Correlations between experimental and predicted equilibrium distribution coefficient of chlorobenzene and chlorophenol compounds in soil-water systems using partial solubility parameters

Many pesticides are degraded to become chlorinated aromatic compounds in soils. Equilibrium distribution of chlorobenzene and chlorophenol compounds in soil-water systems of Yangmingshan loam, Pingcheng silty clay loam and Annei silty loam was studied with the integral distribution equilibrium equation involving the partial solubility parameters of the chemicals. If the adsorption of chemicals on soils is partitioning in soil organic matter surrounding the soil mineral particles, the absorption constant (Kd) of a chemical in soil-water system could be stated as the distribution coefficient (or partition constant, Koc) of the chemical in the two adjunct immiscible phases--water and soil organic matter. The distribution coefficient (Koc) of chemicals calculated from the integral distribution equilibrium equation agrees well with the experimental adsorption coefficient (Kd, or experimental Koc) of chemicals determined in this study, for all the three different types of soils in water according to multiple-regression analysis. Reference data of Karger or Tijssen are employed to estimate the Koc for both polar and non-polar chemicals. The integral distribution equilibrium equation can exactly describe the distribution behavior of nonionic compound of chlorobenzenes and chlorophenols in soil-water systems.     

Degradation of chlortoluron in water disinfection processes: a kinetic study

The kinetics of the reaction between chlortoluron, a phenylurea herbicide [N'-(2-hydroxy-4-methyl-5-chlorophenyl)-N,N-dimethylurea], and hypochlorite, the active species in water disinfection processes involving chlorine, were investigated by HPLC-UV and HPLC-electrospray ionisation mass spectrometry (HPLC-ESI-MS). In particular, the concentrations of the main chlortoluron by-products were monitored as a function of time by HPLC-ESI-MS and a kinetic model was developed to fit the relevant curves. The results showed that chlortoluron degradation starts with two parallel pathways, namely, chlorination and hydroxylation of the aromatic ring, which are then followed by consecutive chlorination reactions, and after almost 2 weeks by ring opening and partial mineralisation, as confirmed by head-space solid-phase microextraction gas chromatography-MS (SPME-GC-MS) and total organic carbon (TOC) measurements. Kinetic constants for the first reactions of the overall process, under pseudo-first-order conditions (hypochlorite excess), were estimated by a fitting procedure.     

Speciation of heavy metals in marine sediments from the East China Sea by ICP-MS with sequential extraction

Twelve elements (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Sn, Cd and Pb) in 24 sediment samples at eight sites (S1-S8) from the East China Sea were analyzed with the BCR sequential extraction (SE) protocol to obtain the metal distribution patterns in this region. The results showed that the heavy metal pollutions in S4 and S8 were more severe than in other sampling sites, especially Cd and Pb pollution. In the top sediments at S4 and S8, both the total contents and the most dangerous non-residual fractions of Cd and Pb were extremely high. More than 90% of the total concentrations of V, Cr, Mo and Sn existed in the residual fraction. Fe, Co, Ni, Cu and Zn mainly (more than 60%) occurred in the residual fraction. While Mn, Pb and Cd dominantly presented in the non-residual fractions in the top sediments. The metal distribution patterns with depth and the correlations between total organic carbon (TOC) and the total Fe-Mn content were also investigated. The results showed that, for most of the elements except Fe, the concentration of elements in fraction A in the top sediments was higher than that in other depth. The similar rule was also found in fraction B but not in fraction C. Besides, the distributions of V, Cd in fraction B and Pb, Cd, Cu in fraction C might be affected by TOC.     

Transient dynamics of pelagic producer-grazer systems in a gradient of nutrients and mixing depths

Phytoplankton-grazer dynamics are often characterized by long transients relative to the length of the growing season. Using a phytoplankton-grazer model parameterized for Daphnia pulex with either flexible or fixed algal carbon:nutrient stoichiometry, we explored how nutrient and light supply (the latter by varying depth of the mixed water column) affect the transient dynamics of the system starting from low densities. The system goes through an initial oscillation across nearly the entire light-nutrient supply space. With flexible (but not with fixed) algal stoichiometry, duration of the initial algal peak, timing and duration of the subsequent grazer peak, and timing of the algal minimum are consistently accelerated by nutrient enrichment but decelerated by light enrichment (decreasing mixing depth) over the range of intermediate to shallow mixing depths. These contrasting effects of nutrient vs. light enrichment are consequences of their opposing influences on food quality (algal nutrient content): algal productivity and food quality are positively related along a nutrient gradient but inversely related along a light gradient. Light enrichment therefore slows down grazer growth relative to algal growth, decelerating oscillatory dynamics; nutrient enrichment has opposite effects. We manipulated nutrient supply and mixing depth in a field enclosure experiment. The experimental results were qualitatively much more consistent with the flexible than with the fixed stoichiometry model. Nutrient enrichment increased Daphnia peak biomass, decreased algal minimum biomass, decreased the seston C:P ratio, and accelerated transient oscillatory dynamics. Light enrichment (decreasing mixing depth) produced the opposite patterns, except that Daphnia peak biomass increased monotonously with light enrichment, too. Thus, while the model predicts the possibility of the "paradox of energy enrichment" (a decrease in grazer biomass with light enrichment) at high light and low nutrient supply, this phenomenon did not occur in our experiment.     

Testing the abundant center model using range-wide demographic surveys of two coastal dune plants

It is widely accepted that species are most abundant at the center of their geographic ranges and become progressively rarer toward range limits. Although the abundant center model (ACM) has rarely been tested with range-wide surveys, it influences much thinking about the ecology and evolution of species' distributions. We tested ACM predictions using two unrelated but ecologically similar plants, Camissonia cheiranthifolia and Abronia umbellata. We intensively sampled both throughout their one-dimensional distributions within the Pacific coastal dunes of North America, from northern Baja California, Mexico, to southern Oregon, USA. Data from > 1100 herbarium specimens indicated that these limits have been stable for at least the last 100 years. Range-wide field surveys detected C. cheiranthifolia at 87% of 124 sites and A. umbellata at 54% of 113 sites, but site occupancy did not decline significantly toward range limits for either species. Permutation analysis did not detect a significant fit of geographical variation in local density to the ACM. Mean density did not correlate negatively with mean individual performance (plant size or number of seeds/plant), probably because both species occur at low densities. Although size and seeds per plant varied widely, central populations tended to have the highest values for size only. For C. cheiranthifolia, we observed asymmetry in the pattern of variation between the northern and southern halves of the range consistent with the long-standing prediction that range limits are imposed by different ecological factors in different parts of the geographical distribution. However, these asymmetries were difficult to interpret and likely reflect evolutionary differentiation as well as plastic responses to ecological variation. Both density and seeds per plant contributed to variation in seed production per unit area. In C. cheiranthifolia only, sites with highest seed production tended to occur at the range center, as predicted by the ACM and assumed by theory proposing that range limits evolve via antagonism between natural selection and gene flow.     

Adaptive phenotypic differentiation across the intertidal gradient in the alga Silvetia compressa

Populations of intertidal species span a steep environmental gradient driven by differences in emersion time. In spite of strong differential selection on traits related to this gradient, the small spatial scale over which differences occur may prevent local adaptation, and instead may favor a single intermediate phenotype, or nongenetic mechanisms of differentiation. Here I examine whether a common macroalga, Silvetia compressa, exhibits phenotypic differentiation across the intertidal gradient and evaluate how local adaptation, developmental plasticity, and maternal effects may interact to shape individual phenotypes. Reciprocal transplants of both adults and embryos showed a "home-height advantage" in two of the three populations tested. In laboratory trials, the progeny of upper-limit individuals survived exposure to air significantly better than lower-limit progeny from the same population. I compared the emersion tolerance of full-sib families generated from gametes produced in the field to those produced under common garden conditions. The relative advantage of upper-limit lineages was robust to maternal environment during gametogenesis; this pattern is consistent with genetic differentiation. The possible role of local adaptation has historically been ignored in studies of intertidal zonation. In S. compressa, phenotypic differentiation may have important consequences for vertical range, both within and among sites.     

Tracing sources of coal combustion using stable sulfur isotope ratios in epilithic mosses and coals from China

In China, coal combustion is the most important source of atmospheric sulfur pollution. Moss sulfur isotopic signatures have been believed to hold source-specific information that can serve as a fingerprint to identify atmospheric sulfur sources. In cities where only local coals were combusted, we observed a good correspondence of average sulfur isotope ratios in urban mosses (Haplocladium microphyllum) to the values of local coals (δ(coals) = 1.455δ(mosses)- 3.945, R(2) = 0.975, p = 0.01). But if different types of coals were combusted, we did not know whether moss sulfur isotope ratios can indicate mixed coals. To confirm this, using a mixing model we estimated the ratios of imported coal to local coals at cities where both coals were used. We found that the estimated ratios at large cities (>1 million people) where both coals were used were similar to the reported ratios in their respective provinces. For small cities (<0.5 million people) in Jiangxi Province and other provinces, the estimated ratios were higher than the reported ratios because the relatively cheaper local coals were less used in all the small cities except in cities where local coal deposits were found nearby. The comparison results showed that moss sulfur isotope is a useful tool for indicating coal-derived sulfur even in cities where mixed coals were combusted.     

安防软件厂商的发展之路

一、深挖"联网、智能、高清"的行业应用,是各安防企业下一步的工作重点目前,安防行业的各大应用市场正处于快速转换期,其主要特征主要表现在从模拟向数字的不断转移,从IP标清到IP高清的扩张,从区域监控向联网监控的快速推进。同时,随着国家相关行业的大型建设项目的有效推动,以及各大行业用户进行的安防     

Erratum to: Elephants Also Like Coffee: Trends and Drivers of Human–Elephant Conflicts in Coffee Agroforestry Landscapes of Kodagu,Western Ghats,India

Kodagu district produces 2% of the world’s coffee, in complex, multistoried agroforestry systems. The forests of the district harbour a large population of the Asian elephant (Elephas maximus). The combined effects of high elephant density and major landscape changes due to the expansion of coffee cultivation are the cause of human–elephant conflicts (HEC). Mitigation strategies, including electric fences and compensation schemes implemented by the Forest Department have met with limited success. Building on previous studies in the area, we assessed current spatial and temporal trends of conflict, analysed local stakeholders’ perceptions and identified factors driving elephants into the estates. Our study, initiated in May 2007, shows that the intensity of HEC has increased over the last 10 years, exhibiting new seasonal patterns. Conflict maps and the lack of correlation between physical features of the coffee plantations and elephant visits suggest elephants move along corridors between the eastern and western forests of the district, opportunistically foraging when crossing the plantations. Dung analyses indicate elephants have selectively included ripe coffee berries in their diet. This is, to our knowledge, the first report of wild elephants feeding on coffee berries. If this new behaviour spreads through the population, it will compound an already severe conflict situation. The behavioural plasticity, the multiplicity of stakeholders involved, the difficulty in defining the problem and the limits of technical solutions already proposed suggest that HEC in Kodagu has the ingredients of a “wicked” problem whose resolution will require more shared understanding and problem solving work amongst the stakeholders.     

Volatile Organic Compounds in Ambient Air at Four Residential Locations in Seoul, Korea

To investigate the environmental behavior of volatile organic compounds (VOCs) in urban areas, their concentrations were measured at four urban monitoring sites (namely, N, S, E, and W) in Seoul, Korea (February to December 2009). A total of 27 compounds were quantified that consist of four chemical groups: aromatic (AR), halogenated aromatic, halogenated paraffin, and halogenated olefin. Results were evaluated by focusing on these four functional groups just mentioned and their summation term as total VOC (TVOC) along with several individual species (mainly AR species, that is, benzene, toluene, ethylbenzene, and xylene). The highest concentration of chemical groups was found from AR (71.1±42.1?ppbC), while that for individual species confirmed the dominance of toluene (7.48±3.88?ppb). The analysis of spatial distribution indicated that high TVOC levels were recorded at sites N and W, while it was not so significant such as S and E in terms of TVOC budget. Seasonal variation of these VOCs was characterized by the peak values in December to reflect the combined effects of pronounced source activities and meteorological conditions. Analysis of spatial variations in VOC levels between the four urban sites indicated that their distributions are tightly affected by local source processes in each area.