Mercury in an ultraoligotrophic North Patagonian Andean lake (Argentina): Concentration patterns in di erent components of the water column

The deep, ultraoligotrophic piedmont lakes of Northern Patagonia (Argentina) are located in pristine and barely impacted areas, along a wide latitudinal range. Several studies have reported moderate to high total mercury (Hg) concentrations and contrasting methylmercury (CH3Hg+) production in di erent lake compartments. Sources of Hg for western Patagonian terrestrial and aquatic ecosystems are still not clear; while point sources can be ruled out and atmospheric deposition is a plausible source, along with contribution from active volcanic areas of the Andes. In this investigation, we reported a noticeably seasonal, spatial (between lake branches), and vertical (between water column strata) heterogeneity in the total Hg concentrations found in the pelagic zone of Lake Moreno. Sterile water samples taken in a depth profile of the lake showed moderate to high concentrations of CH3Hg+ in autumn with a decreasing trend with depth. Our results indicated that Hg is largely allocated in the plankton fraction between 10–53 m; which dominated within the euphotic (epilimnetic) zone of the lake due to the high densities attained by two species of the dinoflagellate Gymnodinium. The 53–200 m planktonic size fraction (comprising rotifers, ciliates and immature stages of crustaceans) and the > 200 m fraction (calanoid copepods and cladocerans) were found to bear strikingly lower total Hg concentrations, suggesting that the magnification of Hg at the planktonic consumer level is negligible.     

Validation of a conductometric bienzyme biosensor for the detection of proteins as marker of organic matter in river samples

This article describes a conductometric bi-layer based bienzyme biosensor for the detection of proteins as a marker of organic matter in rivers. Proteins were chosen to be used as indicators of urban pollution. The working mechanism of the bienzyme biosensor is based on the enzymatic hydrolysis of proteins into several fractions (peptides and amino acids), which results in a local conductivity change depending of the concentration of proteins. In this work, we began with the optimization of biosensor response using bovine serum albumin (BSA) as standard protein. For this objective seven enzymatic biosensors were prepared: four enzymatic sensors with only one layer of enzyme (proteinase K, trypsin, pronase or protease X) and three other enzymatic sensors with two layers (first layer: membrane containing proteinase K; second layer: one of the three other enzymes: trypsin, pronase or protease X). The biosensors were obtained through the deposition of enzymatic layers and the cross-linking process between enzymes and BSA in saturated glutaraldehyde vapour. The response of the various biosensors, described previously, were compared with the values of total organic carbon (TOC), and those of organic nitrogen (Norg), as determined by the laboratory accredits (CEMAGREF of Lyon) using the traditional method of analysis (NF EN 1484, infrared spectroscopy) and (NF EN 25663, mineralization/colorimetry assay) respectively for each water sample obtained from di erent sites in Lyon (France). The linear correlations obtained with the response of the seven biosensors showed the most important indices of correlations for the biosensor with two enzymatic layers: proteinase K + pronase (pkp). The optimum conditions for the preparation of the pkp biosensor increased the sensitivity and gave a limit of quantification of 0.583 g/L for TOC and 0.218 g/L for Norg in water samples. This sensor shows good reproducibility (2.28%), a capacity to be used at temperatures range 10– 30°C (depending on the season) and moreover a long lifetime (5 weeks).     

Watershed land use effects on lake water quality in Denmark

Mitigating nutrient losses from anthropogenic nonpoint sources is today of particular importance for improving the water quality of numerous freshwater lakes worldwide. Several empirical relationships between land use and in-lake water quality variables have been developed, but they are often weak, which can in part be attributed to lack of detailed information about land use activities or point sources. We examined a comprehensive data set comprising land use data, point-source information, and in-lake water quality for 414 Danish lakes. By excluding point-source-influenced lakes (n = 210), the strength in relationship (R2) between in-lake total nitrogen (TN) and total phosphorus (TP) concentrations and the proportion of agricultural land use in the watershed increased markedly, from 10-12% to 39-42% for deep lakes and from 10-12% to 21-23% for shallow lakes, with the highest increase for TN. Relationships between TP and agricultural land use were even stronger for lakes with rivers in their watershed (55%) compared to lakes without (28%), indicating that rivers mediate a stronger linkage between landscape activity and lake water quality by providing a "delivery" mechanism for excess nutrients in the watershed. When examining the effect of different near-freshwater land zones in contrast to the entire watershed, relationships generally improved with size of zone (25, 50, 100, 200, and 400 m from the edge of lake and streams) but were by far strongest using the entire watershed. The proportion of agricultural land use in the entire watershed was best in explaining lake water quality, both relative to estimated nutrient surplus at agricultural field level and near-lake land use, which somewhat contrasts typical strategies of management policies that mainly target agricultural nutrient applications and implementation of near-water buffer zones. This study suggests that transport mechanisms within the whole catchment are important for the nutrient export to lakes. Hence, the whole watershed should be considered when managing nutrient loadings to lakes, and future policies should ideally target measures that reduce the proportion of cultivated land in the watershed to successfully improve lake water quality.     

Effect of land use and land cover change on soil erosion and the spatio-temporal variation in Liupan Mountain Region, southern Ningxia, China

The Liupan Mountains are located in the southern Ningxia Hui Autonomous Region of China, that forms an important divide between landforms and biogeographic regions. The populated part of the Liupan Mountain Region has suffered tremendous ecological damage over time due to population pressure, excessive demand and inappropriate use of agricultural land resources. To present the relationship between land use/cover change and spatio-temporal variation of soil erosion, data sets of land use between the late 1980s and 2000 were obtained from Landsat Thematic Mapper (TM) imagery, and spatial models were used to characterize landscape and soil erosion conditions. Also, soil erosion in response to land use and land cover change were quantified and analyzed using data from geographical information systems and remote sensing. Soil erosion by water was the dominant mode of soil loss, while soil erosion by wind was only present on a relatively small area. The degree of soil erosion was classified into five severity classes: slight, light, moderate, severe, and very severe. Soil erosion in the Liupan Mountain Region increased between the late 1980s and 2000, both in terms of acreage and severity. Moderate, severe, and very severe eroded areas accounted for 54.86% of the total land area. The lightly eroded area decreased, while the moderately eroded area increased by 368817 ha (22%) followed by severe erosion with 146552 ha (8.8%), and very severe erosion by 97067.6 ha (5.8%). Soil loss on sloping cropland increased with slope gradients. About 90% of the cropland was located on slopes less than 15°. Most of the increase in soil erosion on cropland was due to conversion of steep slopes to cropland and degradation of grassland and increased activities. Soil erosion was severe on grassland with a moderate or low grass cover and on dry land. Human activities, cultivation on steep slopes, and overgrazing of pastures were the main reasons for the increase in erosion severity.     

漳泽水库水体污染对黑斑蛙蝌蚪遗传毒性的野外调查研究

通过野外采集漳泽水库不同采样点的黑斑蛙蝌蚪,采用微核、核异常、彗星试验3种方法,研究了水体污染对蝌蚪红细胞微核率、核异常率和DNA断裂3种遗传毒性指标的影响。微核试验结果显示:各采样点红细胞微核率除泽头采样点外,均明显高于阴性对照(P0.01),其中水库入口店上采样点的微核率最高,为6.87‰,位于水库上、中、下游3个采样点的微核率逐渐下降,从大到小依次为:下韩(5.45‰)、台上(3.71‰)、泽头(2.33‰)。核异常试验结果显示:各采样点核异常率均明显高于阴性对照(P0.01),核异常率与微核率二者变化趋势趋于一致。彗星试验结果显示:各采样点红细胞尾长、尾矩与阴性对照相比差异均极显著(P0.01),尾长、尾矩的变化趋势与微核试验结果一致。对同样位于水库中游的采样点司徒和台上的4个指标进行多重比较分析发现:微核率、核异常率和彗星尾长差异均不显著(P0.05),而尾矩差异显著(P0.05)。综上可知,漳泽水库各采样点水体具有较高的遗传毒性,主要毒性作用为引起染色体(DNA)断裂;各采样点遗传毒性指标变化规律与水体污染物变化规律趋于一致,因此应用这3种方法可以有效地对水体遗传毒性进行检测。     

中国大陆省级无意产生的五氯苯和六氯苯多源大气排放清单

基于技术分类方法构建了动态排放因子数据库,再采用排放因子法,自下而上构建了1960～2019年中国大陆省级无意产生的五氯苯和六氯苯的多源大气排放清单,并探究其时空分布特征.研究结果显示,五氯苯的最大排放源是含氯化学品生产,而六氯苯的最大排放源则是金属冶炼;五氯苯和六氯苯的排放密度均表现为东部地区高于西部地区的特征.从1960～2019年,五氯苯和六氯苯的排放量从1277.9,81.2kg分别上升至11862.3,439.7kg,但排放强度(单位GDP的排放量)却从869.3,55.2g/亿元分别下降至12.0,0.4g/亿元.     

彗星试验检测地下水有机污染物的遗传毒性效应

应用人外周血淋巴细胞和小鼠淋巴细胞彗星试验,对长治市5个样点的地下水有机浓集物进行了遗传毒性研究。结果表明,各水样中有机浓集物在3个染毒剂量50,200,800 m L·管-1条件下均可对人外周血淋巴细胞和小鼠淋巴细胞DNA产生不同程度的遗传损伤,并且随着浓度的升高,DNA损伤程度明显增加,各实验组与溶剂对照组相比有P<0.05或P<0.01显著差异。研究表明,上述2种淋巴细胞彗星试验可有效地检测地下水体有机污染物的遗传毒性。     

应用小鼠淋巴细胞彗星试验检测地下水遗传毒性

应用小鼠淋巴细胞彗星试验对长治市5个点位地下水水质作遗传毒性研究。结果表明,各水样有机浓集物均可对小鼠淋巴细胞DNA产生不同程度的遗传损伤,随着剂量的增加,Olive尾矩与阴性对照组(0.72±0.09)相比均有显著性差异(P0.05,P0.01)。在试验浓度范围内,以彗星尾部DNA含量、彗星尾长、尾矩和Olive尾矩所指示的DNA损伤程度随剂量增大而逐渐增加,存在显著的剂量-效应关系,其相关系数0.815。     

Physical symptoms in young adults and their use of different computers and mobile phones

This paper presents the use of new technical equipment by young adults (30 years old or younger), and the physical symptoms they have. The paper then analyses how the symptoms are associated with the use of computers and mobile phones, taking into account the background information. The study is based on a survey of 15 000 working-age (18-65) Finns. The responses (1563) covering young adults' physical symptoms were analysed. Altogether 53.3% of all young adults had pretty often or more frequently pain, numbness or aches in the neck and 32.2% had aches in the hip and lower back. Women experienced more pain, numbness or aches in the neck (65.0%) than men (34.5%). The use of different computers at leisure quite often had an association with some symptoms in different parts of the body. In addition, exhaustion at work had associations with some physical symptoms. In the future, it is essential to note ergonomic reasons and exhaustion at work when young adults experience pain, numbness or aches.