Carbon, nitrogen, oxygen and sulfide budgets in the Black Sea: A biogeochemical model of the whole water column coupling the oxic and anoxic parts

Carbon, nitrogen, oxygen and sulfide budgets are derived for the Black Sea water column from a coupled physical-biogeochemical model. The model is applied in the deep part of the sea and simulates processes over the whole water column including the anoxic layer that extends from ?115 m to the bottom (?2000 m). The biogeochemical model involves a refined representation of the Black Sea foodweb from bacteria to gelatinous carnivores. It includes notably a series of biogeochemical processes typical for oxygen deficient conditions with, for instance, bacterial respiration using different types of oxidants (i.e denitrification, sulfate reduction), the lower efficiency of detritus degradation, the ANAMMOX (ANaerobic AMMonium OXidation) process and the occurrence of particular redox reactions. The model has been calibrated and validated against all available data gathered in the Black Sea TU Ocean Base and this exercise is described in Gregoire et al. (2008). In the present paper, we focus on the biogeochemical flows produced by the model and we compare model estimations with the measurements performed during the R.V. KNORR expedition conducted in the Black Sea from April to July 1988 (Murray and the Black Sea Knorr Expedition, 1991). Model estimations of hydrogen sulfide oxidation, metal sulfide precipitation, hydrogen sulfide formation in the sediments and water column, export flux to the anoxic layer and to the sediments, denitrification, primary and bacterial production are in the range of field observations.With a simulated Gross Primary Production (GPP) of 7.9 mol C m⁻² year⁻¹ and a Community Respiration (CR) of 6.3 mol C m⁻² year⁻¹, the system is net autotrophic with a Net Community Production (NCP) of 1.6 mol C m⁻² year⁻¹. This NCP corresponds to 20% of the GPP and is exported to the anoxic layer. In order to model Particulate Organic Matter (POM) fluxes to the bottom and hydrogen sulfide profiles in agreement with in situ observations, we have to consider that the degradation of POM in anoxic conditions is less efficient that in oxygenated waters as it has often been observed (see discussion in Hedges et al., 1999). The vertical POM profile produced by the model can be fitted to the classic power function describing the oceanic carbon rate (C_R=Z^−α) using an attenuation coefficient α of 0.36 which is the value proposed for another anoxic environment (i.e. the Mexico Margin) by Devol and Hartnett (2001). Due to the lower efficiency of detritus degradation in anoxic conditions and to the aggregation of particles that enhanced the sinking, an important part of the export to the anoxic layer (i.e. 33%, 0.52 mol C m⁻² year⁻¹) escapes remineralization in the water column and reaches the sediments. Therefore, sediments are active sites of sulfide production contributing to 26% of the total sulfide production.In the upper layer, the oxygen dynamics is mainly governed by photosynthesis and respiration processes as well as by air-sea exchanges. ?71% of the oxygen produced by phytoplankton (photosynthesis+nitrate reduction) is lost through respiration, ?21% by outgasing to the atmosphere, ?5% through nitrification and only ?2% in the oxidation of reduced components (e.g. Mn²⁺, Fe²⁺, H₂S).The model estimates the amount of nitrogen lost through denitrification at 307 mmol N m⁻² year⁻¹ that can be partitioned into a loss of ?55% through the use of nitrate for the oxidation of detritus in low oxygen conditions, ?40% in the ANAMMOX process and the remaining ?5% in the oxidation of reduced substances by nitrate.In agreement with data analysis performed on long time series collected since the 1960s (Konovalov and Murray, 2001), the sulfide and nitrogen budgets established for the anoxic layer are not balanced in response to the enhanced particle fluxes induced by eutrophication: the NH₄ and H₂S concentrations increase.     

Toxic mine drainage from Asia’s biggest copper mine at Malanjkhand,India

This paper has studied the environmental deterioration due to copper mining in Malanjkhand at Central-east India. No data is available on environmental degradation at the studied site although geological aspects are well studied. Mine drainage from the mines is definitively toxic. The site is also undergoing various stages of acid mine drainage (AMD) particularly from the heap leaching sites and the tailing area. AMD impacted water steam and sediment were also analysed. Results show substantial level of contamination of almost all segments of environment. Presence of elevated level of other heavy metal viz. Au, Ag, Pb, Cr, Cd, Fe, Cu and base metals like Na, K in AMD impacted water and sediments is due to metal leaching effect of AMD. Bio monitoring with the help of benthic macro invertebrates and metal accumulation in plants was also carried to know the impact of the toxic drainage. Results prove a very significant impact on the environmental health.     

Acid Deposition and Integrated Zoning Control in China

China's rapidly growing economy is coupled with the consumption of large amounts of coal. An energy mix dominated by coal and inefficient energy utilization processes have led to increasingly serious problems of acid rain and sulfur dioxide pollution. Moreover, trends in the emissions of acidifying air pollutants lead to predictions of a very serious acid deposition problem in the future. In the absence of mitigating actions, these trends foretell a future of increasingly detrimental impacts to ecosystems in China and, potentially, to ecosystems in neighboring countries. China has implemented a two control zone (TCZ) policy, resulting in the establishment of acid rain and sulfur dioxide control zones, in an attempt to implement a cost-effective approach to mitigating acid deposition problems. While some short-term successes have resulted from management actions associated with the TCZ policy, it is clear additional measures and new policy directions are needed to reverse worsening acid deposition problems in the long term. To this end the following recommendations are presented: adjusting the primary energy mix, placing a greater emphasis on abating the effects of acid deposition, concentrating pollution control on large point sources, implementing an emission permit system for coal-fired power plants, utilizing an integrated approach in designing and evaluating control measures, and developing a greater research capacity. Research strategies must be developed that will lead to: (1) an improved scientific understanding of the sources of acidifying pollutants, their associated migration patterns, and their impacts; and (2) an identification of cost-effective mitigating strategies for the entire country.     

Preliminary Caesium Data From A Cooperative Us/Ussr Monitoring Survey for Chernobyl Radioactivity in the Black Sea

In June 1990, scientists from the US Environmental Protection Agency's (EPA) Office of Radiation Programs (ORP), and the Woods Hole Oceanographic Institution (WHOI), travelled to Sevastopol in the Soviet Union to work with radioecologists and marine scientists from the USSR Institute of Biology of the Southern Seas (IBSS). the purpose of this cooperative programme was to conduct a monitoring survey for radioactivity in the northwestern Black Sea. Samples of sediment, surface and in-situ water, and biota were collected from fourteen stations for post-survey radionuclide analyses to determine levels of radioactivity in the Black Sea environment resulting from the Chernobyl nuclear power plant explosion and subsequent transport of radioactivity via the Dnepr and Danube rivers. This paper presents the preliminary data for caesium-137 and caesium-134 in sediment samples analyzed by the EPA/ORP. Caesium-137 was measured at four shallow (20-114 m) stations on the shelf near the mouth of the Dnepr and Danube Rivers, but was not detected in sediments from comparable depths at stations further off shore or in slope sediments at depths of 510-1288 meters. Caesium-134 was detected only in sediments from the shallow-water station nearest to the Danube River.     

我国酸雨地区水体会酸化吗——重庆水体酸化的调查

调查结果表明:重庆地区已出现酸化水体,水体 pH 值可低至4.57,ANC 低至77.92μg/L。酸化原因主要与酸沉降、集水区土壤及植被等有关。重庆的水体酸碱度的分布规律大致与土壤酸碱度分布一致。海拔在500m 以下的水体 pH 值多在7～8之间,甚至大于8,且 ANC 和HCO_3~-都高,有较强的缓冲性。而海拔500m 以上的水体,pH 值小于7.0,缓冲能力弱,在长期的酸沉降影响下,由于其集水区土壤缺乏缓冲能力,最终水体将面临进一步酸化。     

Effects of Soil Conditions on Survival and Growth of Black Willow Cuttings

Current streambank restoration efforts focus on providing bank stability, enhancing water quality, and improving woody habitat using native vegetation rather than traditional engineering techniques. However, in most cases harsh site conditions limit restoration success. A two-year field study was conducted at Twentymile Creek, in northern Mississippi, investigating edaphic factors governing the survival of black willow (Salix nigra) cuttings used for streambank restoration. Low height growth, above-ground biomass production, and average leaf area were observed in willow cuttings grown in plots subjected to moisture deficits. However, sediment texture emerged as the dominant factor determining willow post growth, health, and survival. Shoot biomass, leaf biomass, and total above-ground biomass were 15-, 10-, and 14-fold greater for large willow cuttings (posts) grown in plots with sandy sediments relative to those grown in plots with similar moisture and soil redox potential but with silt and clay sediments. Average leaf size, average leaf mass and specific leaf area were all lower in fine textured plots. Under moisture conditions present at our sites, coarse-grained sediment (sand) was more conducive to willow growth, biomass production, and survival than were fine-grained sediments (silt/clay). Our results strongly suggest that soil texture and moisture conditions can determine restoration success. Therefore, it is critical that site conditions are factored into the selection of project locations prior to the initiation of willow planting restoration projects.     

Evaluation of Air Quality over the Black Sea: Major Ionic Composition of Rainwater

This article attempts to put the light on the air quality of the Black Sea region of Turkey. In addition to that, it endeavors to locate the possible sources of the different pollutants at local, regional and long range transported scales. About 196 rainwater samples were collected over the Black Sea region of Amasra between 1995 and 1999, and analyzed for major ions and trace elements using spectrophotometric techniques. Andersen wet only rain samples were used to collect rain events, where the rain sample was filtered inline using 0.45 m cellulose acetate filters. Major anions (SO₄ ^2-, NO₃ ^- and Cl^-) were determined using ion chromatography, whereas metals (Ca, Mg, Al, Fe, Na, K), werequantified using ICP-AES. This study shows that, the Black Sea region receives different amounts and types of anthropogenic pollutants via long-range transport according to trajectory models. Although the pH of rain water is not considered acidic (pH = 5.21) yet the neutralizing species are lower than other sites around Europe.     

Predicting mosaics and wildlife diversity resulting from fire disturbance to a forest ecosystem

A model for predicting community mosaics and wildlife diversity resulting from fire disturbance to a forest ecosystem is presented. It applies an algorithm that delineates the size and shape of each patch from grid-based input data and calculates standard diversity measures for the entire mosaic of community patches and their included animal species. The user can print these diversity calculations, maps of the current community-type-age-class mosaic, and maps of habitat utilization by each animal species. Furthermore, the user can print estimates of changes in each resulting from natural disturbance. Although data and resolution level independent, the model is demonstrated and tested with data from the Lewis and Clark National Forest in Montana.     

城市景观水体中腐殖酸的臭氧氧化去除

以南京师范大学德风园池底泥中提取的腐殖酸(HA)为研究对象,采用臭氧氧化技术对其进行去除,对初始pH值、混合气体流量、腐殖酸(HA)初始浓度以及水中常见离子等因素对去除效果的影响进行了研究。实验结果表明:腐殖酸(HA)的去除率随初始pH值的升高而提高,随混合气体流量减少而提高;当腐殖酸(HA)初始浓度为5 mg/L时,反应过程中溶液的UV254升高,紫外扫描结果发现,溶液在200~220 nm内出现杂乱的吸收峰,表明有新物质生成;水中常见的无机阴离子(CO32-、HCO3-)和二价金属离子(Ca2+、Cu2+)的存在会降低臭氧对腐殖酸(HA)的去除率。     

UV/Fenton反应对直接黑38的脱色与矿化

为了研究过程参数对photo-Fenton法降解偶氮染料直接黑38人工废水的影响,进行了实验室规模的UV/Fenton反应光催化降解染料直接黑38的研究。在一定的时间段内检测水溶液直接黑38的UV吸光度、总有机碳(TOC)浓度的变化,确定了直接黑38废水的降解速度。以单因素实验方法确定了pH值、[Fe2+]、[H2O2]比例及其初始浓度对降解速度的影响。实验结果表明,在pH为3,染料浓度为30mg/L,[Fe2+]/[H2O2]比例1:100,[Fe2+]=0.12mmol/L,[H2O2]=12mmol/L条件下,UV/Fenton方法能在50min内使染料脱色率达90%,使TOC的去除率达到57%。实验证明了photo-Fenton法对于含有偶氮染料废水的脱色与矿化具有很好的应用前景。