Scientist replacing mercuric chloride with benzalkonium chloride to preserve a vibrant coral reef

Is Your Water Safe? The Surprising Alternative to Toxic Preservatives in Seawater Samples

Lena Voss in Climate & Environment August 2025 • 4 min read.

"Ditch the Mercury: Discover how benzalkonium chloride (BAC) could revolutionize seawater preservation, offering a safer, eco-friendly alternative for scientific research."

Imagine needing to collect seawater samples for crucial research, only to face the challenge of preserving them without harming the environment. For decades, scientists have relied on mercuric chloride (HgCl2) to inhibit microbial activity in these samples, ensuring accurate analysis back in the lab. However, this seemingly simple solution comes with a dark side: HgCl2 is highly toxic, accumulates in ecosystems, and requires costly, specialized disposal.

The environmental risks and financial burdens associated with mercuric chloride have fueled a global search for safer alternatives. Enter benzalkonium chloride (BAC), a widely used disinfectant found in everything from hospitals to household cleaners. But could this common antimicrobial agent effectively preserve precious seawater samples without the hazards of mercury?

A groundbreaking study published in "Ocean Science" investigates the potential of BAC as a suitable substitute for HgCl2. The findings could revolutionize how we approach seawater preservation, offering a pathway to more sustainable and environmentally conscious research practices. Let's dive into the details of this innovative research and explore the potential implications for our oceans and beyond.

The Mercury Problem: Why We Need a Change

Scientist replacing mercuric chloride with benzalkonium chloride to preserve a vibrant coral reef

Mercuric chloride's effectiveness as a preservative is undeniable. It halts microbial activity, preventing the alteration of key parameters like oxygen levels, inorganic carbon, and nutrients in seawater samples. This preservation is crucial for accurate analysis when immediate testing isn't possible. However, the cost of this convenience is steep.

The dangers of mercury are well-documented. It's a potent neurotoxin that can wreak havoc on aquatic ecosystems and human health. Its persistence in the environment, coupled with its ability to bioaccumulate in the food chain, poses a long-term threat. Furthermore, the strict regulations governing mercury waste disposal translate into significant expenses for research institutions.

Environmental Hazard: Mercury contaminates aquatic environments, harming wildlife.
Health Risks: Mercury exposure can lead to severe health problems in humans.
Bioaccumulation: Mercury concentrates in the food chain, posing risks to top predators.
Costly Disposal: Mercury waste requires specialized and expensive handling.

The search for a mercury alternative isn't just about reducing environmental impact, it's about making scientific research more sustainable and accessible. A safer, cost-effective preservative would empower researchers to conduct vital oceanographic studies without the burden of hazardous waste management.

The Future of Seawater Preservation

The research on benzalkonium chloride as a seawater preservative marks a significant step forward in sustainable oceanographic research. While further studies are needed to fully understand its long-term effects and optimal applications, BAC holds immense promise as a safer, more environmentally friendly alternative to mercuric chloride. By embracing such innovations, we can minimize our impact on delicate marine ecosystems while continuing to unlock the mysteries of our oceans. The journey toward sustainable science is one small step at a time.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.5194/os-11-947-2015, Alternate LINK

Title: Technical Note: Could Benzalkonium Chloride Be A Suitable Alternative To Mercuric Chloride For Preservation Of Seawater Samples?

Subject: Cell Biology

Journal: Ocean Science

Publisher: Copernicus GmbH

Authors: J. Gloël, C. Robinson, G. H. Tilstone, G. Tarran, J. Kaiser

Published: 2015-12-07

Everything You Need To Know

Why has mercuric chloride (HgCl2) been traditionally used in seawater sample preservation, and what are its drawbacks?

Mercuric chloride (HgCl2) has been used to preserve seawater samples by inhibiting microbial activity. This prevents changes to key parameters like oxygen levels, inorganic carbon, and nutrients, ensuring accurate analysis. However, mercuric chloride is highly toxic, accumulates in ecosystems, and requires costly, specialized disposal, making it environmentally unsustainable.

What is benzalkonium chloride (BAC), and why is it being considered as an alternative to mercuric chloride for preserving seawater samples?

Benzalkonium chloride (BAC) is being investigated as a safer substitute for mercuric chloride in preserving seawater samples. BAC is a common disinfectant found in various applications, and research suggests it could effectively inhibit microbial activity in seawater without the environmental and health risks associated with mercury. This offers a more sustainable approach to oceanographic research.

What are the primary environmental and economic drawbacks associated with the use of mercuric chloride in oceanographic research?

The primary drawbacks of using mercuric chloride include its toxicity to aquatic ecosystems and human health. It bioaccumulates in the food chain, posing risks to top predators, and its persistence in the environment leads to long-term contamination. Additionally, the stringent regulations for mercury waste disposal result in significant expenses for research institutions. Because of these issues, there is a search for alternatives.

How effective is benzalkonium chloride in preserving the integrity of seawater samples, specifically concerning key parameters?

Research indicates that benzalkonium chloride can effectively preserve seawater samples by preventing microbial activity, similar to mercuric chloride. This preservation is crucial for maintaining the integrity of parameters such as oxygen levels, inorganic carbon, and nutrients, which are essential for accurate scientific analysis of seawater composition. This could allow researchers to obtain reliable data without introducing a potent toxin into the environment.

What are the potential implications of switching from mercuric chloride to benzalkonium chloride for seawater preservation in terms of environmental impact and research sustainability?

Switching to benzalkonium chloride for seawater preservation would promote more sustainable and environmentally conscious scientific research. It would minimize the introduction of toxic mercury into marine ecosystems, reducing the risk of bioaccumulation and harm to wildlife and human health. Furthermore, it could lower waste disposal costs and make oceanographic research more accessible to institutions with limited resources for hazardous waste management. However, further studies are needed to fully understand the long-term effects and optimal applications of BAC.