Integrated Field Lysimetry and Porewater Sampling for Evaluation of Chemical Mobility in Soils and Established Vegetation

Summary

Field lysimetry and porewater sampling allow researchers to evaluate the fate of chemicals applied to soils and established vegetation. The goal of this protocol is to demonstrate how to install required instrumentation and collect samples for chemical analysis during integrated field lysimetry and porewater sampling experiments.

Abstract

Potentially toxic chemicals are routinely applied to land to meet growing demands on waste management and food production, but the fate of these chemicals is often not well understood. Here we demonstrate an integrated field lysimetry and porewater sampling method for evaluating the mobility of chemicals applied to soils and established vegetation. Lysimeters, open columns made of metal or plastic, are driven into bareground or vegetated soils. Porewater samplers, which are commercially available and use vacuum to collect percolating soil water, are installed at predetermined depths within the lysimeters. At prearranged times following chemical application to experimental plots, porewater is collected, and lysimeters, containing soil and vegetation, are exhumed. By analyzing chemical concentrations in the lysimeter soil, vegetation, and porewater, downward leaching rates, soil retention capacities, and plant uptake for the chemical of interest may be quantified. Because field lysimetry and porewater sampling are conducted under natural environmental conditions and with minimal soil disturbance, derived results project real-case scenarios and provide valuable information for chemical management. As chemicals are increasingly applied to land worldwide, the described techniques may be utilized to determine whether applied chemicals pose adverse effects to human health or the environment.

Introduction

Potentially toxic chemicals are routinely applied to land from sources such as pesticides, fertilizers, sewage/biosolids, industrial wastes, and municipal wastes^1,2. The fate of these chemicals – which may include nutrients, trace elements, organics, and their associated metabolites – is often not well understood³. If the chemicals are not managed properly, they have the potential to threaten human and environmental health through their transfer to and buildup in plants, surface water, and groundwater. With a global population that may reach 10 billion people by 2050, there are growing demands on waste management and food production

Protocol

Field sampling is performed in this experiment and is under the authorization of the North Carolina Department of Agriculture & Consumer Services.

1. Field Lysimeter Installation

1. Choose an experimental site on which lateral movement of applied chemicals is unlikely (i.e. sites with little or no slope). Select sites based on soil and vegetation properties of interest.
2. If plots are vegetated, pull vegetation plugs prior to lysimeter installation (Figure 1A).
3. Drive the lysimeters downward into the desired plots (with or without vegetation) using an inverted post driver, leaving ~1-2....

Results

This method allows for the accumulation of data on the fate of chemicals applied to bareground and vegetated soil systems^5,10. This approach was used to evaluate arsenic (As) downward leaching, absorption, and translocation into plants for bermudagrass (Cynodon dactylon) systems following application of the organic arsenical herbicide monosodium methyl arsenate (MSMA)⁹. Since the 1960s, MSMA has been used in non-cropland, turfgrass, and cotton production, but there is growing concern that a.......

Discussion

Utilizing an integrated field lysimetry and porewater sampling approach allows researchers to assess spatial and temporal distributions of a wide variety of land-applied chemicals. The fate of chemicals in soils and vegetated systems may be controlled by a number of environmental processes and attributes, such as downward leaching, volatilization, hydrolysis, photolysis, microbial transformation/degradation, plant uptake, soil type, and soil pH^16,17. Unlike greenhouse or laboratory-based experiments, results f.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Prenart Super Quartz Samplers (PFTE/Quartz)	Prenart Equipment ApS	N/A	Any samplers for  trace metal analysis can be used (e.g. SoilMoisture Equipment Corp.)
Prenart installation kit	Prenart Equipment ApS	N/A	Contains all items necessary to install porewater samplers
2 L collecting bottles	Prenart Equipment ApS		Bottles can also be purchased from Fisher Scientific (02-923-2) or other laboratory supply companies, but fittings will need to be adjusted. Bottles can be covered with dark material if light sensitive
Portable vacuum pump	Prenart Equipment ApS	N/A	Vacuporter from Decagon Devices or other field battery-operated or hand vacuum pump may be used
1 oz HDPE Nalgene bottles	Fisher Scientific	03-313-4A	Sample bottle type will depend on analyte of interest and may be glass
Concentrated nitric acid	Fisher Scientific	A509-P212	Oxidizing and corrosive-other acids may be needed for preservation and should be used with caution
25 mm 0.2 µm nylon syringe filters	VWR	28145-487	Other filter types and pore sizes may be used, dependent on the analyte of interest and analytical instrumentation
60 ml Luer-Lok syringes	Fisher Scientific	13-689-8	Other sizes may be used depending on sample volume collected
Portable pH meter	VWR	248481-A01	Other pH meters can be used following calibration
Graduated cylinder	any	N/A
Field lysimeters (metal, plastic, etc.)	N/A	N/A	Often these are constructed based on the researchers specifications
Inverted post driver tractor	N/A	N/A	Any tractor can be used to install the lysimeters
Handheld boom sprayer	N/A	N/A	To apply the rate needed for application
Polyethylene bags	Johnson & Johnson	N/A	Other brands may be used for soil storage
Reciprocating saw	Black & Decker	N/A	Any reciprocating saw can be used with a metal cutting attachment