K. G. Karthikeyan

Copper and cadmium sorption onto kraft and organosolv lignins.

The relative metal sorption ability of kraft and organosolv lignins was examined as a function of solution chemistry (pH, ionic strength (I), sorbate-to-sorbent ratio) and reaction time. The surface charge characteristics and functional group composition of these lignins, especially kraft lignin, are favorable for metal sorption. Sorption of Cu and Cd increased with increasing pH and decreasing I. Description of sorption isotherms required the more complex Sips equation, as compared to the simpler Langmuir and Freundlich formulations, indicative of the presence of binding sites with varying affinities on these lignin biosorbents. Sorption capacity varied in the following order: softwood organosolv lignin<hardwood organosolv lignin<hardwood kraft lignin<softwood kraft lignin with sorption maximum of 21.5, 40, 66.7, and 80.6 micromol/g, respectively, for Cu, and 8.2, 18.3, 25.2, and 28.7 micromol/g for Cd. Both Cu and Cd sorption kinetics were rapid with equilibrium levels attained within 80 min and faster uptake was noticed for Cu. Strong competitive effects exhibited by H(+) and Na(+) in limiting Cu and Cd sorption are suggestive of the occurrence of weak ion-exchange type interactions involving the carboxylic and phenolic functional groups. Additional pretreatment and surface modifications of these biosorbents might be required to increase metal sorption capacity and enhance their use in waster/wastewater treatment.

Root Uptake of Pharmaceuticals and Personal Care Product Ingredients

Crops irrigated with reclaimed wastewater or grown in biosolids-amended soils may take up pharmaceuticals and personal care product ingredients (PPCPs) through their roots. The uptake pathways followed by PPCPs and the propensity for these compounds to bioaccumulate in food crops are still not well understood. In this critical review, we discuss processes expected to influence root uptake of PPCPs, evaluate current literature on uptake of PPCPs, assess models for predicting plant uptake of these compounds, and provide recommendations for future research, highlighting processes warranting study that hold promise for improving mechanistic understanding of plant uptake of PPCPs. We find that many processes that are expected to influence PPCP uptake and accumulation have received little study, particularly rhizosphere interactions, in planta transformations, and physicochemical properties beyond lipophilicity (as measured by Kow). Data gaps and discrepancies in methodology and reporting have so far hindered development of models that accurately predict plant uptake of PPCPs. Topics warranting investigation in future research include the influence of rhizosphere processes on uptake, determining mechanisms of uptake and accumulation, in planta transformations, the effects of PPCPs on plants, and the development of predictive models.

Anaerobic digestion of thin stillage for energy recovery and water reuse in corn-ethanol plants

Recycling of anaerobically-digested thin stillage within a corn-ethanol plant may result in the accumulation of nutrients of environmental concern in animal feed coproducts and inhibitory organic materials in the fermentation tank. Our focus is on anaerobic digestion of treated (centrifugation and lime addition) thin stillage. Suitability of digestate from anaerobic treatment for reuse as process water was also investigated. Experiments conducted at various inoculum-to-substrate ratios (ISRs) revealed that alkalinity is a critical parameter limiting digestibility of thin stillage. An ISR level of 2 appeared optimal based on high biogas production level (763 mL biogas/g volatile solids added) and organic matter removal (80.6% COD removal). The digester supernatant at this ISR level was found to contain both organic and inorganic constituents at levels that would cause no inhibition to ethanol fermentation. Anaerobic digestion of treated-thin stillage can be expected to improve the water and energy efficiencies of dry grind corn-ethanol plants.

Humic acid complexation of basic and neutral polycyclic aromatic compounds

Complexation by humic acid (HA) of basic (quinoline) and neutral (naphthalene) polycyclic aromatic compounds (PACs) was compared using fluorescence spectroscopy and equilibrium dialysis (ED). These compounds sorb to HA via cation exchange and hydrophobic interactions, respectively. Ionization of quinoline strongly affects its sorption to HA; maximum sorption is observed at pH close to logKb (4.92), and competition with H+ and electrolyte cation (Li+) is evident. Spectroscopic experiments indicate that quinolinium (QH+) cation fluorescence is quenched via a static mechanism (i.e., a dark complex is formed) when the protonated form is adsorbed via ion exchange to HA. The extent of sorption, calculated from fluorescence data using the Stern-Volmer equation, was compared to independent ED measurements. Although both methods indicated the same trends with solution chemistry, fluorescence quenching data suggested more extensive complexation than that measured using ED. In contrast to ionizable PACs, studied here and previously, interaction of naphthalene with HA is unaffected by changes in solution conditions (pH, ionic strength).

Quantifying the Impact of Seasonal and Short-term Manure Application Decisions on Phosphorus Loss in Surface Runoff

Agricultural phosphorus (P) management is a research and policy issue due to P loss from fields and water quality degradation. Better information is needed on the risk of P loss from dairy manure applied in winter or when runoff is imminent. We used the SurPhos computer model and 108 site-years of weather and runoff data to assess the impact of these two practices on dissolved P loss. Model results showed that winter manure application can increase P loss by 2.5 to 3.6 times compared with non-winter applications, with the amount increasing as the average runoff from a field increases. Increased P loss is true for manure applied any time from late November through early March, with a maximum P loss from application in late January and early February. Shifting manure application to fields with less runoff can reduce P loss by 3.4 to 7.5 times. Delaying manure application when runoff is imminent can reduce P loss any time of the year, and sometimes quite significantly, but the number of times that application delays will reduce P loss is limited to only 3 to 9% of possible spreading days, and average P loss may be reduced by only 15% for winter-applied manure and 6% for non-winter-applied manure. Overall, long-term strategies of shifting manure applications to low runoff seasons and fields can potentially reduce dissolved P loss in runoff much more compared with near-term, tactical application decisions of avoiding manure application when runoff is imminent.

Phosphorus Flow and Characterization in Dry-Grind Corn Ethanol Plants

Both the high phosphorus (P) content and P bioavailability of the animal feed coproducts of the corn-ethanol industry could potentially contribute to increased manure and soil P levels and associated environmental issues (e.g., eutrophication). Therefore, a detailed modeling of total P mass flow to the coproducts (i.e., dry distillers grains with solubles, DDGS) was performed. Distribution of P between inorganic P and phytase-hydrolyzable P forms was quantified for selected coproducts (thin stillage, DDGS, modified DDGS [mDDGS]). The P mass balance indicated that although corn is the major P contributor to the coproducts (80.2%), a substantial portion (19.4%) comes from yeast addition. Of the two components constituting DDGS, wet distillers grains and condensed solubles, the latter contributes to only one-third of the mass but, importantly, yields 70.9% of P. The phytase enzyme used, , was very effective in hydrolyzing the nonorthophosphate P components of thin stillage, DDGS and mDDGS. Our results would help track P movement during various dry-grind processing steps and formulate strategies for phytase enzyme supplementation to various postfermentation coproducts from corn-ethanol plants.

Inorganic Phosphorus Forms and Extractability in Anaerobically Digested Manure

The focus of this study was on the effect of anaerobic digestion on phosphorus [P] extractability and the stability of inorganic P phases in dairy manure. Influent (substrate) and effluent (inoculum) samples were collected from a dairy farm in WI that has a full scale anaerobic digester in operation. The effect of organic solids destruction on P dynamics of anaerobically treated manure was investigated using mesophilic (35 oC), no-mix batch reactors operating at two significantly different inoculum-to-substrate ratios [ISRs], i.e., 2 (high inoculum-to-substrate [HIS]) and 0.3 (low inoculum-to-substrate [LIS]) g VS inoculum/g VS substrate. Serial (increasing extractant-to-sample ratio (EMR) between 3 and 127) protocol was applied on the HIS and LIS samples before and after anaerobic digestion. De-ionized water and 0.01 M MgCl2 were used as extractants in the extractions. After anaerobic treatment, WEP in LIS extracts decreased 24- 28 % at an EMR of 3 whereas the opposite was true for the HIS system (WEP increased by 40 %). At an EMR of 127, average WEP of the treated manure was 80 and 81% for the HIS and LIS systems, respectively, whereas the corresponding levels were 74 and 72% for the untreated manure. Volatile solids destruction was positively correlated with DRP removal and P extractability. A Mg- P solid phase controlled P extractability of dairy manure at lower EMRs (< 63) whereas a Ca- P solid phase controlled P extractability at higher EMRs for both untreated and treated manure.

Chemical Treatment of Dairy Manure Using Alum, Ferric Chloride and Lime

Chemical treatment of dairy manure with alum [Al2(SO)4)3], ferric chloride [FeCl3] and lime is capable of achieving good solid-liquid separation and concentrating phosphorus [P] in the solid phase. Batch level jar tests conducted using dairy manure containing 0.8 % and 1.6% total solids [TS] indicate that very high removal [>90%] of dissolved reactive P [DRP], total dissolved P [TDP] and total P [TP] can be achieved with chemical addition. In the absence of coagulants, 43% of TP and 30% of TS were removed via gravity settling. Treatment performance varied with chemical type, dosage rate and the initial manure solids concentration. FeCl3 and alum were similar in their efficiency to separate P and solids from the manure slurry. At 8 mM as Al dosage rate for 0.8% TS, alum reduced solution DRP, TDP, and TP levels by 99%, 92%, and 92%, respectively. Lime was less effective than alum/FeCl3 in concentrating TDP and TP with the trend being reversed for TS. At 40 mM as Ca dosage, lime removed 96%, 70% and 69% of DRP, TDP and TP, respectively, for 0.8% TS. Under all treatment conditions, TS and TP removal levels were lower than the extent of removal of other solid and P forms. At the same coagulant dosage, separation of solids and P decreased with an increase in initial manure solid concentration [from 0.8% to 1.6% TS].

Temperature and Manure Placement in a Snowpack Affect Nutrient Release from Dairy Manure during Snowmelt

Agricultural nutrient management is an issue due to N and P losses from fields and water quality degradation. Better information is needed on the risk of nutrient loss in runoff from dairy manure applied in winter. We investigated the effect of temperature on nutrient release from liquid and semisolid manure to water, and of manure quantity and placement within a snowpack on nutrient release to melting snow. Temperature did not affect manure P and NH-N release during water extraction. Manure P release, but not NH-N release, was significantly influenced by the water/manure solids extraction ratio. During snowmelt, manure P release was not significantly affected by manure placement in the snowpack, and the rate of P release decreased as application rate increased. Water extraction data can reliably estimate P release from manure during snowmelt; however, snowmelt water interaction with manure of greater solids content and subsequent P release appears incomplete compared with liquid manures. Manure NH-N released during snowmelt was statistically the same regardless of application rate. For the semisolid manure, NH-N released during snowmelt increased with the depth of snow covering it, most likely due to reduced NH volatilization. For the liquid manure, there was no effect of manure placement within the snowpack on NH-N released during snowmelt. Water extraction data can also reliably estimate manure NH-N release during snowmelt as long as NH volatilization is accounted for with liquid manures for all placements in a snowpack and semisolid manures applied on top of snow.

Identifying Sources of Suspended Sediment using Radionuclides in an Agricultural Watershed in South Central Wisconsin

Phosphorus (P) is an essential nutrient for plant and livestock growth. However, P loss in agricultural runoff can increase the frequency of toxic algal blooms and fish kills in receiving waters. Agricultural P loss occurs in both dissolved and particulate (sediment bound) forms. Suspended sediments play an important role in the transport of particulate P from fields to surface waters. Implementing appropriate management practices to control soil erosion and subsequent sediment delivery requires quantification of the relative contribution of sediment sources (e.g. stream bed, stream bank and upland areas under various land uses). Sediment fingerprinting using atmospheric fallout radionuclides can be used to apportion sediment sources, and thus provide valuable guidance for management decisions. Due to their long half-lives, the fallout radionuclides 137Cs and unsupported 210Pb are ideally suited for evaluating sediment transport processes that occur over long time scales. This fingerprinting method is independent of soil and rock type and can be used to differentiate between surficial and channel sources of suspended sediments. The objective of this study was to identify sources of in-stream suspended sediment in an agricultural watershed using the atmospheric fallout radionuclides 137Cs and 210Pb. The study was conducted in the non-glaciated region of southwestern Wisconsin in the Sugar Pecatonica River Basin, which is part of the Upper Mississippi River Basin. The watershed is approximately 5000 ha in size and contains primarily agriculture, forest, and grass land cover. The average watershed slope is about 11% with silt loam soils. Fieldwork included collection of both source materials (upland, streambed, and stream bank) and in-stream suspended sediments. In-stream suspended sediment samples were collected monthly for four months using passive time integrated in-stream tube samplers (Phillips et al., 2000). The samplers consist of a 10.2 cm diameter PVC tube with 0.4 cm diameter inlet and outlet, and collect a sample that is statistically representative of the grain size distribution in small streams. All source material samples were collected from the top 2.5 cm. Upland soil samples were collected from fields that represented various combinations of land use, soil type, and slope within the watershed. Upland samples were collected in a 20 m x 20 m grid with 5 m spacing and composited for analysis. Representative samples were also collected from the top 2.5cm of stream beds and eroding stream banks. All samples collected were stored at 40 °C and analyzed for organic matter content (percent volatile solids) and 137Cs and unsupported 210Pb. Radionuclide analysis was done through low background gamma counters. Over a four month period (mid-April through mid-August, 2010), results indicate that approximately two-thirds of in-stream suspended sediment originated from eroding stream banks and the remainder from upland areas. Within the upland categories (cultivated, pasture, woodland, grassland), cultivated lands followed by woodlands were significant contributors to in-stream sediments.