected to be relatively high.     

The Presence of Calcium Oxalate Dihydrate (Weddellite) in Street Sediments from Niterói, Brazil and Its Health Implications

Established research in first world urban environments has shown street sediments to be effective sinks for heavy metals and emphasises the health risks to children by its inhalation or ingestion. In third world countries with fewer pollution controls, contamination may be augmented by additional pollutants such as sewage discharge into urban streets and/or periodic inundation with sewage-laden run-off. This pollutant not only contains heavy metals and organic matter, but calcium oxalates that may derive directly from the sewage itself. To study this premise street sediments were collected from sites of varying industrialisation and sewage contamination within the city of Niteroi, Brazil. Calcium oxalate dihydrate (weddellite) was identified by X-ray diffraction, fourier transform infra red and scanning electron microscopy techniques and oxalate concentrations in <63m and colloidal (clay and organic matter) fractions, were determined by ion chromatography. Oxalate in colloidal fractions averaged 43601mgkg^–1 in sewage contaminated industrialised urban zones, 4519mgkg^–1 in suburban areas and 17477mgkg^–1 in suburbs with favelas (shantytowns-of Niterói). Oxalate concentrations coincide with high levels of metal ions (Fe, Mn, Zn, Pb, Ni, Cr) that stabilise calcium oxalate dihydrate and prevent its dehydration to the monohydrate (whewellite). Lower levels of oxalate were found in lichen-covered roof sediment, plaster and mortar samples. Oxalate concentration coincides with sewage contamination and street sediments appear to act as a sink for calcium oxalate dihydrate derived from sewage. Previous studies have shown that low levels of exposure can damage kidneys and the nervous system, while prolonged exposure can cause severe corneal, retinal and skin damage, cyanosis and possibly gangrene. Contact with blood serum may result in hypocalcemia, muscular stimulation, convulsions and finally collapse. The conditions described are common throughout urban areas of the developing world and may suggest a particular environmental hazard in these regions.     

A new voltammetric method for the simultaneous monitoring of heavy metals in sea water,sediments, algae and clams: application to the Goro Bay ecosystem

Arsenic(III), selenium(IV), copper(II), lead(II), cadmium(II),zinc(II) have been determined in sea water, sediments, algae andclams by differential pulse cathodic (DPCSV) and anodic (DPASV)stripping voltammetry. The voltammetric measurements are carriedout using a conventional three-electrode cell and the ammonia-ammonium chloride buffer pH 9.2 as supporting electrolyte.The analytical procedure has been verified by the analysisof the standard reference materials (Estuarine SedimentBCR-CRM 277, Ulva Lactuca BCR-CRM 279 and Mussel Tissue BCR-CRM278). The precision and the accuracy are less than 5%. Thisprocedure is utilized for the monitoring of heavy metals inthe Po river mouth area (Italy).     

青海湖黑马河黄土的高密度光释光测年

西风环流与亚洲季风交互控制下的青海湖流域,对气候变化响应敏感。该区广泛分布的黄土记录了古环境古气候信息,但其在不同时间尺度上的沉积模式和沉积连续性尚不明晰。本文以青海湖西南的黑马河黄土剖面（HMHW）为研究对象,通过高密度光释光（optically stimulated luminescence,OSL）测年,结合粒度、磁化率和色度指标探讨其环境演变特征。结果表明：（1）黑马河黄土的沉积模式以快速堆积为主,集中于较冷的末次冰消期（13—12 ka）和晚全新世（~2 ka）;（2）早中全新世（11—4 ka）存在~7 ka的沉积间断;（3）黑马河黄土剖面（HMHW）的土壤粒度组分,以体积占68.68%的粉砂为主,砂次之,黏粒最少;整个剖面的平均粒径和亮度低值对应古土壤层,高值对应黄土层;磁化率的最大值在115 cm处为74.30×10 ^?8 m ³·kg ^?1,110 cm处的OSL年代为(1.52±0.16) ka,指示晚全新世（~2 ka）有古土壤发育。