The Freshwater Mussel Parreysia Favidens (Benson) As A Biological Indicator of Polonium - 210 in A Riverine System

The concentration of ²¹⁰Po, an alpha emitter from the natural uranium series was measured in the soft tissues (total), shell, and different organs - digestive glands, gills, mantle and foot - of the freshwater mussel, Parreysia favidens (Benson), collected from the river Kaveri, at Tiruchirapalli in South India. the analyses were made in three size groups based on shell length (Group 1: 2-4 cm; Group 2: 4-5 cm; Group 3: 5-6 cm). the soft tissues of the mussel accumulated higher concentrations of ²¹⁰Po (74.0-125.5 Bq kg^-1 fresh) than the shell (2.9-3.9 Bq kg^-1 fresh). Further, younger mussels (1 group) showed higher concentrations (125.5+2.0 Bq kg^-1 fresh) in total soft tissues than older ones (III Group) (74.0+1.6 Bq kg^-1 fresh); concentration factors were 1.59x 10⁵ in I group and 9.37 × 10⁴ in III group. the ²¹⁰Po was observed to be non-uniformly distributed among the internal organs, which maintained the following descending order with reference to ²¹⁰Po accumulation: digestive glands, ranging from 286.2+3.5 Bq kg^-1 fresh to 43+1.3 Bq kg^-1 fresh. the concentration of ²¹⁰Po in the mussels was distinctly higher than that in the grass, Echinochloa colonum (J. Koenig), and carp, Cirrhinus cirrhosa (Bloch), from the same river. These data indicate that younger mussels could be used as an excellent biological indicator of ²¹⁰Po and among soft tissues, digestive glands are preferable to other tissues to monitor the distribution of ²¹⁰Po in the riverine system.     

Radioactive Isotopes of Strontium, Caesium and Plutonium in Sediments of the Northern Adriatic Sea

Sediment samples of different strata (0-3 and 12-15 cm) were collected between 1990 and 1992 during seasonal cruises in the Northern Adriatic Sea. A complete mapping of the Sr-90, Cs-137, Pu-238 and Pu-239(240) concentrations was obtained for samples covering a wide area, stretching from the Gulf of Trieste towards the Ancona shoreline. Sr-90 concentrations varied between 1.5 and 6.5 Bq kg^-1 dw, Cs-137 was in the range 0.9-38.9 Bq kg^-1 dw, Pu-239(240) in the range 0.08-1.5 Bq kg^-1 dw and Pu-238 around 0.03 Bq kg^-1 dw. Special reference was also put on the comparison between the off-shore environment and data obtained from samples collected inside the Po river delta. in spite of the major accumulation of Cs-137 inside the estuarine environment, higher concentrations of strontium and plutonium isotopes were detected in the offshore environment.     

Radioactivity in the Baltic Sea

The Baltic Sea is, like the Mediterranean, a marginal sea, which with the Black Sea, were marine environments contaminated from the Chernobyl accident.

Radiocaesium and plutonium isotopes were studied in water, sediment and macroalgae in the Baltic Sea since 1982. the inventory of ¹³⁷Cs in the Baltic increased from 0.65 PBq to 5.85 PBq following the Chernobyl accident. the corresponding increase for ^{239 + 240}Pu was less significant and yielded 1.5 TBq to a total value of 16.5 TBq.

For plutonium, 98% is trapped in the sediment and the net-exchange of this element through the Baltic straits is very small (1 GBq/year), while for radiocaesium, 45% is in the water phase and there is a net-loss of 60 000 GBq annually into the adjacent water (Kattegatt).     

Partitioning of Cs-137 Between Sediment and Water From the Black Sea

As part of a joint USA/USSR Environmental Agreement to determine the distribution and concentration of Chernobyl radioactivity in the northwest Black Sea area, the sediment from eight stations was collected and analyzed to assess the ability of this material to adsorb radiocaesium. Batch tests were conducted in which Cs-137 tracer was added to mixtures of sediment and bottom water, with contact solutions ranging from 85 Bq ml^-1 to 1,760 Bq ml^-1. This work was done in an argon atmosphere at 9.5°C, which is the average temperature of the sediment. Isotherms were linear for all cores and distribution ratios (R_D) calculated from the slopes of the isotherms ranged from 660 to 1,660 ml g^-1. These isotherms fit a simplified Freundlich isotherm. Correlations of R_D to a number of sediment parameters describing texture and mineralogy were determined. A close relationship was observed between R_D for caesium and the percentage of illite contained in the samples.     

茂名近岸海域中、小型浮游动物群落特征及其与环境因子的关系

近年来,随着茂名经济迅猛发展及涉海工程建设,其近海海域遭到日益严重的污染,海域环境日趋恶化。为更好地了解茂名近岸海域中小型浮游动物群落结构及其与环境因子的关系,摸清中小型浮游动物的种类组成及其空间分布状况,保护近岸海域生物多样性,分别于2019年夏季(6月)和秋季(9月)对茂名近海浮游动物进行调查。调查共发现浮游动物52种,以桡足类为主(达到40种,占比76.92%)。秋季浮游动物平均丰度和平均生物量(分别为29.82 ind·m^-3和282.08 mg·m^-3)均高于夏季(分别为15.71×10³ ind·m^-3和110.23 mg·m^-3)。短角长腹剑水蚤(Oithona brevicornis)、小长腹剑水蚤(Oithona nana)、强额拟哲水蚤(Paracalanus crassirostris)和小拟哲水蚤(Paracalanus parvus)为茂名近岸海域春、夏季优势种。夏季和秋季浮游植物物种多样性指数平均值分别为3.06和2.69,丰富度指数平均值分别为3.65和3.38,均匀度指数平均值分别为0.71和0.66。运用BIO-ENV方法分析了浮游动物群落结构以及与浮游植物丰度、环境因子之间的关系,结果表明浮游植物丰度、溶解氧、盐度、水温、水深是影响夏季浮游动物群落的主要环境因子,水深、浮游植物丰度是影响秋季浮游动物群落的主要环境因子。     

蚯蚓粪复配硼钼调理剂对土壤改良和茄子生长的影响作用

土壤质量决定着农产品的质量和农业生产的可持续发展,然而土壤退化成为农业生产的重要限制因素之一,施用土壤调理剂有利于减缓土壤退化的速度。该研究配制土壤调理剂,即蚯蚓粪:草菇渣:蛭石=6:3:1、钼酸钠50 g·kg^-1、硼酸13.3 g·kg^-1,并设5个不同的处理CK、QY-T1、QY-T2、QY-T3、QY-T4,研究该调理剂对土壤理化性质和肥力的影响作用,分析其对茄子硼、钼和生长状况的促进作用。结果表明,该调理剂能提高土壤温度,5 cm、09:00的土壤温度QY-T4较高,但10 cm、14:00的土壤温度QY-T3最高;土壤容重随着施用量的增大而显著降低至1.50 g·cm^-3以下,土壤pH值从CK的4.93提高到QY-T4的5.57、微生物量碳分别比CK高29.9%、36.1%、47.6%和52.2%,有机质分别比CK高10.8%、11.7%、12.5%和7.0%,QY-T2、QY-T3、QY-T4土壤有效硼达到0.35、0.36、0.42mg·kg^-1,QY-T1、QY-T2的有效钼分别为0.107、0.140mg·kg^-1,随着调理剂的增多而增多,但QY-T3、QY-T4分别为0.101、0.092 mg·kg^-1反而随着调理剂的增多而下降,茄子硼、钼含量都随着调理剂的增加而增大,且显著高于对照(P<0.01);总产量比CK分别提高了29%、36%、190%和66%,总个数分别增加了25%、28%、155%和66%,59 d株高和叶片面积分别比CK增高了23%、1.4%、23%、16%和6.8%、11%、9.3%、7.4%,而叶片数量,所有的处理差异不显著,因此推荐该土壤调理剂用量与QY-T3相同,为1.5×10⁴kg·hm^-2。该研究可为土壤调理剂修复土壤退化的应用提供依据。     

137Cs Inventory in Abiotic Component and Biota From the Aegean and Ionian Sea - Greece

This study deals with ¹³⁷Cs dispersion and behaviour in the Aegean and Ionian Sea based on work done during the period 1984-1994, as a brief general review. Sea water, sediment and marine biota were analysed and measured by gamma spectrometry and the activity concentrations of ¹³⁷Cs were evaluated with consideration to the sources of pollution. According to ¹³⁷Cs levels the period is distinguished into three sub-periods, the pre-Chernobyl, the early Chernobyl influence and the late Chernobyl influence period. During the early period of the Chernobyl accident the ¹³⁷Cs levels in the Greek marine environment increased roughly up to an order of magnitude if compared with the pre-accident ones. Since 1988, the late impact of the accident is focused mainly in the North Aegean Sea, at the Dardanelles mouth, due to the Black Sea outflow.     

天津市夏季PM2.5中碳组分时空变化特征及来源解析

为研究天津市夏季PM_2.5中碳组分的时空变化特征及来源,于2019年7—8月设立2个点位分昼夜采集天津市PM_2.5样品,并测定了其中有机碳(OC)和元素碳(EC)的含量。结果表明,城区PM_2.5、OC和EC浓度日均值分别为(53.4±20.8)μg·m^-3、(8.72±2.56)μg·m^-3和(1.67±0.90)μg·m^-3,郊区PM_2.5、OC和EC浓度日均值分别为(54.2±24.5)μg·m^-3、(7.54±2.50)μg·m^-3和(1.82±1.06)μg·m^-3;白天PM_2.5、OC、EC的平均浓度分别为(47.3±16.1)μg·m^-3、(8.7±2.1)μg·m^-3和(1.5±0.6)μg·m^-3,夜间PM_2.5、OC、EC的平均浓度分别为(60.2±26.2)μg·m^-3、(7.5±2.9)μg·m^-3和(2.0±1.2)μg·m^-3。OC浓度表现为城区高于郊区,白天高于夜间;EC及PM_2.5浓度表现为郊区高于城区,夜间高于白天。OC/EC比值分析得,城区(6.04)高于郊区(5.08);白天(6.58)高于夜间(4.54)。城区OC与EC相关性弱于郊区,白天OC与EC相关性弱于夜间。采用EC示踪法与MRS模型对SOC含量进行估算,得到白天与夜间SOC浓度分别为(5.71±1.35)μg·m^-3和(3.81±1.20)μg·m^-3,白天SOC污染比夜间严重。丰度分析与主成分分析的结果表明,天津市夏季城郊区PM_2.5中碳组分均主要来源于燃煤和机动车尾气排放。     

Inventories and Distribution of Radiocaesium in Arctic Marine Sediments: Influence of Biological and Physical Processes

Extensive surveys of sediment burdens of radiocaesium, specifically ¹³⁷Cs, and other radioactive contaminants in the Arctic during the 1990's, indicate that almost all anthropogenic radionuclides buried on continental shelves adjacent to Alaska are derived from global bomb fallout. the ¹³⁷Cs (half-life: 30.2y) activities observed in surface (0-4 cm) marine sediments however, vary widely, albeit much less than the expected current inventory resulting from bomb fallout at this latitude (∼100mBq cm^-2). This observed geographical variation provided the opportunity to evaluate physical and biological mechanisms that may affect caesium biogeochemistry on Arctic continental shelves. We investigated whether high biological productivity in portions of the Bering and Chukchi Seas is effective in removing dissolved radiocaesium from the water column, and whether biological production in overlying water affects total radiocaesium inventories in sediments. Based upon C/N ratios in the organic fraction of shallow sediments, we found no evidence that higher inventories or surface activities of radiocaesium are present in areas with higher deposition of particulate organic matter. Based upon stable carbon isotope ratios of organic matter in sediments, we found no evidence that terrestrial runoff contributes proportionally to higher surface activities, although terrestrial runoff may affect total inventories of the radionuclide. Radiocaesium content of surface sediments was significantly correlated with total organic carbon content of sediments and the proportion of sediments in the finest sediment fractions. Because high current flow can also be expected to influence distributions of those sedimentary parameters, we conclude that re-distribution of     

Denitrification potential in a Louisiana wetland receiving diverted Mississippi River water

Excess nitrate in Mississippi River water entering offshore areas is reported to contribute to low oxygen (hypoxia) conditions in the Gulf of Mexico. Excessive algal growth driven by the excess nitrogen results in a decrease in dissolved oxygen in bottom water. Reintroduction of Mississippi River waters into a Louisiana coastal wetland has the potential to reduce the amount of nitrate reaching offshore waters. In this study, reduction in the concentration of added NO₃^- was determined in sediment-water-columns collected from a wetland site in Breton Sound estuary receiving nutrient inputs from the Mississippi River. The capacity of a wetland to process nitrate in floodwater was determined in the laboratory. The rates of NO₃^- removal (determined from change in nitrate concentration in the floodwater) averaged 97 mg N m^-2 d^-1 over 16 d for a 1750-mg NO₃-N m^-2 addition, and 170 mg N m^-2 d^-1 over 16 d for a 3500-mg NO₃-N m^-2 addition. The total N₂O-N emissions from the 1750- and 3500-mg NO₃-N m^-2 additions were 19 and 54 mg N m^-2 accounting for 1.1% and 1.5% of the applied NO₃-N, respectively. Using the acetylene-inhibition technique, the average denitrification rate was determined to be 57 and 87 mg N m^-2 d^-1 (21 and 32 g N m^-2 yr^-1) during the most active denitrification period of 5 d after incubation for 1750 and 3500 mg NO₃^--N m^-2 of added nitrate in floodwater, respectively. The total N evolved over 11 d as N₂O + N₂ was equivalent to 436 and 921 mg N m^-2 (24.9% and 26.3%, respectively, of added N). Increasing the amount of NO₃^- applied to the overlying water increased the rate of NO₃^- loss and N₂O emission significantly. The thickness of the oxidized surface sediment layer was also influenced by the NO₃^- application to the floodwater with a significant linear correlation between nitrate addition and thickness of the oxidized layer (r = 0.9998, p = 0.01). This study indicates that wetlands receiving diverted Mississippi River water have the potential to process and remove NO₃^- in the river water, reducing the amount of NO₃^- reaching to offshore areas.