Participatory organic certification in Mexico: an alternative approach to maintaining the integrity of the organic label

Over the past two decades the growth of the organic sector has been accompanied by a shift away from first party, or peer review, systems of certification and towards third party certification, in which a disinterested party is responsible for the development of organic standards and the verification of producer compliance. This paper explores some of the limitations of the third party certification model and presents the case of Mexico as an example of how an alternative form of participatory certification has emerged. The paper suggests that participatory guarantee systems (PGS) are reflective of the growing “beyond organic” movement, which focuses on reconstructing the local and re-embedding food systems into their socio-ecological contexts. It argues that PGS offers a number of benefits for producers and consumers, particularly in the South, but that it faces a number of challenges as well, such as a lack of formal recognition, social conflicts and dependence on donated resources.     

Sulphur supply impairs spread of Verticillium dahliae in tomato

Vascular wilt caused by the soil-borne fungus Verticillium dahliae is a major yield and quality-limiting disease across a broad spectrum of crop plants worldwide. Sulphur-enhanced plant defence mechanisms provide an opportunity to effectively and environmentally safely constrain the wilt disease levels in planta. To evaluate the influence of sulphur nutrition on the protective potential of these mechanisms, two near-isogenic tomato genotypes differing in fungal susceptibility, were treated with low or supra-optimal sulphur supply. Microscopic analysis revealed a significant sulphur-induced decrease in the amount of infected vascular cells in both genotypes. However, plant shoot and severely pathogen-affected root growth did not display this distinct alleviating influence of sulphur nutrition. Rates of leaf photosynthesis were impeded by Verticillium dahliae infection in both genotypes especially under low sulphur nutrition. However, assimilate transport rates in the phloem sap were enhanced by fungal infection more in the resistant genotype and under high sulphur nutrition suggesting a stronger sink for assimilates in infected plant tissues possibly involved in sugar-induced defence. A SYBR Green-based absolute quantitative Real-Time assay using a species-specific primer was developed which sensitively reflected sulphur nutrition-dependent changes in fungal colonization patterns. High sulphur nutrition significantly reduced fungal spread in the stem in both tomato genotypes. Concentrations of selected sulphur-containing metabolites revealed an increase of the major anti-oxidative redox buffer glutathione under high sulphur nutrition in response to fungal colonization. Our study demonstrates the existence of sulphur nutrition-enhanced resistance of tomato against Verticillium dahliae mediated by sulphur-containing defence compounds.     

When structure means conservation: Effect of aggregate structure in controlling microbial responses to rewetting events

Rewetting events after a drought produce a pulse of soil respiration (the “Birch Effect”) that leads to a loss of carbon from soil, especially in Mediterranean ecosystems. Two main hypotheses have developed to explain the Birch effect: the “metabolic explanation”, based on the rapid consumption of intracellular osmolytes previously accumulated to survive to dry conditions, and the “physical explanation”, based on the consumption of carbon made accessible by physical destruction of internal structures of the soil.Here, we compared the respiration response of intact and crushed 9–4 mm aggregates from a California grassland soil under two different rewetting schemes: (1) successive short dry/wet events and (2) increased drought periods followed by a single rewetting. In intact aggregates, both microbial biomass and respiration rates were relatively stable through both experimental treatments. In crushed aggregates, through multiple short dry/wet cycles, both respiration rate and microbial biomass increased, while as drought length increased, biomass was unaffected but the magnitude of the following rewetting pulse increased. A mechanism that explains both these results is that crushing aggregates exposes occluded particular material that must be degraded into an immediately bioavailable form for microbes to take it up and metabolize it. Nitrification was generally higher in intact than crushed aggregates, suggesting the importance of physical association between nitrifiers and resources in regulating overall soil nitrification.This work suggests that physical processes are most important in driving respiration pulses through multiple rewetting cycles and that the physical association of organisms, substrates, and mineral particles are critical in controlling the functioning of the “microbial landscape”.     

Germination differentiation patterns of wild and domesticated columnar cacti in a gradient of artificial selection intensity

Germination of wild and managed populations of columnar cacti was compared to analyze differences associated to management intensity. The species studied: Polaskia chende, Escontria chiotilla, Myrtillocactus schenckii, Polaskia chichipe, and Stenocereus pruinosus are in a gradient from lower to higher management intensity, respectively. Within each species wild, silvicultural, and cultivated populations also represent a gradient from lower to higher management intensity. We hypothesized that seeds of plants under higher management intensity would require more water to germinate than others since managed environments are relatively wetter than unmanaged environments. Such pattern could be visualized within and among species according to management intensity. We tested germination of seeds from different populations of the different species to the water potentials: 0.0, ?0.2, ?0.4, ?0.6, ?0.8, and ?1.0 MPa. In all species studied seeds of managed populations had significantly more mass than seeds from wild populations. Each species had different susceptibility to water availability decrease, which could be related to particular adaptations to drought resistance. Stenocereus pruinosus and Polaskia chende were the most and least susceptible species, respectively. In control treatments of all species, seeds of managed populations had higher germination rate than seeds from wild populations, but when water availability decreased the pattern was the contrary. Our results suggest that artificial selection for larger fruits and heavier seeds in plants established in wetter environments have affected germination patterns. Although species have particular critical points of water availability for germination, differences in germination patterns are more pronounced according to management and artificial selection intensity.     

Influence of two-phase olive mill waste application to soil on terbuthylazine behaviour and persistence under controlled and field conditions

Purpose  

Terbuthylazine is one of the most common herbicides used to control weeds in olive groves. Application of two-phase olive mill waste (OW) to soils may play a fundamental role in the management of leaching losses of pesticides, especially in Mediterranean areas where soils are characterized by low organic matter levels. We evaluated the impact of OW amendments on the sorption–desorption, degradation, leaching, and persistence of the herbicide terbuthylazine in a representative olive grove soil from Portugal.     

Dynamics of Atmospheric Aerosol Number Size Distributions in the Eastern Mediterranean During the ��SUB-AERO�� Project

Measurements of number size distributions of submicron aerosols have been performed at the Eastern part of Mediterranean as part of an extensive measurement campaign to study photo-oxidants and aerosols (SUB-AERO Project). The measurements were made at the Finokalia station on the island of Crete (Greece) and onboard the research vessel ??Aegaeon??. Two campaigns were performed during July 2000 and January 2001 using two scanning mobility particle sizers. The particle distributions measured in the range between 7.8 < d _p < 327 nm during the summer measurements and between 7.5 < d _p < 316 nm during the winter measurements, where d _p is the mobility particle diameter. The concentration of ultrafine particles (7.5 < d _p < 30 nm) was higher during the winter period and varied mainly between 5 × 10¹ and 2 × 10³?cm^?3 with concentration peak values for this mode exceeding 1 × 10⁴?cm^?3. During the summer campaign, an average number concentration of 1 × 10²?cm^?3 at Finokalia and about 5 × 10¹?cm^?3 aboard the ??Aegaeon?? vessel was measured. An average concentration of 1 × 10³?cm^?3 was measured for the particles in the size range between 30 and 100 nm, whereas in the size range 100?C300 nm, the measured concentration ranged between 1 × 10² and 5 × 10³?cm^?3. Diurnal patterns in number concentrations were observed in connection with the transport of air masses and local sources. During the winter period, three nucleation events were observed in connection with the appearance of a particle mode at 20 nm.     

Assessment of PCDD/Fs and PCBs in Sediments from the Spanish Northern Atlantic Coast

Fluid catalytic cracking of heavy ends to high-value liquid fuels is a common unit operation in oil refineries. In this process, the heavy feedstock that contains sulfur is cracked to light products. Sulphur content is hence redistributed in the liquid and gaseous products and coke of the catalyst used in this process. The coke is later burnt in the regenerator releasing sulfur into the discharged flue gas as SO₂. In the present work, comprehensive emission inventories for a fluid catalytic cracking unit in a typical oil refinery are prepared. These inventories are based on calculations that assume complete combustion of catalyst coke in the regenerator. Yearly, material balances for both SO₂ and particulate matters emissions are carried out taking into account seasonal variations in the operation of the process unit. The results presented in this article reflect the variation of sulfur in feedstock originating from various units in the refinery. The refinery operations are not dependant on seasons but controlled by market-driven conditions to maximize the profit. The seasonal impact on refinery emissions is minimal due to its operation at optimum capacity fulfilling the international market demand. The data presented and analyzed here can be used to assess the hazardous impact of SO₂ and particulate matter emissions on surrounding areas of the refinery.     

Evaluation of Deammonification Process by Response Surface Models

The influence of the operational variables on the Anammox process has been generally researched considering each variable separately. However, the optimization of the process also requires the identification of the more significant variables and their possible interactions. Response surface models were successfully applied to evaluate the performance of the Anammox process in a deammonification system (i.e., one-stage biofilm Anammox process) taking into account the combined effects caused by two sets of three variables. Specific Anammox activity was measured by a manometric method and used as the response variable. The obtained models pointed out that the significant variables were the temperature, the value of pH, and the ratio between the unionized species of the substrates (free ammonia and free nitrous acid (FA/FNA)). There were interactions among them caused by chemical equilibriums. Total nitrogen concentration and ammonium concentration were found to be not significant in the tested range. According to the models, the optimum values of temperature, pH, and free ammonia to free nitrous acid ratio within the test ranges were, respectively, 30°C, 7.0, and 0.3. Further research at higher temperatures and lower values of pH and FA/FNA ratios would be necessary in order to find the absolute optimum conditions for the process. The obtained model can be also useful in order to develop control strategies that take into account the significant variables and their optimum ranges. A strategy to control deammonification reactors has been proposed, according to the results of the modeling.     

The Role of Leaky Boreholes in the Contamination of a Regional Confined Aquifer. A Case Study: The Campo de Cartagena Region, Spain

Poorly constructed wells (leaky or without a gravel pack) and abandoned wells can behave as conduits for the interconnection of aquifers at different depths and facilitate the transfer of contaminants between these aquifers. This is the case with Campo de Cartagena (SE Spain) where the primary land use is intensive irrigated agriculture, along with a high density of wells. The unconfined aquifer is heavily impacted by a high concentration of nitrate associated with agricultural activities. The present work provides a methodological approach to evaluate the impact of the unconfined aquifer on the water quality of the confined aquifer caused by leaky wells in high-density areas of production wells. The research approach included the use of geochemical and isotopic tools; specifically, nitrate was used as a tracer for evaluating the impact, and the code MIX_PROGRAM was used for mixing calculations. Results show an increase of the impact of the unconfined aquifer on the confined aquifer along the groundwater flow direction toward the coast, although this general pattern is controlled by local factors (pumping, intensity of agricultural practices, density of wells, and groundwater residence time).     

Lead Isotopic and Metallic Pollution Record in Tree Rings from the Copperbelt Mining�CSmelting Area, Zambia

The composition of tree rings and soils was studied at several locations affected by smelting and transportation in the vicinity of Kitwe (Copperbelt, Zambia). The contents of cobalt (Co), copper (Cu), manganese (Mn), and lead (Pb) and the ²⁰⁶Pb/²⁰⁷Pb isotope ratios in the tree rings were interpreted in relation to potential sources of contamination such as smelter production, acidification of the environment, soil composition, raw material processing, and atmospheric suspended particulate matter (SPM). The highest Co contents in the tree rings correspond to maximum ore production in the mid-1970s. Acidification through SO₂ emissions is documented in the increased Mn contents from the mid-1980s. The isotopic composition of the tree rings of the studied tree species varies in the interval 1.16?C1.34 and the youngest parts of all the studied trees exhibit a low ²⁰⁶Pb/²⁰⁷Pb ratio (<1.17). The soil isotope composition varies in the range ²⁰⁶Pb/²⁰⁷Pb?=?1.18?C1.35. The Pb isotope composition in the soils and tree rings was formed by a combination of lithogenic Pb (²⁰⁶Pb/²⁰⁷Pb????1.3), Pb in processed ores (²⁰⁶Pb/²⁰⁷Pb????1.2), and SPM (automobile) Pb (²⁰⁶Pb/²⁰⁷Pb??1.1). As the soils in the distant region have high ²⁰⁶Pb/²⁰⁷Pb ratios (>1.3) in the whole profile and simultaneously the youngest parts of the tree rings of tree species growing in this soil have a low ²⁰⁶Pb/²⁰⁷Pb ratio (<1.17), it can be assumed that the Pb in the youngest parts of the tree species is derived from absorption of SPM Pb through the bark rather than root uptake. The absence of Pb with a low ²⁰⁶Pb/²⁰⁷Pb ratio in soils in the distant area is probably affected by fires in the herbaceous and bush undergrowth and plant litter, which prevents Pb from biomass from entering the soil and mobilize it back into the atmosphere.