The potential for biochar to mitigate the impact of climate change

The United Arab Emirates produces over 44 million date palm trees yearly, where date palm is mainly used as source of food and shelter. Each tree generates approximately 20 Kilograms of palm frond waste per year and this waste is currently sent to landfills. In this study, we proposed that in the arid climate and soil conditions found in the UAE, this date palm waste could be converted to biochar and used to improve the water holding capacity of UAE soils. Therefore, the aim of this study was to test whether amendments of date palm frond (DPF) and its biochar could improve the water holding capacity of soils. A mesocosm design and a plant growth experiment were used in the laboratory to assess the treatments under UAE summer temperature conditions. For the mesocosm, there were 6 different biochar and DPF treatments (1%, 3%, 6%, 12%, 15% and 18% biochar or DPF in soil) along with the controls (sharp sand, DPF biochar and DPF). The experiment was divided into 3 cycles (wet, dry, and dry without water bowl (wow)). The impact of the experimental treatments was assessed using ANOVA. Both Biochar and DPF had no significant effect during the first two cycles (wet and dry) but during the third cycle, the DPF appeared to have better water holding capacity than Biochar. A plant growth experiment was conducted with 6 different treatment (controls - sand, DPF and Biochar; and Biochar at 1%, 6% and 15%). Cat grass was used as a quick growing crop with its height and leaf area monitored while the soil was monitored for its moisture and pH. Water was irrigated during the first 3 weeks then the soil treatments left to dry. The results show the greatest growth for 1% Biochar. The processes are being investigated using thermal gravimetric analysis (TGA) to assess water binding capacity and strength of the Biochar, DPF and soil. Please click Additional Files below to see the full abstract

Comparison of the transformation of organic matter flux through a raised bog and a blanket bog

This study has proposed that organic matter transfer and transformation into and through a peatland is dominated by preferential loss of carbohydrates and the retention of lignin-like molecules. Here we used elemental analysis and thermogravimetric analysis to analyse the biomass, litter, peat soil profile, particulate organic matter, and dissolved organic matter fluxes sampled from a continental raised bog in comparison a maritime blanket bog. The macromolecular composition and thermodynamic analysis showed that in the raised bog there had been little or no transformation of the organic matter and the accumulation was rapid with comparatively little transformation with only 13% loss of cellulose by 1 m depth compared to 92% removal of cellulosic material in the blanket bog. The lack of transformation is reflected in a difference in long term carbon accumulation rates between raised and blanket bog sites. We propose that raised bogs, with their lack of a stream outfall, have high stable water tables that mean the pore water become thermodynamically closed and reactions cease higher in the peat profile than in a blanket bog where sloping sites mean a frequent flushing of pore water and discharge of water leading to fluctuating water tables, flushing of reaction products and pore spaces remaining open

River water temperature demonstrates resistance to long‐term air temperature change

Ecosystem health and water quality of rivers are dependent on their temperature. With ongoing human-induced climate change causing increases in air temperature across the globe, it is anticipated the stream temperatures will rise too—in turn increasing the rates of biogeochemical stream processes and potentially threatening the viability and health of aquatic organisms. To understand the relationship between climate change and stream temperature response, the longer the records that can be analysed, the more the robust the analysis for detecting change. In this study, we analyse records from 263 catchments from across the United Kingdom for 45 years from 1974 to 2019 to assess the link between air temperature and stream temperature change. To give the most precise analysis of these long records, Bayesian hierarchical modelling was used and showed that: (i) The Bayesian hierarchical approach was 59% more precise, that is, reduced uncertainty on long-term trends, than using simple linear regression. (ii) The increase in annual average air temperature over 45 years across the United Kingdom showed no significant differences between 22 weather stations and gave a 45-year change of 1.35 ± 0.9°C. (iii) Trends in annual mean stream temperature change varied from −2.3 °C to 2.0 °C over 45 years, with the mean over 263 sites being 0.5 °C over 45 years. (iv) 1% of rivers showed a stream temperature trend significantly greater than the air temperature trend but 3% of sites showed a stream temperature trend significantly lower than zero. (v) 74% of all river sites showed no significant monotonic trend, either positive or negative, in water temperature even after 45 years. The observed declines in stream temperature could be ascribed to the closures of thermoelectric power stations but it is unclear why the stream temperature at some sites has risen faster than air temperature. The study shows that mean river temperature was well buffered against changes in air temperature—a 1°C rise in air temperature giving 0.37°C in mean stream temperature

Chemical Oxygen Demand as a Measure of Fluvial Organic Matter Oxidation State

The oxidative ratio (OR) of the terrestrial biosphere is directly related to the size of the terrestrial biosphere carbon sink. In turn, OR of naturally occurring organic matter can be directly related to the oxidation state of the carbon in naturally occurring organic matter (Cox). Chemical oxygen demand (COD) is a widely measured water quality parameter that has been used as a short‐term substitute for the biochemical oxygen demand (BOD). Here, we propose that if the concentration of reduced species is known, then COD measurement can be used to assess the oxidation state (Cox) of fluvial organic C. Using a Bayesian hierarchical modeling approach, this study analyzed 21 years of water quality monitoring across England to calculate Cox of fluvial organic matter. The study showed that (a) COD could not be considered separately from the reduced species (e.g., NH4) commonly occurring in freshwater water samples, but it was still possible to calculate the Cox of dissolved organic carbon (DOC) and particulate organic carbon (POC). (b) The median Cox of DOC was 0.23 with a 95th percentile range of −0.1 to 0.4. (c) The median Cox of POC was 0.20 with a 95th percentile range of 0.03–0.37. (d) The estimated Cox in fluvial systems confirms that BOD is decoupled from the production of CO2. Including new Cox estimates in the global estimate of OR gives a new median value of 1.059 with a 95th percentile range of 1.047–1.071, giving the annual flux of CO2 to land (fland) of 1.45 ± 0.1 Gt C/year

Human impact on long-term organic carbon export to rivers

Anthropogenic landscape alterations have increased global carbon transported by rivers to oceans since preindustrial times. Few suitable observational data sets exist to distinguish different drivers of carbon increase, given that alterations only reveal their impact on fluvial dissolved organic carbon (DOC) over long time periods. We use the world's longest record of DOC concentrations (130 years) to identify key drivers of DOC change in the Thames basin (UK). We show that 90% of the long-term rise in fluvial DOC is explained by increased urbanization, which released to the river 671 kt C over the entire period. This source of carbon is linked to rising population, due to increased sewage effluent. Soil disturbance from land use change explained shorter-term fluvial responses. The largest land use disturbance was during the Second World War, when almost half the grassland area in the catchment was converted into arable land, which released 45 kt C from soils to the river. Carbon that had built up in soils over decades was released to the river in only a few years. Our work suggests that widespread population growth may have a greater influence on fluvial DOC trends than previously thought

The problem of underpowered rivers

This study has hypothesized that for many rivers the trade‐off between flow accumulation and the decrease in slope along channel length means that stream power increases downstream and, moreover, that given the low slope angles in headwater and low‐order streams, they would have insufficient stream power to erode let alone transport sediment. The study considered the stream power profile, the particle travel distances and the application of the Hjulström curve based on the velocity profile of nine, large UK catchments. The study showed that: Some rivers never showed a maximum in their longitudinal stream power profile, implying that some rivers never develop a deposition zone before they discharge at the tidal limit. Particle travel distances during a bankfull discharge event showed that for some rivers 91% of the upper main channel would not be cleared of sediment. Furthermore, while some rivers could transport a 2 mm particle their entire length in one bankfull event, for another river it would take 89 such events. The Hjulström curve shows that for three of the study rivers the upper 20 km of the river was not capable of eroding a 2 μm particle. The study has shown that for all rivers studied, erosion is focused downstream and deposition upstream. Many UK rivers have a dead zone where, on time scales of the order of centuries, no erosion or transport occurs and erosion only occurs in the lower courses of the channel where discharge rather than slope dominates – we propose these as underpowered rivers

Fluxes of inorganic carbon from two forested catchments in the Appalachian Mountains

Abstract: This study uses long-term records of stream chemistry, discharge and air temperature from two neighbouring forested catchments in the southern Appalachians in order to calculate production of dissolved CO 2 and dissolved inorganic carbon (DIC). One of the pair of catchments was clear-felled during the period of the study. The study shows that: (1) areal production rates of both dissolved CO 2 and DIC are similar between the two catchments even during and immediately after the period of clear-felling; (2) flux of total inorganic carbon (dissolved CO 2 C DIC) rises dramatically in response to a catchment-wide acidification event; (3) DIC and dissolved CO 2 are dominantly released on the old water portion of the discharge and concentrations peak in the early autumn when flows in the study catchments are at their lowest; (4) total fluvial carbon flux from the clear-felled catchment is 11Ð6 t km 2 year 1 and for the control catchment is 11Ð4 t km 2 year 1 . The total inorganic carbon flux represents 69% of the total fluvial carbon flux. The method presented in the study provides a useful way of estimating inorganic carbon flux from a catchment without detailed gas monitoring. The time series of dissolved CO 2 at emergence to the stream can also be a proxy for the soil flux of CO 2

Constraining the Carbon Budget of Peat Ecosystems: Application of Stoichiometry and Enthalpy Balances

We consider how the stoichiometry and energy content of organic matter reservoirs and fluxes through and from a peatland enable the fluxes and storage of carbon within a peatland to be constrained. We include the elemental composition of the above- and below-ground biomass, litter, the peat profile, and the dissolved and particulate organic matter within a blanket bog in northern England for which the C budget has previously been measured. The study shows, based only on the elemental composition, and calculation of oxidation and energy contents, that: (a) Dissolved organic carbon (DOC) in first-order streams is significantly more oxidized than in peat pore water but that there was no significant difference in organic carbon oxidation state down the peat profile; (b) The occurrence and speciation of N uptake and release in the peatland with N used and recycled can be predicted; (c) The relatively high oxidation state of DOC in stream water acts as an endpoint for peat-forming reactions; (d) Methanogenesis does not result in deep peat formation as its requirement for energy consumes too much organic matter to form residual peat at depth; (e) Sulfate reduction does occur during the formation of deep peat; (f) Organic matter elemental composition could be constrained to within three bounding equations though the proportions of carbon species could not be specified. (g) The formation of deep peat in this catchment could only be achieved if the dissolved organic matter (DOM) in the peat pore water is the dominant electron acceptor and energy source in the production of residual organic matter; however, it is unclear as to the flux of DOM up or down the peat profile

Factors influencing mass drug administration adherence and community drug distributor opportunity costs in Liberia: A mixed-methods approach

Background Preventive chemotherapy delivered via mass drug administration (MDA) is essential for the control of neglected tropical diseases (NTDs), including lymphatic filariasis (LF), schistosomiasis and onchocerciasis. Successful MDA relies heavily on community drug distributor (CDD) volunteers as the interface between households and the health system. This study sought to document and analyse demand-side (households) and supply-side (health system) factors that affect MDA delivery in Liberia. Methods Working in two purposively selected counties, we conducted a household MDA access and adherence survey; a CDD survey to obtain information on direct and opportunity costs associated with MDA work; an observational survey of CDDs; and key informant surveys (KIS) with community-level health workers. Data from the CDD survey and Liberian minimum wage rates were used to calculate the opportunity cost of CDD participation per MDA round. The observational data were used to calculate the time spent on individual household-level tasks and CDD time costs per house visited. KIS data on the organisation and management of the MDA in the communities, and researcher reflections of open-ended survey responses were thematically analysed to identify key demand- and supply-side challenges. Results More respondents were aware of MDA than NTD in both counties. In Bong, 39% (103/261) of respondents reported taking the MDA tablet in the last round, with “not being informed” as the most important reason for non-adherence. In Maryland, 56% (147/263) reported taking MDA with “being absent” at the time of distribution being important for non-adherence. The mean cost per CDD of participating in the MDA round was −$11.90 (median$5.04, range −$169.62 to$30.00), and the mean time per household visited was 17.14 min which equates to a mean opportunity cost of $0.03 to$0.05 per household visited. Thematic analysis identified challenges, including shortages of and delays in medicine availability; CDD frustration over costs; reporting challenges; and household concerns about drug side effects. Conclusions Improved adherence to MDA and subsequent elimination of NTDs in Liberia would be supported by an improved medicine supply chain, financial compensation for CDDs, improved training, healthcare workforce strengthening, greater community involvement, capacity building, and community awareness

The entropy budgets of UK peatlands – are some peatlands near equilibrium?

The energy budget of an ecosystem must obey the 2nd law of thermodynamics even if it is an open system. Several studies have sought to use a consideration of entropy budgets to understand ecosystem energy budgets and more specifically evaporation. It has been assumed that ecosystems are far-from-equilibrium systems and as such would always seek to maximise their entropy production. Although the approach has been used to consider the behaviour of environments there are no studies that have tested the approach or its implications: maximum entropy production (MEP) is a prediction of the far-from-equilibrium assumption that could be tested. The simplest way for an ecosystem to maximise entropy production is to maximise water loss through evaporation. To test whether a system is acting to maximise entropy production this study chose to consider how the energy budget of a peatland system responded to changes in incoming energy, specifically how a change in net radiation was transferred to changes in latent heat flux (E/Rn). An ecosystem maximising its entropy production would transfer the majority of change in net radiation to change in latent heat flux. Previously using this approach we have been able to show that for nine UK peatlands the average proportion of a change in net radiation that was transferred to change in latent heat flux varied from 24 to 63%. That is for some sites where the majority of change in input was transferred to latent heat while at another site where the majority was transferred to sensible heat flux. We now show that the sites significantly divided between two groups those with[U+F044][U+F06C]E/[U+F044]Rn > 0.4 and those with E/Rn < 0.3. To understand what this results means we have now considered the entropy budget of each site to test whether high values E/Rn are actually reflected in greater entropy production and how these approaches relate to the Bowen ratio