Mercury in different environmental compartments of the Pra River Basin, Ghana

Artisanal gold mining (AGM) with metallic mercury has a long history in Ghana. It is believed to be over 2,000 years old. Today, AGM has escalated in a new dimension consuming about half of the country where gold lode deposits exist along riverbanks or rivers are alluvial-gold rich. The Pra River in southwestern Ghana is a site of on going application of metallic mercury in prospecting gold, and this paper examines mercury (Hg) contamination in the different environmental compartments in its watershed. Samples of water, sediment, soil and biota (i.e., human hair and fish) were collected from locations along the course of the river during the rainy and dry seasons of 2002 and 2003, respectively. Besides the obvious Hg point sources along the Pra and its tributaries, the obtained results show that Hg levels and speciation in the studied aquatic system are controlled by precipitation, which drives the hydrology and differences in flow regimes versus seasons. The seasonal difference in Hg speciation suggests that methyl mercury (MeHg) found in the aqueous phase and riverine sediments is likely of terrestrial origin where its production is favored during the rainy season by high soil water and organic matter content. The use of the enrichment factor (EF) for the assessment of sediment quality indicated moderate to severe contamination of surface sediments in the rainy season, while in the dry season, the EF index indicates nearly no pollution of surface sediments. Accordingly, most of the Hg introduced into this river system is likely transported to depositional downstream terminal basins (e.g. the river delta and the Gulf of Guinea). With regard to biota, Hg measured in hair in the dry period was higher than data obtained on samples collected during the wet period. This could be explained at least in part by the shift in diet as a result of abundance of fish in the local markets and the concurrent increase and more active fishing during the dry season. Mercury data obtained on a very limited number of fish samples collected during the dry period only are also presented.     

Anthropogenic impacts on mercury concentrations and nitrogen and carbon isotope ratios in fish muscle tissue of the Truckee River watershed, Nevada, USA

The lower Truckee River originates at Lake Tahoe, California/Nevada (NV), USA and ends in the terminal water body, Pyramid Lake, NV. The river has minimal anthropogenic inputs of contaminants until it encounters the cities of Reno and Sparks, NV, and receives inflows from Steamboat Creek (SBC). SBC originates at Washoe Lake, NV, where there were approximately six mills that used mercury for gold and silver amalgamation in the late 1800s. Since then, mercury has been distributed down the creek to the Truckee River. In addition, SBC receives agricultural and urban nonpoint source pollution, and treated effluent from the Reno-Sparks water reclamation facility. Fish muscle tissue was collected from different species in SBC and the Truckee River and analyzed for mercury and stable isotopes. Nitrogen (delta(15)N) and carbon (delta(13)C) isotopic values in these tissues provide insight as to fish food resources and help to explain their relative Hg concentrations. Mercury concentrations, and delta(15)N and delta(13)C values in fish muscle from the Truckee River, collected below the SBC confluence, were significantly different than that found in fish collected upstream. Mercury concentrations in fish tissue collected below the confluence for all but three fish sampled were significantly greater (0.1 to 0.65 microg/g wet wt.) than that measured in the tissue collected above the confluence (0.02 to 0.1 microg/g). Delta(15)N and delta(13)C isotopic values of fish muscle collected from the river below the confluence were higher and lower, respectively, than that measured in fish collected up river, most likely reflecting wastewater inputs. The impact of SBC inputs on muscle tissue isotope values declined down river whereas the impact due to Hg inputs showed the opposite trend.     

An assessment of anthropogenic source impacts on mercury cycling in the Willamette Basin, Oregon, USA

In Oregon's Willamette River Basin (Basin), methylmercury levels in fish triggered health advisories and required development of a mercury Total Maximum Daily Load (TMDL) for the Willamette River. A seasonally-responsive dynamic systems model is used to identify the principal sources of natural and anthropogenic mercury, the relative contributions of these sources to the river, the impact of hypothetical reductions in specific natural and anthropogenic sources on mercury levels in surface water, sediment, and fish tissue, and the degree to which any such changes would be clearly discernible to environmental managers and Basin stakeholders. Two scenarios are modeled: "PRES", which considered all currently known natural and anthropogenic mercury sources and "LEEM", which (hypothetically) eliminated all local, but not global, anthropogenic sources and greatly lowered native soil erosion rates. Elimination of local air emissions reduces runoff of air-deposited mercury by approximately 34% and advection from the Basin by approximately 12%, while lowering erosion rates reduces particulate runoff by approximately 57%, deposition from the water column to surficial sediment by approximately 33%, and fluvial load by approximately 24%; for a net reduction of 25.6% in the total mercury load to the river. Such hypothetical reductions bring methylmercury concentrations in predatory fish to levels that would allow restoration of fish consumption as a beneficial use. However, several factors, primarily technical feasibility and global sources, may impede attempts to attain this beneficial use. Actualizing the hypothetical 100% elimination of local anthropogenic sources and a >50% reduction in erosion could pose significant technical challenges. Because local anthropogenic emissions make relatively smaller contributions to the Basin than do persistent global sources (sources over which there is little, if any, possibility of local control), localized environmental management actions alone may not be adequate to address mercury impacts within the Basin.     

The distribution, occurrence and environmental effect of mercury in Chinese coals

Mercury (Hg) is a toxic, persistent, and globally distributed pollutant due to its characteristic properties such as low melting and boiling points, conversion between chemical forms and participation in biological cycles. During combustion mercury in coal is almost totally emitted to the atmosphere. With a huge amount of coal consumed, coal combustion is one of the main anthropogenic sources of this element in the environment. In this study, Hg data of 1699 coal samples of China has been compiled, and the concentration, distribution, modes of occurrence, and the impact of Hg emissions on the environment are investigated. Most Chinese coals have Hg content in the range of 0.1 to 0.3 ppm, with an average of 0.19 ppm, which is slightly higher than the average Hg content of world coals and is close to that of the U.S. coals. The Hg content in coals varies in different coal basins, geological ages and coal ranks. The most likely mode of occurrences of Hg in high-sulfur and high Hg content coals is as solid solution in pyrite. But in low-sulfur coals, modes of occurrence of Hg are variable, and the organic-bound and sulfide-bound Hg may dominate. Silicate-bound Hg may be the main form in some coals because of magmatic intrusion. Mercury emissions during coal combustion have resulted in serious environmental contamination in China, particularly in the northeastern and southwestern China, where a high Hg content in the atmosphere occurs.     

Binding, distribution, and plant uptake of mercury in a soil from Oak Ridge, Tennessee, USA

A large amount of mercury has been discharged on the U.S. Department of Energy's Oak Ridge Site (Tennessee) as a part of the U.S. nuclear weapon program during the 1950s through the early 1960s. Increases in mercury concentration in fish and in lower East Fork Poplar Creek of Oak Ridge have been recently reported. This is an experimental study mimicking the initial stage of transformation and redistribution of mercury in soils, which are comparable to those of the Oak Ridge site. The objectives of this study were to investigate potential transformation, distribution, and plant uptake of mercury compounds in soils. Results show that the H(2)O(2)-oxidizable mercury fraction (organically bound mercury) was the major solid-phase fraction in soils freshly contaminated with soluble mercury compounds, while cinnabar fraction was the major solid phase fraction in soils contaminated with HgS. Langmuir relationships were found between mercury concentrations in plant shoots and in soil solid-phase components. Mercury in HgS-contaminated soils was to some extent phytoavailable to plants. Mercury transformation occurred from more labile fractions into more stable fractions, resulting in strong binding of mercury and decreasing its phytoavailability in soils. In addition, high mercury losses from soils contaminated with soluble mercury compounds were observed during a growing season through volatilization, accounting for 20-62% of the total initial mercury in soils.     

A watershed at a watershed: the potential for environmentally sensitive area protection in the upper San Pedro Drainage Basin (Mexico and USA)

The watershed is advocated as an appropriate unit for ecological planning. Watersheds, or river drainage basins, can be understood through an ecological chorography. The upper San Pedro River basin of southern Arizona (USA) and northern Sonora (Mexico) is used as an example. This watershed is currently facing significant growth pressures. Rapid urbanization, cattle ranching, and irrigated agricultural pumping in the drainage basin are having negative environmental consequences, including water quality and supply problems, increased soil erosion, threats to wildlife habitats, and degradation of scenic resources. Copper mining, just outside the watershed, potentially impacts groundwater and the San Pedro riparian system. The protection of environmentally sensitive areas would help to maintain the biological integrity of the region. This paper focuses on the design of a framework for the identification of environmentally sensitive areas in the watershed and an analysis of existing government plans to protect such areas. The proposed framework can coordinate local, state, and federal efforts to achieve their protection objectives.     

子牙河—海河流域浅层地下水矿化度分布及成因

对天津地区子牙河—海河干流流域浅层地下水矿化度及水化学类型分布进行了调查,发现地下水矿化度由低到高、从微咸水到咸水再到盐卤水渐变特征明显,对其形成原因进行了分析,认为地下水补给不足以及深层地下水开采形成降落漏斗和渤海湾风暴潮等引起的海水入侵是导致该分布特征的主要原因。     

Effect of different parameters on the in situ thermal conductance evaluation

In the last years many studies have been carried out on the possible improvements of the in situ thermal conductance measurement; as well known, this has to be derived by recorded values of temperatures and heat fluxes. A big effort has been addressed in the implementation and comparison of different analysis methods. The aim of this paper is to widen the existent literature in the study of the influence of different kinds of input data on the final result. First the problem of analysing input data with significant drift in temperature is considered, adopting both nominal clean and noise affected data. Then the effect due to the presence of the Heat Flux Meter (HFM) on the thermal field of the testing element has been analysed, as well as the possibility of recording HFM surface temperature. These studies are based on Finite Element Method (FEM) simulations; both nominal clean and noise affected data have been considered as input. Finally, a difference in emissivity between the heat flux meter and internal plaster surface has been analysed by means of FEM simulations based on nominal clean data. An overall estimation of the occurred deviations in the different cases is shown.     

Residual effects of lead and zinc mining on freshwater mussels in the Spring River Basin (Kansas, Missouri, and Oklahoma, USA)

Concentrations of selected trace elements in surface water and fluvial sediment were investigated as possible factors limiting the distribution and abundance of freshwater mussels in the Spring River Basin, a 6600 km(2) watershed overlapping a former Pb and Zn mining and ore processing district in the central USA. Mussel taxa richness surveys and supporting physical habitat assessments were performed in 23 stream reaches dispersed throughout the basin and above and below former mining sites. Quantitative mussel density surveys were performed in the Spring River at one upstream reference location and one downstream location. Concentrations of 16 trace elements in the soft tissues of mussels and Asian clams (Corbicula fluminea) were determined at most survey sites. Comparable analyses were performed on surface water samples collected during base flow and peak flow synoptic surveys and sediment samples collected during base flow periods. Sites on the Spring River immediately upstream of heavily mined areas supported at least 21-25 species of mussels, whereas sites near the lower terminus of the river yielded evidence of 6-8 extant species. Between the upper and lower quantitative survey sites, mean mussel and clam densities declined by 89% and 97%, respectively. Tributary reaches below heavily mined areas lacked evident bivalve communities and contained concentrations of Cd, Pb, and Zn that continually or sporadically exceeded hardness-dependent water quality criteria and consensus-based sediment quality guidelines (probable effect concentrations). In less contaminated stream reaches supporting bivalves, concentrations of Cd, Pb, and Zn in mussels and clams were correlated spatially with the levels occurring in surficial sediment (0.50 < or = tau < or = 0.64, p < or = 0.03). In non-headwater perennial stream reaches, sediment Cd, Pb, and Zn levels were related inversely to mussel taxa richness (-0.80 < or = tau < or = -0.64, p < or = 0.004). Metal contaminant burdens in mussels and clams fluctuated measurably in association with variable stream flow conditions and accompanying changes in surface water and sediment chemistry. Concentrations of Cd, Pb, and Zn in mussels approximately paralleled the levels measured in composite clam samples (0.74 < or = tau < or = 0.79, p<0.001), implying C. fluminea could serve as a possible surrogate for native mussels in future metal bioaccumulation studies. Overall, streams draining heavily mined areas exhibited depauperate (or fully extirpated) mussel assemblages and correspondingly elevated concentrations of Cd, Pb, and Zn in water, sediment, and bivalve tissue. Other evaluated environmental chemistry parameters, and physical habitat conditions assessed at the stream reach scale, demonstrated little general relationship to the degraded status of these assemblages. We conclude that pollution attributable to former mining operations continues to adversely influence environmental quality and impede the recovery of mussel communities in a large portion of the Spring River Basin.     

Sources and temporal dynamics of arsenic in a New Jersey watershed, USA

We examined potential sources and the temporal dynamics of arsenic (As) in the slightly alkaline waters of the Wallkill River, northwestern New Jersey, where violations of water-quality standards have occurred. The study design included synoptic sampling of stream water and bed sediments in tributaries and the mainstem, hyporheic-zone/ground water on the mainstem, and seasonal and diurnal sampling of water at selected mainstem sites. The river valley is bordered by gneiss and granite highlands and shale lowlands and underlain by glacial deposits over faulted dolomites and the Franklin Marble. Ore bodies in the Marble, which have been mined for rare Zn ore minerals, also contain As minerals. Tributaries, which drain predominantly forested and agricultural land, contributed relatively little As to the river. The highest concentrations of As (up to 34 mug/L) emanated from the outlet of man-made Lake Mohawk at the river's headwaters; these inputs varied substantially with season--high during warm months, low during cold months, apparently because of biological activity in the lake. Dissolved As concentrations were lower (3.3 microg/L) in river water than those in ground water discharging into the riverbed (22 microg/L) near the now-closed Franklin Mine. High total As concentrations (100-190 mg/kg) on the <0.63 microm fraction of bed sediments near the mine apparently result from sorption of the As in the ground-water discharge as well as from the As minerals in the streambed. As concentrations in river water were diluted during high stream flow in fall, winter and spring, and concentrated during low flow in summer. In unfiltered samples from a wetlands site, diurnal cycles in trace-element concentrations occurred; As concentrations appeared to peak during late afternoon as pH increased, but Fe, Mn, and Zn concentrations peaked shortly after midnight. The temporal variability of As and its presence at elevated concentrations in ground water and sediments as well as streamwater demonstrate the importance of (1) sampling a variety of media and (2) determining the time scales of As variability to fully characterize its passage through a river system.     

汞晕带内汞元素在土壤环境中分布规律的研究

以国内典型汞矿开采区作为研究试点,通过对汞晕带内土壤中汞元素的含量及存在形式的采样实测,分析了汞晕带内汞元素在土壤中的分布规律,为汞晕带内人居健康的保证以及土壤环境修复提供了基础资料。     

长江流域居住建筑不同供暖模式下的负荷特性分析

通过分析长江流域冬季供暖特点,采用建筑环境动态负荷分析软件DeST-h对该地区典型城市重庆居住建筑在连续供暖和间歇供暖2种供暖模式下的冬季逐时热负荷进行了计算,分析了2种供暖模式下的负荷分布特性。连续供暖的热负荷总体水平较低,波动较小,且与室外空气温度呈负相关,而间歇供暖的热负荷波动较大,具体表现为开始阶段热负荷较大,而后迅速降低并稳定。据此进一步分析了该负荷特性对长江流域居住建筑的空气源热泵机组选型及运行调节的影响。分析得出:按照夏季供冷工况进行设备选型,机组名义工况下的制热量能满足连续供暖的最大热负荷需求和间歇供暖稳定阶段的热负荷需求;连续供暖条件下部分负荷率主要分布在25%~75%之间,机组的运行调节可采用定容量压缩机台数控制方式;间歇供暖条件下部分负荷率主要分布在50%~100%之间,建议采用变容量调节方式。     

Distribution, speciation, and transport of mercury in stream-sediment, stream-water, and fish collected near abandoned mercury mines in southwestern Alaska, USA

Concentrations of total Hg, Hg (II), and methylmercury were measured in stream-sediment, stream-water, and fish collected downstream from abandoned mercury mines in southwestern Alaska to evaluate environmental effects to surrounding ecosystems. These mines are found in a broad belt covering several tens of thousands of square kilometers, primarily in the Kuskokwim River basin. Mercury ore is dominantly cinnabar (HgS), but elemental mercury (Hg degrees) is present in ore at one mine and near retorts and in streams at several mine sites. Approximately 1400 t of mercury have been produced from the region, which is approximately 99% of all mercury produced from Alaska. These mines are not presently operating because of low prices and low demand for mercury. Stream-sediment samples collected downstream from the mines contain as much as 5500 microg/g Hg. Such high Hg concentrations are related to the abundance of cinnabar, which is highly resistant to physical and chemical weathering, and is visible in streams below mine sites. Although total Hg concentrations in the stream-sediment samples collected near mines are high, Hg speciation data indicate that concentrations of Hg (II) are generally less than 5%, and methylmercury concentrations are less than 1% of the total Hg. Stream waters below the mines are neutral to slightly alkaline (pH 6.8-8.4), which is a result of the insolubility of cinnabar and the lack of acid-generating minerals such as pyrite in the deposits. Unfiltered stream-water samples collected below the mines generally contain 500-2500 ng/l Hg; whereas, corresponding stream-water samples filtered through a 0.45-microm membrane contain less than 50 ng/l Hg. These stream-water results indicate that most of the Hg transported downstream from the mines is as finely-suspended material rather than dissolved Hg. Mercury speciation data show that concentrations of Hg (II) and methylmercury in stream-water samples are typically less than 22 ng/l, and generally less than 5% of the total Hg. Muscle samples of fish collected downstream from mines contain as much as 620 ng/g Hg (wet wt.), of which 90-100% is methylmercury. Although these Hg concentrations are several times higher than that in fish collected from regional baseline sites, the concentration of Hg in fish is below the 1000 ng/g action level for edible fish established by the US Food and Drug Administration (FDA). Salmon contain less than 100 ng/g Hg, which are among the lowest Hg contents observed for fish in the study, and well below the FDA action level.     

Environmental fate of Triclosan in the River Aire Basin, UK

The concentrations and removal rate of Triclosan, an antibacterial ingredient in consumer products, were measured at advanced trickling filter (TF) and activated sludge (AS) wastewater treatment plants (WWTPs) in the River Aire basin in the UK in September 2000. Additionally, the in-stream removal of Triclosan was measured directly in Mag Brook, the stream receiving the treated effluent from the TF plant, using a fluorescent dye tracer to determine the water plug travel times. The in-stream removal of the dissolved and un-ionized (i.e. bioavailable) fraction of the compound was measured using semipermeable membrane devices (SPMDs) deployed at various distances downstream from the WWTP discharge point. The estimated removal rates were used in the GREAT-ER (Geography-Referenced Regional Exposure Assessment Tool for European Rivers) model to predict the site-specific distribution of Triclosan concentrations in the Aire basin as well as to calculate regional concentrations. High WWTP (approximately 95%) and in-stream (0.21-0.33 h-1) removal rates of Triclosan in Mag Brook confirm that this chemical is rapidly eliminated from the aquatic environment.     

Effect of environmental conditions on the properties of concretes with different cement types

The paper reports on the changes in properties of concretes with different cement types associated with environmental conditions. Three strength classes with three different cement types (ordinary portland cement PC 42.5 (CEM I 42.5), portland composite cements PKC-A 42.5 (CEM II/A-M 42.5) and PKC-B 32.5R (CEM II/B-M 32.5R)) were used in the study. Also, a mixture was prepared with PC 42.5 and silica fume (SF). The effects of variable ambient conditions on plastic shrinkage of fresh concrete and cement paste, compressive strength, modulus of elasticity, capillary absorption and drying shrinkage of hardened concrete were investigated. In contrast to PC 42.5 cement paste, plastic shrinkage cracks were observed in PKC-B 32.5 and PKC-A 42.5 pastes. Water absorption coefficients of all concretes stored in natural environment were higher at all ages as compared to coefficients of concretes kept in laboratory. Drying shrinkage values of concrete with SF, except the first week, were significantly lower than those of others. Although different behaviors for different cement types were observed, water–cement ratio was one of the dominating factors determining the behavior of concrete. This ratio should be lowered to improve the durability of concrete.     

A sensitivity analysis on the atmospheric transformation and deposition of mercury in north-eastern USA

This paper presents the results of a sensitivity analysis on the factors that affect dry and wet deposition of atmospheric mercury (Hg), using a regional scale air quality model. Simulations were conducted for the north-eastern USA during a summer week and a winter week in 1997. Simulation results for the summer week and the winter week in general showed similar responses to changes in emission, environmental conditions, and alternative chemical mechanisms. Reduction of the ambient concentrations of soot or ozone was shown to reduce the wet deposition of Hg. When averaged over the summer and the winter week, the total deposition to the simulation domain would be reduced by 26% by reducing Hg emission from anthropogenic sources within the domain by 50%. For individual grids, however, only locations near local sources obtained noticeable reductions in ambient concentration and wet deposition due to the influence of re-emission from the natural surfaces and regional/global scale transport. The reduction in deposition would reach 36% if all Hg(II) emitted from anthropogenic sources were attached to particles. The total deposition was predicted to decrease by 22% when the gas phase Hg(II)-Hg(p) partitioning was included in the model. Only small changes in total deposition were observed by including the gas-phase ozone-Hg(0), reaction and the aqueous phase chlorine-Hg(0), reaction, and by lowering ambient concentrations of Hg(II) and Hg(p) at the upper lateral boundaries. During the summer week, Hg(II) deposition contributed 40% or more to the total deposition. The contribution increased to 70% in the winter week.     

Environmental degradation problems in the Heihe River Basin, northwest China

Environmental degradation in the Heihe River Basin of arid northwestern China is discussed in the paper. Under conditions of arid climate and unreasonable human activities, the processes of overuse of water resources by people in the basin have significant effects on the different kinds of environmental degradation, which include water environmental changes, land desertification and salinization, and vegetation degeneration. Furthermore, some proposals for environmental degradation research and control in the study site are put forward.     

The distribution of depleted uranium contamination in Colonie, NY, USA

Uranium oxide particles were dispersed into the environment from a factory in Colonie (NY, USA) by prevailing winds during the 1960s and '70s. Uranium concentrations and isotope ratios from bulk soil samples have been accurately measured using inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) without the need for analyte separation chemistry. The natural range of uranium concentrations in the Colonie soils has been estimated as 0.7-2.1 μg g^− 1, with a weighted geometric mean of 1.05 μg g^− 1; the contaminated soil samples comprise uranium up to 500 ± 40 μg g^− 1. A plot of ²³⁶U/²³⁸U against ²³⁵U/²³⁸U isotope ratios describes a mixing line between natural uranium and depleted uranium (DU) in bulk soil samples; scatter from this line can be accounted for by heterogeneity in the DU particulate. The end-member of DU compositions aggregated in these bulk samples comprises (2.05 ± 0.06) × 10^− 3235U/²³⁸U, (3.2 ± 0.1) × 10^− 5236U/²³⁸U, and (7.1 ± 0.3) × 10^− 6234U/²³⁸U. The analytical method is sensitive to as little as 50 ng g^− 1 DU mixed with the natural uranium occurring in these soils. The contamination footprint has been mapped northward from site, and at least one third of the uranium in a soil sample from the surface 5 cm, collected 5.1 km NNW of the site, is DU. The distribution of contamination within the surface soil horizon follows a trend of exponential decrease with depth, which can be approximated by a simple diffusion model. Bioturbation by earthworms can account for dispersal of contaminant from the soil surface, in the form of primary uranium oxide particulates, and uranyl species that are adsorbed to organic matter. Considering this distribution, the total mass of uranium contamination emitted from the factory is estimated to be c. 4.8 tonnes.     

Changes in the landscape structure of the Nagara River Basin, central Japan

A watershed is a structural and functional unit of a landscape consisting of various environments and sustaining a certain biodiversity. Conservation of watershed environments is important at both the regional and the national level. As a basis for conservation management, sufficient information about landscape structure should be provided for the whole terrestrial area of a watershed. In the present study, we reconstructed the former landscape structure and elucidated the changes in land use patterns during a period of about 80 years after 1900 (late Meiji era) in the Nagara River Basin, central Japan. We used three sets of maps for the analyses: old and modern topographical maps made in 1909, 1971 and 1992 by the Geographical Agency. Each map (ca. 18 km×22 km) was divided into 400 (20×20) grid cells, according to latitude and longitude. The dimension of each grid cell was about 1 km² (0.9 km×1.1 km). In each grid cell, all land-cover types were inventoried and the most dominant one was determined to be the dominant land-cover. The relative dominance (RD), frequency (FQ) and similarity index (SI) were calculated for analyses. The relative dominance of broad-leaved forest decreased, whereas those of conifer forest and residential areas increased throughout the whole study area during the 80-year period. However, regional differences in landscape change were found. In the upriver area, the relative dominance of broad-leaved forest decreased, while that of conifer forest increased. In the mid-river area, the relative dominance of conifer forest decreased, while that of broad-leaved forest increased. In the present study, we revealed the basic regional differences in landscape structure and their changes in the Nagara River Basin. Land use history with reference to socio-economics should be considered as an important factor affecting the present landscape structure.