DDT residue contamination in sediments from Lake Sibaya in northern KwaZulu-Natal,South Africa: Implications for conservation in a World Heritage Site

Maputaland in northern KwaZulu-Natal is a biodiversity hotspot and host to a number of ecologically important systems, including Lake Sibaya, southern Africa’s largest natural freshwater lake. The region is malaria endemic and this study reports the presence of DDT and its metabolites in the sediments of Lake Sibaya that have resulted from the widespread and continued use of DDT in the region. DDT residues (p,p′-DDT, p,p′-DDD, and p,p′-DDE) were detected at all 11 sites sampled, with total concentrations ranging from 0.8 to 123 ng g⁻¹. Total DDT concentrations at Lake Sibaya represent some of the highest levels reported in South Africa, with most samples exceeding sediment quality guideline values. The findings from this study raise concerns and indicate that urgent further work is needed to investigate the potential for bioaccumulation, which could adversely affect breeding fish, bird, and crocodile populations in the region. While this study represents the first report on DDT contamination in Lake Sibaya, results have important implications for a number of other aquatic ecosystems within the Maputaland ecoregion, as well as the many local people who depend on them.     

Control of Organic Emissions from Surface Coating Operations

ABSTRACT

Step tracer tests were carried out on lab-scale biofilters to determine the residence time distributions (RTDs) of gases passing through two types of biofilters: a standard biofilter with vertical gas flow and a modified biofilter with horizontal gas flow. Results were used to define the flow patterns in the reactors. “Non-ideal flow” indicates that the flow reactors did not behave like either type of ideal reactor: the perfectly stirred reactor [often called a "continuously stirred tank reactor" (CSTR)] or the plug-flow reactor.

The horizontal biofilter with back-mixing was able to accommodate a shorter residence time without the usual requirement of greater biofilter surface area for increased biofiltration efficiency. Experimental results indicated that the first bed of the modified biofilter behaved like two CSTRs in series, while the second bed may be represented by two or three CSTRs in series. Because of the flow baffles used in the horizontal biofilter system, its performance was more similar to completely mixed systems, and hence, it could not be modeled as a plug-flow reactor. For the standard biofilter, the number of CSTRs was found to be between 2 and 9 depending on the airflow rate. In terms of NH₃ removal efficiency and elimination capacity, the standard biofilter was not as good as the modified system; moreover, the second bed of the modified biofilter exhibited greater removal efficiency than the first bed. The elimination rate increased as biofilter load increased. An opposite trend was exhibited with respect to removal efficiency.     

Uncertainty requirements of the European Union’s Industrial Emissions Directive for monitoring sulfur dioxide emissions: Implications from a blind comparison of sulfate measurements by accredited laboratories

When annual average PM_2.5 (fine particulate matter sized 2.5 microns and less) data for 2005 became available in April 2006 and the 3-yr average PM_2.5 concentration in an area just north of the Houston Ship Channel reached 15.0 µg/m³, the Texas Commission on Environmental Quality (TCEQ) initiated daily collection of quartz fiber as well as Teflon PM_2.5 filter samples for chemical speciation analysis. The purpose of the chemical speciation analysis was to use the speciation data, together with meteorological data and hourly TEOM (tapered element oscillating microbalance) PM_2.5 mass data, to identify the causes of the high PM_2.5 concentrations affecting the monitoring site and the neighborhood. The ultimate purpose was to target emission reduction efforts to sources contributing to the high measured PM_2.5 concentrations. After a year of data collection, it was recognized that a specific source, unpaved driveways and loading areas along the Ship Channel and dirt tracked onto Clinton Drive, the main artery running east-west north of the Ship Channel, were the primary cause for the Clinton Drive site's measuring PM_2.5 concentrations significantly higher than other sites in Houston. The source characterization and remediation steps that have led to sustained reduced concentrations are described in this paper.

Implications: With PM_2.5 exceedances it can be essential to have or develop chemical speciation data as part of the process of identifying the source types causing exceedances of an annual standard. Positive matrix factorization (PMF) analysis proved to be a powerful tool that identified the two locally emitted species contributing to exceedances, which did not occur at other sites in the region. They were calcium sulfate (gypsum), an industrial by-product, and soil minerals. Other data analysis approaches were necessary to distinguish North African dust events, which PMF failed to identify.     

Total mercury determination in sand boxes from Montreal

Direct mercury analysis was successfully applied to determine trace levels of total mercury in samples from sand boxes in Montréal (Québec, Canada). Twenty sand boxes were sampled from across the city and divided into two size fractions, a fine fraction (<100 microm) and a whole fraction. The concentrations of mercury ranged from 1.6 to 35 microg Hg kg(-1) dry soil for the fine fraction and from 0.7 to 6 microg Hg kg(-1) dry soil for the whole fraction. The mercury concentrations correlated with the soil organic carbon content (R2= 0.67) in the sand. The ratio of the concentration of mercury in the fine over the whole fraction varied from 2.2 to 18. Using published soil ingestion rates for children, the calculated daily intake values varied from 0 to 0.5 ng Hg kg(-1) bw d(-1) with an estimated oral ingestion of 200 mg of sand and from 0.2 to 4.7 ng Hg kg(-1) bw d(-1) with an ingestion of 1750 mg of sand. None of the sand boxes contain sufficient amounts of mercury so as to exceed the currently accepted daily intake threshold of 0.105 microg Hg kg(-1) bw d(-1) established by Health Canada.     

Hydrologic Landscape Characterization for the Pacific Northwest,USA

We update the Wigington et al. (2013) hydrologic landscape (HL) approach to make it more broadly applicable and apply the revised approach to the Pacific Northwest (PNW; i.e., Oregon, Washington, and Idaho). Specific changes incorporated are the use of assessment units based on National Hydrography Dataset Plus V2 catchments, a modified snowmelt model validated over a broader area, an aquifer permeability index that does not require preexisting aquifer permeability maps, and aquifer and soil permeability classes based on uniform criteria. Comparison of Oregon results for the revised and original approaches found fewer and larger assessment units, loss of summer seasonality, and changes in rankings and proportions of aquifer and soil permeability classes. Differences could be explained by three factors: an increased assessment unit size, a reduced number of permeability classes, and use of smaller cutoff values for the permeability classes. The distributions of the revised HLs in five groups of Oregon rivers were similar to the original HLs but less variable. The improvements reported here should allow the revised HL approach to be applied more often in situations requiring hydrologic classification and allow greater confidence in results. We also apply the map results to the development of hydrologic landscape regions.     

GAME-THEORETIC ANALYSES OF ENFORCEMENT OF ENVIRONMENTAL LAWS AND REGULATIONS1

ABSTRACT: Game-theoretic models are developed for describing and analyzing the inspection and enforcement process, especially as it relates to environmental laws and regulations in North America. Based on these models, systems using irrevocable control orders can be compared to those relying on court determination of guilt and punishment. The cost-effectiveness of environmental enforcement can be systematically assessed in terms of factors such as the private gains for violators, the costs of inspection, penalties, and the social value of deterring violations. The policy implications of the analysis, especially with reference to environmental protection, are emphasized.     

The composition,leaching, and sorption behavior of some alternative sources of phosphorus for soils

Concerns about the sustainability of inorganic fertilizers necessitate the characterization of alternative P source materials for agronomic P-efficiencies and P losses via leaching. Firstly, this study examined nutrient compositions including P speciation of seven soil amendments: sewage sludge (SS), anaerobic digestate (AD), green compost (GC), food waste compost (FWC), chicken manure (CM), biochar, and seaweed. Secondly, soil P leaching and availability was studied on a subset of four materials (SS, AD, GC, and CM). Sorption of extracts onto columns of a test soil showed strong P retention for SS and compost, but weak P sorption for CM and especially AD, suggesting short-term leaching risks for soil applied AD. Limited P desorption with water or citrate indicated sorbed P was strongly fixed, potentially limiting crop availability. These data indicate that variation in P forms and environmental behavior should be understood to maximize P usage, but minimize leaching and soil P accumulation. Hence, different alternative P source materials need differing recommendations for their agronomic management.